Human Anatomy mid.pdf

CHAPTER 1 Introduction to Human Anatomy and Physiology Overview of Anatomy and Physiology Structural organization of the human body Anatomical Terminology Body cavities and membranes Human Anatomy and Physiology I HUAP 210 Objectives After this chapter, you will be able to: Distinguish between anatomy and physiology, and identify several branches of each. Describe the structure of the body, from the chemical level to organismal how they build upon each other. Identify key characteristics and examples at each level of organization. Utilize appropriate anatomical terminology to identify key body structures, body regions, and directions in the body. Define and locate the major body cavities (dorsal and ventral). Explain the role of serous membranes in reducing friction between organs. Human Anatomy and Physiology I HUAP 210 Overview of Anatomy & Physiology Anatomy The study of the external and internal structures of the body parts, and their relationship to one another. A cutting open Study of Form Anatomy is divided into: Gross anatomy Microscopic anatomy Human Anatomy and Physiology I HUAP 210 Gross Anatomy Gross anatomy - a science of macroscopic anatomy; studying large body structures visible with the unaided (naked) eye. Several approaches: Regional anatomy Systemic anatomy Surface anatomy Human Anatomy and Physiology I HUAP 210 Gross Anatomy approaches Regional anatomy: the study of all the structures (including muscles, bones, nerves, blood vessels, etc.) in a particular region of the body, such as the head. Systemic anatomy: the study of all the structures of particular system in the body regardless of location, for example, cardiovascular system. Surface anatomy: the study of internal structures as they relate to the overlying skin surface. Human Anatomy and Physiology I HUAP 210 Microscopic Anatomy Microscopic anatomy -The examination of structures that are too small to be seen without magnification. Divided into: Cytology Histology Human Anatomy and Physiology I HUAP 210 Microscopic Anatomy divisions Cytology - The study of cells, their components, and their functions. Histology – The study of tissues – a group pf specialized cells work together to perform a function. Human Anatomy and Physiology I HUAP 210 Physiology The study of the chemistry and physics of the structures of the body and the ways in which they work together to support the functions of life. More complex and interrelated with anatomy Study of FUNCTION Physiology is divided into: Individual organs. Organ systems. Human Anatomy and Physiology I HUAP 210 Complementarity of structure and function The principle of complementarity of structure and function - the function of any body part always reflects structure. Example FUNCTION Blood flows in one direction through the heart because the heart has valves that prevent backflow. STRUCTURE Human Anatomy and Physiology I HUAP 210 Structural Organization of Human Body Levels of Organization Chemical Level Cellular Level Tissue Level Organ Level Organ system Level Organismal Level Human Anatomy and Physiology I HUAP 210 Tissue Level Tissues are group of cells provide specific functions for the body. Tissues are divided into four primary types: Epithelial tissue Connective tissue Muscle tissue Nervous tissue Human Anatomy and Physiology I HUAP 210 Epithelial Tissue PSA Function – Protection, secretion, absorption, and excretion. Location – Cover body surface, cover and line internal organs, and compose glands. Characteristics - Lack blood vessels, readily divided, cells are tight packed. Human Anatomy and Physiology I HUAP 210 Connective Tissue Function – Bind, support, protect, fill spaces, store fat, and produce blood cells. Location – Widely distributed throughout the body. Characteristics - Have good blood supply, and cells are farther apart than epithelial cells. Human Anatomy and Physiology I HUAP 210 Muscle Tissue Function – Body movement. Location – Attached to bones, in the walls of hollow internal organs, heart. Characteristics - Able to contract in response to specific stimuli. Human Anatomy and Physiology I HUAP 210 Nervous Tissue Function – Transmit impulses for coordination, regulation, integration, and sensory reception. Location – Brain, Spinal cord and nerves. Characteristics - Cell communication with each other and other body cells. Human Anatomy and Physiology I HUAP 210 Organ System Level Organ system is a group of organs work together to provide specific functions to the body. The human organism is made up of many organ systems. Human has eleven (11) systems. Human Anatomy and Physiology I HUAP 210 Integumentary System ↳ protective layer Organs – Skin, accessory structures, hair, and nails Functions – External support, protection of the body, temperature regulation, barrier for immune function Human Anatomy and Physiology I HUAP 210 Skeletal System Organs – Bones, cartilage, joints Functions – Internal support, protection of organs, flexible framework for body movement, forms blood cells, and mineral storage Human Anatomy and Physiology I HUAP 210 Muscular System Organs – Skeletal muscles, and tendons Functions – Locomotion, support, and body heat production Human Anatomy and Physiology I HUAP 210 Nervous System Organs – Brain, spinal cord, peripheral nerves Functions – Detects and processes sensory information, directs responses to that stimuli by coordinating activities of other organ systems Human Anatomy and Physiology I HUAP 210 Endocrine System Organs – Hormone secreting glands Functions – Secretion of hormones, which act as signals for other parts of the body, regulating body processes Human Anatomy and Physiology I HUAP 210 Circulatory System Organs – Heart, blood, and blood vessels Functions – Transport of nutrients to cells, and waste products from cells, homeostasis of body temperature Human Anatomy and Physiology I HUAP 210 Lymphatic and Immune System Organs – Lymph nodes, lymphatic vessels, spleen, thymus gland, bone marrow, and tonsils. (Immune cells). Functions – Returning extracellular fluid to the blood, houses immune cells, provides protection against infection and disease, transports lymph, absorbs and transports fats. Human Anatomy and Physiology I HUAP 210 Respiratory System Organs – Lungs, trachea, larynx, and nasal passages Functions – Gas exchange (O2 and CO2) between air and circulating blood Human Anatomy and Physiology I HUAP 210 Digestive System Organs – Salivary glands, esophagus, stomach, small intestine, large intestine, liver, and gallbladder Functions – Intake, breakdown, and absorption of food in order to acquire nutrients, minerals, vitamins, and water, as well as the elimination of feces Human Anatomy and Physiology I HUAP 210 Urinary System Organs – Kidneys, ureters, urinary bladder, and urethra Functions – Controls water balance in the body, filters the blood to remove nitrogenous wastes, eliminates excess water, salts, and waste products, controls pH, and electrolyte balance Human Anatomy and Physiology I HUAP 210 Reproductive System - Male Organs – Testes, scrotum, prostate gland, seminal vesicles, epididymis, and penis It Functions – Production and delivery of sperm (gametes), production of sex hormones Human Anatomy and Physiology I HUAP 210 Reproductive System - Female Organs – Ovaries, uterus, vagina, and mammary glands Functions – Production of egg (gamete), secretion of sex hormones, copulation, and support of fetus/infant Human Anatomy and Physiology I HUAP 210 Anatomical Terminology Anatomical Position Anatomical Position - Standard body position, used for consistency. The body is: Standing upright (or laying down face up). Feet slightly apart at shoulder width. The upper limbs are at the body's sides with the palms face forward and thumbs point away from the body. Human Anatomy and Physiology I HUAP 210 Directional Terms & Superior/inferior Cranial/caudal 8 Posterior/anterior Dorsal/ventral Right/left Lateral/medial Proximal/distal Deep/superficial Human Anatomy and Physiology I HUAP 210 Superior (Cranial) /Inferior (Caudal) Superior (cranial) _ above; toward the head end or upper part of the structure or body. Inferior (caudal) _ below; away from the head end or toward the lower part of the structure or body. Human Anatomy and Physiology I HUAP 210 Anterior (Ventral) /Posterior (Dorsal) Anterior (ventral) _ toward or at the front of the body. Posterior(Dorsal) _ toward or at the back of the body. Human Anatomy and Physiology I HUAP 210 Medial / Lateral Medial _ toward or at the longitudinal axis of the body. Lateral _ away from the longitudinal axis of the body. Human Anatomy and Physiology I HUAP 210 Proximal/ Distal Proximal _ closer to the origin of the body part or the point of attachment of a limb to the body trunk. Distal _ farther from the origin of a body part or the point of attachment. Human Anatomy and Physiology I HUAP 210 Superficial / Deep Superficial (external) _ toward or at the body surface. Deep (internal) _ away from the body surface; more internal. Human Anatomy and Physiology I HUAP 210 Body Planes Sagittal Frontal (coronal) Transverse Oblique Human Anatomy and Physiology I HUAP 210 Sagittal plane A vertical plane that divides the body into right and left parts Midsagittal (median) _ the plane dividing the body exactly in the midline. Parasagittal _ all other sagittal planes offset from the midline Human Anatomy and Physiology I HUAP 210 Frontal plane (Coronal) Any plane dividing the body into anterior and posterior portions. Human Anatomy and Physiology I HUAP 210 Transverse plane (Horizontal) A plane dividing the body into superior and inferior portions. Human Anatomy and Physiology I HUAP 210 Oblique plane Cuts made diagonally (on the cross) between the horizontal and vertical planes. Human Anatomy and Physiology I HUAP 210 Regions of the Human Body The fundamental divisions of major body regions including: Axial Part Appendicular Part The main axis of the body, Consists of the hands, feet, upper including the head, neck, and extremity, lower extremity, shoulder trunk girdle, and pelvic bones which are attached to the body's axis. Human Anatomy and Physiology I HUAP 210 Axial Parts Head Trunk (Torso-) Facial region - Includes thorax, abdomen including eyes, nose, and pelvic region Neck and mouth. Cranial region - Cervical region - Support brain. supports head and permits its movements. Human Anatomy and Physiology I HUAP 210 Thorax Region Mammary regions _ surrounds nipples Sternal region_ between mammary regions Axillary region_ area surrounding armpit Vertebral region_ area of vertebral column Human Anatomy and Physiology I HUAP 210 Abdominopelvic quadrants and regions Abdominopelvic Quadrants: Right upper quadrant: contains liver Left upper quadrant: contains the stomach and spleen Left lower quadrant: contains descending colon Right lower quadrant: contains the cecum and ascending colon Human Anatomy and Physiology I HUAP 210 Abdominopelvic quadrants and regions Abdominopelvic Regions: Umbilical: centermost region deep to and surrounding the umbilicus (navel). Epigastric: superior to the umbilical region. Hypogastric (pubic): located inferior to the umbilical region. Right and left hypochondriac: lateral to the epigastric region and deep to the rips. Right and left lumbar: lies lateral to the umbilical region Right and left iliac (inguinal): lateral to the hypogastric region Human Anatomy and Physiology I HUAP 210 Appendicular Parts hands, feet, upper extremity, lower extremity, shoulder girdle, and pelvic bones Human Anatomy and Physiology I HUAP 210 Body Cavities and Membranes Body Cavities Body cavities are closed to the outside and provide protection to the organs within them. Internal body cavities include: Dorsal body cavity_ consists of cranial cavity and vertebral (spinal) cavity. Ventral body cavity_ consists of thoracic cavity and abdominopelvic cavity. The Dorsal and ventral body cavities are lined with serous membranes secrete a watery, lubricating fluid. Human Anatomy and Physiology I HUAP 210 Dorsal body cavity Cranial cavity _ contains the brain Vertebral (spinal) cavity _ contains the spinal cord Human Anatomy and Physiology I HUAP 210 Ventral body cavity houses internal organs of the body collectively called the viscera or “guts”. Divided into two smaller cavities: Thoracic cavity ⚬ Pleural cavity ⚬ Mediastinum ⚬ Pericardial cavity Abdominopelvic cavity ⚬ Abdominal cavity ⚬ Pelvic cavity Human Anatomy and Physiology I HUAP 210 Ventral body cavity Thoracic cavity ⚬ Pleural cavity_ contains lungs ⚬ Mediastinum_ space between the pleural cavities; containing the thymus, lymph vessels, esophagus, trachea, and nerves. ⚬ Pericardial cavity_ houses the heart Abdominopelvic cavity ⚬ Abdominal cavity_ contains the digestive organs ⚬ Pelvic cavity_ contains bladder, reproductive organs and rectum Human Anatomy and Physiology I HUAP 210 Other less significant body cavities Nasal cavity_ for the passage of air into the respiratory tract Orbital cavity_ area of the skull that houses the eye Middle ear cavity_ contains the ossicles Synovial cavity_ are joint cavities filled with synovial fluid Human Anatomy and Physiology I HUAP 210 Body membranes Body membranes are thin layers of connective and epithelial tissues that cover , support & separate visceral organs. There are two types: Mucous membrane Secretes mucus-sticky fluid. It lines the esophagus, urinary system, nasal and oral cavities. Serous membrane secretes serous fluid and cover the visceral organs (guts), thoracic and abdominopelvic cavities. Human Anatomy and Physiology I HUAP 210 Serous membranes Meninges line the dorsal body cavity. Pleura line the pleural cavity. Pericardium lines the pericardial cavity. Peritoneum lines the abdominal cavity. Some organs are retroperitoneal such as the urinary and reproductive organs. Human Anatomy and Physiology I HUAP 210 Pericardium lines the pericardial cavity. Human Anatomy and Physiology I HUAP 210 Type the correct in the blanks below using the following terms: Proximal, Distal, Anterior, Posterior,( Dorsal, ventral) , Superior, Inferior, Deep, Medial, Lateral, Superficial. You may need to find a picture in Google to use as a reference. inferior 1. The diaphragm is ……………….. to the lungs. 2. The heart is superior ………………….. to the diaphragm. 3. The head is Superior …………………….to the neck. proximal 4. The wrist is …………………. to the hand. 5. The brain is superior …………………. to the spinal cord. 6. The fingers are proximal ……………… to the hand. later 7. The eyes are …………………. al to the bridge of the nose. medial 8. The nose is …………………. to the ears. lateral 9. The thumb is ……………………… to the hand. deep 10. Bones are ……………………..to the skin. 11.The spleen is……………….. superior to the kidneys inferior 12.The kidneys are ……………. to the adrenal glands. 13.The stomach is inferior ……………..to the heart. inferior 14.The diaphragm is…………… to the lungs inferior 15. The uterus is…………………to the intestines posterior 16.The spinal cord is…………………….. to the vertebral column. distal 17. The thumb is ………………..to the elbow. 18.The humerus is …………………l superior to the ulna. lateral 19. The lungs are ……………… to the heart. inferior 20.The bladder is………………….. to the small intestine. CHAPTER 2 HOMEOSTASIS & CELLULAR FLUIDS 2.1. Homeostasis 2.2. Body Fluid Compartments Human Anatomy and Physiology I HUAP 210 Objectives After this chapter, you will be able to: 1. Define homeostasis and explain its importance to normal human functioning. 2. Predict the physiological variables regulated by homeostasis. 3. Differentiate between negative and positive feedback regulation. 4. Report the composition of fluids inside and outside the body cells. 5. Describe the major fluid compartments of the body, their percentage distribution, and the permeabilities of the barriers that separate them. 6. Calculate the volume of the different bodily fluids in people with different ages and body weights. Human Anatomy and Physiology I HUAP 210 Homeostasis Section 2.1 Homeostasis Homeostasis refers to the dynamic state of equilibrium "balance", in which internal conditions "physiological variables" stay within relatively narrow limits. Homeo- "the same" -stasis "to stay" Physiological variables: the factors "events" including: body temperature, pH, pressure, volume, concentration of nutrients. Human Anatomy and Physiology I HUAP 210 Homeostasis Regulation Homeostasis - Regulated by two body systems: Nervous system Endocrine system Three components for homeostatic systems: Receptor Control center Effector Homeostatic regulation systems: - Negative feedback system - Positive feedback system Human Anatomy and Physiology I HUAP 210 Components of homeostatic regulation system Receptor (sensor) : detects changes in either the internal or external environment, or stimulus. Control center (integrator): receives and process the information supplies by the receptor and sends out commands. Effector : responds to the commands by opposing or amplifying the stimulus. Human Anatomy and Physiology I HUAP 210 Homeostatic Systems Negative feedback mechanisms - Essential for maintaining homeostasis. Positive feedback mechanisms – Amplify and reinforce a change brought on by the stimulus; not typically used for homeostasis. Human Anatomy and Physiology I HUAP 210 Negative Feedback System Negative feedback mechanism-The response reverses "opposes" the original stimulus. Shuts off or reduces the original stimulus. Helps to stabilize situation; essential for maintaining homeostasis. Examples: body temperature, heart rate, breathing rate and depth, and blood-glucose levels. Human Anatomy and Physiology I HUAP 210 Negative Feedback System Human Anatomy and Physiology I HUAP 210 Human Anatomy and Physiology I HUAP 210 Human Anatomy and Physiology I HUAP 210 Human Anatomy and Physiology I HUAP 210 Case Scenario Mohammed was standing outside, his body temperature increased. His brain send signals to the sweat glands to produce sweat and as a result his body temperature drop to normal level. - Draw a flow chart of the regulation system used in the scenario? - What was the physiological variable was regulated by homeostasis? Human Anatomy and Physiology I HUAP 210 Positive Feedback System Positive feedback mechanism-The response amplifies "enhance" the original stimulus. It pushes the organism further out of homeostasis. It is necessary for keeping life “survival”. Examples: Giving birth “deliver a baby”, blood clotting & breastfeeding “lactation”. Human Anatomy and Physiology I HUAP 210 amplify Positive Feedback System Human Anatomy and Physiology I HUAP 210 Giving Birth Human Anatomy and Physiology I HUAP 210 Blood clotting Human Anatomy and Physiology I HUAP 210 Case Scenario During lactation (breastfeeding), signals sent to the brain to stimulate the hypothalamus to secrets Oxytocin hormone that cause the ejection of the milk to the baby’s mouth. As long as the baby is nursing the oxytocin levels increases, and will stop producing once the baby stop nursing. - Draw a flow chart of the regulation system used in the scenario? - What was the physiological variable was regulated by homeostasis? Human Anatomy and Physiology I HUAP 210 What happens if the homeostatic mechanisms get disrupted? Body fluid compartments Section 2.2 Body Fluids The percentages of body water among different ages: The % of body water decreases progressively with age Human Anatomy and Physiology I HUAP 210 Body Fluid Compartments Intracellular Fluid (ICF): The fluid inside the cells. Extra cellular Fluid (ECF): The fluid outside the cells. Interstitial fluid: Fluid around tissues. Plasma: The watery compartment of the blood. Human Anatomy and Physiology I HUAP 210 Body Fluid distibution Human Anatomy and Physiology I HUAP 210 For healthy adult whose weight is 65-Kg, calculate the volume of the following fluid compartments: bes 100 Total body water volume. 40x65 Intercellular fluid volume. - 100 Extracellular fluid volume.> - 20x65 - 100 Plasma. - > 4X65 Interstitial. 45 - Movements of body fluid between compartments ECF always serves as an intermediary between the cells and the extracellular environment. Human Anatomy and Physiology I HUAP 210 Ionic Composition of the body fluid compartments Ionic composition of ICF and ECF are completely different. Because of the selective permeability of cell membrane. The osmolarity of the ICF and ECF is the same as the number of particles/L is the same. Human Anatomy and Physiology I HUAP 210 Barriers Between Different Compartments Almost all the material pass from plasma to interstitial fluid via capillary wall. So the composition of plasma and interstitial fluid is almost the same, except for plasma proteins. Whereas cell membrane is selectively permeable, it allows only selective substances to pass through it, so the composition of interstitial fluid and intracellular fluid is different. Human Anatomy and Physiology I HUAP 210 Barriers Between Different Compartments Human Anatomy and Physiology I HUAP 210 Cell Membrane Human Anatomy and Physiology I HUAP 210 Wrap up Any Questions CHAPTER 3 CELL MEMBRANE PHYSIOLOGY - ACTION POTENTIAL 3.1. Cell Membrane Structure 3.2. Membrane Transport 3.3. Membrane Potential 3.4. Action Potential Human Anatomy and Physiology I HUAP 210 Objectives You will be able to: 1. Describe the structure and function of the cell membrane, including its regulation of materials into and out of the cell 2. Recognize the significant of membrane potential. 3. Describe the function of ion channels and sodium/potassium pump in maintaining membrane potential. 4. Describe the stages of action potential and explain the threshold potential. 5. Identify the characteristics of action potential. 6. Describe the conduction of action potential along nerve fibers. Human Anatomy and Physiology I HUAP 210 Cell Membrane Structure Section 3.1 Cell Membrane Cell membrane of the cell is a semi-permeable phospholipid bilayer containing many different molecular components, including proteins and cholesterol, some with carbohydrate groups attached. Phospholipid Bilayer consists of two adjacent sheets of phospholipids, arranged tail to tail. The polar heads contact the fluids. Human Anatomy and Physiology I HUAP 210 Phospholipid Structure Phospholipid molecule consists of: Polar phosphate “head” - hydrophilic, having an affinity for water; capable of interacting with water molecules. Non-polar lipid “tail” - hydrophobic, lacking affinity for water, and tending to repel water molecules. Human Anatomy and Physiology I HUAP 210 Cell Membrane Functions Isolation of the cytoplasm from the external body fluids Identification Communication - Action Potential Regulation of solute exchange through the membrane Human Anatomy and Physiology I HUAP 210 Membrane Transport Section 3.2 Cell Membrane Transport Passive Transport - It is the movement of solutes down their concentration gradient without energy (ATP). Active Transport – It is the movement of solutes up their concentration gradient requiring energy (ATP). Human Anatomy and Physiology I HUAP 210 Passive Transport Simple diffusion: small, non-polar molecules (O2 and CO2). Facilitated diffusion: big (Glucose) and polar (ions) molecules. Osmosis: water molecules. Human Anatomy and Physiology I HUAP 210 Active Transport Primary Active transport: Sodium/Potassium Pump. Secondary Active Transport (Coupled): Glucose active transport. Bulk Transport: Phagocytosis, Exocytosis and Pinocytosis (Macromolecules). Human Anatomy and Physiology I HUAP 210 CHAPTER 3 CELL MEMBRANE PHYSIOLOGY - ACTION POTENTIAL 3.1. Cell Membrane Structure 3.2. Membrane Transport 3.3. Membrane Potential 3.4. Action Potential Human Anatomy and Physiology I HUAP 210 Objectives You will be able to: 1. Describe the structure and function of the cell membrane, including its regulation of materials into and out of the cell 2. Recognize the significant of membrane potential. 3. Describe the function of ion channels and sodium/potassium pump in maintaining membrane potential. 4. Describe the stages of action potential and explain the threshold potential. 5. Identify the characteristics of action potential. 6. Describe the conduction of action potential along nerve fibers. Human Anatomy and Physiology I HUAP 210 Membrane Potential Section 3.3 Membrane Potential Membrane potential is the difference created by the unequal distribution of ions across the membrane, with positively charged ions being more concentrated outside the cell and negatively charged ions being more concentrated inside the cell. All plasma membranes have a membrane potential. Membrane potential is measured in mV. Human Anatomy and Physiology I HUAP 210 Differences in the concentration of ionic composition across the membrane Human Anatomy and Physiology I HUAP 210 All plasma membrane have membrane potential but Excitable cells - Nerves and Muscles - have the ability toAll change it and generate electrical signals. Resting Membrane Potential (RMP) Resting membrane potential (RMP)- the constant membrane potential present when the excitable cells is electrically at rest (not producing electrical signals “Action Potential”). RMP for neuron cell = - 70 mV. Human Anatomy and Physiology I HUAP 210 Neuron Cell Neuron cell is the functional unit of the nervous system. consist of: Soma: Cell body. Dendrites: Carry nerve impulses from surrounding cells to the soma. Axon Hillock: The neural action potential is created here. Axon: conduct impulses from soma to the axon terminal. Axon Terminal: Pass the impulses to another cell. Human Anatomy and Physiology I HUAP 210 Action Potential Section 3.4 Action Potential An action potential in neurons, the rapid rise in membrane potential, depolarization, is an all-or-nothing event that is initiated by the opening of sodium ion channels within the plasma membrane. The subsequent return to resting potential, repolarization, is mediated by the opening of potassium ion channels. up - depolarization the by is Nat channels opening of 5- repolarization up is by the Opening of k channels + Ionic movement is triggered by an electrical, chemical, thermal or mechanical stimulus. The stimulus causes the opening of the gates of ion channels leading to the ionic movement. Human Anatomy and Physiology I HUAP 210 Action Potential Depolarization : The membrane becomes less polarized that is inside becomes less negative or more positive compared to RMP. Repolarization: The membrane returns to the RMP. 70mv Hyperpolarization: The membrane potential becomes more polarized: The inside becomes more negative than RMP. Human Anatomy and Physiology I HUAP 210 Ionic Channels The role of Sodium and Potassium gates (channels) during action potential Human Anatomy and Physiology I HUAP 210 Ionic Channels The role of Sodium and Potassium gates (channels) during action potential Human Anatomy and Physiology I HUAP 210 Generation and Propagation of Action Potentials (All-or- Nothing Rule) For an action potential to fire (be generated), the stimulus has to be strong enough bring the membrane potential to the threshold potential (about -55 mV) and move towards the 0 (depolarization) Human Anatomy and Physiology I HUAP 210 Threshold Potential The threshold potential is the critical level to which a membrane potential must be depolarized to initiate an action potential At threshold potential explosive depolarization takes place because of opening large number of voltage gated ion (sodium) channels. Human Anatomy and Physiology I HUAP 210 1. At rest (RMP = -70 mV) At resting potential all Na+ and K+ voltage- gated channels are closed Human Anatomy and Physiology I HUAP 210 2. Threshold potential (-55mV) A triggering event depolarizes the membrane toward threshold potential Opens some voltage- gated channels Human Anatomy and Physiology I HUAP 210 3. Action Potential - Depolarization (-55 _ +30 mV) All voltage-gated Sodium channels open Explosive Na+ influx (moving inside the cells) Depolarization Human Anatomy and Physiology I HUAP 210 4. Action Potential - Peak of Action Potential (+30 mV) Na+ influx continues moving the membrane towards Na+ equilibrium potential At the peak of action potential, Na+ inactivation gates close and K+ voltage- gated channels open. Entry of Na+ stop K+ starts to leave the cell Human Anatomy and Physiology I HUAP 210 5. Action Potential - Repolarization (+30 _ -70 mV) Outward movement of K+ makes the inside of the cell progressively less positive and the outside less negative Repolarization Human Anatomy and Physiology I HUAP 210 6. Hyperpolarization (-70 _ -90 mV) Continuous outward movement of K+ (K+ efflux) restores the resting membrane potential Further outward movement of K+ through the still-open K+ voltage-gated channels transiently hyperpolarize the membrane Human Anatomy and Physiology I HUAP 210 Sodium/Potassium Pump The Na+/K+ pump is a major contributor to the resting state or equilibrium of the cell. It is responsible for maintaining the large excess of Na+ outside the cell and the large excess of K+ ions on the inside. It is an active transport process which makes use of the ATP energy currency of the cell. Human Anatomy and Physiology I HUAP 210 Action Potential Transmission The original action potential does not travel along the membrane. Instead it triggers an identical new action potential in the nearby area of the membrane. Human Anatomy and Physiology I HUAP 210 Frequency of Action Potential A stronger stimulus does not produce a larger action potential since almost all the sodium channels are opened when threshold is reached, but it does trigger greater number of action potentials/ sec. (frequency). Strength of a stimulus is coded by the frequency of action potentials. Human Anatomy and Physiology I HUAP 210 Wrap up and Questions CHAPTER 5 ANATOMY & PHYSIOLOGY OF THE MUSCULOSKELETAL SYSTEM Neuromuscular Junctions (NMJs) Human Anatomy and Physiology I HUAP 210 Objectives Describe the sequence of events at the NMJ Distinguish between actin and myosin in their function and structure Explain the muscle contraction cycle Explain the process of excitation-contraction coupling and relaxation Predict the consequences of the deficiency in any step of the excitation-contraction coupling and relaxation process. Interpret the effect of different bodily activities on muscle action, structure, and condition. Interpret some muscular disorders Human Anatomy and Physiology I HUAP 210 Neuromuscular Junctions NMJ It is a an area (called synapse) formed between a motor neuron and a muscle fiber. The activity in this area causes muscle contraction and thus is necessary for movement. Human Anatomy and Physiology I HUAP 210 Motor Neuron A motor neuron is the neuron whose axon controls effector organs, mainly skeletal muscles leading to movement. Human Anatomy and Physiology I HUAP 210 Components of the Neuromuscular Junction Neuron membrane Sarcolemma: is the muscle membrane Synaptic cleft: a gap between the neuron membrane and the muscle membrane at where the chemical signal can cross Ach (Acetylcholine): a neurotransmitter Neurotransmitter is a type of chemical messenger which transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron (nerve cell) to another "target" neuron, muscle cell, or gland cell. Neuron and muscle membranes do not touch Human Anatomy and Physiology I HUAP 210 Sequence of events at NMJ Human Anatomy and Physiology I HUAP 210 Sequence of events at NMJ How does the production of Where is AchE enzyme muscle action potentials present? terminate or stop? On muscle cell membrane at motor end Any remaining Ach in the synaptic cleft is plate (MEP) or (NMJ) degraded (broken down) by an enzyme called Acetylcholinesterase AchE causing the action potentials to stop and excitation of the muscle cells to end. Human Anatomy and Physiology I HUAP 210 The Role of Actin & Myosin in Muscle Contraction Actin and myosin are called contractile muscle proteins. During contraction there is an overlapping of actin and myosin filaments over each other but the actual length of actin and myosin remains same. Human Anatomy and Physiology I HUAP 210 The Role of Actin & Myosin in Muscle Contraction Human Anatomy and Physiology I HUAP 210 Muscle Contraction Cycle Human Anatomy and Physiology I HUAP 210 Excitation Contraction Coupling This is the process by which an action potential of a muscle fiber initiates muscle contraction. One single action potential causes one twitch Human Anatomy and Physiology I HUAP 210 Excitation Contraction Coupling and Relaxation (Muscle twitch cycle) Human Anatomy and Physiology I HUAP 210 1.Initiation of Action Potential (latent phase) Human Anatomy and Physiology I HUAP 210 2. Excitation Contraction Coupling Phase Human Anatomy and Physiology I HUAP 210 3.Relaxation Phase Human Anatomy and Physiology I HUAP 210 Types of Muscle Contraction Human Anatomy and Physiology I HUAP 210 Summation & Tetanus Summation: rapid sequence of stimuli leading to muscle twitches fusing into each other Tetanus: very rapid sequence of stimuli preventing relaxation. If tetanus occurs in short period of time it is called spasm. Human Anatomy and Physiology I HUAP 210 Effect of Exercise on Muscles Flexibility exercises: such as stretching, improve the range of motion of muscles. Long sustained aerobic exercises: such as cycling, promote increased oxidative capacity, blood vessel supply, mitochondria>> making the muscle more effective and efficient. Anaerobic (high intensity short burst) exercises: such as sprinting, promote increased glycolytic activity and synthesis of myofibrils >> make the muscle bigger in size. Human Anatomy and Physiology I HUAP 210 Muscle Fatigue It is a decline in the ability of a muscle to sustain contraction due to: Decreased energy supply (glucose, glycogen, fatty acids) Decreased oxygen supply Build-up of lactic acid Decreased neurotransmitters at the synapse Psychological causes Human Anatomy and Physiology I HUAP 210 Clinical Correlations Myalgia Myalgia is muscular pain: Fibromyalgia: mysterious chronic pain syndrome (affects mostly women) Polymyalgia: muscle inflammation Human Anatomy and Physiology I HUAP 210 Muscle Dystrophy (MD) Group of genetic diseases characterized by muscle weakness and loss of the skeletal muscle tissue (muscle dystrophy). The affected muscles enlarge with fat and connective tissue. Human Anatomy and Physiology I HUAP 210 Muscle Paralysis It is the loss of muscle function. Neuromuscular junctions are exposed to several chemical agents that could cause any of the following and lead to muscle paralysis: agents that cause excessive release of Ach from storage vesicles leading to prolonged depolarization agents that block the release of Ach preventing muscle depolarization agents that block Ach receptors leading to decreased stimulation of the MEP thus decreased depolarization Human Anatomy and Physiology I HUAP 210 Myasthenia Graves An autoimmune disease that occurs primarily in women where antibodies bind to ACh receptors in NMJs and receptors are removed from muscle fiber by endocytosis, resulting in decreased muscle stimulation Symptoms include: Rapid fatigue and muscle weakness Eyes and facial muscles are often involved first (lazy eye) Swollen muscles and limb weakness Human Anatomy and Physiology I HUAP 210 Botulism It is a muscular paralysis caused by toxin from Clostridium Botulism It prevents the release of Ach at the synapse. A vaccine of this toxin can sometimes be carefully used for cosmetic purposes (diminishing wrinkles). Human Anatomy and Physiology I HUAP 210 Rigor Mortis After death by 2 - 6 hours, There is no enough ATP to unbind the actin myosin bridge and calcium can no longer be kept out of the cell cytosol causing continuous muscle contraction. Depending on temperature and other conditions Rigor Mortis lasts for approximately 72 hours. Human Anatomy and Physiology I HUAP 210

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