ANATOMY AND PHYSIOLOGY THE UNITY OF FORM AND FUNCTION CHAPTER 11 EXAM, Exams of Advanced Education

Download ANATOMY AND PHYSIOLOGY THE UNITY OF FORM AND FUNCTION CHAPTER 11 EXAM and more Exams Advanced Education in PDF only on Docsity!

ANATOMY AND PHYSIOLOGY THE UNITY OF

FORM AND FUNCTION CHAPTER 11 EXAM

Main purpose of muscle cells - --muscle cells are capable of converting the chemical energy of ATP into mechanical energy Characteristics of muscle - ---responsiveness (excitability) -conductivity -contractility -extensibility -elasticity responsiveness (excitability) - --_______ to chemical signals, stretch and electrical changes across the plasma membrane conductivity - --local electrical change triggers a wave of excitation that travels along the muscle fiber contractility - --shortens when stimulated extensibility - --capable of being stretched between contractions elasticity - --returns to its original resting length after being stretched skeletal muscle - --voluntary, striated muscle attached to one or more bones

striations - --alternating light and dark transverse bands; results from an overlapping of internal contractile proteins voulntary - --usually subject to conscious control muscle cell, muscle fiber (myofiber) - --as long as 30cm endomysium - --connective tissue around muscle cells perimysium - --connective tissue around muscle fasicles epimysium - --connective tissue surrounding entire muscle collagen - --somewhat extensible and elastic; stretches slightly under tension and recoils when released collagen - --resists excessive stretching and protects muscle from injury collagen - --returns muscle to its resting length collagen - --contribute to power output and muscle efficiency sarcolemma - --plasma membrane of a muscle fiber sarcoplasm - --cytoplasm of a muscle fiber

myofibrils - --long protein bundles that occupies the main portion of the sarcoplasm glycogen - --stored in abundance to provide energy with heightened exercise myoglobin - --red pigment- stores oxygen needed for muscle activity multiple nuclei - --flattened nuclei pressed against the inside of the sarcolemma myoblasts - --stem cells that fuse to form each muscle fiber satellite cells - --unspecialized myoblasts remaining between the muscle fiber and endomysium; may multiply and produce new muscle fibers to some degree repair by fibrosis - --______ __ ______ rather than regeneration of functional muscle mitochondria - --packed in spaces between myofibrils sarcoplasmic reticulum (SR) - --smooth ER that forms a network around each myofibril- calcium reservoir terminal cisternae - --dilated end-sacs of SR which cross muscle fiber from one side to the other T tubules - --tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side

triad - --a T tubule and two terminal cisterns thick myofilaments - --made of several myosin molecules thick myofilaments - --shaped like a golf club; two chains intertwined to form a shaft-like tail, double globular head thick myofilaments - --heads directed outward in a helical array around the bundle; heads of the thick filament angle to the left, heads on the other half angle to the right, bare zone with no heads in the middle thin myofilaments - --consist of: fibrous (F) actin, tropomyosin, tropinin fibrous (F) actin - --two intertwined strands; string of globular (G) actin subunits each with an active site that can bind to head of myosin tropomyosin - --molecules; each blocking 6 or 7 active sites on G actin subunits troponin - --molecule- small, calcium-binding protein on each tropomyosin molecule elastic myofilaments - --made of titin (connectin) titin (connectin) - --huge spongy protein; flank each thick filament and anchor it to the Z disc, helps stabilize the thick filaments

titin (connectin) - --center it between the thin filaments, prevents over stretching contractile proteins - --myosin and actin; do the work regulatory proteins - --tropomyosin and troponin; like a switch that determine when the fiber can contract and when it cannot regulatory proteins - --contraction activated by release of calcium into sarcoplasm and its binding to troponin; troponin changes shape and moves tropomyosin off the active sites on actin dystrophin - --most clinically important; links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous endomysium surrounding the entire muscle cell dystrophin - --transfers forces of muscle contraction to connective tissue around muscle cell dystrophin - --genetic defects in _______ produce disabling disease, muscular dystrophy striations - --myosin and actin are proteins that occur in all cells; function in cellular motility, mitosis, transport of intacellular material striations - --organized in a precise way in sketelal and cardiac muscle A band - --dark- ___ stands for anisotropic; part of band where thick and thin filaments overlap is especially dark

H band - --in the middle of A band- just thick filaments M line - --is in the middle of the H band I band - --alternating lighter bad, ___ stands for isotropic; the way the bands reflect polarized light z disc - --provides anchorage for thin filaments and elastic filaments; bisects I band sarcomere - --the segment of the myofibril from one Z disc to the next sarcomere - --functional contractile unit of muscle fiber sarcomere - --cells shorten because their individual sarcomeres shorten; Z disc (Z lines) are pulled closer together as thick and thin filaments slide past each other sarcomere - --neither thick nor thin filaments change length during shortening, only the amount of overlap changes denervation atrophy - --shrinkage of paralyzed muscle when connection of nerve-muscle relationship is not restored somatic motor neurons - --nerve cells whose cell bodies are in the brainstem and spinal cord that serve skeletal muscles

somatic motor fibers - --their axons that lead to the skeletal muscle; each nerve fiber branches out to a number of muscle fibers; each muscle fiber is supplied by only one motor neuron muscle fibers of one motor unit - --dispersed throughout the muscle; contract in unison; produce weak contraction over wide area muscle fibers of one motor unit - --provides ability to sustain long-term contraction as motor units take turns contracting (postural control) small motor units - --fine degree of control; 3-6 muscle fibers per neuron; eye and hand muscles synapse - --point where a nerve fiber meets its target cell neuromuscular junction (NMJ) - --when target cell is a muscle fiber Synaptic nob - --Swollen end of nerve fiber; contains synaptic vesicles filled with acetylcholine (ACh) Synaptic cleft - --Tiny gap between synaptic knob and muscle sarcolemma Schwann cell - --Envelopes & isolates all of the NMJ from surrounding tissue fluid; synaptic vesicles undergo exocytosis releasing ACh into synaptic cleft ACh receptors - --50 million; proteins incorporated into muscle cell plasma membrane

Junctional folds - --Of sarcolemma beneath synaptic knob; increases surface area holding ACh receptors; lack of receptors leads to paralysis in disease myasthenia gravis Basal lamina - --Thin layer of collagen and glycoprotein separates Schwann cell and entire muscle cell from surrounding tissues; contains acetylcholinesterase (AChE) that breaks down ACh after contraction causing relaxation Tetanus (lockjaw) - --A form of spastic paralysis caused by toxin of clostridium tetani; glycine in the spinal cord normally stops motor neurons from producing unwanted muscle contractions Tetanus (lockjaw) - --______ toxin blocks glycine release in the spinal cord and causes overstimulation and spastic paralysis of the muscles botulism - --type of food poisoning caused by a neuromuscular toxin secreted by the bacterium clostridium botulinum botulism - --block the release of ACh causing flaccid paralysis botox cosmetic - --injections for wrinkle removal electrically excitable cells - --muscle fibers and neurons are ________ ______ _____; their plasma membrane exhibits voltage changes in response to stimulation electrophysiology - --the study of the electrical activity unstimulated (resting) cell - --there are more anions (negative ions) on the inside of the plasma membrane than on the outside

unstimulated (resting) cell - --the plasma membrane is electrically polarized (charged) unstimulated (resting) cell - --there are excess sodium ions (Na+) in the extracellular fluid (ECF) unstimulated (resting) cell - --there are excess potassium (K+) in the intracellular fluid (ICF) unstimulated (resting) cell - --also in the ICF, there are anions such as proteins, nucleic acids, and phosphates that cannot penetrate the plasma membrane; these anions make the inside of the plasma membrane negatively charged by comparison to its outer surface voltage (electrical potential) - --a difference in electrical charge from one point to another resting membrane potential - --about -90mV; maintained by sodium-potassium pump stimulated (active) muscle fiber or nerve cell - --ion gates open in the plasma membrane; Na+ instantly diffuses down its concentration gradient into the cell; these cations override the negative charges in the ICF; depolarization; immediately, Na+ gates close and K+ gates open; K+ rushes out of cell; repelled by the positive sodium charge and partly because of its concentration gradient; repolarization depolarization - --in a stimulated (active) muscle fiber or nerve cell; inside of the plasma membrane becomes briefly positive

repolarization - --turns the membrane negative again action potentioal - --quick up-and-down voltage shift from the negative RMP to a positive value, and back to the negative value again RMP - --a stable voltage seen in a waiting muscle or nerve cell stimulated (active) muscle fiber or nerve cell - --an action potential at one point on a plasma membrane causes another one to happen immediately in front of it, which triggers another one a little farther down and so forth major phases of contraction and relaxation - ---excitation -excitation-contraction coupling -contraction -relaxation excitation - --the process in which nerve potentials lead to muscle action potentials excitation-contraction coupling - --events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing then to contract contraction - --step in which the muscle fiber develops tension and may shorten relaxation - --when its work is done, a muscle fiber relaxes and returns to its resting length

excitation (steps 1 and 2) - ---nerve signal opens voltage-gated calcium channels in synaptic knob -calcium stimulates exocytosis of ACh from synaptic vesicles -ACh released into synaptic cleft excitation (steps 3 and 4) - ---two ACh molecules bind to each receptor protein, opening Na+ and K+ channels -Na+ enters shifting RMP goes from -90mV to +75mV, then K+ exits and RMP returns to -90mV- quick voltage shift is called an end-plate potential (EPP) excitation (setep 5) - --voltage change (EPP) in end-plate region opens nearby voltage-gated channels producing an action potential that spreads over muscle surface excitation-contraction coupling (steps 6 and 7) - ---action potential spreads down into T tubules -opens voltage-gated ion channels in T tubules and Ca+2 channels in SR -Ca+2 enters the cytosol excitation-contraction coupling (steps 8 and 9) - ---calcium binds to troponin in thin filaments -troponin-tropomyosin complex changes shape and exposes active sites on actin contraction (steps 10 and 11) - ---activates the head "cocking" it in an extended position -- ADP + Pi remainattached -head binds to actin active site forming a myosin-actin cross-bridge

contraction (steps 12 and 13) - ---myosin head releases ADP and Pi, flexes pulling thin filament past thick- power stroke -upon binding more ATP, myosin releases actin and process is repeated --each head performs 5 power strokes per second --each stroke utilizes one molecule of ATP relaxation (steps 14 and 15) - ---nerve stimulation & ACh release stop -AChE breaks down ACh & fragments reabsorbed into synaptic knob -stimulation by ACh stops relaxation (step 16) - ---Ca+2 pumped back into SR by active transport. Ca+ binds to calsequestin while in storage in SR -ATP is needed for muscle relaxation as was as muscle contraction rigor mortis - --hardening of muscles and stiffening of body beginning 3 to 4 hours after death rigor mortis - ---deteriorating sarcoplasmic reticulum releases Ca+ -deteriorating sarcolemma allows Ca+2 to enter cytosol -Ca+2 activates myosin-actin cross-bridging -muscle contracts, but cannot relax rigor mortis - --muscle relaxation requires ATP, and ATP production is no longer produced after death

• fibers remain contracted until myofilaments begins to decay

rigor mortis - --____ ____ peaks about 12 hours after death, then diminishes over the next 48 to 60 hours length-tension relationship - --if overly contracted at rest, a weak contraction results -thick filaments too close to Z discs and can't slide length-tension relationship - --if too stretched before stimulated, a weak contraction results -little overlap of thin and thick does not allow for very many cross bridges to form optimum resting length - --produces greatest force when muscle contracts

• muscle tone- central nervous system continually monitors and adjusts the length of the resting muscle, and maintains a state of partial contraction threshold - --the minimum voltage necessary to generate an action potential in the muscle fiber and produce a contraction twitch - --a quick cycle of contraction when stimulus is at threshold or higher phases of a twitch contraction - ---latent period -contraction phase -relaxation phase latent period - --2 msec delay between the onset of stimulus and onset of twitch response
• time required for excitation, excitation-contraction coupling and tensing of elastic components of the muscle

internal tension - --force generated during latent period and no shortening of the muscle occurs contraction phase - --phase in which filaments slide and the muscle shortens

• once elastic components are taut, muscle begins to produce external tension- in muscle that moves a load; short-lived phase relaxation phase - --SR quickly reabsorbs Ca+2, myosin releases the thin filaments and tension declines -muscle returns to resting length -entire twitch lasts from 7 to 100 msec stimulus frequency - --stimuli arriving closer together produce stronger twitches twitches in vary in strength depending on: - ---stimulus frequency -concentration of Ca+ -how stretched muscle was before it was stimulated -temperature of the muscles -lower than normal pH of sarcoplasm weakens the contraction; fatigue -state of hydration of muscle affects overlap of thick and thin filaments recruitment of multiple motor unit (MMU) summation - --the process of bringing more motor units into play

twitch strength & stimulus frequency - --10-20 stimuli per second produces treppe (staircase) phenomenon; Ca+2 concentration in the cytosol rises higher and higher with each stimulus causing subsequent twitches to be stronger incomplete tetanus - --20-40 stimuli per second; each new stimulus arrives before the previous twitch is over; new twitch "rides piggy-back" on the previous one generating higher tension; temporal summation; wave summation temporal summation - --results from two stimuli arriving close together wave summation - --results from one wave of contraction added to another incomplete tetanus - --each twitch reaches a higher level of tension than the one before; muscle relaxes only partially between stimuli incomplete tetanus - --produces a state of sustained fluttering contraction complete tetanus - --40-50 stimuli per second; muscle has no time to relax between stimuli complete tetanus - --twitches fuse to a smooth, prolonged contraction; produces about four times the tension as a single twitch complete tetanus - --rarely occurs in the body, which rarely exceeds 25 stimuli per second complete tetanus - --smoothness of muscle contractions is because motor units function asynchronously; when one motor unit relaxes, another contracts and takes over so the muscle does not lose tension

isometric muscle contraction - --muscle is producing internal tension while an external resistance causes it to stay the same length or become longer isometric muscle contraction - --can be a prelude to movement when tension is absorbed by elastic component of muscle isometric muscle contraction - --important in postural muscle function and antagonistic muscle joint stabilization isotonic muscle contraction - --muscles change in length with no change in tension; concentric contraction; eccentric contraction concentric contraction - --muscle shortens while it maintains tension eccentric contraction - --muscle lengthens as it maintains tension muscle metabolism - --all muscle contraction depends on ATP ATP supply depends on: - --oxygen and organic energy sources such as glucose and fatty acids main pathways of ATP synthesis - --anaerobic fermentation, aerobic respiration anaerobic fermentation - --enables cells to produce ATP in the absence of oxygen; yields little ATP and toxic lactic acid, a major factor in muscle fatigue

aerobic respiration - --produces far more ATP; less toxic end products (CO2 and water); requires a continual supply of oxygen immediate energy needs - --short, intense exercise (100m dash); oxygen need is briefly supplied by myoglobin for a limited amount of aerobic respiration at onset- rapidly depleted immediate energy needs - --muscles meet most of ATP demand by borrowing phosphate groups (Pi) from other molecules and transferring the to ADP needed phosphate transfers - --myokinase, and creatine kinase myokinase - --transfers Pi to from one ADP to another converting to latter to ATP creatine kinase - --obtains Pi from a phosphate-storage molecule creatine phosphate (CP); fast-acting system that helps maintain the ATP level while other ATP-generating mechanisms are being activated phosphagen system - --ATP and CP collectively; provides nearly all energy used for short burst of intense activity EX. one minute of brisk walking, 6 seconds of sprinting or fast swimming, important in activities required brief but maximum, i.e. football, baseball, and weight lifting Short-term energy needs - --as the phosphagen system is exhausted; muscles shift to anaerobic fermentation; glycogen-lactic acid system; produces enough ATP for 30-40 seconds of maximum activity

anaerobic fermentation - --muscles obtain glucose from blood and their own stored glycogen; in the absence of oxygen, glycolysis can generate a net gain of 2 ATP for every glucose molecule consumed; converts glucose to lactic acid glycogen-lactic acid system - --the pathway from glycogen to lactic acid long-term energy needs - --after 40 seconds or so, the respiratory and cardiovascular systems "catch up" and deliver oxygen to the muscles fast enough for aerobic respiration to meet most of the ATP demands. long-term energy needs - --aerobic respiration produces 36 ATP per glucose; efficient means of meeting the ATP demands of prolonged exercise