Health Promotion: Cells and Tissues PDF

**[Week 1 - Cells and tissues]** [Prokaryota] - Lack of nucleus, organised with a membranous envelop - Contain a few cells organelles - Tend to be heterotrophic. [Eukaryotes] - Protoctista - Unicellular or assemblages of similar cells - Possess an organised membrane bound nuclei....

**[Week 1 - Cells and tissues]** [Prokaryota] - Lack of nucleus, organised with a membranous envelop - Contain a few cells organelles - Tend to be heterotrophic. [Eukaryotes] - Protoctista - Unicellular or assemblages of similar cells - Possess an organised membrane bound nuclei. - Eukaryotes e.g. algae and protozoa. - Fungi - Have protective cell wall made in chitin - Heterotrophic - Have multi-nucleated hyphae - Produce spores - Secretes enzymes to digest food [Plants] - *Plantae* - Multicellular - Eukaryotes - Autotrophic - Cellulose -- cell wall [Animals] - Animalia - Multicellular, heterotrophic, eukaryotes - Further broken down by phylum: - Chordata -- vertebrate - Nematodes -- worms - Arthropods - Echinoderms -- starfish - Porifera -- sponges [Cell biology] - The study of cells is known as cytology - Assumptions of cell biology - All living material is made up of cells or the products of cells - All cells are derived from previously existing cells - Cells are the most elementary unit of life - Every cell is bound by a plasma membrane - All cells have strong biochemical similarities - Most cells are small [Three main functions] - Maintenance - Synthesis of cell products - Cell division [Cell structure] - Cell surface membrane - Structure -- 2 layers of phospholipids which contain other molecules such as proteins. - Function -- controls the movement of molecules in and out of the cell and acts as a boundary between the cell and the surrounding environment. - Ribosomes - Structure -- tiny particles made up of RNA and protein. - Function -- present in large numbers in the cell either attached to the endoplasmic reticulum or free in the cytoplasm, they are the site of protein synthesis within the cell. - Endoplasmic reticulum - Structure -- a system of membrane bound flattened sacks. Rough ER has ribosomes attached and is generally found surrounding the nucleus of the cell. Smooth ER does not have ribosomes - Function -- RER transports proteins made by the ribosomes throughout the cell. SER is used in the production of lipids and steroids like cholesterol and reproductive hormones. - Mitochondrion - Structure -- double membrane, the inner section of which is called the matrix and has finger-like folds which are known as christae. - Function -- site of internal cellular respiration. Energy from respiration is converted into ATP which is a form of chemical energy. - Golgi apparatus - Structure -- type of endoplasmic reticulum forming membrane bound flattened sacks. - Function -- processes and modifies bio-chemicals e.g. attaches haem to globin to form haemoglobin. collects, sorts and packages material for transport throughout the cell or for secretion out of the cell. - Lysosomes - Structure -- known as suicide bags, they are small spherical sacs surrounded by a single membrane. They contain digestive enzymes but must be kept separate from the rest of the cell. - Function -- autophagy -- digestion of worn out parts of th ecell for excretion. Autolysis -- self-destruction of the cell. - Microfilaments - Structure -- rod-like structures made of contractile protein. - Function -- provide support and aid movement. - Microtubules - Structure -- hollow, cylindrical tube -- like structures which form part of the cell skeleton (known as they cytoskeleton). - Function -- they help to give the cell shape and form and are involved in the transport of materials. - Centrioles - Structure -- small hollow cylinders found in pairs close to the nucleus that appear as a ring of microtubules. - Function -- they help to produce the spindle in cell division. - Nucleus - Structure -- largest cell organelle and is enclosed by a nuclear envelope. It contains chromatin and a nucleus. - Function -- nucleoli are the site of RNA synthesis. Whilst the chromatin is loosely coiled form chromosomes. Chromosomes contain DNA which carries hereditary information. - Cytoplasm -- sometimes known as the ground substance, it is 90% water. It is substance in which all the bio-chemicals within the cell are dissolved and the organelles are suspended in it. - Tissues - The tissues of the human body include four major types: - Epithelial tissue -- form protective coverings and functions in secretion and binds absorption. - Connective tissue -- supports and binds structure together - Muscular tissue -- body movement - Nervous tissue -- conducts impulses to control and coordinate body activities. 1. Epithelial tissue - Found throughout the body - Covers organs, lines cavities and hollow organs - Anchored to a basement membrane - Has little blood supply - Functions include: - Protection - Secretion - Absorption - Excretion - Types of epitheliums - There are several types of epitheliums depending on location and function. - Thin flat cells (squamous epithelium); squared shaped cells (cuboidal epithelium), elongated cells (columnar epithelium). - Can be a single layer or multiple layers -- stratified - Depends on the location and function - Specialist epithelium -- transitional epithelium - Designed to stretch or distend and return to normal size. - Found in the urethra and bladder. - Glandular epithelium - Made up of cuboidal or columnar cells - Produces and secretes substances into ducts or into body fluids. 2\. Connective tissue - Acts to bind, support, protect, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infection, and help repair tissue damage. - Losse connective tissue - Areolar tissue -- delicate, thin membranes that bond body parts together such as skin and underlying organs. - Mostly fibroblasts are separated by gel-like ground substance containing collagenous and elastic fibres. - Adipose tissue - Fat store - Found beneath the skin, around joints, padding internal organs, and in certain abdominal membranes - Cells are called adipocytes - Also function to store energy for the body. - Dense connective tissue - Consists of densely packed collagen fibres. - Very strong but lacks a good blood supply - Tendons, ligaments, and the white layer of the eyeball. - Cartilage - Rigid connective tissue - Provides a supportive framework. Lacks a vascular system. - Consists of chondrocytes within lacunae in the gel-like fluid matrix. - Most common in hyaline cartilage -- found at end of bones, in respiratory system and is important for bone growth and embryonic development. - Elastic cartilage - Provides a framework for external ears and parts of the larynx. - Fibrocartilage - Has many collagen fibres - Tough tissue that provides a shock -- absorbing function in intervertebral discs and in the knees and pelvic girdle. - Bone - Most rigid connective tissue, with deposits of calcium mineral salts and collagen within the matrix. - Supports the body, protects, forms muscle attachments and is the site for blood cell formation. - Osteocytes lie within lacunae and are arranged in concentric circles with Haversian canals. - Good blood supply enables rapid recovery after an injury. - Blood - Composed of formed elements suspended a liquid matrix called plasma - Includes red blood cells to carry oxygen, white blood cells for protection, and platelets for blood clotting. - Blood functions to transport substances throughout the body. 3\. Muscle tissue - General characteristics: - Muscle cells, or fibres, can contract and shorten to provide movement. Consist of three major types: skeletal, smooth and cardiac. - Generally, do not divide but do grow larger. - Skeletal muscle - Attach to bone and can be controlled by conscious effort. - Muscle fibres are long and cylindrical nuclei and contract from nervous impulse. - Smooth muscle - Lacks striations is uni-nucleated and consists of spindle-shaped cells. - Involuntary muscle is found in the walls of internal organs, such as in digestive tract, blood vessels, and urinary bladder. - Cardiac muscle - Unique, found only in the heart and consists of branching fibres that are connected to each other with intercalated discs. - Involuntary muscle has a single nucleus in each cell but appears striated. 4\. Nervous tissue - Found in the brain, spinal cord, and nerves. - Neurons (nerve cells) conduct electrical impulses to other neurons, muscles, and glands. - Helper cells, or neuroglia, support, nourish, and communicate with the neurons but do not conduct impulses. **[Week 2 - Cardiovascular system ]** ***[Video/presentation on blackboard]*** The cardiovascular system is made up of the heart and blood vessels. There are two circuits: - Pulmonary circuit: - Transports oxygen -- poor blood to the lungs, and back to the heart - In the lungs, blood picks up oxygen and drops off carbon dioxide - System circuit: - Transports oxygen -- rich blood from the heart back to all body cells, and back to the heart - Blood delivers nutrients to cells and removes waste [The heart] - Hollow, cone-shaped, muscular pump - In the mediastinum of thoracic cavity, superior to the diaphragm - Heart contains 4 chambers: - 2 atria (upper chambers) - 2 ventricles (lower chamber, pumping action) - Surrounded by pericardium -- multiple layers of membrane. [Walls of heart] Layers Composition Function ----------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------- --------------------------------------------------------- Epicardium (visceral pericardium) Serous membrane of connective tissue covered with epithelium, blood capillaries, lymph capillaries and nerve fibers Form a protective outer covering; secretes serous fluid Myocardium Cardiac muscle tissue separated by connective tissue separated by connective tissue and including blood capillaries, lymph capillaries and nerve fibers Contracts to pump blood from the heart chambers Endocardium Membrane of epithelium and underlying connective tissue including blood vessels Form protective lining of the chambers and valves. [Valves] Valves Location Function ------------------ -------------------------------- ----------------------------------------------------------------------------------------------------- Tricuspid Right atrioventricular orifice Prevent blood flowing from the right ventricle into the right atrium during ventricular contraction Pulmonary Entrance to pulmonary trunk Prevent blood flowing from pulmonary trunk into right ventricular relaxation Mitral(bicuspid) Left atrioventricular orifice Prevents blood flowing from the left ventricle into the left atrium during ventricular contraction. Aortic Entrance to aorta Prevents blood flowing from aorta into left ventricle during ventricular relaxation The heart is covered with a framework of capillaries and coronary blood vessels. [Cardiac cycle] - Events of the heartbeat - Heart chambers function in coordinated manner - Heart actions are regulated so that atria contract (atrial systole) while ventricles relax (ventricular diastole); then ventricles contract (ventricular systole) while atria relax (atrial diastole) [Heart sounds] - Lubb - First heart sound - Occurs during systole - Associated with closing mitral and tricuspid valve. - Dubb - Second heart sound - Occurs during ventricular diastole - Associated closing of the pulmonary and aortic (semi-lunar) valves Murmur -- abnormal heart sound deprived from incomplete closure of cusps of a valve. [Cardiac conduction system] - Major components of the cardiac conduction system - SA (sinoatrial) node: pacemaker, initiates rhythmic contractions of the heart. - Internodal atrial muscle conducts impulses from SA to atria - Junctional fibers: conducts impulses from SA node to AV node - AV (atrioventricular) node conducts impulses to AV bundles; delays impulses' so that atria finish contracting before ventricles contract - AV (atrioventricular) bundle (of His): conducts impulses rapidly between SA nide and bundle branches. - Left and right bundle branches: split off from AV bundle, conduct impulses to Purkinje fibers on both side of the heart. - Purkinje fibers: large fibers that conduct impulses to ventricular myocardium. [Regulation of cardiac cycle] - The SA node (pacemaker) normally controls the heart rate. - Sympathetic and parasympathetic fibers modify the heart rate in response to changing conditions such as: - Physical exercise - Body temperature - Fight or flight response - Concentration of various ions, such as potassium and calcium ions. - Parasympathetic impulse via vagus nerves decreases heart rate, due to influence on SA and AV nodes - Sympathetic impulses via accelerator nerve increases heart rate, due to influence of SA and Av nodes, and ventricular myocardium. - Baroreceptor reflexes in the cardiac control centre in medulla oblongata; balance inhibitory and sympathetic fibres. - Cardiac control centre regulates autonomic impulses to the heart. [Blood vessels] - Arteries -- carry blood away from the ventricles of the heart - Arterioles -- receive blood away from the arteries and carry it to the capillaries - Capillaries -- site of exchange of substances between the blood and body cells - Venules -- receives the blood from the capillaries and conduct it to the veins - Veins -- receive blood from venules and carry it back to the atria of the heart. [Arteries and arterioles] - Thick, strong walls, thicker than veins - Transport blood under high blood pressure. - Give ride to smaller arterioles [Veins and venules] - Thinner walls than arteries (3 layers of tunic) - Tunica media less developed - Carry blood relatively low pressure - Function as blood reservoirs - Many have flap-like valves. [Capillaries] - Capillaries are smallest diameter blood vessel - Connect the smallest arterioles and smallest venules - Extensions of the inner lining of smallest arterioles - Walls consist of endothelium (simple squamous epithelium) only - Semi-permeable - Blood flow regulated mainly by precapillary sphincters: smooth muscle surrounding capillary when it branches off arterioles or metarteriole. Capillary exchange occurs during single layer of endothelium. Blood comes in under high blood pressure. High hydrostatic pressure forces water and substances into surrounding tissue Pressure outside increases as water pushed out Inward osmotic pressure so water and substances move back Get a net outward flow Move across capillary hydrostatic pressure decreases and more osmotic pressure [Pulses] - Number of beats per minute - The average adult heart rate is between 60 and 100 bpm. - Average child heart rate is between 70 and 120 bpm depending on age [Blood pressure ] - Pressure which blood exerts on the walls of the blood vessels - Pressure is greatest in the large arteries leaving the heart and lowest in large veins approaching the heart. - Arterial blood pressure is the result of the discharge of blood from the left ventricle. - When the left ventricle contacts and pushes blood into the aorta, the pressure produced is called systolic blood pressure - When the heart is relaxing following the ejection of blood, the pressure within the arteries is called diastolic blood pressure. - Blood pressure is measured by a sphygmonameter is written systolic and diastolic. [Cardiac output] - Stroke volume -- volume of blood that enters the arteries with each ventricular contraction \~ 70ml/beat - Cardiac output -- volume of blood discharged from a ventricle each minute. cardiac output = stroke volume \* heart rate - Blood pressure varies with cardiac output - Increase in SV or HR increase in CO, which increases blood pressure. [Cardiac pathologies] Hole in the heart. Heart attack Cardiac arrest Blocked vessels *Shock* - Shock is the reduced blood flow to a tissue, therefore not meeting metabolic demand. - Anaphylactic shock -- body shuts down because of allergic reaction - Septic shock -- decrease of carbon dioxide in the body. - Hypovolemia shock -- when there is not enough blood in the body -- blood decreases - Neurogenic shock -- problem with neuro system. - Cardiogenic shock -- when the heart can't pump enough to meet the body's demand. Thrombosis -- blood accumulates in the blood vessels. Embolisms -- mass of any material blocking a blood vessel. Arteriosclerosis -- narrowing of arteries to damage not from atheroma. Affects Tunic Media. Atheroma -- plaque presents in tunica intima. Cholesterol, foam cells, smooth muscle accumulation, fibrous cap and eventually, after rupture, thrombus. Atherosclerosis -- restriction or occlusion of blood flow. Restriction is common in lower limbs. Myocardial infarction is the cardia tissue dies as result of occlusion or restriction of blood flow also knows as a heart attack. Angina -- restriction of blood flow with infarction. Management - CABG -- coronary artery bypass graft - PPCI/PCI/Stent - Medical Mx - Cardiac rehabilitation [Heart Failure] Inability of heart to provide output required. Both sides of the heart can fail with different effects. [Dysrhythmia/Arrythmias] Slowed rhythm = bradycardia \100 bpm Ventricular Dysrhythmias -- cardiac arrest Ventricular tachycardia - \>100bpm Ventricular fibrillation = same as AFib, erratic, uncoordinated contraction of ventricles, resulting in reduced cardiac output. PEA = pulseless, electrical activity. No cardiac output but ongoing firing electrical impulse. Asystole = no heart activity ***[Week 3 - Respiratory system]*** [Upper respiratory tract] *Nose* - Nostrils are entrance - Provides protection of naval cavity *Nasal cavity* - Immediately posterior to the nose, divided mentally by the nasal septum - Lined with mucus membrane that warms, moistures and filters the air - Particles are trapped and moved to the back of the throat to be swallowed *Paranasal sinuses* - Air filled spaces in the skull - Lined with mucus membrane like nasal cavity. *Pharynx* - Common passage for air and food - Aids in producing sounds - Three subdivisions -- nasopharynx, oropharynx and laryngopharynx [Lower respiratory tract] *Larynx* - Enlargement in the airway superior to the trachea and inferior to the pharynx - Keeps particles from entering the trachea and houses the vocal cords - Composed of muscles and cartilage bound by elastic tissue - Larynx chords are located here and are responsible for producing sound - True vocal cords are part of epiglottis, which closes off the trachea when swallowing - During normal breathing, the vocal cords are relaxed, and the glottis is a triangular slit - During swallowing, the false vocal cords and epiglottis close of the glottis *Trachea* - Extends downwards anterior to the oesophagus and into the thoracic cavity where it splits into right and left primary bronchi. - The inner wall of the trachea is lined with a ciliated mucous membrane with many goblets cells that serve to trap incoming particles. - Traches walls are supported by 20 complete cartilaginous ring that keep the airways open *Bronchial tree* - Consist of branched mucous membrane -- lined tubes leading from the trachea to the alveoli. - It begins with the two main (primary) bronchi, each leading to a lung. - Next are the lobar (secondary) bronchi going to each lobe. - Segmental bronchi further subdivided into terminal bronchioles, respiratory bronchioles, the alveolar ducts. *Lungs* - Soft, spongy, cone-shaped lungs are separated medically by mediastinum and are enclosed by the diaphragm and ribcage. - Primary bronchus and large blood vessels enter each lung in the median surface - Layer of serous membrane, the visceral pleura is attached to the lungs, and the parietal pleura lines the thoracic cavity; serous fluid lubricates the pleural cavity between these two membranes - Right lung has three lobes (superior, middle and inferior), and the left lung has two lobes (superior and inferior) - Each lobe contains air passages, alveoli, nerves, blood vessels, lymphatic vessels, and connective tissue. [Breathing] - Ventilation (breathing), the movement of air in and out of the lungs, is composed of inspiration and expiration. *Inspiration* - Atmsopheric is the force that moved air into the lungs - When pressure on the inside of the lungs decreases, higher pressure in the air flows in from the outside. - Air pressure in the lungs is decreased by increasing the size of the thoracic cavity. - Due to the surface tension between the two layers of pleura, the lungs follow with the chest wall and expand. - Process of inspiration: - The diaphragm contracts and moved downwards - The external intercostal muscles contract and move the ribs and sternum upward and outward - The thoracic cavity enlarges, and the lungs expand - Intra-alveolar volume increases, causing the pressure to decrease and air rushes in. - To take a deep breath, the diaphragm and external intercostal muscles contract more forcefully, plus the pectoral minor, sternocleidomastoid and scalene muscles pull the ribcage up more. *Expiration* - Forces of expiration are due to the elastic recoil of lung and muscle tissues and from the surface tension within the alveoli; normal expiration is passive. - Process of expiration: - Diaphragm and external intercostal muscles relax and the lungs recoil, decreasing the volume of the thoracic cavity. - Increased surface tension of the alveoli decreases their volume. - Intra-alveolar pressure increases air rushes out - Forced expiration is aided by internal intercostal muscles that compress the ribcage and abdominal wall muscles that compress the abdomen against the diaphragm. [Peak flow] - Used to assess how much air moves in and out of the lungs - Reduced air flow out of the lungs nay indicates a narrowing of airways - Normal valves can differ depending on age, height, weight, fitness levels or use of lungs. - On average the healthy adult over the age of 30 will have a peak flow of between 400-700 litres/minute [Respiratory air volume] - Spirometry is used to measure the capacity of the lungs - Measures the volume of the lungs - Tidal volume is the measure of the amount of air that enters or leaves the lungs in a single cycle - During maximal forced expiration, an expiratory reserve volume can be exhaled. - There remains a residual volume in the lungs. [Control of breathing ] - Normal breathing is a rhythmic, involuntary act even though the muscles are under voluntary control - Groups of neurons in the brain stem comprise the respiratory areas, which control breathing by causing inspiration and expiration and by adjusting the rate and depth of breathing - The medullary rhythmicity centre contains neurons that are responsible for basic rhythm of breathing and stimulate the respiratory muscles - Inflation reflex stimulates the vagus nerve preventing over inflation of the lungs [Factors affecting breathing] - Respiratory areas, chemicals, lung tissue stretching and emotional state affect breathing - The respiratory centre is sensitive to changes in blood concentration of carbon dioxide and hydrogen ions. - If the hydrogen ions (pH decreases) in the cerebrospinal fluid (CSF), breathing rate increases. - More CO2 is exhaled, blood and CSF h+ levels fall and breathing then returns to normal - Breathing rate decreases if CO2 or hydrogen ions concentration decreases to build up CO2 levels to normal. - Oxygen has a very minor role in respiratory control - Blood O2 levels must be very low to stimulate the peripheral chemoreceptor in the carotid and aortic bodies - If this happens breathing rate and tidal volume will increase. [Gaseous exchange] - Alveoli are the only place where gaseous exchange occurs between the atmosphere and the blood - They are tiny sacs at the end of the alveolar ducts [Respiratory membrane] - It consists of the simple squamous epithelial cells of the alveolus, the endothelial cells (simple squamous epithelium) of the capillary, and two fused basement membranes of these layers. - Gas exchange occurs across the respiratory membrane [Diffusion across the membrane] - Gases exchange from areas of higher pressure to areas of lower pressure - In a mixture of gases, each gas accounts for a portion of the total pressure, the amount of pressure each gas exerts is equal to its partial pressure. - When the partial pressure of oxygen is higher in the alveolar air than it is in capillary blood, oxygen will diffuse into the blood - When the partial pressure of carbon dioxide is greater on the blood than in the alveolar air, carbon dioxide will diffuse out of the blood and into the alveolus. - A number of factors favour increased diffusion; more surface area, shorter distance, greater solubility and a steeper partial pressure gradient. **[Week 4 -- cellular transpiration and the cell cycle]** [Movement through the cell membrane] - Cell membrane is semi-permeable - Two types of transport: - passive transport -- movement of small non-polar molecules - Doesn't require energy - Active transport -- movement of large or polar molecules. - Requites energy [Cell membrane] - Made up of phospholipids bilayer - Phosphorous head (hydrophilic) and lipid (hydrophobic) tail - Cholesterol stabilises the membrane - Protein acts as pores, channels, receptors, cell identification. [Diffusion] - Gases such as oxygen and carbon dioxide diffuse rapidly through membranes - These molecules will move from where they are high concentration to where they are at lower concentration along a concentration gradient. - Diffusion is a passive process; it requires no energy input from the cell - Trying to achieve equilibrium [Facilitated diffusion] - Occur where molecules are too large to move across the membrane - Transport proteins embedded in the membrane assist with the passage - Create a chemical channel - No energy required used - Rate depends on the number of transport proteins embedded in the membrane. [Osmosis] - Osmosis is the diffusion of water only - Osmosis is the net movement of water from a dilute to a concentrated solution, through a partially permeable membrane. - Osmotic pressure is the pressure needed to lift a volume of water; more impermeable solutes create more pressure. - A solution with the same osmotic pressure as body fluids is called isotonic; 0.9% NaCl solution is isotonic to human cells - One with higher osmotic pressure than body fluid is hypertonic - One with lower osmotic pressure is hypotonic - A Red blood cell in an isotonic solution; equal amounts of water move in and out; no change to the cell. - A Red blood cell in a hypertonic solution; more water moves out than moves in; cell shrinks - A Red blood cell in a hypotonic solution; more water moves into the cell than moves out; cell swells and may burst - Form of facilitated diffusion - Needs specific proteins called aquaporins to allow polar water molecules to pass through the membrane - Discovered in 1992 -- Nobel Prize awarded 2003 (Agre and McKinnon) [Active transport ] - Sometimes substances must be oved against the concentration gradient - This usually requires a transport protein plus energy - Usually ATP - To push the ions against the gradient. - Contact between the specific particle to be transported with its carrier protein triggers the release of cellular energy (ATP) - This alters the shape if the carrier protein allowing the particle to pass through the membrane - Includes sugars, amino acids, sodium, potassium, Calcium and hydrogen ions, as well as nutrient molecules in the intestines. [Endocytosis and exocytosis] - Handles the movement of: - Really large molecules such as long protein chains and ring structure - Bulk volume of small molecules - Transport out of the cell is exocytosis - Transport into the cell is endocytosis. - *Endocytosis* - Cell membrane enfolds material forming a vesicle - Phagocytosis ingests solid materials - Pinocytosis ingests liquids - Receptor- mediated endocytosis allows the cell to take in very specific molecules that pair up with specific receptors on the cell surface - *Exocytosis* - Waste products or hormones, are contained in a vesicle - The vesicle fuses with the cell membrane and the contents are expelled [Transcytosis] - Rapid movement across a cell, where cells are tightly packed together - Receptors facilitated endocytosis followed by rapid exocytosis - E.g. movement of HIV across the membranes of the anus or vagina. [Cell cycle] - Essentially the life cycle of the cell - There are 3 main stages: - Interphase - Mitosis - Cytokinesis [Interphase] - a very active period in the cell cycle - Cell grows - Cell maintains normal functions - Cell replicates genetic materials (DNA) to prepare for mitosis (nuclear division) - Cell synthesises organelles, membranes, and biochemicals to prepare for cytokinesis (division of cytoplasm). [Cell division] - Mitosis -- nuclear division - *Prophase* - First stage of mitosis - DNA condenses into replicated chromosomes (made of two chromatids connected with centromere) - Centrioles migrate to the poles and from into spindle fibres - Nucleus 'disappears' - *Metaphase* occurs as spindle fibres attach to centromeres on the chromosomes that randomly on the chromosomes that randomly align midway between centrioles. - *Anaphase* occurs as the spindle fibres contract and pull the sister chromatids towards the centrioles. - *Telophase* -- the final stage of mitosis - Chromosomes complete their migrates to opposite sides, the nuclear envelope and nucleolus reappear, the spindle fibres disassemble, and the chromosomes begin to unwind. - *Cytokinesis* - The process of splitting the cell in half to ensure that each daughter cell has a nucleus and half of the cytoplasm and organelles. - A protein band forms in the middle of the cell, which contracts (cleavage furrow) - It keeps contracting until the two cells separate [Cellular differentiation] - The process by which cells develop into different types of cells with specialised functions - Genetic control of the nucleus whereby certain genes is turned on while others are turned off - Stem cells retain the ability to divide without specialisation - Progenitor cells are daughters of stem cells that are partially specialised [Apoptosis] - Cell death that is a normal part of development - Removed overgrown tissues or damages cells - Steps: - Cell rounds up and bulges - Nuclear membrane break downs - Chromatin condenses and enzymes cut up the chromosomes - Cell shatters into many membrane-bound pieces - Scavenger cells phagocytose the cell fragments [Cellular metabolism] - Chemical energy is held in the bonds of molecules and is released when the bond break. - Release of chemical energy in the cell often occurs through the oxidation of glucose in a process called cellular respiration. - This energy cannot be used directly so it is stored and molecule called ATP. [Adenosine Triphosphate] - ATP molecules contain 3 phosphates in a chain connected by high energy bonds - A cell uses ATP for many functions including active transport and synthesis of various compounds - Energy is stored in the last phosphate bond of ATP. - Energy is stored while converting ADP to ATP, when energy is released, ATP becomes ADP\< ready to be regenerated into ATP. - 40% of the energy is released as chemical energy - 60% is released as heat (exothermic) [Cellular respiration] - Conversion of glucose into ATP - Three stages - Glycolysis - Citric acid cycle - Krebs cycle - Electron transport chain/oxidative phosphorylation - *Glycolysis* - Series of 10 reactions - Breaks down glucose into 2 pyruvic acid molecules - Occurs in cytosol (outside of mitochondria) - Anaerobic phase of cellular respiration - Yields 2 ATP molecules per glucose molecules broken down - Fast release used in sprinting - Build up of lactic acid prevent further glycolysis. - *Citric acid cycle* - Aerobic -- pyruvic acid from glycolysis is converted to acetyl CoA - Begins when acetyl CoA combines with oxaloacetic acid to produce citric acid - Citric acid is changed into oxaloacetic acids through a series of reactions - Cycle repeats if pyruvic acid and oxygen are available. - B1 ATP is produced for each cycle - *Electron transport chain* - ETC is a series of enzyme complexes located in the inner membrane of mitochondria - Energy from electrons is transferred to the enzyme ATP synthase - ATP synthase uses energy to catalyse phosphorylation of ADP to ATP - Water is formed - Yields between 26-28 ATP **[Week 5 -- Blood]** [Vocabulary] - Erythr -- red e.g. erythrocyte - Leuko -- white e.g. leukocyte (also spelt leuco) - Osis -- abnormal condition, inflammation, leukocytosis -- overproduction of leukocytes - Thromb -- clot, thrombocyte -- blood platelet involved in clotting. [Characteristics of blood] - It is a connective tissue - Main function is transportation of vital substances - Maintains stability of interstitial fluid - Distributes heat and maintains body temperature - Blood is about 8% of body weight; adult hood blood volume is about 4-5 litres in a female and 5-6 litres in a male. - In a centrifuged blood sample: - 55% plasma - 45% is redd blood cells - white blood cells and platelets are \ - Percentage of red blood cells is called the haematocrit (HCT) or packed cell volume (PCV) [Haematopoiesis of blood] - Formation of blood cells - Takes place in the bone marrow from haematopoietic stem cells [Red blood cells] - Biconcave disc shapes called erythrocytes - One third haemoglobin: - Oxyhaemoglobin (with O2) - Deoxyhaemoglobin (without O2) - Not trye cells - Lack nuclei and mitochondria - Cannot divide - Can produce ATP through glycolysis [Erythropoiesis] - Occurs in red bone marrow - Low blood oxygen causes kidneys and liver to release EPO (Erythropoietin), which stimulates red blood cell production - A negative feedback mechanism - EPO enter the blood stream and makes its way to the bone marrow where it stimulates haematopoietic stem cells [White blood cells] - Leukocytes: - Protect against disease - Have limited life spans - White blood cells are produced in red bone marrow, under control of hormones; interleukins and colony-stimulating factors - There are 5 types of white blood cells, in 2 categories: - Granulocytes, which have granular cytoplasm, and short life span: - Neutrophils - Eosinophils - Basophils - Agranulocytes, which do not have noticeable granules: - Lymphocytes - Monocytes - Granulocytes -- neutrophils: - Small, might purple granules in acid- base stain - First to arrive at infection sit e - Strong phagocytes - 54%- 62% of leukocytes - Elevated in bacterial infections - Eosinophils: coarse granules: stain deep red in acid stain - Moderate allergic reactions - Defend against worm infestations - 1%-3% of leukocytes - Elevated in parasitic worm infestations and allergic reactions. - Basophils: - Large granules; stain deep blue in basic stain - Granules can obscure view of nucleus - Release histamine to stimulate inflammation - Release heparin to stop blood from clotting - Less than 1% of leukocytes - Like eosinophils in size and shape of nuclei. - Agranulocytes -- monocytes: - Largest of the white blood cells - Spherical, kidney-shaped, oval or lobed nuclei - Leave bloodstream to become macrophages - 3%-9% of leukocytes live for weeks -- months - Phagocytise bacteria, dead cells and debris - Lymphocytes: - Slightly larger than red blood cells; smallest white blood cell - T cells and b cells are major types; both important in immunity - T cells directly attack pathogens, tumor cells - B cells produce antibodies - 25% - 33% of leukocytes - May live for years - White blood cell count: - Normal white blood cell is between 3,500 and 10,000 mm3 - Leukocytosis -- high white blood cell count - Acute infection, vigorous exercise, catastrophic dehydration - Leukopenia -- low white blood cell count: - Typhoid fever flu, measles, mumps, chicken pox, AIDS, polio anaemia [Platelets ] - Thrombocytes -- produced by hemocytoblasts in response to the hormone, thrombopoietin - Lack a nucleus, and are less than half the size of a red blood cell - Help in haemostasis (stopping in bleeding) in damaged blood vessels, by sticking to broken surfaces - Release serotonin, which causes smooth muscles in walls of broken blodo vessels to contract. [Plasma] - Clear, straw-colored - Liquid portion of blood - 55% of blood volume - 92% water - Contains organic and inorganic chemicals - Transports nutrients gases, hormones and vitamins - Helps regulate fluid and electrolyte balance and maintain pH [Plasma proteins ] Protein Percentage of total Origin function ----------------- --------------------- ------------------- -------------------------------------------- Albumins 60% Liver Helps maintain colloid osmotic pressure Globulins 36% Alpha globulins liver Transports lipids and fat-soluble vitamins Beta globulins liver Transports lipids and fat-soluble vitamins Gamma globulins Lymphatic tissues Constitute the antibodies of immunity Fibrinogen 4% Liver Plays a key role in blood coagulation. [Haemostasis] - Refers to stopping blood loss (bleeding) - Actions that limit or prevent blood loss include: - Blood vessel (vascular) spasm - Platelet plug formation - Blood coagulation [Vascular spasm] - Stimulated by cutting or breaking a small blood vessel - Smooth muscle in blood vessel contracts rapidly - Slows blood loess very quickly, and ends of vessel may close completely - Triggered by stimulation of blood vessel wall, pain receptor reflexes - Response lasts few minutes, but effective continues for 30 minutes - This allows time for a platelet plug to form and blood to coagulate - Serotonin released from platelets cause vasoconstriction which further helps to reduce blood loss [Platelet plug formation] 1. Break in vessel wall 2. Blood escaping through break 3. Platelets adhere to each other, to the end of the blood vessel, and to exposed collagen 4. Platelet plug helps control blood loss - Triggered by exposure of platelets to collagen - Platelets adhere to rough surface to form a plug [Blood coagulation] - Most effective haemostatic mechanism, occurs within 5 to 15 minutes - Form blood clot in a series of reactions known as a cascade - Initiated by 2 different methods: extrinsic or intrinsic clotting mechanism. - Many chemicals used in coagulation are called clotting factors - Vitamin K necessary for functioning some of the clotting factors - Major event is conversion of soluble fibrinogen to insoluble threads of fibrin, which traps blood cells. [Extrinsic bloos clotting] - Triggered by blood coming in contact with tissues outside of blood vessels or damaged wall of blood vessel - Damaged tissues release tissue thromboplastin (factor III) - Cascade begins, involving sequential activation of several clotting factors - Thrombin converts fibrinogen into soluble fibrin threads - Fibrin threads stick to damaged blood vessel surfaces, and trap blood cells and platelets. This mass is a blood clot. - This is an example of a positive feedback mechanism; once clotting begin, it promotes additional clotting. [Intrinsic blood clotting] - Can start without tissue damage - Activated when blood encounters foreign surface, such as collagen - Triggered by Hageman factor XII (found inside blood) - As in extrinsic clotting mechanism, this begins sequential activation of severl clotting factors - Results in the same way as extrinsic clotting mechanism, with formation of fibrin mesh and a blood clot. [After the blood clot] - After a blood clot forms, it retracts and pulls the edges of a broken blood vessel together while squeezing serum from the clot - Serum = plasma minus fibrinogen and most clotting factors - Platelet-derived growth factor stimulates smooth muscle cells and fibroblasts to repair damaged blood vessel walls. Plasmin digests fibrin threads, and dissolves the blood clot - A thrombus is abnormal blood clot that forms in a blood vessel - An embolus is a blood clot moving through the blood vessels - DVT [Blood groups and transfusions] - Blood groups were discovered in around 1900 by Karl Landsteiner - He found three different types of blood existed and called them A, B and C - But C was very different to A and B and eventually became known as O - They are now known to be 4 different types of blood [Antigens and antibodies] - Antigen - Any molecule that evokes an immune response - Is immune system find a foreign antigen in the body, it produces against the antigen - Antibodies - Proteins that react against a specific antigen - In an incompatible blood transfusion, donor red blood cells evoke an immune response in the recipient, and the antibodies in the recipient's plasma agglutinate the donor red blood cells - Agglutination - Clumping of red blood cells, which occurs when an antibody (in recipient's plasma) encounters its specific antigen (on donor red blood cells). - There are 33 known antigens on red blood cells membranes, but only a few evoke a serious transfusion reaction - Only the antigens of the ABO and Rh groups evoke serious transfusion reactions. [ABO blood group] - ABO blood group is based on the presence or absence of two major antigens on red blood cell membranes: Antigen A and Antigen B. - Antigen A and B are carbohydrates - Antibodies are associated with some blood types; in general, a person produces antibodies against antigens that are not present on his/ her red blood cell membranes Blood type Antigen Antibody ------------ ----------------- --------------------------- A A Anti- B B B Anti-A AB A and B Neither anti-A nor anti-B O Neither A nor B Both anti-A and anti B [Percentage blood groups UK] O A B AB ----- ----- ---- ---- 47% 42% 8% 3% +--------+--------+--------+--------+--------+--------+--------+--------+ | O+ | O- | A+ | A. | B+ | B- | AB+ | AB- | +========+========+========+========+========+========+========+========+ | 40% | 7% | 36% | 6% | 7% | 1% | 2.5% | 0.5% | +--------+--------+--------+--------+--------+--------+--------+--------+ When red blood cells come in contact with antibodies against them, they will agglutinate. [Compatible types and transfusions] Blood type of recipient Preferred blood type of donor If preferred blood type is unavailable, permissible blood type of donor (in an extreme emergency) ------------------------- ------------------------------- --------------------------------------------------------------------------------------------------- A A O B B O AB AB A, B, O O O No alternative types - Type O = universal donor - Type O lacks the A and B antigens, so type O red blood cells could be donated to a person with any blood type. Often, when given to a person with a different blood type, only the red blood cells are donated (since plasma contains antibodies). - Type AB = universal recipient: - Type AB blood lacks both anti-A and anti-B antibodies, so an individual with type AB can receive donors red blood cells of any type. [Rhesus blood group] - The RH blood group was named for the rhesus monkey, in which it was first studied the group included several rh antigens or factors, but most important one is antigen D - Rh positive: presence of antigen D or other rh antigens on red blood cells membranes - Rh negative: do not have the Rh antigens on red blood cell membranes - Anti-Rh antibodies form only in Rh-negative individuals in response to the presence of red blood cells with Rh antigens - The seriousness of the Rh blood group is evident in a foetus that develops the condition erythroblastosis fetalis or haemolytic disease of the newborn. **[Week 6 -- gastrointestinal tract ]** [Vocabulary] - Aliment -- food, alimentary canal -- the tube running from the mouth to the anus. - Gastr -- stomach, e.g. gastric juices -- secretions into the stomach - Lingu -- tongue, lingual frenuloum -- the membrane that attaches the tongue to the floor of the mouth - Faec -- from the Latin faex meaning 'dregs' plural is faeces [Gastrointestinal tract ] - Alimentary canal is the rube that runs from the mouth to teh anus - Accessory organs attached to the alimentary canal help with the digesting of food - Digestion is the process of the mechanical and chemical breakdown of food into nutrients that can be absorbed [Alimentary canal] - Around 9m (30ft) long - Passesd through the thoracic and abdominopelvic cavities [Definitions] - ingestion -- taking food into the mouth - Prehension -- the act of seizing or grasping food - Motility -- the mixing and propulsion of ingesta through the GIT - Ingesta -- food and drink taken in as nourishment - Absorption -- passage of nutrients into the blood and lymph - Defaecation (defecation) - elimination of waste products [Basal cavity] - Moth, teeth and salivary glands - Mastification -- first process of digesting, involves chewing food and forming into bolus (ball od food suitable to be swallowed) [Salivary glands] - Made up of: - Serous cells -- produce watery fluid and salivary amylase - Mucous cells -- produce mucus - Controlled by autonomic nervous system - Parasympathetic system triggers production of saliva at sight and smell of food - Major salivary glands - Parotoid glands lying in front of the ear, are the largest of the major salivary glands; they secrete a clear, watery fluid (serous) rich in amylase - Submandibular glands located on the floor of the mouth, secrete a more viscous fluid (serous and mucus) - Sublingual glands inferior to the tongue, smallest of the major salivary glands and secrete a saliva that is thick stringy (mucus). [Saliva] - Moistens food - Salivary amylase -- begins breakdown of starch (carbohydrate) - Produce between 1000 -- 1500 mls per day [Teeth] - Two set of teeth - Deciduous (milk teeth) - 20 teeth, 8 incisors, 4 canines, 8 molars - Permanent (adult teeth) - 32 teeth, 8 incisors, 4 canines, 8 premolars, 12 molars [Cheek, lips and tongue] - Soft tissues in the mouth - Lips are highly mobile involved in prehension -- can judge temperature and texture of food - Tongue -- large muscle covered in mucus membrane and papillae - Papillae contain taste buds, and provide friction to move food around the mouth - Receptors for bitter, sweet, sour and salty [Pharynx and oesophagus ] - Pharynx - Located posterior to the mouth - Extends from nasal cavity to oesophagus - Oesophagus (Esophagus) - Tube runs from pharynx to stomach - \~ 25cm long (adult) and 2cm diameter - Passes through oesophageal hiatus of diaphragm about level with the inferior end of the sternum (xiphoid process) [Deglutition] - Swallowing - Food is formed into a bolus (ball) - Tongue moves it into the oropharynx (voluntary) - Swallowing reflex takes over as sensory receptors n pharynx are triggered - Stimulates peristalsis [Movement in the Alimentary canal] - Rhythmic segmentation -- smooth muscles alternately contract and relax mixing chyme - Peristalsis -- wavelike contraction of muscle behind mass of food pushes it into the next section of the tube [The stomach] - Oesophagus connects the mouth to the stomach - Stomach -- J --shaped muscular organ - Secrets gastric juices that start the breakdown processes - Very limited absorption of nutrients -- some lipid soluble drugs (aspirin) and alcohol - Chyme is the food that has been churned into the stomach [Regions of the stomach] - Cardia -- opening into the stomach at the cardiac sphincter - Fundus -- superior and to the left of the cardia - Non-excretory often contain gas - Body -- inferior to the fundus - Pylorus -- connecting to the duodenum, ends at the pyloric sphincter  [Gastric secretions] - Gastric glands contain 3 types of secretory cells - Mucous cells -- produce mucus that protects the lining of the stomach - Chief cells -- secret pepsin as inactive pepsinogen (activated by HCL) - Pepsin is enzyme that breaks down protein - Parietal cells secret hydrochloric acid (HCL) - Together excretions form gastric juice - Gastric juice also contains intrinsic factor - This is required for vitamin B12 absorption in the small intestine [Regulation of gastric secretion] - Parasympathetic impulses control digestion and release the hormone gastrin from the gastric glands - As the food moves into the small intestine, secretion of gastric juice from the stomach walls is inhibited by sympathetic impulses - Presence of fast and proteins in upper small intestine causes the release of cholecystokinin from the intestinal wall, which also decreases gastric mobility [Accessory organs] - Liver - Involved in the storage and metabolism of nutrients including sugars (glucose) and proteins, iron and vitamin A, D and B12 - Major role in digestion is to secret bile into the gall bladder -- production of bile - Gall bladder - Pear-shaped sac that lies inferior to the liver  [Bile] - Bile is yellowish-green liquid -- it includes water, bile salts, bile pigments (bilirubin and biliverdin), cholesterol, and electrolytes - Only the bile salts have a digestive function -- emulsification of lipids [Pancreas] - Large organ, closely associated with the small intestine - Located on the right side of the abdominal cavity, inferior to the diaphragm and superior to the stomach [Pancreatic juice] - Pancreatic juice contains enzymes that digest carbohydrates, fats, proteins and nucleic acids - Protein-digesting enzymes are released in an inactive form (zymogen granules) and are activated upon reaching the small intestine - Pancreatic enzymes include: - Pancreatic amylase -- breaks down carbohydrates to disaccharides - Pancreatic lipase -- breaks down triglycerides and fatty acids - Teo nucleases -- break down nucleic acids to nucleotides - Trypsin, chymotrypsin, and carboxypeptidase -- break down proteins and dipeptides [Small intestine] - Very long \~20 feet (6m) and 2.5-3 cm (1 inch) in diameter - Consists of the duodenum, jejunum, and ileum - Duodenum is the shorted and most fixed portion of the small intestine; the rest is mobile and lies free in the peritoneal cavity - Suspended from the posterior abdominal wall by a double-layered fold of peritoneum called mesentery - Mesenteries support blood vessels, nerves, and lymphatics that serve the intestinal wall - Greater omentum drapes over the intestine [Structure of the small intestine] - Inner wall is lines with finger-like intestinal villi - Each villus consists of simple columnar epithelium with a core of connective tissue housing blood capillaries and a lymphatic capillary called a lacteal - Between bases of adjacent villi are tubular intestinal glands [Secretion of small intestine] - Goblet cells are abundant throughout the mucosa and secrete mucus - Intestinal glands at the bases of the villi secrete large amounts of watery fluid that carry digestive products into the villi - Epithelial cells of the mucosa have embedded digestive enzymes on their microvilli - Peptidases -- break down dipeptides to amino acids - Sucrase, maltase and lactase -- break down disaccharides to monosaccharides - Intestinal lipase -- break down triglycerides to fatty acids and glycerol - Enterokinase -- activates trypsin from trypsinogen [Absorption] - Major site of absorption - Monosaccharides and amino acids are absorbed by the villi through active transport or facilitated diffusion and enter blood capillaries - Fatty acids are absorbed and transported differently that the other nutrients - Fatty acids molecules dissolve into the cell membranes of the villi - The endoplasmic reticula of the cells reconstruct the lipids - These lipids collect in clusters that become encased in protein (chylomicrons) - Chylomicrons are carried away in lymphatic lacteals until they eventually join the bloodstream - Chylomicrons transport dietary fats to muscle and adipose tissue - The intestinal villi also absorb water (by osmosis) and electrolytes (by active transport)  [Transit through small intestine] - The small intestine carries on segmentation and peristaltic waves - Movements are slow, taking 3 to 10 hours to travel its length - The ileocal sphincter at the junction of the small and large intestines usually remains closed unless a gastroileal reflex is elicited after a meal - A strong peristaltic wave moved the material through too quickly causing diarrhoea. [Large intestine] - \~1.5m long but very large diameter \~10cm - The large intestine consists of the caecum (pouch at the beginning of the large intestine with the appendix projecting downward from it) colon (ascending, transverse, descending, and sigmoid regions), the rectum and the anal canal. - The anal canal open to the outside as the anus; it is guarded by an involuntary internal anal sphincter and a voluntary external anal sphincter muscle [Structure of teh large intestine] - The large intestinal wall similar structure to other areas of the alimentary canal, but lacks many of the features of the small intestinal mucosa such as villi - Fibres of longitudinal muscle are arranged in taeniae coli that extended the entire length of the colon, creating a series of pouches (haustra) [Function of the large intestine] - Large intestine is home to \~100 trillion friendly bacteria (intestinal flora) - These are responsible for the synthesis of vitamins K, B1, B2, B6, B12 and biotin - Vitamin K is almost exclusively produced here and is essential for blood clotting - Bacterial fermentation also breaks down cellulose - Used as building blocks for vitamins - Absorption of electrolytes, water and water soluble products (vitamins and some carbohydrates) [Mechanisms of the large intestine] - Chime moves through the ileocecal sphincter into the caecum - Haustral churning -- each haustra relax and become distended while they fill up - When the distension reaches a certain point, the walls contract and squeeze the contents into the next haustra - Peristalsis occurs at a slower rate 3 -- 12 contractions per minute - Mass peristalsis -- a strong wave that begins at the transverse colon and quickly drives the contents of the colon into the rectum - This usually takes place after a meal [Waste products] - Chyme is prepared for elimination by the action of bacteria - Faeces are composed of undigested material, water, electrolytes, mucus, shed intestinal cells, and bacteria - Both the colour of faces and its odour is due to the action of bacteria - Bacterial fermentation of cellulose release gases (flatulence) - Also converted remaining proteins to amino acids, then to simpler substances which gives faeces their odour - Bacteria also decompose bilirubin (stercobilin which gives faeces their colour) - Defecation is stimulated by defecation reflex that forces faeces into the rectum where they can be expelled **[The renal system and the liver]** *[Renal system]* [Urien system] - Consists of two kidneys, two ureters, a urinary bladder, and a urethra to convey nitrogenous waste substance to the outside - Helps maintain normal concentration of electrolytes and water - Regulates pH and fluid volume - Helps control red blood cell production and blood pressure  [Kidneys] - Reddish brown, bean-shaped organ 12 centimetres long; enclosed in a tough, fibrous capsule - Location: - Positioned retroperitoneally on either side of the vertebral column between the tewlfth thoracic and third lumbar vertebrae, with the left kidney slightly higher than the right - Connective tissue and adipose tissue hold the kidneys in place [Structure of the kidney] - A medial depression called hilum leads to a hollow renal sinus into which blood vessels, nerves, lymphatic vessels, and the ureter enter - The renal pelvis is subdivided into major and minor calyces; small renal papillae project into each minor calyx - Two distinct regions are found within the kidney: a renal medulla and renal cortex - Renal medulla houses renal pyramids leading to papillae - Renal cortex surrounds the medulla and dips down in between the renal pyramids (renal columns) - The functional unit of the kidney is the nephron [Functions of the kidney] - Regulate the volume, composition, and pH of body fluids and remove metabolic wastes from the blood in the process - Control the rate of blood cell formation by secreting erythropoietin and regulate blood pressure and volume by secreting renin - Plays a role in activation of vitamin D. [Blood supply to the kidneys] - Teh abdominal aorta gives ride to renal arteries that enter the kidneys at the renal sinus - As renal arteries pass into the kidneys, they branch into successively smaller arteries: interlobar arteries, arcuate arteries, cortical radiate arteries (interlobular arteries), and afferent arterioles leading to the nephrons - The renal vein then joins the inferior vena cava in the abdominal cavity  [Nephrons] - Each kidney contains one million nephrons, each of which consist of a renal corpuscle and a renal tubule - Renal corpuscle is teh filtering portion - Made up of a ball of capillaries called glomerulus and a glomerular (Bowman's) capsule that receives the filtrate - Renal tubule leads away from the glomerular capsule becoming the highly coiled proximal convoluted tubule, then the nephron loop (ascending and descending limbs), and finally the distal convoluted tubule - The distal convoluted tubules join to become a collecting duct passing into the medulla, emptying into a minor calyx at the papilla  [Nephrons] - 2 types of nephrons in the kidney - Cortical nephrons - Sit high in cortex, with short nephron loops - Majority of nephrons - Juxtamedullary nephrons - Sir low in cortex and have ling nephrons loops; important in regulating water balance, and urine concentration - Small percentage of nephrons [Juxtaglomerular Apparatus] - A structure that regulates the secretion of renin - Teh top portion of the ascending limb of the nephron loop of each nephron passes between the afferent and efferent arterioles - At this point, the ascending limb encounters the afferent arteriole, to form the juxtaglomerular apparatus. [Urine formation] - Involves three processes - Glomerular filtration - Tubular reabsorption - Tubular secretion [Glomerular filtration] - First step of urine formation - Substances move from the blood in the glomerulus into the glomerular capsule - Water, electrolytes, glucose, urea, and uric acid - Glomerular capillaries are many times more permeable than other capillaries, due to fenestrae, tiny opening in walls glomerular filtrate is formed as substances filter from glomerulus into the glomerular capsule - Filtrate has about the same composition as tissue fluid [Filtration rate] - Filtration rate is controlled by the hydrostatic pressure within glomerulus and the glomerulus capsule - When the afferent arteriole constricts, the pressure decreases and filtration decreases - When the efferent arteriold constricts, pressure increases, and filtration increases - \~125 ml per minute or 180L in 24 hours [Tubular reabsorption] - Most of reabsorption occur in the proximal convoluted tubule, where cells possess microvilli within carrier proteins - Carrier proteins have limited transport capacity, so excessive amounts of a substance will excreted into the urine (renal plasma threshold) - Glucose and amino acids are reabsorbed by active transport, water by osmosis, and proteins by pinocytosis. - Other substances reabsorbed by active transport with limited transport capacities include: creatine, lactic acid, citric acid, uric acid, ascorbic acid, phosphate sulphate, calcium, potassium, and sodium. [Sodium and water reabsorption] - Sodium ions are reabsorbed by active transport, and negatively charged ions (CI- and HCO3-) follow passively (passive transport) - As sodium is reabsorbed, water follows by osmosis  [Tubular secretion] - Tubular secretion transports certain substances from the plasma into the renal tubule - Active transport mechanisms move excess hydrogen and potassium ions into the renal tubule along various organic compounds [Regulation of urine concentration and volume] - Kidneys maintain the inetrnal environment due to their ability to ceoncentrate urine by reabsorbing large volume of water - The distal tubule and the collecting duct are impermeable to water in the absence of ADH (antidiuretic hormone), so water may be excreted as dilute urine - If ADH is present, these segments become permeable, and water is reabsorbed by osmosis into the extremely hypertonic medullary interstitial fluid - Urine becomes very concentrated, under the direction of ADH - Although the majority of nephrons are cortical, the juxtamedullary nephrons are more important in the regulation of water reabsorption. [ADH mechanism] 1. As blood passes through the hypothalamus is monitors the blood pressure (and blood volume) 2. If it is too low ADH is released from the pituitary gland 3. ADH reached the kidneys through the bloodstream 4. The distal tubule and collecting ducts become permeable to water 5. Water moves into highly hypertonic interstitial fluid through osmosis 6. Reabsorption of water continues, urine volume decreases and water in conserved 7. ADH is inhibited and tubules are no longer permeable to water [Urea and uric acid excretion] - Urea is a by-product of amino acid metabolism; uric acid is a by-product of nucleic acid metabolism - Urea is passively reabsorbed by diffusion but about 20% of urea is excreted in the urine - Most uric acid is reabsorbed by active transport and a small amount is secreted into the renal tubule [Urine composition] - \~95% water - Usually going to contain metabolic waste products: urea, uric acid, and creatinine - Likely to contain trace amounts of amino acids and varying amounts of electrolytes - Urine volume: 0.6 - 2.5 L/day; 50-60 ml of urine output/ hour is normal; volume varies with fluid intake and environmental factors - \ - Beeturia, in which urine turns pink after eating beetroot - Urinary excretion of odoriferous component of asparagus [The liver] - The largest solid organ in the body - \~1.2 - 1.5 kg - Sits on the right side just below the diaphragm - Reddish-brown in colour - It is divided into right and left lobes and is enclosed by a fibrous capsule - Each lobe is separated into hepatic lobules consisting of hepatic cells radiating from a central vein - Hepatic sinusoids separate groups of hepatic cells - The hepatic portal vein carriers blood rich in nutrients to the liver - Blood passes from the sinusoids into the central vein of a lobule and exits teh liver via the hepatic vein - Kupffer cells carry on phagocytosis in the liver - Secretions from hepatic cells are collected in bile canals that converge to become hepatic ducts and finally form the common hepatic duct [Functions of the liver] Carbohydrate - Converts glucose into glycogen fro storage - Converts excess carbohydrate and protein into fat for storage - Converts stored molecules into glucose for energy metabolism Lipids - Oxidise fatty acids - Synthesises lipoproteins, phospholipids and cholesterol Protein - Deaminates amino acids - Forms urea - Synthesises plasma proteins - Converts some amino acids into other amino acids Storage - Stores glycogen, iron, and vitamin A, D and B12 Blood filtering - Removed damaged red blood cells and foreign substances by phagocytosis Detoxification - Removes toxins from the blood Secretion - Produces and secretes bile **[Week 8 -- the endocrine system]** [Vocabulary] - Endo -- inside: endocrine gland -- gland that internally secretes into a body fluid - Exo -- outside: exocrine gland -- gland that secretes to the outside through the duct - Hyper -- above: hyperthyroidism -- condition resulting from an above -- normal secretion of thyroid hormone - Hypo -- below -- hypothyroidism -- condition resulting from a below -- normal secretion of thyroid hormone [The endocrine system] - Made up of ductless glands that secrete hormones directly into the body fluids (blood or tissues fluids) - Messenger system, effects can last for days - Unlike nervous system that delivers impulses - Slower delivery system, effects can last for days - But very precise, only able to target receptor cells  [Major glands] - Endocrine system is unconnected system - Major glands do not connect to one another - Major glands are - Hypothalamus - Pituitary gland - Thyroid gland - Adrenal glands - Pancreas - Specialist glands produce the sex hormones [Chemistry of hormones] - 2 types: - Steroidal hormones -- lipid based hormone - Produced from cholesterol - Sex hormones are steroidal hormones - Non-steroid hormones - Amines -- from tyrosine (adrenaline/noradrenaline) - Proteins -- long chain amino acids (growth hormones) - Peptides -- short chain amino acids (oxytocin) - Glycoproteins -- have carbohydrates attached to proteins (TSH) [Hormones actions] - Hormones alter metabolic processes by - Altering enzyme activity - Altering rate of membrane transport of substance - Bind to their receptors on/ in target cell - Only small amounts of hormones needed to have an effect - Number of receptors determines strength of response, and can be changed to alter the response: - Upregulation -- increase in number of receptors on target cell. In response to a decrease in hormone level - Downregulation -- decrease in number of receptors on target cell, due to an increase in hormone level [Steroid hormone action] - Lipid based hormone can readily diffuse across the cell membrane - Enters nucleus and combines with hormone receptor to form hormone-receptor complex - Triggers DNA to produce mRNA - MRNA travels to ribosome where it is read and used to make a protein [Non-steroid hormone action] - Water soluble so cannot across the membrane - Binds to receptor on cell membrane - Activates enzyme called adenylate cyclase - Converts ATP into cAMP which activates specific proteins leading to cellular changes [Prostaglandins] - Known as paracrine substances - Very potent but not stores in cells, synthesised just before release - Rapidly inactivated after use - Regulate cellular responses to hormones - Can activate responses to hormones - Can activate or inhibits adenylate cyclase - Control cAMP production - Have a wide variety of effects, such as contracting or relaxing smooth muscle, stimulating or inhibiting secretion, regulating blood pressure, controlling movement of water and sodium in kidneys, promotes inflammation [Control of hormones ] - Negative feedback mechanism - Rising hormones levels results in decreased secretion - 3 control mechanisms - Trophic hormones -- increase in one hormone will act on a gland regulating their secretion - Nervous system 0 direct stimulation of a gland in response to a nerve impulse - Internal environment -- response to a chnage of specific substances in blood e.g. glucose levels - Hormones are excreted in the urine when no longer required - Can be tested in urine - Lies at the base of the brain and is attached to hypothalamus by pituitary stalk - Regulated by the hypothalamus via hypothalamus releasing hormone - Controlled by various negative feedback mechanisms depending to the target hormone. [Anterior pituitary hormones] - Growth hormone -- stimulates cells to enlarge and divide rapidly, increases amino acids uptake and protein synthesis, decreases rate of carbohydrate usage, increases rate of fat usage - Prolactin -- promotes milk production in females, uncertain in males - Thyroid-stimulating hormone -- stimulates secretion of thyroid hormones (T3 and T4) from thyroid gland - Adrenocorticotropic hormone -- stimulates secretion of cortisol and other glucocorticoids from adrenal cortex - Follicle-stimulating hormone -- causes growth and developemnt of ovarian follicles in females, sperm production in males - Luteinizing hormone -- causes ovulation in females, sex hormone production in both genders [Thyroid gland] - Lies just below the larynx, anterior and lateral to the trachea - Has special ability to remove iodine from blood - Thyroid gland produces 3 hormones: - Thyroxine (T4) - Triiodothyronine (T3) - Calcitonin - Follicular cells produce T3 and T4 - Extra or parafollicular cells produce calcitonin [Thyroid hormones ] - Thyroxine (T4) - increases rate of energy from carbohydrates; increases rate of protein synthesis; accelerates growth; necessary nervous system maturation - Triiodothyronine (T3) - same as above but 5x more potent - Calcitonin -- lowers blood calcium and phsophate ion concentrations by inhibiting release of calcium and phosphate ions from bones and by increasing teh rate at which calcium and phosphate ions are deposited in bones; increases excretion of calcium by the kidneys [Parathyroid] - Located on posterior surface pf the thyroid gland - There are usually 4 parathyroid gland they secrete 1 hormone, PTH -- parathyroid hormone - PTH regulates calcium and phosphate concentrations in blood [Adrenal glands] - The adrenal glands are closely associated with the kidneys, sitting like a cap on each kidney - Hormones are secreted from two different areas of the gland, the adrenal cortex and the adrenal medulla - Adrenal hormones play roles in maintaining blood sodium levels and responding to stress. They also include certain sex hormones. [Hormones of adrenal medulla] - Adrenalin (Epinephrine) and Noradrenalin (norephephrine) - Actions of adrenalin - Heart rate increases - Force of contraction increases - Vasodilation - Blood pressure increases a little due to increased cardiac output - Airways dilate - Acts on the liver to promotes breakdown of glycogen t- glucose, increasing blood sugar level - Increases metabolic rate [Hormones of the adrenal cortex] - Aldosterone -- helps regulate the concentration of extracellular electrolytes by conserving sodium ions and excreting potassium ions - Cortisol -- decreases protein synthesis, increases fatty acids release, and stimulates glucose synthesis from non carbohydrates - Adrenal androgens -- supplement sex hormones form the gonads; may be converted into oestrogens [Pancreas] - Only concerned with endocrine functions - 3 hormones are secreted from the endocrine islet cells: - Alpha cells secrete glucagon - Beta cells secrete insulin - Delta cells secrete somatostatin [Hormones of the pancreas] - Glucagon -- stimulates the liver to break down glycogen and convert noncarbohydrates inot glucose; stimulates breakdown of fats - Insulin -- promotes formation of glycogen from glucose, inhibits conversion of noncarbohydrates inot glucose, and enhances movement of glucose through adipose and muscle cell membrane, decreasing blood glucose concentration; promotes transport of amino acids into cell; enhances synthesis of proteins and fats - Somatostatin -- helps regulate carbohydrates [Other endocrine glands] - Pineal gland - Secretes melatonin - Regulates circadian rhythms - Thymus gland - Secretes thymosin - Promotes development of T-lymphocytes - Important in tole of immunity - Reproductive organs - Ovaries produce oestrogens and progesterone - Testes produce testosterone - Placenta produces oestrogens, progesterone and a gonadotropin [Stress response -- fight or flight] - Survival depends on maintaining homeostasis - Factors that change the internal or external environment are potentially life threatening - Certain potentially dangerous detect changes, they send nerve impukses to the hypothalamus - Hypothalamus activates sympathetic nervous system and increases secretion of adrenal hormones - Types of stress: - Psychological stress: danger, personal loss, anger, fear and guilt - Physical stress: temperature extremes, infection, injury, o2 deficiency  [In class] Hormone: chemical mediators released in one part of the body but regulates the activity of cells in other parts of the body **[Week 9 -- integumentary system]** Made up of: - Skin - Accessory organs such as nails and hair [Vocabulary] - Cut-: skin e.g. cutaneous -- relating to or affecting the skin: subcutaneous - Derm-: skin dermis -- layer of skin: epidermis -- epi means upon so outer layer of the skin [Structure of the skin] - The outer layer is the epidermis - It is avascular and made up of keratinised stratified squamous epithelium - At the base of the epidermis is layer of reproducing cells -- these have an excellent blood supply from the dermis - Cells are pushed outwards as new cells are made - They become keratinised as they die - Distinct layers can be seen -- these are known as stratum [Epidermis] - An extra layer stratum lucidum is found of the palms and soles - Important to prevent water lose, injury, and stop chemicals and micro-changing entering - Keratinocytes: most abundant - Produce keratin (fibrous protein) - Protective: waterproofing the skin - Continuous mitosis - Form in the deepest layer called the stratum basale - Cells push their way up to the surface where they are dead cells filled with keratin; will slough off - Regenerates every 24-45 days - Contains melanocytes - Cells that produce melanin [Melanocytes] - Produces the pigment melanin - They absorb UV light from the sun (and sunbeds) - Increasing the production of melanin and helping to protect the skin from UV damage [Skin colour] - Skin colour results from a combination of genetic, environmental, and physiological factors - All people have on average the same number of melanocytes - Genetic differences in skin colour result from differing amount of melanin and the size and distribution of melanin granules - Exposure to sunlight, UV light from sun lamps, and X-rays cause darkening of skin as melanin production increases - Circulation within dermal blood vessels affect skin colour - Well oxygenated blood gives a pinkish colour - Poorly oxygenated blood gives cyanosis - Yellowish skin colour can come from eating too many foods with carotene or from jaundice due to liver disease [Dermis] - Binds the epidermis to underlying tissues - Epidermal ridges and dermal papillae cause the border to be uneven - Genetically determined pattern of friction ridges formed by dermal papillae give unique fingerprints - Capecitabine; adermatoglyphia - Consists of areolar and dense connective tissue with collagen and elastic fibres within a gel-like ground substance - Dermal blood vessels carry nutrients to upper layer of skin and helps to regulate temperature - Contains nerve fibres, sensory receptors, hair follicles, sebaceous glands and sweat glands [Function of the skin] 1. Responsible for maintaining homeostasis 2. Temperature regulation 3. Protecting of underlying tissues 4. Slows water loss 5. Houses sensory receptors 6. Synthesises certain biochemicals 7. Excretes wastes 8. Part of the process to make vitamin D [Accessory organs] - Nails - Hair - Glands - Nerves - If the accessory organs remain intact the dermis can regenerate when injured [Nails] - Nails are protective coverings over the ends pf fingers and toes - Nails consists of a nail plate and stratified squamous epithelial cells overlying the nail bed, with the lunula as the most actively growing region of the nail roots - As new cells are produced, older ones are pushed outward and become keratinised  [Hair] - Hair can be found in nearly all regions of the skin except palms, soles, lips, nipples and portions of external genitalis - Each hair develops form epithelial stem cells at the base fo a tube-like depression called the hair follicle. The dermis contains the hair root - As new cells are formed, old cells are pushed outward and become keratinised and die forming the hair shaft - Hair colour is determined by genetics; melanin from melanocytes is responsible for most hair colours - Dark hair has eumelanin (brownish-black), while blonde and red hair have pheomelanin (reddish-yellow) - Genetic lack of melanin causes albinism - A bundle of smooth muscle cells, called the arrector pili muscle, attaches to each hair follicle. These muscles cause goose bumps when cold or frightened - Hypertrichosis [Skin glands] - Sebaceous glands are associated with hair follicles and secrete sebum that waterproofs and moisturises the hair shafts and skin - Sweat glands (sudoriferous glands) - secretion exit via a surface pore - Eccrine -- which respond to body temperature - Apocrine, which become active at puberty and respond to body temperature, stress and sexual arousal. Most numerous in axilla and groin. - Modified sweat glands, called ceruminous glands, secrete wax in the ear canal - Mammary glands, another type of modified sweat gland, secretes milk [Skin as a sensory organ] - Skin is the largest sensory organ in the body - Contains numerous sensory receptors -- nerve endings within the dermis, close to the epidermis - Pain receptors (nociceptors) - sense tissue damage - Thermoreceptors -- sense temperature changes - Mechanoreceptors -- sense touch -- pressure, stretch, tension, blood pressure  [Touch and pressure sensors] - Free nerve endings - Sense itching - Tactile (Meissner's) corpuscles - Detect fine touch and texture - Lamellated (Pacinian) corpuscles - Detect heavy pressure and vibration [Temperature sensors] - Free nerve ending -- 2 types - Warm receptors -- sensitive to temperatures \25, unresponsive \ 45oC - Cold receptors -- sensitive to temperatures between 10oC and 20oC - Temperature higher or lower than these will trigger pain receptors [Pain sensors] - Free nerve endings - Stimulated by tissue damage, chemical, mechanical forces or extremes in temperature - Respond to temperatures \45oC with burning sensation [Wound healing] - Inflammation, in which blood vessels dilate and become more permeable, causing tissues to become red and swollen, is the body's normal response to injury - Superficial cuts are filled in by reproducing epithelial cells - A deeper injury with broken blood vessels involves the formation of a blood clot [Blood clot formation] - The blood clot and dried tissue fluids form a scab - Fibroblasts migrate into the area and secrete collagen fibres to bind the edges of the wound together - Phagocytic cells remove debris from dead cells - Damaged tissue is replaced, and the scab sloughs off [Deep wounds] - If the wound is deep, extensive production of collagenous fibres may form an elevation above the normal epidermal surface forming a scar - Large wounds leave scars, and healing may be accompanied by the formation of granulations - a new branch of a blood vessel grows into the area - The vessel is accompanied by a cluster of fibroblasts that begin repair [Quiz in class] 1. Demis 2. Producing melanin 3. Epidermis 4. Collagen 5. Exocrine 6. B 7. B 8. A 9. D 10. C\# Role of melanin in skin colour and protection **[Week 10 -- the brain and the nervous system]** [Neurons] - Functional unit of the nervous system - Transmit nerve impulses along nerve fibres to other neurons - Typically have a cell body, an axon, and dendrites - Nerves are made up of bundles of nerve fibres(axons) - Can be unipolar, bipolar and multipolar - Sensory neurons - Afferent neurons: have receptors end in tips of dendrites - Interneurons - Association neurons: found entirely within brain and spinal cord - Motor neurons - Efferent neurons: conduct impulses from CNS to PNS [Neuroglia] - Cells that fill the spaces in the nervous system, have a protective function - Microglia: phagocytes - Oligodendrocytes: produce myelin to form the myelin sheath - Astrocytes: regulate movement between blood vessels and neurons - Schwann cells: found in PNS and produce thick myelin sheath. [Nerve impulses] - The nerve cell at rest - Behaves like any other cell at rest - Interior bears a negative charge compared to the outside of the cell - Nerve cells exploit this charge on their cell membrane when stimulated - Potential difference voltage of --70mV across the membrane - Therefore, the membrane is said to be polarised. [Transmission of nerve impulse] - If the axon is stimulated the voltage reverses itself - Teh charge inside the membrane momentarily become positive - This quickly reverts to the resting membrane potential - The sudden chnag eis called the action potential - The action potential travels along the axon from the point of stimulation - The farther from the stimulation point the longer the delay before an action potential appears. [Ion channels] - Intracellular fluid in neurons have: - High potassium (K) concentration - Low sodium (Na) concentration - Extracellular fluid in the opposite - At rest most ion channels allow K ions to diffuse down the concentration gradient - Sodium ion diffusion is prevented. - Stimulus causes Na channels to open - Na rushes in faster than K moves out of the axon - This causes the axon to become positively charged - The portion of the action potential during which the membrane is positive is called the overshoot - Na channels immediately close - In turn extra K channels open - K moves out to leave the membrane potential more negative than before - This is called the undershoot - The axon is the hyperpolarised - The extra K channels close - Membrane returns to the resting potential [Synapse] - In the junction between two communicating neurons; there exists a synaptic cleft between them across which the impulse must be conveyed - The neuron sending the impulse is the presynaptic neuron - The neuron receiving the impulse is the postsynaptic neuron. [Synaptic transmission] - Neurotransmitters are biochemicals that carry out the synaptic transmission process in the synaptic cleft - Distal end of the exons has extensions called synaptic knobs which contain synaptic vesicles filled with neurotransmitters - The action of the neurotransmitter is either excitatory or inhibitory - When an impulse reaches the synaptic knobs of an axpn, synaptic vesicles release a neurotransmitter into synaptic cleft - The neurotransmitter reacts with specific receptors on the postsynaptic membrane. - When an action potential reaches the synaptic knob, calcium ions rush inward, in response, some synaptic vesicles fuse with the membrane and release their contents to the synaptic cleft - They diffuse across the cleft and attach to the postsynaptic receptors polarising the membrane and causes a new impulse. Neurotransmitters Location Major actions ------------------------------ ---------- ------------------------------------------------- Acetylcholine CNS Control skeletal muscle actions Acetylcholine PNS Stimulates skeletal muscle contractions. Noradrenaline/norepinephrine CNS Create a sense of wellbeing Noradrenaline/norepinephrine PNS may excite or inhibit ANS actions Dopamine CNS Create a sense of wellbeing Dopamine PNS Limits actions of ANS Serotonin CNS Inhibitory; leads to sleepiness, blocked by LSD Histamine CNS Release promotes alertness GABA and glycine CNS Inhibitory Glutamate CNS Most abundant excitatory neurotransmitter Enkephalins, endorphins CNS Generally inhibitory, reduce pain Substance P PNS Excitatory, pain perception Nitric oxide CNS Thought to play a role in memory Nitric oxide PNS Vasodilation [Disorders related to neurotransmitters] Condition Symptoms Imbalance of neurotransmitter in brain --------------------- ---------------------------------------------------------------------------------------------------- --------------------------------------------------------- Clinical depression Debilitating, inexplicable sadness Deficient norepinephrine and/or serotonin Epilepsy Seizures, loss of consciousness Excess GABA leads to excess norepinephrine and dopamine Huntington disease Cognitive and behavioural changes, loss of coordination, uncontrollable dancelike movements, death Deficient GABA Hypersomnia Excessive sleeping Excess serotonin Insomnia Inability to sleep Deficient serotonin Mania Elation, irritability, overtalkativeness, increased movements Excess norepinephrine Parkinson disease Tremors of hands, slowed movements, muscle rigidity Deficient dopamine Schizophrenia Inappropriate emotional responses, hallucinations Deficient GABA leads to excess dopamine Tardive dyskinesia Uncontrollable movements of facial muscles Deficient dopamine [Reflex] - Simplest nerve pathway is the reflex arc - Reflex arc components - A sensory receptor detects changes - Sensory neuron that carries the information towards the CNS - An interneuron in the CNS (reflex centre) - Motor neuron carries response to effectors - An effector that responds to the initial change [The brain] - Largest part of the nervous system, made up of 100 billion neurons - Made up of cerebrum, cerebellum, diencephalon and the brain stem - Blood-brain barrier protect the brain [Cerebrum] - Consists of two cerebral hemispheres - It has 4 lobes names after the associated bones - Frontal parietal, occipital and temporal lobes - A fifth lobe -- insula - Cerebral cortex -- thin layer of grey matter on the cerebrum - Contains 75% of the cell bodies in the nervous system - Under this is mass of white matter made up of myelinated nerve fibres connecting the cell bodies of the cerebral cortx with the rest of the nervous system. [Function cerebrum] - Provides higher brain functions including interpretation of sensory input, initiating voluntary muscular movements, memory, and integrating information for reasoning - Cerebral cortex has three functional areas - Sensory areas - Association areas - Motor areas [Functional areas of cerebral cortex] - Sensory areas interpret sensory information and produces feeling and sensations - Association areas of the brain analyse and interpret sensory impulses and function in reasoning, judgement, emotions, verbalising ideas, and storing memory [Motor areas] - The primary motor areas lie in the posterior frontal lobes - This region includes the pyramidal cells that are also called upper motor neurons. They synapse with lower motor neurons that exit the s0pinal cors and reach muscles - Broca\'s motor speech area is in the frontal lobe - Frontal eye field -- controls voluntary eye movements - Sensory and motor fibres cross over in the spinal cord or brain stem so centres in the right hemisphere interpret or control the left side of the body, and vice versa. [Diencephalon] - lies between the cerebral hemispheres and above the midbrain - the main parts are the thalamus and hypothalamus [Thalamus] - Functions in sorting and directing sensory information arriving from other parts of the nervous system - Pinpoints the origin of the sensory input - Produces general awareness of the sensation - Descending fibres from the cerebral cortex also communicate with the thalamus [Hypothalamus] - Maintains homeostasis by regulating a wide variety of visceral activities and by linking the endocrine system with the nervous system. - Regulates heart rate and arterial blood pressure - Regulates body temoerature, water and electrolytes balance, hunger and body weight - Control movements and secretions od the digestive tact - Helps regulate sleep and wakefulness - Stimulates the posterior pituitary gland to secrete stored hormones. [Limbic system] - part os diencephalon - Controls emotional experience and expression - Generates pleasant or unpleasant feelings about expereinces - Guides behaviour that may enhance the chance of survival [Brain stem] - Consists of the midbrain, pons, and medulla oblongata, lies at the base fo teh cerebrum, and connects the brain to the spinal cord - Midbrain - Conveys impulses to and from higher parts of the brain - Serves as centre fro auditory and visual reflexes - Pons \- transmits regulate the rate and depth of breathing Ventral surfaces have transverse fibres that communicate with the cerebellum [Medulla oblongata] - Transmits all ascending and descending impulses between the brain and spinal cord - Houses nuclei that control visceral functions - Other nuclei in the medulla oblongata are associated with coughing, sneezing, swallowing and vomiting [Spinal cord] - Begins at the base of the brain at the foramen magnum and extends to the level of the intervertebral disc between the first and second lumbar vertebrae - Teh spinal cord consists of 31 segments, each of which gives rise to a pair of spinal nerves - As well as reflex centres, there are tracts carrying sensory information to the brain are called ascending tracts; descending tracts carry motor information from the brain. [Meninges] - Surround the brain and spinal cord, and lie between the bone and soft tissue - The outermost meninx is made up of tough, white dense connective tissue, contains many blood vessels, and is called the dura mater. - It forms the inner periosteum od the skull bones, - Can from partitions between lobes of the brain, or the dural sinuses - The sheath around the spinal cord if separated from the vertebrae by an epidural space. - The middle meninx, the arachnoid mater is thin and lacks blood vessels. - It does not follow the convolutions of the brain - Between the arachnoid and pia mater is the subarachnoid space containing cerebrospinal fluid (CSF) - The innermost pia meter is thin and contains many blood vessels and nerves - It is attached to the surface of the brain and spinal cord and follows their contours [The central nervous system] - Sensory, motor and association centres in the brain and spinal cord - It is organised into lower and higher centres - Lower centres only make direct contact with the PNS - Higher centres go through lower centres to communicate with periphery [Peripheral nervous system (PNS) ] - Sensory receptors - Detects chnages in both the external and internal environment - Communicates these changes to the CNS using afferent sensory nerves - The PNS also contains motor effectors - Voluntary muscles - Smooth muscles - Glands - efferent motor nerves relay messages from the CNS to these organs - The PNS divides into: - Somatic system - Voluntary system - Autonomic system - Visceral effectors - Differ in motor output nerves and targets - Share peripheral sensors and certain central nervous centres [Autonomic nervous system] - consists of two sets of opposing neurons that have opposite effects on most of the internal organs - One set is called the parasympathetic system and prepares the body for activities that gain and conserve energy by: - Stimulating the salivary glands and digestive juices - Decreasing the heart and respiratory rates - The other set is called the sympathetic system and prepare the body for energy consuming activities like fight or flight by: - Inhibiting the digestive system - Increasing heart and respiratory rates - Encouraging live to release glucose into the blood - Stimulating adrenal gland to release hormones - Bones are the organs of the skeletal system - Composed of bone tissue, cartilage, dense connective tissues, blood and nervous tissue - Bones are alive and multifunctional - Support and protect softer tissues - Provide points of attachment for muscles - House blood-producing cells - Store inorganic salts [Type of bones] - Long bones - Long and narrow - Have expanded ends - Shorts bones - Cube-like, length=width - Include sesamoid (round) bones, which are embedded in tendons. - Flat bones - Plate-like, with broad surfaces - Irregular bones - Variety of bones - Most are connected to several other bones [Composition of bones] - Made up of osteocytes with fibrous cartilage - Compact bone: - Consists of cylindrical unitd called osteons - Strong and solid - Weight-bearing - Resists compression - Spongy bone - Consists of branching placed called trabeculae - Somewhat flexible, has spaced between trabeculae that reproduce the bone'd weight [Long bones ] - Epiphysis: expanded end - Diaphysis: bone shaft - Metaphysis: between diaphysis and epiphysis, widening part - Articular cartilage: covers epiphysis - Periosteum: encloses bone; dense connective tissue - Compact (cortical) bone: wall of diaphysis - Spongy (cancellous) bone: make up epiphysis - Trabeculae: branching bony plates, make up spongy bone - Medullary cavity: hollow chamber in diaphysis; contain