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83 Cards in this Set
- Front
- Back
muscle cells |
are essentially a device for converting the chemical energy of ATP into the mechanical energy of movement |
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excitability
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responsiveness; when stimulated by chemical signals, stretch, and other stimuli; muscle cells respond w/ electrical changes across plasma membrane
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conductivity |
local electrical change triggers wave of excitation that travels rapidly along cell and initiates processes leading to contraction |
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contractility |
ability to shorten substantially when stimulated, enabling them to pull on bones/other organs to create movement |
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extensibility |
ability to stretch b/w contractions-skeletal muscle cells can stretch 3x their contracted length (other cells would rupture) |
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elasticity |
when muscle cell is stretched and then released it recoils to shorter length (elastic recoil); prevents resting muscles from being too slack |
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skeletal muscles |
voluntary, striated muscle usually attached to one or more bones |
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striations |
alternate light and dark transverse bands; reflect overlapping arrangement of their internal contractile proteins |
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myofibers/muscle fibers |
because of their extraordinary length |
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muscle fibers |
have a complex, tightly organized internal structure in which even the special arrangement of protein molecules is closely tied to its contractile function |
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sarcolemma |
plasma membrane of muscle fiber |
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sarcoplasm |
cytoplasm of a muscle fiber; occupied by myofibirls; contains glycogen and myoglobin |
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myofibrils |
long protein cords |
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glycogen |
starchlike carb that provides energy for cell during heightened levels of exercise |
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myoglobin |
red oxygen-binding pigment which provides some of oxygen needed for muscular activity |
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myoblasts |
stem cells |
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multinuclear muscle fibers |
myoblasts fuse to produce each fiber with each myoblast contributing one nucleus |
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satellite cells |
unspecialized myoblasts; between the muscle fiber and endomysiym; important in regeneration of damaged skeletal muscles |
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sacroplasmic recticulum |
aka smooth ER; forms network around each myofibril; periodically exhibiting terminal cisternae |
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terminal cisternae |
dilated end-sacs; that cross the muscle fiber from one side to the other |
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transverse (T) tubules |
sarcolemma tubular infoldings; penetrate through the cell and emerge on the other side |
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triad |
T-tubule +2 terminal cisternae |
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muscle contraction process |
t-tubule signals SR when to release calcium into cytosol to active the contraction |
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myofilaments |
a bundle of parallel protein microfilaments in a myofibril |
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thick filaments |
made of 100s of myosin |
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myosin |
shaft-like tail; double globular head projecting from it at an angle (like a golf club) in a helical array around the bundle |
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bare zone |
in the middle, no heads |
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thin filaments |
composed primarily of two intertwined strands of a fibrous (F) actin protein |
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globular (G) actin |
protein made up string of subnits (beaded necklace) F actin& beads = G actin |
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active site |
each G actin has one that can bind to a myosin head |
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tropomyosin |
blocks active sites of 6-7 G actin- prevents mysoin from binding when relaxed |
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troponin |
smaller Ca binding protein of each tropomyosin molecule |
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elastic filaments |
made of titin; run through the core of each thick filament and anchor it to a Z disc at one end and M line at other |
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titin |
huge springy protein; stabilizes thick filament; centers it b/w thin fliaments, prevents overstretching and recoils like spring after muscle is stretched |
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contractile proteins |
mysoin and actin; shorten the muscle fiber |
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regulatory proteins |
troponin and tropomyosin; act like switch to determine when fiber can contract and when it cant |
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dystrophin |
enormous protein b/w sarcolemma and outermost myofilaments; links actin filaments to peripheral protein |
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muscular dystrophy |
genetic defect of dystrophin |
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striated muscles |
dark A bands alternating with lighter I bands |
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A Bands |
anisotropic; thick filaments lying side by side; each thick filament is surrounded by hexagonal array of thin filaments where they overlap(very dark) |
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I Band |
isotropic |
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H Band |
middle/lighter region of A Band |
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M-line |
the thick filaments of the middle of H-Band links through dark, transverse protein complex |
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Z disc/Z line |
a dark narrow line that bisects I Band; provides anchorage for thin and elastic filaments |
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sarcomere |
segment of myofibril b/w z discs; functional contractile unit of muscle fibers |
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denervation atrophy |
severed connection of muscle is never restored; paralyzed muscle wastes away in a shrinkage |
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somatic motor cells |
nerve cells; cell bodies are found in brainstem and spinal cord; serve skeletal system |
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somatic motor fibers |
axons of the somatic motor cells |
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motor unit |
one nerve fiber+ all muscle fibers innervated by it; dispersed through muscle; weak contraction |
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small motor units |
used where fine control is needed; provide fine degree of control; subtle change; 1000muscle fibers may be innervated by 200 neurons |
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large motor units |
used in areas where strength is needed; greater change; 1000 muscle fibers may be innervated by only 1-2neurons |
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motor units in work shifts |
when muscle fibers are subjected to constantstimulation, some become fatigued – other motor neurons take over whilefatigued ones recover so muscle can sustain long-term contraction
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synapse |
point where a nerve fiber meets any target cell; fingerlike projections |
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neuromuscular junction/motor end plate
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when the target cell(synapse) is a muscle fiber |
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synaptic knob |
the bulbous swelling at end of nerve fiber; |
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synaptic cleft |
separates synaptic knob from muscle fiber |
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schwann cells |
envelops entire junction, isolating it from surrounding tissue fluid |
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synaptic vessicles |
organelles filled with neurotransmitter ACh |
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ACh |
functions as a chemical messenger from the nerve cells to the muscle cells |
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electrical signal |
aka nerve impulse; cannot cross synaptic cleft, instead causes synaptic vesicles to undergo exocytosis and release ACh into cleft |
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ACh receptors |
transmembrane proteins incorporated into its plasma membrane across from synaptic knobs; binds to ACh |
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junctional folds |
infoldings in sarcolemma; increase surface area of ACh |
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myasthenia gravis |
a disease of a deficiency of ACh receptors that leads to muscle paralysis |
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basal lamina |
made of collagen and glycoproteins; surrounds entire muscle fiber and schwann cell of NMJ; separates them from surrounding connective tissue; fills synaptic cleft |
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acetylcholinesterase(AChE) |
found in sarcolemma and part of basal lamina; enzyme breaks down ACh after the ACh has stimulated the muscle cell |
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electrophysiology |
study of electrical activity of cells; key to learning nervous activity, muscle contractions |
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ICF |
intracellular fluid; greater concentration of negative ions than ECF; net negative charge inside cell; membrane polarized, K+ |
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ECF |
extracellular fluid; Na+; adjacent to plasma membrane |
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electrical potential/voltage |
difference in electrical charge from 1 point to another; -90 mV for sarcolemma of muscle cell |
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resting potential membrane (RMP) |
the voltage; maintained by the sodium-potassium pump |
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action potential |
quick up and down voltage shift from negative RMP to positive value then back to RMP |
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RMP vs. Action Potential |
stable voltage in waiting cell vs. quickly fluctuating voltage in active, stimulated cell |
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nerve impulses |
wave of action potentials; one causes another to happen immediately in front of it; travel along the sarcolemma along nerve fibers |
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Excitation |
the process by which action potentials in the nerve fiber lead to action potentials in the muscle fibers |
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end-plate potential (EPP) |
rapid fluctuation in voltage at the motor end plate |
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Excitation- contraction coupling |
refers to events that link action potentials on the sarcolemma to activation of the myofilaments; preparing them to contract |
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contraction |
the step in which the muscle fiber develops tension and may shorten |
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sliding filament theory |
mechanism of contraction; like pulling a boat anchor hand over hand |
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myosin ATPase |
an enzyme in the head, hydrolyzes this ATP into ADP and phosphate |
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cross-bridge |
between myosin and actin; formed when myosin binds to the active site |
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power stroke |
myosin releases the ADP and phosphate and flexes into a bent, low-energy position; tugging the thin filament along |
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recovery stroke |
recock; hydorlyze the new ATP; repeat the whole process |
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Relaxation |
when the nerve fiber stops stimulating it, a muscle fiber relaxes and returns to its resting length |