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101 Cards in this Set
- Front
- Back
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the ability to receive and respond to stimuli |
excitability |
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the ability to be stretched or extended |
extensibility |
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the ability to recoil and resume the original resting length |
elasticity |
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What is each muscle composed of? |
muscle tissue blood vessels nerve fibers connective tissue |
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the muscle(s) that are found in the heart and pumps blood throughout the body |
cardiac muscle |
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What are the main characteristics that distinguish skeletal muscle (5)? |
-each muscle cell contains several nuclei located around the periphery of the fiber -striated -a single fiber can extend from one end of a muscle to another -contracts rapidly but tires easily -voluntary
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a general term for connective tissue sheets |
fascia |
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What are the three muscular fascia? |
epimysium perimysium endomysium |
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an overcoat of dense collagenous connective tissue that surrounds the entire muscle |
epimysium |
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fibrous connective tissue that surrounds groups of muscle fibers called fascicles (bundles) |
perimysium |
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fine sheath of connective tissue composed of reticular fibers surrounding each muscle fiber |
endomysium |
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What are the roles of connective tissue in muscle (2)? |
-provides a pathway for blood vessels and nerves to reach muscle fibers -forms tendons |
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muscle cell plasma membrane |
sarcolemma |
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cytoplasm of a muscle cell |
sarcoplasm |
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What are the three prefixes used to refer to muscle? |
myo- mys- sarco- |
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Muscle contraction depends on which two myofilaments? |
actin myosin |
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densely packed, rod-like contractile elements; make up most of muscle volume |
myofibrils |
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thin myofilaments that consist of two helical polymer strands of F actin, tropomyosin, and troponin |
actin |
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compose F actin; contains the active sites to which myosin heads attach during contration |
G actin |
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regulatory subunits bound to actin |
tropomyosin troponin |
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thick myofilaments that enable the muscle to stretch |
myosin |
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Each myosin molecule contains what three things? |
head - contains ATPase to break down ATP hinge - enables head to move rod |
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this is formed when a myosin head binds to the active site on G actin |
cross-bridge |
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the smallest contractile unit of a muscle |
sarcomere |
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Sarcomeres are bound by _______ that hold actin myofilaments. ______ actin filaments surround a myosin filament. Myofibrils appear striated because of ______ and ______. |
Z discs six A bands I bands |
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_____ filaments extend the entire length of an A band. _____ extend across the I band and partway into the A band. |
thick thin |
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a coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another |
Z disc |
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in this lighter zone, thin filaments do not overlap thick filaments |
H zone |
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these appear darker due to the presence of desmin |
M lines |
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Actin and myosin myofilaments do not _________ during contraction. |
change in length |
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Upon stimulation, ______ bind to _____ and sliding begins. Each _______ binds and detaches several times during contraction, acting like a ratchet to generate ______ and propel the thin filaments to the center of the _______. As this occurs, the muscle _____. The ______ and ______ become narrower during contraction and the _______ remains constant in length. The ______ are brought closer together. |
myosin heads actin myosin head tension sarcomere shortens I band H zone A band Z discs |
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In the relaxed state, thin and thick filaments ______________. During contraction, thin filaments _______ the thick filaments so that the actin and myosin filaments ____________. |
overlap only slightly slide past overlap to a greater degree |
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In a fully contracted muscle, the ends of the ___________ overlap at the center of the sarcomere and the _________ disappears. |
actin myofilaments H zone |
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The nervous system stimulates muscles to contract through electric signals called _____. The plasma membranes become polarized so that the inside of the plasma membrane becomes _________ than the outside. |
action potentials more positive |
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What are the two types of ion channels that contribute to action potentials? |
ligand-gated channels voltage-gates channels |
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During depolarization, ______ channels are opened and _____ are closed. During repolarization, _______ are opened and ______ are closed. |
sodium potassium potassium sodium |
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________ results from an increase in the permeability of the plasma membrane to sodium ions. |
depolarization |
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Action potentials _____ across the plasma membrane. |
propagate |
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Skeletal muscles are stimulated by which neurons? |
motor neurons |
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Each axonal branch of a motor neuron forms a __________ with a single muscle fiber. |
neuromuscular junction |
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Axonal endings in NMJs have small membranous sacs called _______ that contain ______. |
synaptic vesicles acetylcholine |
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The specific part of a sarcolemma that is part of the NMJ is called the _______. It contains ________. |
motor end plate ACh receptors |
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space that separates the axonal ends and muscle fibers |
synaptic cleft |
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__________ removes ACh from the synaptic cleft by breaking it down into acetic acid and choline. |
acetylcholinesterase |
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What three things must happen in order for skeletal muscle to contract? |
- stimulation by a nerve ending -an action potential must be propagated along its sarcolemma -there must be a rise in intracellular calcium ion levels (the final trigger for contraction) |
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linking the electrical signal to the contraction |
excitation-contraction coupling |
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Invaginations of the sarcolemma form ______, which wrap around the sarcomeres and penetrate into the cells interior at each A band-I band junction |
T tubules |
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an elaborate, smooth endoplasmic reticulum that mostly runs longitudinal and surrounds each myofibril |
sarcoplasmic reticulum (SR) |
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found at the ends of the sarcoplasmic reticulum; form perpendicular cross channels |
terminal cisternae |
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What is the function of the sarcoplasmic reticulum? |
it regulates intracellular calcium levels |
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a T tubule and two terminal cisternae |
triad |
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An action potential from the NMJ propagates along the _____ via the _____. The depolarization of the _____ causes calcium channels in the ______ to open. Calcium ions diffuse from the SR into the ______. There, they bind to ______, which causes _____ to move and expose the active sites of _____. The heads of ____ are then free to bind to these active sites to form cross-bridges. |
sarcolemma T tubules T tubule sarcoplasmic reticulum sarcoplasm troponin tropomyosin G actin myosin |
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when energy stored in the myosin head is used to move the myosin head, causing the actin myofilament to slide past the myosin |
power stroke |
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the myosin head is returned to its resting position and energy is stored in the myosin head |
recovery stroke |
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this occurs when the calcium ions are transported back into the sarcoplasmic reticulum and diffuse away from troponin, which moves the tropomyosin back onto the active sites |
muscle relaxation |
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the contraction of a muscle as a results of one or more muscle fibers contracting; has lag, contraction, and relaxation phases |
muscle twitch |
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A muscle fiber or motor unit contracts with a _______ force in response to each action potential. |
consistent |
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for a whole muscle, stimuli of increasing strength result in graded contractions of increased force as more motor units are recruited |
multiple motor unit summation |
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stimulus of increasing frequency increase the force of contraction |
multiple-wave summation |
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partial relaxation between contractions |
incomplete tetanus |
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no relaxation between contractions |
complete tetanus |
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increase in the force of contraction during the first few contractions of a rested muscle |
treppe |
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contractions that cause a change in muscle tension but no change is muscle length |
isometric contractions |
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contractions that cause a change in muscle length but no change in muscle tension |
isotonic contractions |
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contractions that increase tension on a muscle as it shortens |
concentric contractions |
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contractions that increase tension on a muscle as it lengthens |
eccentric contractions |
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maintenance of steady tension for long periods of time |
muscle tone |
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contractions that produce smooth, steady muscle contractions |
asynchronous contractions |
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A muscle contracts with less than maximum force if its initial length is _____ or ______ than optimal. The maximum force is between ____% and ____% of resting sarcomere length. |
shorter longer 80 120 |
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the decreased ability to do work |
fatigue |
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Fatigue can be caused by what two things? |
-CNS (psychologic fatigue) -depletion of ATP in muscles (muscular fatigue) |
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the inability of muscles to contract or relax |
physiologic contracture |
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stiff muscles after death |
rigor mortis |
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What two things can result from muscular fatigue? |
rigor mortis physiologic contracture |
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ATP is synthesized when ADP reacts with ________ to form ______ and ATP. This can be used as energy for a short time (no oxygen required). |
creatine phosphate creatine |
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_______ is ATP synthesis that provides energy for a short time at the beginning of exercise and during intense exercise. It produces energy less ____ but more ____ than aerobic respiration. It increases ______ levels while producing __ ATP. This process is called ______. |
anaerobic respiration efficiently rapidly lactic acid 2 (per glucose molecule) glycolysis |
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______ requires oxygen. It produces energy for muscle contractions under resting conditions or during endurance exercise. It produces ___ ATP via the ____ and _____. |
aerobic respiration 38 (per glucose molecule) citric acid cycle electron transport chain |
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____ fibers contract more slowly than ____ fibers and _____ fibers because they have slower myosin ATPases that FG and FOG fibers |
SO (slow-twitch oxidative) FG (fast-tiwtch glycolytic) FOG (fast-twitch oxidative glycolytic) |
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SO fibers are ______ and rely on _____ respiration. They have many _________, a ______ blood supply, and ________. |
fatique-resistant aerobic mitochondria rich myoglobin
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FG fibers are _____ and rely on ____ respiration. They have a high concentration of _______. |
fatiguable anaerobic glycogen |
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FOG fibers have fatigue resistance that is intermediate between SO and FG fibers. They rely on ______ respiration. |
aerobic and anaerobic |
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SO fibers maintain _____ and are involved in ______. Example: ________ have a higher percentage of SO fibers. |
posture prolonged exercise long-distance runners |
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FG fibers produce _______ of ____ duration. Example: ________ have a higher percentage of FG fibers. |
powerful contractions short sprinters |
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FOG fibers support __________ endurance exercises. |
moderate-intensity |
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increase in the size of muscle |
hypertrophy |
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Hypertrophy results from an increase in the ____ of muscle fibers resulting from an increase in the ________. |
size number of myofibrils |
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What two things cause muscle hypertrophy and of which muscle fibers? |
aerobic exercise - increases muscle vascularity; greater hypertrophy of SO vs. FG intense anaerobic exercise - greater hypertrophy of FG vs. SO |
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decrease in the size of a muscle |
atrophy |
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By 80 years, ___% of muscle mass is gone. This is due to a loss in ____. ___ fibers decrease in number more rapidly than ___ fibers. This can be slowed if the person remains __________. |
50 muscle fibers FG SO physically active |
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Visceral smooth muscle fibers have ______ gap junctions and contract _______. They contract ________ or when stimulated _______. |
many as a single unit auto-rhythmically externally
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Multiunit smooth muscle fibers have _____ gap junctions and contract _______. They contract when externally stimulated by _____, _____ or ______. |
few independently nerves hormones other substances |
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Smooth muscle cells are ____-shaped with a ______. They have actin and myosin filaments that are connected to ______ and ______. They have no _____ system and most have less _____ than skeletal muscle. There is also no _____. |
spindle single nucleus dense bodies dense areas T tubule sarcoplasmic reticulum troponin
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the muscle(s) that help maintain blood pressure and squeezes or propels substances through organs |
smooth muscle |
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the muscle(s) that are responsible for most body movements |
skeletal muscle |
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the ability to shorten forcibly |
contractility |
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What are the 7 functions of muscle? |
body movement maintenance of posture respiration production of body heat communication constriction of organs and vessels heartbeat |
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In contraction of smooth muscle, ____ ions enter the cell to initiate contraction. These ions bind to _____ to activate _____. This transfers a phosphate group from ATP to myosin to form ____. Relaxation results when ____ removes a phosphate group from the myosin molecule. |
calcium calmodulin myosin kinase cross-bridges myosin phosphatase |
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Smooth muscle cells contract _____ than skeletal muscle cells. |
more slowly |
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the ability for smooth muscles to maintain a steady tension for long periods of time with little energy expenditure |
smooth muscle tone |
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Smooth muscle in the walls of hollow organs maintain a relatively constant ______ despite changes in _____. The force of contraction is ______. |
pressure volume constant |
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Cardiac muscle cells are striated and have a ________. They are connected by ________ and capable of ______. They contract at a ______ set by the heart's _______. Neural controls allow the heart to respond to changes in bodily needs. |
single nucleus intercalated disks autorhythmicity steady rate pacemaker |
