Renal System - Test 3 PDF

Test 3  Renal system Urinary System kidneys Vreters bladder Urinary Urethra Functions Excretion- removal of organic waste products from body. Elimination – discharge the waste products into environment. Homeostatic re...

Test 3  Renal system Urinary System kidneys Vreters bladder Urinary Urethra Functions Excretion- removal of organic waste products from body. Elimination – discharge the waste products into environment. Homeostatic regulation Functions of Kidneys i. Regulation of blood volume and BP ii. Regulation of plasma concentrations of electrolytes / ions iii. Helps in stabilization of blood pH iv. Conservation of valuable nutrients such as glucose and amino acids v. Elimination of organic waste products such as urea and uric acid vi. Production of active form of Vit. D for strong bones The Kidneys Description paired organs bean-shaped, reddish-brown organs retroperitoneal Location lie on either side of vertebral column located on trans-pyloric plane level of L1 vertebra the right kidney lies slightly lower than the left kidney due to large size of R lobe of liver  Renal system Anatomy et kidney Hilus Renal capsule Entrance (medial) of kidney which transmits - Fibrous capsule covers kidney cortex-outer layer ~ medullar Inner layer composed of about a dozen renal pyramids separated by renal columns Renal artery Renal vein- · Lymphatic Vessels · Sympathetic nerves fibres Renal pyramids apex projects medially into minor calyx  Renal system Anatomy et kidney Blood supply Arterial supply Minor Renal artery (20% of cardiac output) Calyses Venous drainage A few of minor calyces subsequently Renal veins drain into IVC (inferior vena cava) form 2-3 major calyces Major Calyces unite to form pelvis which continue downwards as ureter * Microscopy of kidney Structural organisation of the * SAQ kidney * * SAQ Each kidney contains 1 million nephrons One Nephron is a functional unit of kidney Consists of Renal corpuscle Glomerulus and Bowman’s capsule Renal tubule long tube through which many processes takes place and urine is formed. Urine is emptied into the collecting duct system.  Microscopy of kidney Renal Tubule 50 mm long passageway Consists of i. Proximal convoluted tubule (PCT) ii. Loop of Henle Descending and Ascending limbs iii. Distal convoluted tubule (DCT) Located near afferent and efferent arterioles of glomerulus PCT, DCT are in renal cortex Loop of Henle extends into medulla * Functions ef nephron A Function of renal corpuscle Produce filtrate Function of Proximal convoluted tubule (PCT) Reabsorb water, ions & other nutrients. Function of Loop of Henle Reabsorb water (descending limb) Reabsorb Na+ & Cl− ions (ascending limb Function of Distal convoluted tubule (DCT) Active secretion of ions (H+, K+) , drugs, toxins. Na+ absorption with water in exchange of H+, K+ under control of hormone aldosterone. collecting system Makes final adjustments to composition of urine Begins as collecting duct which receives tubular fluid from many nephrons Several collecting ducts merge to form papillary duct Delivers urine to a minor calyx Reabsorbs water only in the presence of antidiuretic hormone (ADH) Function of Renal Tubules Changes composition of filtrate to eventually form urine through renal absorption and secretion Juxtaglomerular Apparatus (JGA) Formed by Macula densa (cells of Distal convoluted tubule, DCT closest to glomerulus) Juxtaglomerular cells (smooth muscle fibers in wall of afferent arteriole) Secretes renin, erythropoietin  Ureters, urinary bladder & urethra Ureters 30 cm long muscular tubes Upper end is expanded to form a funnel Renal pelvis Histology Contains transitional epithelium Smooth muscle in 2 layers Course of Ureter Emerges from hilus of kidney Enters pelvis by crossing bifurcation of common iliac artery Ends at posterior wall of bladder Urinary Bladder Hollow muscular organ stores urine temporarily Situated behind pubic bones Dimensions vary Empty bladder is pyramidal in shape In the adult, it lies entirely within the pelvis As bladder fills, it becomes rounded Superior wall rises up into hypogastric region  Ureters, urinary bladder & urethra Internal Anatomy et Bladder  Ureters, urinary bladder & urethra Blood Supply et Bladder Arterial supply superior and inferior vesicle arteries Venous drainage Vesicle veins drain into internal iliac veins  Ureters, urinary bladder & urethra Female Urethra Micturition Reflex & Urination Urine is expelled from bladder by micturition Coordinated by micturition reflex Stretch receptors in bladder wall are stimulated when bladder fills up with 200ml of urine Stimulation et Stretch Receptors in Bladder Then send signals to Parasympathetic motor neurons in spinal cord Adequate stimulation causes contraction of bladder Brain to cause conscious awareness of “bladder fullness” Micturition Reflex & Urination  Glomerular Filtration Glomerular Filtration Rate (GFR) Amount of filtrate produced in both kidneys each minute In the normal adult, GFR is about 125 ml/ min or 125 x 60 x 24 = 180,000 ml per day! GFR is good indicator of renal function * * SAQ Formation & Composition of Urine Urine Formation * To maintain homeostasis by regulating volume, composition of blood Involves excretion of waste products Urea Most common organic waste Produced during breakdown of amino acids Creatinine Produced in skeletal muscle from breakdown of creatinine phosphate Uric acid Produced during breakdown of ribonucleic acid (RNA) Normal and Abnormal Constituents of Vrine Physical Characteristics of Urine Volume 1200 ml/24 hours but varies Color yellow or amber but varies Turbidity transparent when freshly voided Odour mildly aromatic but become ammonia-like upon standing pH between 4.6 to 8.0; average 6.0, varies with diet Specific gravity 1.003 to 1.030; the higher the concentration of solutes, the higher the specific gravity Abnormal constituents Albumin Albuminuria indicates an ↑ in permeability of filtering membranes Glucose Glycosuria usually indicates diabetes mellitus Red blood cells Hematuria indicates a pathological condition White blood cells Pyuria indicates infection of urinary system Ketone bodies Indicates DM, starvation  Hormonal control of kidneys Hormonal control of kidney Function Major hormones involved in regulating kidney function 1. Angiotensin II 2. Anti-Diuretic Hormone (ADH) 3. Aldosterone 4. Atrial Natriuretic Peptide (ANP). Angiotensin I 1 ↓ in BP & blood volume causes JGA to release renin Renin results in formation of Angiotensin II through a series of steps Effects of Angiotensin II. ADH (Anti-Diuretic Hormone) 2  Hormonal control of kidneys Hormonal control of kidney Function Major hormones involved in regulating kidney function 1. Angiotensin II 2. Anti-Diuretic Hormone (ADH) 3. Aldosterone 4. Atrial Natriuretic Peptide (ANP)  Introduction to the Endocrine System & Mechanism of action of hormones The Endocrine System Includes all endocrine cells and tissues Functions together with nervous system Regulates the body activities Maintains homeostasis The Endocrine cells glandular secretory cells release their secretions into the extracellular fluid Hormones are chemical messengers released in one tissue and transported by the bloodstream to target cells in other tissues Organs and Tissues of the Endocrine system Hypothalamus Pituitary gland Pineal gland Thyroid gland Parathyroid glands Adrenal glands Pancreas (Pancreatic islets) Organs with secondary endocrine functions (heart, thymus, adipose tissue, digestive tract, kidneys, gonads) Three Groups of Hormones Based on their chemical structure: 1. Amino acid derivatives (e.g. epinephrine, norepinephrine, thyroid hormones) 2. Peptide hormones (e.g. antidiuretic hormone, oxytocin) 3. Lipid derivatives (e.g. corticosteroids, sex hormones) Hormone Action Change types, activities, locations, or quantities of structural proteins and enzymes Sensitivity of target cell to hormone depends on presence or absence of receptors for that hormone · Receptors are located either on plasma membrane or inside the cell  Introduction to the Endocrine System & Mechanism of action of hormones Controlet Endocrine Activity Negative feedback control for the majority of hormones ↑ blood hormone levels inhibit further secretion of the hormone ↓ blood hormone levels stimulate further secretion of the hormone Hypothalamus and Endocrine Control Hypothalamus provides highest level of endocrine control Hypothalamus regulate nervous and endocrine systems in three ways 1. Secretes two hormones directly into general circulation: Antidiuretic hormone (ADH) and oxytocin 2. Secretes releasing and inhibiting regulatory hormones to control anterior pituitary secretions 3. Contains autonomic nervous system (ANS) centers that control adrenal medullae through sympathetic innervation ·  The Pituitary Gland Pituitary Gland (Location ( Also called the hypophysis Protected by the sella turcica of the sphenoid bone Hangs from hypothalamus by infundibulum Divided into anterior and posterior lobes The Anterior Lobe of the Pituitary Gland Also known as adenohypophysis Contains endocrine cells Cells are surrounded by a complex capillary bed called the hypophyseal portal system Regulatory hormones from the hypothalamus diffuse onto target cell in anterior lobe through hypophyseal portal system Seven hormones from Anterior Lobe of the Pituitary Gland # SAQ 1. Thyroid-stimulating hormone (TSH) 2. Adrenocorticotropic hormone (ACTH) 3. Follicle-stimulating hormone (FSH) 4. Luteinizing hormone (LH) 5. Prolactin (PRL) 6. Growth hormone (GH) 7. Melanocyte-stimulating hormone (MSH) 1 Thyroid-Stimulating Hormone (TSH). Released in response to thyrotropin-releasing hormone (TRH) from hypothalamus Targets thyroid gland and triggers the release of thyroid hormones Increases in thyroid hormones cause decrease in TRH and TSH secretion (negative feedback). Adrenocorticotropic Hormone 2 (ACTH) Released in response to corticotropin-releasing hormone (CRH) from the hypothalamus Targets adrenal cortex and stimulates secretion of glucocorticoids · Increases in glucocorticoids cause decrease in ACTH and CRH secretion Gonadotropins Released in response to gonadotropin-releasing hormone (GnRH) from hypothalamus Target the male and female gonads Includes two hormones Follicle-stimulating hormone (FSH) Luteinizing hormone (LH)  The Pituitary Gland. Follicle-Stimulating Hormone (FSH) 3 Females Promotes ovarian follicles development Secretion of oestrogen Males Promotes sperm maturation 4. Luteinizing Hormone (LH) Females Induces ovulation Secretion of estrogens and progesterone Males Secretion of testosterone 5 Prolactin (PRL). Released in response to prolactin-releasing factor (PRF) from the hypothalamus Targets mammary glands in females In pregnancy and nursing, stimulates production of milk 6. Growth Hormone (GH) Regulated by: Growth hormone-releasing hormone (GH–RH) and growth hormone-inhibiting hormone (GH–IH) from the hypothalamus Stimulates cell growth and replication of all cells, especially skeletal muscle and chondrocytes 7. Melanocyte-stimulating Hormone CMSH) Increases activity of melanocytes in skin to increase melanin production Appears to be nonfunctional in adults ·  The Pituitary Gland Posterior Lobe of the Pituitary Gland * SAQ The two hormones secreted by neurons in the hypothalamus and transported to the posterior pituitary are: 1. Antidiuretic hormone (ADH) 2. Oxytocin (OXT) Antidiuretic Hormone LADH) Stimuli for its release an increase in concentration of solutes in the blood decrease in blood volume and pressure Primary target is the kidneys Effects to increase reabsorption of water Oxytocin (8xT) stimulates contraction of uterine muscles during labour and delivery stimulates contraction of cells surrounding milk secretory cells in mammary glands (milk letdown reflex) ·  The Thyroid Gland · Location Structure Relations Histology Reddish organ located in the neck at C5 to T1 level Lies on anterior surface of trachea and inferior to the thyroid cartilage Moves with swallowing Structure Surrounded by 2 coverings true capsule false capsule (pretracheal fascia) Has two lobes connected by a narrow isthmus Each lobe has an apex and a base Relations Anterolateral - neck muscles Lateral - carotid sheath (common carotid artery, internal jugular vein, vagus nerve) Posterior – trachea, oesophagus, recurrent laryngeal nerve Histology Contains many spherical thyroid follicles Lined by simple cuboidal epithelium Filled with viscous colloid containing many proteins and thyroid hormone molecules Surrounded by the network of capillaries Parafollicular cells or C cells (secrete calcitonin) Formation of Thyroid Hormones Follicular cells make thyroid hormones and store in colloid TSH causes release of thyroid hormones Derived from amino acid tyrosine, and iodine Thyroxine (T4) or tetraiodothyronine has four atoms of iodine Triiodothyronine (T3) has three iodine atoms More potent than T4 The Effects of Thyroid Hormones Affect nearly every cell in body Increase rate of ATP production in mitochondria Essential to normal development of skeletal, muscular, and nervous systems (for normal development of the brain especially during the 1st year of life) Regulationef thyroid hormones secretion A negative feedback mechanism Hypothalamic control of TSH TRH from the hypothalamus -> acts on the anterior pituitary-> control the release of TSH Thyroid stimulating hormone (TSH) from the anterior pituitary -> ↑ thyroid hormones secretion Feedback control by plasma T4 & T3 ↓ T4 & T3 -> stimulates TSH ↑ T4 & T3 -> inhibits TSH Calcitonin Secreted by the parafollicular cells or C cells Decreases the blood calcium levels Targets Kidneys (increased calcium excretion) Bones (increased calcium deposition)  The Parathyroid Glands prod Two pairs of small glands embedded in posterior surface of thyroid Parathyroid (chief) cells produce parathyroid hormone (PTH) The Parathyroid Hormone (PTH) Increases blood calcium levels Targets Kidneys (increased reabsorption of calcium) Bones (increased calcium release) GIT (increased calcitriol production by kidneys causes calcium absorption by GIT) Regulation of blood calcium levels By two hormones 1. Calcitonin 2. Parathyroid hormones (PTH)  Adrenal Glands Anatomy of the Adrenal Glands · Location Structure · Relations · Histology · Location Also called the suprarenal glands Yellow, pyramid-shaped, retroperitoneal organs Located on superior border of each kidney Lies at the level of 12th ribs Firmly attached to the kidneys by the fibrous capsule Highly vascularized Structure Two portions 1. Adrenal cortex (Outer part) 2. Adrenal medulla (Inner part) Relations Right adrenal gland Pyramidal in shape Lies behind the right lobe of liver, the inferior vena cava Left adrenal gland Crescent shaped Lies behind: the pancreas, the stomach Histology Outer Cortex (yellowish) divided into 3 zones Zona glomerulosa Zona fasciculata Zona reticularis Inner Medulla (reddish) Adrenal Cortex # SAQ Zona Glomerulosa Outer most layer Produce mineralocorticoids Zona Fasciculata Forms 78% of cortical volume Produce glucocorticoids Zona Reticularis Narrow band next to medulla Produce small amount of androgens (gonadocorticoids)  Adrenal Glands Adrenal Medulla * SAQ Produce catecholamines Adrenaline (epinephrine) Noradrenaline (norepinephrine) Minerals corticoids Affect electrolyte balance in body fluids Aldosterone The principal mineralocorticoids Secreted in response to low plasma Na+, low BP, high plasma K+, or presence of angiotensin II Triggers reabsorption of sodium ions and elimination of potassium ions Glucocorticoids Affect glucose metabolism Most important are cortisol (hydrocortisone), corticosterone, and cortisone Secreted in response to ACTH Increase rates of glucose synthesis and glycogen formation, resulting in increase in blood glucose levels Also act as anti-inflammatory The Androgens Small quantities produced in both males and females Stimulate development of pubic hair in boys and girls before puberty Not important in adult men In adult women, produce muscle mass, blood cell formation, and support sex drive The Catecholamines Epinephrine (adrenaline) Norepinephrine (noradrenaline) Increase cardiac activity, blood pressure, glycogen breakdown, blood glucose levels, release of lipids by adipose tissue  Pancreas Anatomy of the Pancreas · Location Structure · Relations · Histology · Location Pale nodular organ within the abdominal cavity Retroperitoneal, behind the stomach Structure has the head, body and tail Relations Anteriorly transverse colon, stomach Posteriorly bile duct, inferior vena cava, aorta, left kidney, spleen Histology Has exocrine and endocrine functions 2 million islets of Langerhans in endocrine pancreas 1% of pancreatic cells Surrounded by extensive capillary network Alpha (α)cells produce glucagon Beta (β) cells produce insulin  Pancreas Blood Glucose and Insulin Increases in blood glucose levels activate beta cells to release more insulin Stimulates glucose uptake by cells that have insulin receptors, Increases rates of protein synthesis and fat storage Result is lower blood glucose levels Blood Glucose and Glucagon Decreases in blood glucose levels activate alpha cells to release more glucagon Mobilizes energy reserves Glycogen in liver and muscles broken down to glucose Adipose tissue releases fatty acids Result is higher blood glucose levels Regulation of Blood Glucose 1. Secretion of insulin and glucagon 2. Indirectly affected by any hormone that also influences blood glucose levels Examples: cortisol and thyroid hormones 3. Also affected by ANS activity Parasympathetic stimulation enhances insulin release Sympathetic stimulation inhibits insulin release  Organization of the Nervous system Introduction Nervous system is the main control center Work together with endocrine system Aim To maintain homeostasis Provides quick and brief responses Functions of nervous system Monitors the body’s internal and external environments Integrates sensory information Coordinates voluntary and involuntary responses of many other organ systems Anatomical Divisions of the Nervous System Central nervous system (CNS) Consists of the brain & the spinal cord Integrates, processes, and coordinates sensory input and motor commands Peripheral nervous system (PNS) Includes all the neural tissue outside the CNS Carries the information between the CNS and rest of the body Functional Divisions of the Peripheral Nervous System CPNSI Afferent division Carries sensory information from sensory receptors to central nervous system (CNS) Receptors are sensory structures that either detect changes in the environment (internal or external) of respond to a specific stimuli. Efferent division Carries motor commands from CNS to effectors e.g. muscles, glands These target organs and tissues respond by doing something hence called effectors. Efferent division divided into Somatic Nervous System (SNS) Controls skeletal muscle contractions Autonomic Nervous System (ANS) Autonomic nervous system Provides involuntary regulation of smooth muscles, cardiac muscles and glandular secretions Is further classified into Sympathetic division Parasympathetic division  Neurons L Structure st a multipolor neuron * Structural Classification of Neurons * SAQ * SARA Functional Classification of Neurons 1. Sensory neurons. Moto neurons 2. Interneurons 3. 3. Interneurons 1 Sensory Neurons Also known as afferent neurons Located in the brain, and spinal cord Carry information from sensory receptors to CNS Connect sensory and motor neurons 2 types Responsible for Somatic sensory neurons distribution of sensory information Monitor external environment coordination of motor activity Visceral sensory neurons Also involved in higher functions Monitor internal environment memory, planning & learning 2 Motor Neurons. Also known as efferent neurons Carry instructions from CNS to effectors 2 types Somatic motor neurons Innervate skeletal muscles Visceral motor neurons Innervate cardiac muscle, smooth muscles & glands  Neuroglia Neuroglia. 1 Astrocytes Largest and most numerous neuroglia Functions Form structural framework for CNS Secrete chemicals that maintain blood-brain barrier Repair damaged neurons 2. Oligodendrocytes Have cytoplasmic extensions Wrap around axons to form myelin sheaths Myelination increase speed of nerve transmission Makes nerves appear white White matter of CNS contains myelinated nerves Nodes of Ranvier Gaps between adjacent myelin sheaths. 3 Microglia Smallest and rarest Phagocytic cells derived from WBCs Clean up cellular debris, waste products, pathogens. Ependymal Cells 4 Line central canal of spinal cord, and the ventricles (cavities) of brain In some regions of the brain, they secrete the cerebrospinal fluid (CSF) and in other locations, they help circulate CSF.. Satellite Cells 1 Surround and support neuron cell bodies of PNS Similar to astrocytes of CNS. Schwann Cells 2 Form myelin sheath around peripheral axons Similar to oligodendrocytes of CNS  Nerve conduction Two major functional properties of neuron 1. Irritability The ability to respond to a stimulus and converts it into a nerve impulse 2. Conductivity The ability to transmit the impulse to other neurons, muscles, or glands Resting membrane potential (RMP Positive and negative charges separated by the plasma membrane. Also known as transmembrane potential Membrane potential of an undisturbed cell is called as resting membrane potential. The RMP for a neuron is -70millivolts (mV). Negative voltage indicates the inside of the plasma membrane contains more negative charge compared to outside. The generation of a here impulse or action potential 1. Resting membrane potential is polarized 2. Stimulus initiates local depolarization 3. Depolarization and generation of an action potential 4. Propagation of the action potential 5. Repolarization 6. Restore the initial concentration of ions 1) Resting membrane potential In the resting state, the external face of the neuron’s plasma membrane is slightly positive The internal face is slightly negative The chief extracellular ion is 𝑁A+ The chief intracellular ion is 𝐾+ 2) Stimulus initiates local depolarization A stimuli (e.g. light excites the receptors in the eye) changes the permeability of a local “patch” of the membrane 𝑁a+ ions diffuse rapidly into the cell because 𝑁a+ ion is much higher concentration outside of the cell It changes the polarity of the membrane i.e. the inside becomes more positive, and the outside become more negative (a graded potential) 3) Depolarization When the gated sodium channels are opened, they speed up the entry of 𝑁a+ into the cell. This causes increase in the positive charge on the inner surface of the membrane shifting the membrane potential to 0 millivolt (mV). 3) Depolarization and generation of an action potential If the stimulus is strong enough, depolarization causes membrane polarity to be completely reversed, and an action potential or a nerve impulse is initiated The nerve impulse is an all-or-none response either propagated (conducted or sent) over the entire axon or it does not happen at all  Nerve conduction Information transfer between neuronsf other cells Graded potentials are changes in the membrane potential that cannot spread far from the site of stimulation. occur in plasma membrane of all the cells in response to environmental stimuli. They trigger cell specific function. Action potentials is a propagated change in the membrane potential of entire plasma membrane. Only axon of neuron & skeletal muscle fibres have excitable membranes that conduct action potential. Action potential Action potential in an axon, begins near axon hillock and travels through the length of axon, to reach axon terminal. At axon terminal, it activates the synapse. Action potential in neuron is known as nerve impulse. Action potentials are generated by opening and closing of gated sodium and potassium channels in response to graded potential. Action potential will not appear unless the membrane reaches a level called as “threshold” All or none principle For any stimulus, which brings the membrane to threshold, will generate action potential. So, the stimulus either generates action potential or does not produce any response. 4) Propagation of the action potential Depolarization of the first membrane patch causes permeability changes in the adjacent membrane The events described in step 2 are repeated The action potential propagates rapidly along the entire length of the membrane 5) Repolarization Almost immediately after the 𝑁a+ ions rush into the cell, membrane permeability changes again 𝐾+ ions diffuse out of the cell into the interstitial fluid restore the negative charge on the inside of the membrane and positive charge on the outside surface 6) Restores the initial concentrations of ions The ionic conditions of the resting state are restored by the sodium-potassium pump. 3 𝑁a+ ions are pumped out for every 2 𝐾+ ions pumped back into the cell Propagation of an action potential Continuous propagation Occurs in unmyelinated axons Relatively slow Saltatory propagation Occurs in myelinated axons Much faster  Synapse Transmission of an action potential In the nervous system, Information moves from one location to another in the form of action potentials (nerve impulses) along axons At the end of an axon, The information is transferred to another neuron or to an effector cell This information transfer takes place through the releases of chemicals called neurotransmitters The Synapse Site where neuron communicates with another cell Synapse between a neuron and another cell type is a neuroeffector junction Neuromuscular junction between neuron and muscle cell Neuroglandular junction between neuron and secretory cells Structure of a Synapse * SAQ * Presynaptic neuron Neuron on sending side of synapse Axon terminal holds vesicles containing neurotransmitters Neurotransmitters are released and diffuse across synaptic cleft Postsynaptic neuron Neuron on receiving side of synapse Has receptors for neurotransmitters * * SAQ  Cerebrum Major Regions of the Brain 1. Cerebrum 2. Diencephalon 3. Midbrain 4. Pons Brainstem 5. Medulla oblongata / 6. Cerebellum The Cerebrum The largest component of brain It controls higher mental functions Conscious thought & intellectual functions Divided into 2 hemispheres By longitudinal fissure Connected by corpus callosum Cross-section of the cerebrum Gray matter Thin outer layer Known as cerebral cortex Contains neuron cell bodies White matter Inner layer Contains nerve fibers Cerebral nuclei (Basal nuclei) Areas of gray matter in central white matter Structure of the Cerebral Hemisphere 4 lobes in each cerebral hemisphere Frontal lobe Parietal lobe Temporal lobe Occipital lobe Contains numerous folds and depressions Gyri Elevated ridges that increase surface area of cortex Sulci Practical Shallow depressions * Fissures Deep grooves Sulci Gyri , and Lobes of the Cerebrum Central sulcus Separates frontal lobe and parietal lobe Precentral and postcentral gyrus Lateral sulcus Separates frontal lobe and temporal lobe Parieto-occipital sulcus Separates parietal lobe and occipital lobe Functional Areas of the Cerebrum Each hemisphere Receives sensory info from opposite side of body Sends motor commands to opposite side of body Has specific areas with specific functions cipital lobe 1. Motor and sensory cortices 2. Association areas 3. Higher order centres 4. Hemispheric lateralization  Cerebrum 1 Primary. Motor Cortex Located in precentral gyrus of frontal lobe Directs voluntary movements 1. Primary Sensory Cortex 1 Located in postcentral gyrus of parietal lobe Receives somatic sensory information E.g. touch, pressure, pain, temperature - · Special Sensory Cortices Visual cortex (occipital lobe) Receives visual information Auditory cortex (temporal lobe) Receives information about hearing Olfactory cortex (temporal lobe) Receives information about smell Gustatory cortex (frontal lobe) Receives information about taste. Association Areas 2 Located adjacent to sensory, motor areas Consist of Somatic motor association area (premotor cortex) Coordinates learned movements Somatic sensory association area Interprets sensory information Association areas for vision, hearing 3. Higher Order Centers Integrative centers that receive information from many association areas Direct complex motor or analytical activities Consist of a) General interpretative area b) Speech center c) Prefrontal cortex  Basal Nuclei, Limbic System, Diencephalon, Basal Nuclei (Cerebral Nuclei Masses of gray matter Embedded in white matter of cerebrum Functions Involved in subconscious control of skeletal muscle tone and coordination of learned movement patterns Limbic System Functional group that includes Olfactory cortex Basal nuclei Tracts between cerebrum and diencephalon Functions Establishes emotional states Facilitates memory storage and retrieval It makes you want to do things (drive) Diencephalon Integrates sensory information and motor commands Components a) Epithalamus b) Thalamus c) Hypothalamus A) Epithalamus Forms roof of the diencephalon Anterior part Contains choroid plexus Posterior part Contains the pineal gland that secretes melatonin Hormone that regulates day-night cycles B) Thalamus Round mass of thalamic nuclei Functions Final relay point for all ascending sensory information (except smell) Coordination of voluntary and autonomic functions C) Hypothalamus Located below thalamus, above the pituitary gland Contains important control and integrative centres Functions of Hypothalamus Subconscious control of skeletal muscles During rage, pain, sexual arousal Adjusting of activities of autonomic centres in pons, medulla E.g. HR, BP, breathing, digestion Coordination of activities of nervous system and endocrine system Secretion of hormones Behavioral drives associated with Thirst centre, hunger centre Regulation of body temperature Coordination of day-night cycles of activity  Brain & Cerebellum Brain Stem Three major regions Midbrain Pons Medulla oblongata Midbrain Superior colliculus Inferior colliculus Cerebral aqueduct Cerebral peduncles Reticular activating system (RAS) Midbrain nuclei (e.g. substantia nigra, red nucleus) Nuclei for cranial nerves III, IV 2 pairs of colliculi on posterior surface Contain sensory nuclei associated with Visual reflexes – superior colliculus Auditory reflexes – inferior colliculus Cerebral aqueduct Passageway for cerebrospinal fluid (CSF) in central cavity Cerebral peduncles on ventrolateral surfaces Contain bundles of descending motor fibers from cerebrum to other parts of brain Reticular activating system (RAS) Required for attentiveness and wakefulness Midbrain nuclei (e.g. substantia nigra, red nucleus) For involuntary movements Nuclei for cranial nerves III, IV Pons Links the cerebellum with the brain stem and the spinal cord Contains Respiratory centers Nuclei for Cranial nerves V to VIII Medulla Oblongata Connects the brain to the spinal cord Functions Relays information between the spinal cord and the brain Contains Autonomic centers Vasomotor center, respiratory centers Reflex centers Coughing, vomiting, sneezing, swallowing Nuclei for cranial nerves IX to XII Cerebellum 2nd largest part of the brain 2 hemispheres Connected by the vermis Cerebellar peduncles Contain tracts that link the cerebellum with other parts of CNS 2 important functions Adjusting postural muscles to maintain balance Programs, fine-tunes and smoothens voluntary and involuntary movements DOES NOT initiate movement Damage causes ataxia Disturbance in balance, gait  Meninges, ventricles & cerebrospinal fluid (CSF) The Meninges 3 layers of protective membranes Cover brain & spinal cord completely Arrangement 1. Dura mater - outermost covering 2. Arachnoid mater - middle layer 3. Pia mater - innermost 1. Dura Mater Tough fibrous membrane covering the brain & the spinal cord Structure is slightly different in cranial cavity and vertebral canal Dura mater in Cranial Cavity Consists of 2 layers Outer layer fused to the periosteum of skull Inner layer extends into cranial cavity to form dural folds Support and stabilize brain Contain dural sinuses (venous blood) Dura Mater invertebral column 1 layer Epidural space Between the vertebra & the dura Contains loose connective, blood vessels and fats Used for epidural block. Arachnoid mater 2 Middle layer Thin, delicate network of fibers Like spider-webs Separated from the dura by the subdural space Contains lymph Separated from the pia by the subarachnoid space Contains cerebrospinal fluid (CSF). Pia mater 3 Innermost layer Thinnest membrane Closely applied onto brain surface Contains cerebral vessels Clinical Note Meningitis Inflammation of the meninges Caused by the bacteria & viruses Ventricles of Brain 4 internal cavities Contain the cerebrospinal fluid (CSF) Connected by openings, channels 2 lateral ventricles 1 in each cerebral hemisphere Connect through interventricular foramen Third ventricle of diencephalon Connects via cerebral aqueduct to Fourth ventricle posterior to pons Continues as central canal in spinal cord  Meninges, ventricles & cerebrospinal fluid (CSF) Cerebrospinal Fluid (CSF) Clear watery fluid that surrounds central nervous system (CNS) (150 ml) Circulates through cavities of CNS and subarachnoid space Production- At choroid plexuses (network of ependymal cells & capillaries) of the ventricles CSF Circulation - circulates from the lateral ventricles to the 3rd ventricle via the interventricular foramen, and from the 3rd ventricle to 4th ventricle via the cerebral aqueduct exits the ventricles via the median & lateral apertures to flow around the brain & spinal cord in the subarachnoid space also goes down central canal of spinal cord CSF-Reabsorption At arachnoid granulations Extensions of arachnoid mater from subarachnoid space to dura sinuses Flows into dura sinuses and into venous circulation Cerebrospinal Fluid Functions - Supports brain Cushions the brain & delicate neural structures Maintains chemical stability & removes metabolic waste from CNS through the blood brain barrier Clinical Notes Lumbar puncture or spinal tap puncture made at the subarachnoid space between L3-L4 sampling of CSF for clinical info about CNS injuries, infections or diseases Hydrocephalus Rate of CSF reabsorption < rate of production of CSF Obstruction of CSF flow  Blood supply of the brain Introduction Brain is highly active organ Supplied by 2 pairs of arteries Internal carotid arteries Vertebral arteries Internal Carotid System Internal carotid arteries enter skull through carotid canal Main branches Anterior cerebral artery Middle cerebral artery Anterior Cerebral Artery Supplies Frontal poles of cerebrum Medial, superior surfaces of cerebral hemisphere (except occipital lobe) Functional areas Gustatory cortex Motor, sensory cortices of Lower Limbs Middle Cerebral Supplies Artery Lateral surface of cerebral hemisphere Cerebral nuclei Internal capsule Functional areas Motor, sensory cortices Auditory & Olfactory cortices Language areas (Wernicke’s and Broca’s areas) if dominant hemisphere Vertebrobasilar System Vertebral arteries enter skull through foramen magnum Supplies Spinal cord (cervical) Brain stem Cerebellum Occipital lobe Main branches Spinal arteries Basilar artery Cerebellar arteries Posterior cerebral artery Posterior Cerebral Artery Branch of basilar artery Supplies Occipital lobe Diencephalon, midbrain  Blood supply of the brain Circle of Willis Arterial ring on ventral surface of brain Connects internal carotid and vertebrobasilar systems Significance Provides alternate route in the event of occlusion of any of these arteries Formation of Circle of Willis Internal carotid artery Anterior cerebral artery Anterior communicating artery Posterior communicating artery Posterior cerebral artery Venous Drainage Veins of the brain Do not accompany arteries Do not have valves Drain into dural venous sinuses (in dura layers) E.g. superior sagittal sinus Drain into internal jugular vein in neck to the superior vena cava  Spinal cord Gross anatomy of the Spinal Cord 45 cm long cylindrical tube & tapers caudally Ends at level of 2nd lumbar vertebra (L2) in adult Enlarged at 2 regions -> concerned with the sensory and motor control of the limbs Cervical enlargement -> nerves to the shoulder girdle & upper limbs Lumbar enlargement -> nerves to the pelvis & lower limbs Conus medullaris Conical part below lumbar enlargement Cauda equina Nerve roots extending from conus medullaris Consists of 31 segments 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal Each segment has similar structural features · 31 pairs of spinal nerves Sectional Anatomy of Spinal Cord * SAQ * Posterior median sulcus Shallow groove on dorsal surface Anterior median fissure Deeper groove on anterior surface Central canal Filled with CSF Each spinal segment has a pair of Dorsal roots Contain axons of sensory neurons Dorsal root ganglia Contain cell bodies of sensory neurons Ventral roots Contain axons of CNS motor neurons · Dorsal and ventral roots join distally to form spinal nerves Spinal nerves are mixed nerves Have both sensory and motor fibers * Gray matter Forms “H” around central canal SAQ * Contains neuron cell bodies Has projections (gray horns) Posterior gray horn Contains sensory nuclei Anterior gray horn Contains somatic motor nuclei Lateral gray horn Found only in thoracic and lumbar segments Contains visceral (autonomic) motor nuclei Gray Commissures Contain axons that cross from 1 side of the spinal cord to the other Connect the horns on either side of the spinal cord White matter More superficial Divided into 3 columns containing bundles of sensory (ascending) & motor (descending) nerve fibres tracts Posterior white columns Anterior white columns Lateral white columns  Spinal cord Functions etSpinalcorensuries Passageway for information travelling between the brain and the body Controls spinal reflexes Causes Physical trauma to the spinal cord Spinal meningitis Herniated intervertebral discs Clinical symptoms Loss of sensation (anaesthesia) & voluntary movement (flaccid paralysis) below the level of injury Damage at C4 or C5 vertebra-> Loss of sensation & motor control of the upper & lower limbs (quadriplegia) Damage to the thoracic vertebrae -> Loss of motor control of the lower limbs (paraplegia) ·  Cranial Nerves - Peripheral nervous system (PNS) Peripheral Nervous System Links the central nervous system (CNS) to the rest of the body through peripheral nerves Cranial nerves originate from the brain Spinal nerves connect to the spinal cord Cranial Nerves Twelve pairs Designated with Roman numerals I through XII Classified as: Primarily sensory Primarily motor Mixed (both sensory and motor) Cranial Nerves Table ·  Cranial Nerves - Peripheral nervous system (PNS) Cranial Nerves Table ·  Spinal Nerves Spinal nerves Found in 31 pairs grouped according to the region of the vertebral column 8 pairs of cervical nerves, C1–C8 12 pairs of thoracic nerves, T1–T12 5 pairs of lumbar nerves, L1–L5 5 pairs of sacral nerves, S1–S5 1 pair of coccygeal nerves, Co1 Nerve Plexuses Networks of major nerve trunks Cervical plexus Innervates the muscles of the neck and the diaphragm Brachial plexus Innervates the pectoral girdles and upper limbs Lumbar plexus and sacral plexus Also called lumbosacral plexus Innervate the pelvic girdle and lower limbs. Peripheral Nerves Arise from the nerve plexuses Contain both sensory and motor nerve fibres E.g. sciatic nerve Peripheral neuropathies regional losses of sensory or motor function as a result of nerve trauma or compression Reflexes Rapid, automatic motor responses to specific stimuli Always produce same response Preserve homeostasis through negative feedback Reflex arc refers to the wiring of a single reflex · Begins at a sensory receptor Ends at an effector 5 steps in Neural Reflex arc Step 1: Arrival of stimulus, activation of receptor Step 2: Activation of sensory neuron Step 3: Information processing in CNS Step 4: Activation of motor neuron Step 5: Response of peripheral effector  Spinal Nerves Spinal Reflexes Coordinated within spinal cord Involve synapses Monosynaptic reflexes Simple reflexes with 1 synapse Polysynaptic reflexes Complex reflexes with interneurons Monosynaptic Reflexes Most rapid motor response of nervous system NS Sensory neuron synapses directly with motor neuron E.g. Stretch reflex Polysynaptic Reflexes More complicated Longer delay between stimulus and response Involve at least 1 interneuron between sensory neuron and motor neuron > 1 muscle group involved E.g. Withdrawal reflexes ·  Autonomic nervous system (ANS) Autonomic Nervous System Involved in autonomic regulation of body functions Uses two motor neurons from CNS to effector (cardiac and smooth muscle, glands, and fat cells) Preganglionic neurons communicate with ganglionic neurons whose axons are called postganglionic fibers Two Divisions of the ANS # SAQA Sympathetic division Preganglionic fibers leave thoracic and lumbar spinal segments Ganglia located near spinal cord Short preganglionic fibers Long postganglionic fibers Parasympathetic division Preganglionic fibers originate in brain stem and sacral spinal region Ganglia located near or within target organs Long preganglionic fibers Short postganglionic fibers Neurotransmitters at Specific Synapses All preganglionic fibers Are cholinergic and they release acetylcholine (ACh) Are excitatory Postganglionic parasympathetic fibers Are cholinergic Effects are excitatory or inhibitory, depending on the target cell receptor Most postganglionic sympathetic fibers Are adrenergic and they release norepinephrine (NE) Are usually excitatory Sympathetic Division Components · Sympathetic chain Arises from spinal segments T1–L2 Preganglionic fibers enter the sympathetic chain ganglia just outside the spinal column Sympathetic Division Components Cont. The adrenal medullae Center of the adrenal glands Innervated by preganglionic fibers Modified sympathetic ganglia (neurons) Secrete norepinephrine (NE) and epinephrine (E) into capillaries, functioning like an endocrine gland Effect is nearly identical to that of the sympathetic postganglionic stimulation of adrenergic synapses Sympathetic Division Functions Called the “fight-or-flight” division Effects Increase in alertness, metabolic rate, sweating, heart rate, blood flow to skeletal muscle Dilates the respiratory bronchioles and the pupils Blood flow to the digestive organs is decreased E and NE from the adrenal medullae support and prolong the effect  Autonomic nervous system (ANS) Parasympathetic Division Preganglionic neurons arise from the brain stem and sacral spinal cord Fibers travel within cranial nerves III, VII, IX, and X The vagus nerve (N X) provides about 75% of all parasympathetic outflow Ganglia very close to or within the target organ Preganglionic fibers of the sacral areas form the pelvic nerves Called the “rest-and-digest” division Less divergence than in the sympathetic division, so effects are more localized Effects Constricts pupils, increases digestive secretions, increases digestive tract smooth muscle activity Stimulates urination and defecation Constricts bronchioles, decreases heart rate · Dual Innervation Refers to both divisions affecting the same organs Mostly have antagonistic effects Some organs are innervated by only one division  Pathways - Sensory & Motor Sensory Pathway (Ascending pathways) Posterior columns Carries fine touch, pressure, vibration, proprioception to primary sensory cortex. Spinothalamic pathways Carries crude touch, pressure, pain, temperature to primary sensory cortex. Spinocerebellar pathways Carries proprioceptive information about position of skeletal muscles, tendons, joints Involves only 2 sensory neurons, 2nd neuron Motor Pathways (Descending Pathways Convey motor commands from CNS to peripheral effectors Distributed by Somatic Nervous System To skeletal muscles Autonomic Nervous System To cardiac muscle, smooth muscles, glands Somatic Nervous System Involves 2 neurons Upper Motor Neuron (UMN) Located entirely in the CNS Synapses with LMN · Lower Motor Neuron (LMN) Cell body is in CNS; axon is in PNS Controls skeletal muscles Motor Pathways (Descending pathways Pyramidal (Corticospinal) pathways Provide conscious, voluntary control of skeletal muscles responsible for initiating voluntary movements Upper Motor Neuron originates at the motor cortex, axons descend down to the brainstem & the spinal cord, synapse on lower motor neuron nuclei at anterior gray horn Crossing Over (decussate Lower Motor Neuron exits from the spinal cord to reach skeletal muscle NOTE All axons of corticospinal tract cross over to opposite side of spinal cord As a result, left side is controlled by right cerebral hemisphere, and vice versa  Pathways - Sensory & Motor by Extrapyramidal (Medial and Lateral) pathways Provide subconscious involuntary control of posture, balance, muscle tone Coordinate learned movement patterns Consists of several tracts UMN originate in several parts of brain e.g. basal nuclei, midbrain, cerebellum Renal System Structure & Functions of Nephron SAQ The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine. Each kidney contains about 1 million nephrons. A nephron consists of: 1. Renal Corpuscle - Glomerulus – A network of capillaries that filters blood. - Bowman’s Capsule – A cup-shaped structure that collects the filtered fluid (glomerular filtrate). 2. Renal Tubule - Proximal Convoluted Tubule (PCT)– Reabsorbs nutrients, ions, and water. - Loop of Henle – Maintains the concentration gradient for water reabsorption. - Distal Convoluted Tubule (DCT) – Regulates ion balance and pH. - Collecting Duct – Final site for water reabsorption, leading to urine formation. Functions of the Nephron: - Filtration (in the glomerulus) - Reabsorption (useful substances returned to the blood) - Secretion (waste products secreted into the filtrate) - Excretion (formation of urine) Steps in Urine Formation 1. Glomerular Filtration – Blood pressure forces water and solutes from the glomerulus into Bowman’s capsule, forming filtrate. 2. Tubular Reabsorption – Useful substances (glucose, amino acids, ions, and water) are reabsorbed back into the blood, mainly in the PCT. 3. Tubular Secretion – Additional waste products (H+, K+, ammonia, drugs) are actively secreted into the tubules. 4. Excretion – The final urine is transported to the bladder and excreted. Normal Waste Products in Urine - Urea – From protein metabolism. - Creatinine – From muscle metabolism. - Uric Acid – From nucleic acid breakdown. - Ammonia – From amino acid breakdown. - Ions (Na+, K+, Cl-, HCO₃-) – Maintain electrolyte balance. - Water – Helps remove waste. Endocrine System · Structure of Adrenal Gland & Hormones The adrenal glands are located on top of each kidney and have two parts: 1. Adrenal Cortex (Outer Layer) – Produces steroid hormones: - Mineralocorticoids (Aldosterone) – Regulates Na+ and K+ balance. - Glucocorticoids (Cortisol) – Regulates metabolism and immune response. - Androgens – Contribute to secondary sex characteristics. 2. Adrenal Medulla (Inner Layer) – Produces catecholamines: - Epinephrine (Adrenaline) – Increases heart rate and energy release. - Norepinephrine – Helps regulate blood pressure. Structure of Pituitary Gland & Hormones The pituitary gland (hypophysis) is a pea-sized gland at the base of the brain. It has two parts: 1. Anterior Pituitary (Adenohypophysis) – Produces hormones: - Growth Hormone (GH) – Stimulates growth. - Prolactin (PRL) – Stimulates milk production. - Thyroid-Stimulating Hormone (TSH) – Regulates the thyroid gland. - Adrenocorticotropic Hormone (ACTH) – Stimulates adrenal cortex. - Follicle-Stimulating Hormone (FSH) – Regulates reproductive function. - Luteinizing Hormone (LH) – Stimulates ovulation/testosterone production. 2. Posterior Pituitary (Neurohypophysis) – Stores and releases: - Oxytocin – Stimulates uterine contractions and milk ejection. - Antidiuretic Hormone (ADH, Vasopressin)– Regulates water balance. Nervous System SAQ Structure of Neuron A neuron is the basic unit of the nervous system and consists of: - Cell Body (Soma) – Contains the nucleus and organelles. - Dendrites – Receive signals from other neurons. - Axon – Transmits impulses away from the cell body. - Myelin Sheath – Insulates the axon, speeding up impulse transmission. - Axon Terminals – Release neurotransmitters to communicate with other cells. Classification of Neurons 1. Based on Function: - Sensory (Afferent) Neurons– Carry signals from receptors to the CNS. - Motor (Efferent) Neurons – Carry signals from the CNS to muscles/glands. - Interneurons– Connect sensory and motor neurons within the CNS. 2. Based on Structure: - Unipolar Neurons– Single process, found in sensory neurons. - Bipolar Neurons – Two processes (one dendrite, one axon), found in the retina. - Multipolar Neurons– Multiple dendrites, one axon (most common type). Structure of Spinal Cord Segment Each spinal cord segment consists of: - Gray Matter – Contains nerve cell bodies (butterfly-shaped). - Dorsal Horn– Receives sensory input. - Ventral Horn – Sends motor output. - White Matter – Contains myelinated nerve fibers (ascending and descending tracts). - Central Canal– Contains cerebrospinal fluid (CSF). - Spinal Nerves – Exit the spinal cord to supply different body regions. Structure of Synapse A synapse is the junction between two neurons. It consists of: - Presynaptic Neuron – Sends the signal. - Synaptic Cleft – The gap between neurons. - Postsynaptic Neuron – Receives the signal. - Neurotransmitters – Chemical messengers (e.g., acetylcholine, dopamine, serotonin). · Events Occurring at Synaptic Transmission 1. Action potential reaches axon terminal of the presynaptic neuron. 2. Voltage-gated Ca²⁺ channels open, allowing Ca²⁺ to enter. 3. Neurotransmitters are released into the synaptic cleft. 4. Neurotransmitters bind to receptors on the postsynaptic neuron. 5. Ion channels open, leading to an excitatory or inhibitory response. 6. Neurotransmitters are removed by reuptake, enzymatic breakdown, or diffusion. Divisions of the Autonomic Nervous System (ANS) The ANS regulates involuntary functions and has two divisions: 1. Sympathetic Nervous System ("Fight or Flight") - Increases heart rate, dilates pupils, inhibits digestion. - Uses norepinephrine as a neurotransmitter. 2. Parasympathetic Nervous System ("Rest and Digest") - Decreases heart rate, constricts pupils, stimulates digestion. - Uses acetylcholine as a neurotransmitter.  SAQ Renal Nervous System. The Structure & functions of nephron Structure of Neuron A neuron is the basic unit of the nervous system and consists of: 1 - Cell Body (Soma) – Contains the nucleus and organelles. - Dendrites – Receive signals from other neurons. - Axon – Transmits impulses away from the cell body. - Myelin Sheath – Insulates the axon, speeding up impulse transmission. - Axon Terminals – Release neurotransmitters to communicate with other cells. Classification of Neurons 1. Based on Function: - Sensory (Afferent) Neurons– Carry signals from receptors to the CNS. - Motor (Efferent) Neurons – Carry signals from the CNS to muscles/glands. - Interneurons– Connect sensory and motor neurons within the CNS. 2. Based on Structure: - Unipolar Neurons– Single process, found in sensory neurons. - Bipolar Neurons – Two processes (one dendrite, one axon), found in the retina. ·