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Anatomy Lecture 8
| Definition | Term |
|---|---|
| a type of muscle that is voluntary and striated and is usually attached to fascia and bones | skeletal muscle |
| alternating light and dark transverse bands that reflect an overlapping arrangement of the muscles internal contractile proteins | striations |
| subject to conscious control | voluntary |
| the name for skeletal muscle cells due to their extraordinary length | muscle fibers |
| the plasma membrane of a muscle fiber | sarcolemma |
| the cytoplasm of a muscle fiber | sarcoplasm |
| long protein cords that occupies most of the sarcoplasm | myofibrils |
| the smooth ER of a muscle fiber that forms a network around each myofibril; it functions to store calcium | sarcoplasmic reticulum (SR) |
| dilated end sacs of the SR which crosses the muscle fiber from one side to the other | terminal cisterns |
| tubular infoldings of the sarcolemma which penetrate through the cell and emerge on the other side | transverse tubule (T) |
| a term given for each T tubule closely associated with two terminal cisterns running alongside it | Triad |
| a bundle of parallel proteins that make up the myofibril and are responsible for muscle contraction | myofilament |
| made of several hundred molecules of myosin | thick |
| a motor protein shaped like a golf club with two chains intertwined to form a shaft-like tail and a double globular head directed outward | myosin |
| composed primarily of two intertwined strands of F actin which is also made up of g actin, troponin and tropomyosin | Thin filament |
| two intertwined strands that make up the thin filament; it is like a beaded necklace composed of a string of G actin subunits along with tropomyosin and troponin | F actin (Fibrous actin) |
| subunits that make up the F actin molecule; they contain an active site that can bind to the head of a myosin molecule | G Actin (Globular actin) |
| located along the thin filament; it functions to block the active sites on the G actin and prevents myosin from binding to them | Tropomyosin |
| a small calcium binding protein bound to a tropomyosin molecule | troponin |
| made of titin | elastic filaments |
| a large springy protein; it serves to stabilize the thick filament, centers it between thin filaments, prevents overstretching, and recoils like a spring after muscle is stretched | titin |
| includes titin and at least seven other proteins associated with the thick and thin filaments; the most clinically important is dystrophin | accessory proteins |
| a large protein located between the sarcolemma and the outermost myofilaments which links actin filaments to the inner surface of the sarcolemma | dystrophin |
| genetic defects in dystrophin resulting in a breakdown and weakening of muscle tissue and gradually replacing it with scar tissue & fat | muscular dystrophy |
| the dark band consisting of thick filaments laying side by side (hint: dArk) | A Band |
| the light band consisting of only thin filaments (hint: lIght) | I Band |
| a light region located in the middle of the A band where thin filaments do not reach | IT Band |
| a dark transverse protein complex located in the middle of the H band which links the thick filaments together | M Line |
| bisects each I band and provides anchorage for the thin and elastic filaments | Z Disc |
| each segment of a myofibril from one Z disc to the next; it is considered the contractile unit of the muscle fiber | Sarcomere |
| nerve cells that serve skeletal muscles, whose cell bodies are in the brainstem and spinal cord | Somatic motor neuron |
| axons of somatic neuron cells that lead to the muscles with each one branching out to multiple muscle fibers | Somatic motor fiber |
| refers to the nerve fiber and all the muscle fibers innervated by it | Motor Unit |
| a type of motor unit that is supplied by small, relatively sensitive neurons and located where fine control is needed | Small motor unit |
| a type of motor unit that is innervated by less sensitive neurons with larger cell bodies and located where strength is needed | Large motor unit |
| the point where a nerve fiber meets any target cell | Synapse |
| refers to when the synapse is specifically between a nerve and muscle fiber | Neuromuscular Junction (NMJ) |
| a bulbous swelling on the end of a nerve fiber located at each synapse; it contains synaptic vesicles filled with ACh. | Axon Terminal |
| a neurotransmitter that functions as a chemical messenger from the nerve cell to the muscle cell | Acetylcholine (Ach) |
| a narrow space between the axon terminal and the muscle fiber | Synaptic Cleft |
| proteins incorporated into the sarcolemma across from the axon terminals which bind and respond to ACh | Ach Receptors |
| infoldings of the sarcolemma which increase the surface area and maximize the number of ACh receptors | Postsynaptic folds |
| the process in which action potentials in the nerve fiber lead to action potentials in the muscle fiber | Excitation |
| the process that links action potentials on the sarcolemma to activation of the myofilaments, preparing them to contract | Excitation Contraction (Coupling) |
| explains the step in which the muscle fiber develops tension and may shorten according to the sliding filament theory | Contraction |
| explains how the thin filaments slide over the thick filaments and pulls the Z discs behind them causing each sarcomere as a whole to shorten | Sliding Filament Theory |
| the process in which the nerve fiber ceases stimulation and the muscle fiber relaxes and returns to its resting length | Relaxation |
| a principle that states that the tension generated by a muscle (i.e., force), depends on how stretched or contracted it was at the outset | Length-Tension Relationship |
| results in a weak contraction because there is little overlap between the thick and thin filaments so the myosin heads are unable to get a grip on the thin filaments | Extremely Stretched |
| the position between the two extremes of muscle length in which a muscle responds with the greatest force | Optimum Resting Length |
| results in a weak contraction because the thick filaments would be rather close to the Z discs so the fiber can’t contract much before the the thick filaments butt against the Z discs and stop | Extremely Contracted |
| a chart showing the timing and strength of a muscle’s contraction | Myogram |
| the minimum voltage necessary to generate an action potential in a muscle fiber | threshold |
| a quick cycle of contraction and relaxation caused by a single stimulus at threshold or higher | twitch |
| a delay of about 2 ms between the onset of the stimulus and onset of the twitch which is the time required for excitation, excitation-contraction coupling, and tensing of the elastic components of the muscle | latent period |
| the phase of a twitch in which the muscle begins to produce external tension to move a resisting object or load | contraction phase |
| the phase of a twitch in which the calcium levels in the cytoplasm decrease so that myosin releases the thin filaments and muscle tension declines | relaxation phase |
| the process of bringing more motor units into play; higher voltages excite more nerve fibers in the motor nerve and stimulates more motor units to contract | recruitment |
| states that smaller, less powerful motor units are activated first, which is sufficient for delicate tasks and refined movements; larger motor units with larger, faster nerve fibers are subsequently activated if more power is needed | size principle |
| at higher stimulus frequencies, each new stimulus arrives before the previous twitch is over so that each new twitch rides piggyback on the previous one and generates higher tension | wave summatism |
| a state of sustained fluttering contraction caused by the effects of wave summation | incomplete tetanus |
| when an isolated muscle is stimulated at such high frequency that the twitches fuse into a single, nonfluctuating contraction; this only happens in the laboratory and not in the human body | complete tetanus |
| a type of contraction without a change in length; provides joint stability and maintenance of posture | isometric contraction |
| a type of contraction with a change in length but no change in tension; it begins when internal tension builds to the point that it overcomes the resistance | isotonic contraction |
| a form of isotonic contraction in which a muscle shortens as it maintains tension | concentric isotonic contraction |
| a form of isotonic contraction in which a muscle lengthens as it maintains tension | eccentric isotonic contraction |
| collectively encompasses ATP and CP, which is able to provide nearly all the energy used for short bursts of intense activity | phosphagen system |
| an enzyme that transfers Pi from a creatine phosphate to ADP to make ATP; it is a fast-acting system that helps maintain the ATP level while other ATP-generating mechanisms are being activated | creatine kinase |
| the point at which the muscles transition predominantly to anaerobic fermentation to generate ATP by glycolysis; it results in a rise in blood lactate levels | anaerobic threshold |
| the system in which muscles obtain glucose from the blood and their own stored glycogen and metabolize it to lactate; it can produce enough ATP for 30 to 40 seconds of maximum activity. | anaerobic fermentation |
| an efficient means of meeting ATP demands by generating additional ATP per glucose which occurs once the respiratory and cardiovascular systems catch up to the exercise demand; this system predominates in exercise lasting more than 10 min | aerobic respiration |
| occurs when one’s rate of oxygen consumption rises for 3-4 min and then levels off when aerobic ATP production keeps pace with the demand | steady state |
| point at which rate of oxygen consumption reaches a plateau and increases no further with added workload; the greater value, more oxygen the body can consume, the more effectively the body can use that oxygen to generate the maximum amount of ATP energy | maximum O2 uptake |
| a type of muscle fiber well adapted for endurance and fatigue resistance and is important in muscles that maintain posture | slow-twitch type 1 |
| a type of muscle fiber well adapted for quick responses and are less fatigue resistant | fast-twitch type 2b |
| a type of muscle fiber that combines fast-twitch responses with aerobic fatigue-resistant metabolism; it is relatively rare in humans except in some endurance-trained athletes | Intermediate type 2a |
| abnormal muscle shortening not caused by nervous stimulation; can result from failure of the calcium pump to remove calcium from the sarcoplasm or from contraction of scar tissue, as in burn patients | contracture |
| painful muscle spasms caused by rapid firing of motor neurons; triggered by heavy exercise, cold, dehydration, electrolyte loss, low blood glucose, or lack of blood flow | cramps |
| a shock-like state following the massive crushing of muscles; associated with a high and potentially fatal fever, cardiac irregularities, and kidney failure due to myoglobin causing blockage of the renal tubules | crush syndrome |
| pain, stiffness, and tenderness felt from several hours to a day after strenuous exercise; associated with microtrauma to the muscles and with elevated levels of myoglobin, creatine kinase, and lactate dehydrogenase in the blood | delayed onset muscle soreness (DOMS) |
| reduction in the size of muscle fibers as a result of nerve damage or muscular inactivity | disuse atrophy |
| chronic pain of unknown cause, seeming to come from the muscles and bones but actually arising from abnormal processing of pain signals by the brain | fibromyalgia |
| muscle inflammation and weakness resulting from infection or autoimmune disease | myositis |
| sex-linked recessive trait affecting about 1/3500 live-born boys;muscles shorten and atrophy causing postural abnormalities; it is incurable but is treated with exercise to slow the atrophy and braces to reinforce the weakened hips and maintain posture | Duchenne muscular dystrophy |
| autoimmune disease;antibodies attack NMJs and bind ACh receptors together in clusters;muscle fiber removes clusters causing fibers to be less sensitive to ACh;effects in facial muscles--> difficulty in swallowing,weakness of limbs,poor physical endurance | myasthenia gravis |
| hardening of muscles, stiffening of body begins 3 to 4 hours after death;deteriorating SR releases calcium that activates myosin-actin crossbridging;once bound to actin,myosin cant release without first binding an ATP but no ATP is available ina dead body | rigor mortis |
Created by:
ryan707
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