Human Physiology for Pathologists' Assistants PDF

Human Physiology for Pathologists’ Assistants Muscle Tissue and Organization  Muscles and Coordination 5 Morceaux de Fantasie, Op. 3, No. 1, Elegie in E-Flat Minor, Sergei Rachmaninov performed by Andrei Gavrilov  Chapter Outline Properties of Muscle...

Human Physiology for Pathologists’ Assistants Muscle Tissue and Organization  Muscles and Coordination 5 Morceaux de Fantasie, Op. 3, No. 1, Elegie in E-Flat Minor, Sergei Rachmaninov performed by Andrei Gavrilov  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle  Introduction to the Muscular System 700+ muscles in the human body have been named Muscle tissue is distributed almost everywhere in the body Muscle tissue is responsible for movement: – Movement of the body (skeletal muscle) – Movement through the GI tract (smooth muscle) – Movement of blood (cardiac muscle) Muscles do not “flex”, muscles “contract” – Flexion is a specific movement  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle Properties of Muscle Tissue  Properties of Muscle Tissue Learning Objective: 1. List and explain the four unique properties of muscle tissue.  Properties of Muscle Tissue Excitability Contractility Elasticity Extensibility  Excitability “Responsiveness” – Muscle cells are very responsive to input from stimuli – A stimulus (an electrical charge) initiates an electrical change that sweeps across the entire plasma membrane of a muscle cell – The electrical change sparks the events that lead to muscle contraction  Contractility – Electrical change within muscle cells generates tension with the cell, “contraction” – A shortening of the fibers pulls on bones of the skeleton or causes a movement of a specific body part  Elasticity “The ability to return to its original length”: – Not the ability to stretch – A contracted muscle cell recoils to its resting length when the tension is removed  Extensability The capability of extending in length: – In response to the contraction of opposing muscle cells Example: when the biceps brachii muscle contract (shorten) the triceps brachii muscles lengthen  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle Characteristics of Skeletal Muscle Tissue  Characteristics of Skeletal Muscle Tissue Learning Objectives: 1. Identify the many roles (functions) of skeletal muscle in the body. 2. Describe the levels of organization in a skeletal muscle. 3. Explain how muscles are attached to other body structures. 4. Detail the components of muscle fibers.  Characteristics of Skeletal Muscle Tissue Each skeletal muscle is an organ composed of the 4 tissue types (epithelial, connective, muscle, neural) A single muscle fiber can be as long as the muscle itself Sizes of fibers vary: – A small skeletal muscle fiber in the toe may have a length of about 100 microns (μm) and a diameter of about 10 μm – Biceps brachii may have a muscle fiber that is about 35 cm in length and 100 μm in diameter (about the thickness of a hair) Functions of Skeletal Muscle Tissue Body Movement Maintenance of posture Temperature regulation Storage and movement of materials Support  Temperature Regulation Energy (ATP) is required for muscle tissue contraction – Heat is always produced as a waste product of energy usage Heat generated from muscle contraction maintains our normal body temperature When you exercise, you feel warmer When you are cold, your muscles cyclically contract in an attempt to warm your body Gross Anatomy of Skeletal Muscle  Gross Anatomy of Skeletal Muscle Each skeletal muscle is composed of “fascicles” (fascis = bundle) – A fascicle is a bundle of muscle fibers Muscle fibers contain cylindrical structures called myofibrils Myofibrils are composed of myofilaments  Connective Tissue Components of Skeletal Muscle There are 3 concentric layers of CT (composed of collagen and elastin) that encircle each muscle: – Individual muscle fiber - endomysium – Groups of muscle fibers - perimysium – The entire muscle itself - epimysium Provide protection, a means of attachment, and are sites for blood vessel and nerve distribution  Endomysium endon = within, mys = muscle The innermost CT layer of skeletal muscle A primarily areolar CT layer that surrounds and electrically insulates each muscle fiber Reticular fibers help keep capillary beds and other fibers in place  Perimysium peri = around Surrounds each fascicle Comprised of dense irregular CT Support the “neurovascular bundles” that branch to supply/innervate each individual fascicle  Epimysium epi = upon A layer of dense irregular CT that surrounds the whole skeletal muscle  “The Fascia” Deep Fascia – “visceral” or “muscular” fascia – Includes the “endomysium, perimysium, epimysium” – Separates individual muscles – Binds muscles with similar functions together – Fills space between muscles (fascia = band or filler) Superficial Fascia – Is deep to the dermis, “subcutaneous layer” – Composed of areolar and adipose CT – Separates the muscle from the skin  Muscle Attachments At the ends of a muscle, the CT layers (the deep fascia) merge to form a “tendon” Tendons attach muscle to bone, skin, or another muscle Most commonly, tendons form a thick, cord like structure Sometimes, a tendon may form a thin, flattened sheet, “aponeurosis” Aponeuroses  Muscle Attachments Most skeletal muscles cross a mobile joint Upon muscle contraction, one of the bones remain fixed, while the other moves: – The less mobile attachment of a muscle is called the, “origin” In the limbs, is typically more proximal – The more mobile attachment of a muscle is called the, “insertion” Further classifications found in the book  Blood Vessels and Nerves There is an extensive network of blood vessels and nerve fibers found within the epi- and perimysium Skeletal muscles are classified as “voluntary” muscles because they are controlled by the “somatic nervous system” (the part of our nervous system that allows us to “voluntarily” move): – The neurons that stimulate muscle contraction are called, “motor neurons” – Each motor neuron has a long extension called an “axon” or “nerve fiber” Travels through the epimysium and perimysium – An axon of a motor neuron “penetrates” the endomysium and transmits a nerve impulse (action potential) to a muscle fiber – The junction between the axon and the muscle fiber is called a “neuromuscular junction” Identify: – Endomysium – Perimysium – Capillary – Arteriole Microscopic Anatomy of Skeletal Muscle  Microscopic Anatomy of Skeletal Muscle Skeletal muscle cells have many of the same components as the typical cell, however many of them are named differently: – Sarcolemma = the plasma membrane – Sarcoplasm = the cytoplasm Two cellular structures that are unique to muscle fibers: – Transverse tubules – Sarcoplasmic reticulum  Transverse Tubules “T-tubules” – Invaginations of the sarcolemma (plasma membrane)that extend into the sarcoplasm – Form a network of membranous tubules around the myofibrils When a nerve sends an electrical signal to the muscle fiber, the signal travels rapidly along the sarcolemma and enters the T-tubule network  Sarcoplasmic Reticulum rete = a net Is similar to an endoplasmic reticulum Stores calcium ions (Ca2+) – Action potentials stimulate the release of Ca2+ which initiates the muscle contraction Located parallel and perpendicular to the muscle fiber – Perpendicular tubes are “blind sacs” called “terminal cisternae” Two are located on either side of each T-tubule forming a “triad” – Parallel tubes form a network around the myofibrils  Satellite Cells Skeletal muscle fibers are multinucleated: – During development, groups of embryonic cells (myoblasts) fuse to form single skeletal muscle fibers: As the myoblasts fuse, the nuclei remain; the nucleus of each myoblast contributes to the eventual total number of nuclei per muscle fiber Some myoblasts do not fuse with other cells – Remain in adult skeletal muscle as “satellite cells” – Can be stimulated to differentiate and assist in repair and regeneration  Myofibrils and Myofilaments The sarcoplasm of a skeletal muscle fiber contains hundreds to thousands of long, cylindrical structures termed “myofibrils”: – Each myofibril is 1-2 μm in diameter and extends the entire length of the muscle fiber – During muscle contraction, myofibrils shorten in length as their component proteins change position As the myofibrils shorten, the muscle fibers shorten – Myofibrils consist of bundles of short myofilaments (filum = thread) Many successive groupings of myofilaments span the length of a myofibril The Cellular Level: Sarcolemma = plasma membrane  Myofilaments Thick and Thin Myofilaments: – “Thick filaments” About 11 nanometers in diameter Assembled from bundles of the protein myosin – Each strand has a free globular head and an elongated tail; the tails of two proteins are intertwined Myosin heads form “crossbridges” where they bind with thin filaments – “Thin filaments” 5-6 nanometers in diameter Composed of two helical strands of the protein actin Two regulatory proteins are apart of the thin filament – Troponin – Tropomyosin  Organization of a Sarcomere The functional contractile unit of a skeletal muscle fiber is the sarcomere: – Defined as the distance from one “Z disc” to the next “Z disc” Myofibrils contain multiple sarcomeres lined up end to end and give skeletal (and cardiac) muscle its striated appearance Electron Microscopy  Contraction of Skeletal Muscle Fibers Learning Objectives: 1. Describe the structure of a neuromuscular junction. 2. Explain the process of skeletal muscle contraction. 3. Detail the structure and function of a motor unit. 4. Compare isometric and isotonic contractions.  The Sliding Filament Theory When a muscle contracts, thick and thin filaments slide past each other and the sarcomere shortens The thick and thin filaments maintain their same length whether the muscle is relaxed or contracted – The relative positions between thick and thin filaments changes  Neuromuscular Junctions Motor neuron activity stimulates skeletal muscle contraction Each muscle fiber is controlled by one motor neuron The point where a motor neuron meets a skeletal muscle fiber is called the neuromuscular junction  Components of the Neuromuscular Junction The synaptic knob Synaptic vesicles The motor end plate Synaptic cleft Acetylcholine receptors Acetocholinestarase  The Synaptic Knob The nerve impulse travels down the axon and enters the synaptic knob The synaptic knob is the expanded tip of an axon Covers a relatively large surface area of the sarcolemma  Synaptic Vesicles The cytoplasm of the synaptic knob houses many synaptic vesicles The synaptic vesicles are filled with the neurotransmitter acetylcholine (ACh)  The Motor End Plate A specialized region of the sarcolemma (plasma membrane) with an abundance of folds and indentations – Increases surface area The motor end plate is covered by the synaptic knob The Synaptic Cleft The narrow space separating the synaptic knob and the motor end plate  ACh Receptors Are located in the motor end plate (the specialized region of the sarcolemma) ACh from the synaptic vesicles is released into the synaptic cleft where it binds to ACh receptors  Acetylcholinesterase (AChE) An enzyme which resides in the synaptic cleft Rapidly breaks down molecules of ACh Prevents the continuous stimulation (contraction) of ACh receptors by Ach Review Hirschsprung Disease  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Physiology of Skeletal Muscle Contraction Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle The Physiology of Skeletal Muscle Contraction  Muscle Contraction: A Summary The events of muscle contraction have been called, “excitation-contraction coupling” – The stimulation of a muscle fiber by a nerve impulse results in a series of events that culminates in muscle fiber contraction  Muscle Contraction: A Summary 1. A nerve impulse causes ACh release at a neuromuscular junction. ACh binds receptors on the motor end plate, initiating a muscle impulse. 2. The muscle impulse spreads quickly along the sarcolemma and into the muscle fiber along T-tubule membranes, causing calcium ions to be released into the sarcoplasm. 1. Calcium ions bind to troponin, causing tropomyosin to move and expose active sites on actin. Myosin heads attach to the actin and form crossbridges. 1. Myosin heads go through cyclic “attach–pivot–detach–return” events as the thin filaments are pulled past the thick filaments. ATP is required to detach the myosin heads and complete the sequence of cyclic events. The sarcomere shortens, and the muscle contracts. The cyclic events continue as long as calcium ions remain bound to the troponin. 1. Calcium ions are moved back into the sarcoplasmic reticulum by ATP-driven ion pumps to reduce calcium concentration in the sarcoplasm, leading to relaxation. Termination of the muscle impulse results in the passive sliding of myofilaments back to their original state. Myosin and Actin Crossbridge Formation  Rigor Mortis What would be the result of decreased ATP in the setting of muscle contraction?  Rigor Mortis What would be the result of decreased ATP in the setting of muscle contraction? The myosin would not have the ability to release from the actin filaments…the muscle would not have the ability to “relax”  Rigor Mortis Rigor mortis refers to the “stiffening” of the body observed after death due to postmortem muscle contraction: – This is due to the depletion of adenosine triphosphate (ATP) with resultant development of a stable complex of actin and mysoin thus preventing the muscle fibers from relaxing – Typically begins to develop within 2 hours after death – Appears first in the muscles of the jaw, followed by the face and upper and lower extremities; disappearance occurs in the same order  Rigor Mortis – It usually takes 6-12 hours to develop full rigor mortis – Violent exercise, which depletes ATP, and high body temperatures accelerate the development of rigor – Rigor mortis is lost due to decomposition – In temperate climates, rigor persists 36-48 hours. It may disappear in less than 24 hours in hot weather and persist for several days in cold weather – Instantaneous rigor mortis (cadaveric spasm), i.e. occurring at the moment of death. Is very rare and may be secondary to very high body temperature or violent exertion Reference: Handbook of Forensic Pathology, Dimaio  Motor Units The motor unit is composed of a single motor neuron and all of the muscle fibers it controls: – A motor unit typically controls only some of the muscle fibers in an entire muscle – Most muscles have many motor units; many motor neurons are needed to innervate an entire muscle  Motor Units An inverse relationship exists between the size of the motor unit and the degree of control provided: – The smaller the motor unit the finer the control The motor units of the eye may only innervate 2-3 muscle fibers – The power-generating muscles in our lower limbs may have a single motor unit innervate thousands of muscle fibers  Motor Units Each muscle fiber obeys the “all-or-none principle”: – A muscle fiber contracts completely or does not contract at all – When a motor unit is stimulated, all its fibers contract at the same time – The total force generated by a muscle is entirely dependent upon the total number of motor units activated If greater force is required for a task, more motor units are recruited If a movement requires less force, fewer motor units are activated Stimulation of which motor unit would result in greater force of contraction? Why? Stimulation of which motor unit would result in greater force of contraction? Why? Stimulation of the red motor neuron will result in contraction of all 4 of the muscle fibers it innervates.  Muscle Tone Muscle tone is the resting tension in a skeletal muscle: Motor units are randomly stimulated to maintain constant tension on tendons Tension is produced, but not enough to move the joint Stabilizes the position of bones and joints There are two types of muscle contraction: Isometric contraction Isotonic contraction  Isometric Contraction iso = same, metron = measure The length of the muscle does not change The tension produced by contraction is not enough to exceed the resistance: – A person tries to pick up something that they cant move; tension is generated, but it is not great enough to move the load  Isotonic Contraction iso = same, tonos = tension The tension produced from contraction is equal to or greater than the resistance – The muscle fiber length changes, resulting in movement Two types: – Concentric contractions – Eccentric contractions  Isotonic Contractions Concentric Contractions Contraction actively shortens a muscle The load is less than the maximum tension that can be generated by the muscles Biceps brachii during “flexion” Eccentric Contractions: Contraction with a lengthening of the muscle Biceps brachii during “extension”  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle Types of Skeletal Muscle Fibers  Types of Skeletal Muscle Fibers Learning Objectives: 1. Identify the characteristics of the three types of skeletal muscle fibers. 2. Explain the types of movement facilitated by slow oxidative, fast oxidative, and fast glycolytic muscle fibers.  Types of Skeletal Muscle There are 3 types of skeletal muscle fibers: – Slow oxidative (type I) – Fast oxidative (type IIa) – Fast glycolytic (type IIb) Each skeletal muscle typically contains a percentage of each of these muscle fiber types  The Set Up… FAST VERSUS SLOW FIBERS Fast fibers have higher myosin ATPase (ATP-splitting) activity than slow fibers do. The higher the ATPase activity, the more rapidly ATP is split and the faster the rate at which energy is made available for cross-bridge cycling. The result is a fast twitch, compared to the slower twitches of those fibers that split ATP more slowly. Myoglobin – an oxygen binding pigment found in skeletal muscle fibers – Stores oxygen received from capillary beds Mitochondria – produce large quantities of ATP via oxidative phosphorylation Aerobic Cellular Respiration Anaerobic Cellular Respiration  Slow Oxidative (SO) Fibers “Type I” – Typically have half the diameter of of other skeletal muscle fibers – Contain slow ATPase – Produce contractions that are slower to respond and less powerful – Can remain contracted over long periods of time without fatigue – ATP is primarily supplied through aerobic cellular respiration (mitochondria and oxidative phosphorylation) – Extensive vascular supply – Fibers appear dark red because of the presence of large amounts of myoglobin (oxygen binding protein found in muscle) “Dark meat”  Fast Oxidative (FO) Fibers “Type IIa” or “intermediate fibers” – The least numerous of skeletal muscle fibers – Are intermediate in size and contain fast ATPase – Produce fast, powerful contractions – ATP is provided primarily through aerobic respiration – The vascular network is not as extensive as SO fibers Delivery rate of nutrients and oxygen is lower – Fibers contain less myoglobin (and less color) than SO fibers  Fast Glycolitic (FG) Fibers “Type IIb” or “fast anaerobic fibers” – The most prevalent skeletal muscle fiber type – The largest in diameter – Contains fast ATPase – Provide power and speed – Contraction occurs only in short bursts – ATP is provided through anaerobic cellular respiration – Fibers appear white due to the lack of myoglobin  Relationships How does the rate of ATPase effect the use of ATP? Why does the mechanism of ATP production correlate with the concentration of capillaries? How does the rate of ATPase correlate with contraction velocity? How does the availability of ATP correlate with the resistance to fatigue? Why are there fewer mitochondria in FG fibers? Explain why myoglobin would be more effective in SO versus FG.  Distribution of SO, FO, and FG Fibers The ratios of different fiber types varies between different skeletal muscles – Within a single motor unit, all fibers belong to the same type – Some muscles have no SO fibers, and some have not FG fibers SO fibers dominate the back and calf muscles There are no SO fibers in the muscles of the eye and hand  Distribution of SO, FO, and FG Fibers The ratio of fibers is determined by a persons genetics – Determine an individual endurance capabilities Individuals with relatively high quantities of SO fibers in their legs can outperform long distance runners who have increased numbers of FG fibers in their legs Individuals with increased numbers of FG fibers have the potential to excel at sprinting or weight lifting  Distribution of SO, FO, and FG Fibers The proportion of FO fibers changes with physical conditioning – They can develop characteristics and mimic the functionality of SO or FG Physical conditioning enables the athlete to improve both strength and endurance  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle Skeletal Muscle Fiber Organization Learning Objective 1. Describe the 4 organizational patterns in fascicles.  Skeletal Muscle Fiber Organization Bundles of muscles fibers (fascicles) lie “parallel” to each other within each muscle The organization (and orientation) is fascicles in different muscles often varies 4 patterns of fascicle arrangement: Circular Parallel Convergent Pennate  Circular Muscles “Sphincter” Muscle fibers are concentrically arranged around an opening or recess Contraction closes off the opening, or decreases the diameter of it – E.g. cilliary body within the eye; change in shape of lens and pupil Are located at entrances and exits of internal passageways – E.g. orbicularis oris encircles the opening of the mouth  Parallel Muscles The fascicles run parallel to its long axis Have a central body called a, “belly” or “gaster” The muscle shortens when it contracts and its body increases in diameter Have high endurance, but are not as strong as other types of muscle Examples: – Rectus abdominis – Biceps brachii – Masseter  Convergent Muscles Widespread muscle fibers that converge on a common attachment site: – The attachment may be a single tendon, a tendinous sheet, or a slender band of collagen fibers (raphe, rhaphe = seam) – The muscle is often triangular in shape – Are versatile; direction of pull can be modified With contraction of all the muscle fibers, the force generated is not as forceful as a similar parallel muscle – The fibers are pulling in different directions Example: pectoralis major  Pennate Muscles penna = feather The tendons and muscle fibers resemble a large feather May have one or more tendons extending through their body The fascicles are arranged at an oblique angle to the tendon – The fibers create tension (pull) at an angle relative to the tendon – The tendon does not move as far as a parallel muscle moves its tendon Pennate muscles can generate more tension than a parallel muscle of the same size  Pennate Muscles 3 Types of Pennate Muscles: – Unipennate muscle All muscle fibers are on the same side of the tendon E.g. extensor digitorum – Bipennate muscle – the most common Muscle fibers on both sides of the tendon E.g. Palmar and dorsal interosseous muscles – Multipennate muscle Has branches of the tendon within a muscle E.g. deltoid  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle  The Naming of Skeletal Muscles Learning Objectives: 1. Explain how muscle names incorporate appearance, location, function, orientation and unusual features  The Naming of Skeletal Muscles Skeletal muscles are named according to the following criteria: – Muscle action – Specific body regions – Muscle attachments – Orientation of muscle fibers – Muscle shape and size – Muscle heads/tendons of origin  Chapter Outline Properties of Muscle Tissue Characteristics of Skeletal Muscle Tissue Contraction of Skeletal Muscle Fibers Types of Skeletal Muscle Fibers Skeletal Muscle Fiber Organization The Naming of Skeletal Muscles Characteristics of Cardiac and Smooth Muscle Characteristics of Cardiac and Smooth Muscle Learning Objectives: 1. Describe the similarities and differences among the types of muscle tissue.  Cardiac Muscle “Cardiac myocytes” Individual muscle cells arranged in thick bundles within the heart wall (myocardium): – Are striated, shorter and thicker – Have only 1-2 nuclei – Form Y-shaped branches – Join other myocytes at an “intercalated disc”  Cardiac Muscle Are autorhythmic: – Individual cells can generate a muscle impulse without nervous stimulation; involuntary – The autonomic nervous system controls the rate of or contraction – Is responsible for the repetitious and rhythmic heartbeat (more in chapter 22)  Cardiac Muscle Cardiac muscle cells are dependent upon calcium ions for contraction: – The sarcoplasmic reticulum is less developed and able to store less calcium – Most of the calcium ions that stimulate contraction are found with in the interstitial fluid Cardiac muscle uses aerobic respiration almost exclusively: – Cardiac myocytes contain an abundance of mitochondria  Smooth Muscle Composed of short muscle cells that have a fusiform/spindle shape: – Have a single, centrally located nucleus – Thick and thin filaments are not precisely aligned; no visible striations or sarcomeres are present Filaments attach to “dense bodies” – Cytoskeletal attachments located throughout the cell, adjacent to the sarcoplasm Calcium used to stimulate contraction is located with the interstitial fluid: – Cytoplasmic levels of calcium regulate contractile activity Smooth muscle contraction is slow and under involuntary control Wall of the digestive tract (stomach) Smooth Muscle Multiple spindle-shaped cells  Diseases of the Neuromuscular Junction Antibody-Mediated Diseases of the Neuromuscular Junction: – Myasthenia Gravis – Lambert-Eaton Myasthenic Syndrome  What is an Antibody? “Antibody is a part of the host cell's defense. It's made by a certain type of white blood cell that's called a (plasma) cell. The structure of the antibody consists of two light chains and two heavy chains, and at the very tip of the antibody is a hypervariable region, and this hypervariable region allows the (plasma cell) to make different types of antibodies that will respond to all of the antigens that will assault the body. An antigen is anything that is foreign to the human body. It can be a virus, it can be a bacteria, and in some cases your own body will appear as foreign (autoantigen). And so you can have in certain instances where your own body will make antibodies (autoantibodies) against parts that are part of you.” Bettie J. Graham, Ph.D.  What is an Antibody? Antibodies: – Proteins made by plasma cells – Are the integral component of the humoral immune response – Bind to antigens: If a protein is perceived as foreign, but is actually “self”, the antibody is called an, “autoantibody” Antigens: – Anything perceived as foreign – Initiates an immune response – If the “antigen” is self, but is being perceived as non -self, the antigen is called an, “autoantigen” Hypersensitivity Reactions: – There are 4 classes of “Hypersensitivity Reactions” – Autoantibodies binding to autoantigens is an, “antibody-mediated (type II) hypersensitivity” reaction – Autoantibodies binding to autoantigens can result in: Destruction of cells and inflammation Interference with normal tissue function  Diseases of the Neuromuscular Junction Antibody-Mediated Diseases of the Neuromuscular Junction: – Myasthenia Gravis – Lambert-Eaton Myasthenic Syndrome …..disfunction at the neuromuscular junction…caused by antibodies  Robbins Reading Be able to compare and contrast the etiology and pathogenesis of: – Myasthenia Gravis – Lambert-Eaton Myasthenic Syndrome