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Muscle Exam
A&P1
| Term | Definition |
|---|---|
| functions of muscular tissue | -propels food we eat along gastrointestinal tract -expels waste we produce -changes amount of air that enters the lung -pumps the blood to body tissues |
| 3 types of muscular tissue | -skeletal -smooth -cardiac -composes 40-50% of weight |
| functions of skeletal tissue | -body movement -maintenance of posture -protection and support -storage and movement of materials -heat production |
| excitability | -can be stimulated by nervous system -has receptors to receive a stimulus |
| conductivity | conduct a nerve impulse down muscle membrane |
| contractility | increase in muscle tension which shortens the muscle |
| elasticity | stretch and recoil |
| extension | stretching beyond normal length |
| A band | -dark -contains myosin -central region of sarcomere -does not change in length |
| I band | -light -contains actin and other smaller protein fibers -extend in both directions of a Z disc (bisected by Z discs) -pulled by thick filaments appearing to have disappeared |
| superficial fascia | also known as hypodermis |
| epimysium | connective tissue on outside of muscle |
| fascicles | -bundles of muscle fibers within the epimysium -surrounded by the perimysium |
| endomysium | surrounds individual muscle fibers |
| blood vessels and nerves | -skeletal muscle is vascularized -delivers oxygen and nutrients -innervated by motor neurons |
| satellite cells | -remaining myoblasts -unfused |
| sarcoplasmic reticulum | -Ca2+ pumps embedded here -help move Ca2+ into SR -voltage gated Ca2+ channels open to release Ca2+ from SR -goes into sarcoplasm and causes muscle contraction |
| mitochondria | -found in muscles with high ATP requirement -abundant -for aerobic cellular respiration |
| creatinine phosphate | -used in mitochondria for supplying ATP anaerobically |
| myoglobin | -unique to muscle tissue -reddish protein similar to hemoglobin -binds oxygen when muscle at rest -releases during contraction -provides additional oxygen |
| nerve impulse | -depolarize -makes charge difference across membrane less -opens Ca2+ channels |
| motor units | -size varies -inverse relationship between size of unit and degree of control -ex: eyes-small unit; greater control |
| motor unit recruitment | increases in stimulation cause increase in number of motor units that contract which increases tension -maximum contraction is reached when all units have been recruited |
| all-or-none law of muscle contraction | -if muscle fiber contracts in response to stimuli, it will contract completely -difference in force varies by changing number of units activated |
| first step in skeletal muscle contraction | -neuromuscular junction: excitation of a skeletal muscle fiber -release of neurotransmitter acetylcholine (ACh) from synaptic vesicles and subsequent binding of ACh to ACh receptors |
| second step in skeletal muscle contraction | -sarcolemma, t-tubules, and sarcoplasmic reticulum: excitation-contraction coupling -ACh binding triggers propagation of an action potential along sarcolemma and t-tubules to SR, which is stimulated to release Ca2+ |
| third step in skeletal muscle contraction | -sarcomere: cross bridge cycling -Ca2+ binding to troponin triggers sliding of thin filaments past thick filaments of sarcomeres; causing sarcomeres to shorten, causes contraction |
| synaptic knob | end of axon of neuron |
| synaptic cleft | space between axon and muscle membrane |
| motor end plate | membrane of muscle |
| sarcolemma | -contains voltage gated Na+ and K+ -carries nerve impulse down sarcolemma and into t-tubules |
| muscle twitch | -single, brief episode of stimulation to muscle -minimum stimuli necessary to generate twitch is called threshold |
| latent period | -delay after stimuli is applied -release of Ca2+ from SR -beginning of tension generation in muscle fiber |
| contraction period | -sarcomere cross bridge cycling -repetitive power strokes pull thin filaments past thick filaments -shortens sarcomere -muscle tension increases |
| relaxation period | -release of cross bridges -Ca2+ returns to SR -muscle tension decreases -longer than contraction period |
| muscle fatigue | -decreased excitation at neuromuscular junction -insufficient Ca2+ at neuromuscular junction -decrease in synaptic vesicles -changes in Na+ and K+ levels along sarcolemma -decreased cross bridge cycling |
| first step of cross bridge cycling | -Ca2+ binds to troponin in muscle thin filaments, causing a change in troponin -troponin changes shape and the entire troponin-tropomyosin complex is moved -tropomyosin no longer covers myosin binding site on actin |
| second step of cross bridge cycling | -myosin heads which are in the "cocked" position bid to exposed myosin binding side on actin -forms cross bridge between actin and myosin |
| third step of cross bridge cycling | -myosin head swivels toward center of sarcomere -pulling along the attached thin filament -motion is called power stroke -ADP and Pi are released during this process |
| fourth step of cross bridge cycling | -ATP binds to the ATP binding site on myosin head -causes the release of myosin head from the binding site on actin |
| fifth step of cross bridge cycling | -ATP is split into ADP and Pi by myosin -provides the energy to reset the myosin head |
| cross bridge cycling | -multiple repetitions of attach, pull, release, and rest -leads to fully contracted sarcomere |
| increases in stimulation | -increase in frequency causes muscle to not fully relax so all Ca2+ is not removed from cytosol -generated greater tension with each contraction -allows for more cross bridges to form -heat generation |
| hypertrophy | increase in muscle size due to increase in muscle fiber size due to exercise |
| hyperplasia | increase in muscle fiber number (limited) |
| atrophy | decreasing the muscle fiber size |
| Aging | by mid-30's progressive decrease in skeletal muscle mass |
| slow oxidative (SO) fibers | -slower and less powerful contractions -contract for long periods of time -aerobic cellular respiration -dark red (trunk and calf) |
| fast oxidative (FO) fibers | -fast, powerful contraction -aerobic respiration -fatigue faster than SO -some myoglobin: lighter red -leg muscles |
| fast glycolytic (FG) fibers | -largest; power and speed -fatigue quickly -anaerobic respiration -lack myoglobin -white: upper limbs |
| 3 ways to generate ATP in skeletal muscle fiber | -immediate supply via the phosphagen system -short-term supply via anaerobic cellular respiration -long-term supply via aerobic cellular respiration |
| phosphagen system | immediate energy source |
| anaerobic cellular respiration | short-term energy source |
| aerobic cellular respiration | long-term energy source |
| oxygen debt | -needed to restore pre-exercise conditions -to replace oxygen on hemoglobin and myoglobin -replenish glycogen -replenish ATP and creatine phosphate in phosphagen system -convert lactic acid back to glucose |
| cardiac muscle tissue | -thick bundles within heart wall -branching cells -shorter ad thicker than skeletal -one or two nuclei -striated and contain sarcomeres -large number of mitochondria -use aerobic respiration |
| smooth muscle tissue | -found in organs of many body systems -function is determined by location -lack t-tubules -Ca2+ comes from outside cell |
| smooth muscle sarcolemma | -contains voltage-gated, ligand-gated (chemical), modality-gated calcium channels |
| smooth muscle stimulation | -stretch -hormones -decrease in pH -increased carbon dioxide -certain drugs -pacemaker cells |
| smooth muscle contraction | -actin does not contain troponin -calmodulin and myosin light-chain kinase are required for initiation of contraction |
| first step in smooth muscle contraction | -stimuli (action potential, muscle stretch) -triggers opening of voltage-gated Ca2+ channels -Ca2+ enters the sarcoplasm from interstitial fluid |
| second step in smooth muscle contraction | Ca2+ binds to calmodulin to form a Ca2+ calmodulin complex |
| third step in smooth muscle contraction | Ca2+ calmodulin complex activates MLCK, a phosphorylating enzyme |
| fourth step in smooth muscle contraction | -activated MLCK phosphorylates add phosphate to myosin head -activates myosin head, activating myosin -slow process |
| fifth step in smooth muscle contraction | -activated myosin heads bind to thin filaments to form cross bridges -myosin ATPase hydrolyzes ATP providing energy for power stroke -process is repeated -force generated is transferred to anchoring filaments -smooth muscle cell shortens |
| multiunit smooth muscle | -stimulated to contract independently -autonomic motor units -iris and ciliary body of eyes, arrestor pili muscles in skin, part of bronchial tree, large arteries |
| single-unit smooth muscle | -simulated to contract as a group -autonomic varicosities and gap junctions between cells that spread the stimuli -most smooth muscle; visceral smooth muscle |
| structural organization of skeletal muscle | -tendon -deep fascia -skeletal muscle -epimysium -perimysium -fascicles -endomysium -muscle fibers -myofibrils -myofilaments |
| muscle triad | -t-tubule -terminal cistern -sarcoplasmic reticiulum |
| tropomyosin | -short, thin, twisted filament that is a stringlike protein -binding sites |
| troponin | -globular, or ball like protein attached to tropomyosin -contains the binding site for Ca2+ |
| H zone | -most central portion of A band -does not have thin filament overlap |
| M line | -thin transverse protein meshwork structure in center of H zone -attachment site for thick filaments aligned during contraction |
| first step of excitation of skeletal fiber | -nerve signal propagated down motor axon and triggers the entry of Ca2+ into synaptic knob -Ca2+ binds to proteins in membrane of synaptic vesicle |
| second step of excitation of skeletal fiber | -calcium binding triggers synaptic vesicles to merge with synaptic knob -plasma membrane and ACh is exocytosed into synaptic cleft |
| third step of excitation of skeletal fiber | -ACh diffuses across the synaptic cleft at the motor end plate -binds with ACh receptors |
| first step of excitation-contraction coupling | -ACh binds to Ach receptors in motor end plate -chemically gated ion channels stimulated to open -Na+ rapidly diffuses in and K+ slowly diffuses out of muscle fiber |
| second step of excitation-contraction coupling | -end plate potential (from threshold) initiates action potential (depolarization and depolarization) -depolarization is complete as the voltage-gated Na+ channels close -repolarization occurs when voltage-gated K+ channels open after Na+ channels; K+ mo |
| third step of excitation-contraction coupling | -action potential reaches a triad -voltage-sensitive Ca2+ channels of t-tubules are stimulated -triggers Ca2+ release channels of SR to open -Ca2+ diffuses of of the Sr through Ca2+ release channels into the cytosol of muscle fiber |
Created by:
mamoody246
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