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Side ASide B
Muscle cells capable of shortening and converting the chemical energy of ____ into ______ energy
3 types of muscle
cardiac, smooth, skeletal
5 characteristics of muscle
responsiveness, conductivity, contractility, extensibility, and elasticity
voluntary, striated, attached to bones. Myofibers as long as 30 cm. Alters light and dark transverse...
myofibers bundled together
separates each fascicle from neighboring ones
outer edge of muscle, holds all fibers together; grade imperceptibily into connective tissue...
characteristics of collagen (2)
extensible and elastic; stretches slightly under tension and recoils when released (this protects...
2 types of elastic components
parallel components to parallel muscle cells; series components joined to ends of muscle
muscle fiber nuclei; fused and unfused
flattened inside cell membrane; fusion by multiple myoblasts during development; unfused satellite...
plasma membrane of a muscle fiber; has tunnel-like infoldings or transverse (T) tubules that...
cytoplasm; filled with myofibrils (bundle of myofilaments) and glycogen for stored energy and...
smooth ER; network around each myofibril; dilated end-sacs (terminal cisternea) that store...
T tubule and 2 terminal cisternea
bundle of parallel protein microfilaments
3 types of myofilaments
thick, thin, elastic
made of 200-500 myosin molecules; 2 entwined polypeptides (golf clubs); arranged in a bundle...
bare zone with no heads in thick filaments
two intertwined strands of fibrous (F) actin; composed of globular (G) actin with an active...
held in groove of thin filaments; each block 6-7 active sites of G actin to prevent myosin...
calcium-binding molecule attached to each tropomyosin molecule
composed of springy protein called titin; anchor each thick filament to Z disc. Prevents over...
myosin (thick filaments) and actin (thin filaments); do the work of shortening the muscle fiber
tropomyosin and troponin; switch that starts/stops shortening of muscle cell; contraction activated...
thick filament region; lighter, central H band area contains no thin filaments
thin filament region; bisected by z disc protein connectin, anchoring elastic and thin filaments
Muscle cells shorten because their ____ shorten
individual sarcomeres; (pull z discs closer together)
Neither thick or thin filaments change in length during shortening T/F?
skeletal muscle must be stimulated by ___ or it won't contract
cell bodies of somatic motor neurons are found _____
brainstem and spinal cord
somatic motor fibers
axons of somatic motor neurons; lead to skeletal muscles with each terminal branch supplying...
each motor neuron and all the muscle fibers it innervates; dispersed throughout muscle causing...
ability to sustain long-term contraction as motor units take turns resting
small motor units contain as few as 20 muscle fibers per nerve fiber (i.e. eye muscles)
gastrocnemius muscle has 1,000 fiber per nerve cell
neuromusclar junction (synapse)
functional connection between nerve fiber and muscle cell
tiny gap between nerve and muscle cells
neurotransmitter released from nerve fiber that stimulates muscle cell
swollen end of nerve fiber; contains ACh in synaptic vesicles
junctional folds of sarcolemma
increase surface area for ACh receptors; contain acetycholinesterase that breaks down ACh and...
thin layer of collagen and glycoprotein over all of muscle fiber
cholinesterase inhibitors; binds to acetycolinesterase and prevents it from degrading ACh;...
spastic paralysis caused by toxin of Clostridium bacteria; blocks glycine release...
limp muscles; due to curare that competes with ACh; respiratory arrest
resting membrane potential due to ___ outside of cell and ___ inside of cell
Na+ outside of cell; K+ (and other ions) inside the cell
resting membrane potential
difference in charge across the membrane (-90mV cell)
stimulation opens ion gates in membrane...
Na+ rushes into cell, K+ rushes out of cell
quick up-and-down voltage shift; (from negative RMP to a positive value and then back to negative)
4 actions involved in muscle contraction and relaxation
excitation, excitation-contraction coupling, contraction, relaxation
nerve action potentials lead to action potentials in muscle fiber
5 steps in excitation
nerve signal opens voltage-gated calcium channels; Calcium stimulate exocytosis of synaptic...
4 steps in excitation-contraction coupling
action potential spreading over sarcolema enters T tubules; voltage-gated channels open in...
4 steps in contraction
myosin ATPase in myosin head hydrolyzes and ATP molecule, activating the head and cocking it...
5 steps of relaxation
nerve stimulation ceases and acetylcholinesterase remove ACh from receptors; stimulation of...
stiffening of the body 3-4 hours after death; deteriorating SR releases Ca; Ca activates myosin-actin...
amount of tension generated depends on length of muscle before it was stimulated
weak contraction results; thick filaments too close to Z discs and can't slide
weak contraction results; little overlap of thin and thick filaments doesn't allow for very...
optimum resting length
produces greatest force when muscles contract; CNS maintains optimal length producing muscle...
voltage producing an action potential; a single brief stimulus at that voltage produces a quick...
3 phases of a twitch contraction
latent period, contraction phase, and relaxation phase
delay; only internal tension is generated; no visible contraction occurs since only elastic...
external tension develops as muscle shortens
loss of tension and return to resting length as calcium returns to SR
multiple motor unit summation
bringing more motor units into play/recruitment; i.e. lift a glass of milk versus a gallon...
low frequency (up to 10 stim./sec), produces an identical twitch response
moderate frequency (10-20 stim./sec); each twitch has time to recover but develops more tension...
temporal or wave summation
higher frequency stimulation (20-40/sec) generates gradually more strength of contraction;...
maximum frequency (40-50/sec); muscle has no time to relax at all; twitches fuse into smooth,...
isometric muscle contraction
develops tension without changing length; important in postural muscle function and antagonistic...
isotonic muscle contraction
contraction with a change in length but no change in contraction
concentric isotonic contraction
tension while shortening
eccentric isotonic contraction
tension while lengthening
pathways of ATP synthesis (2)
anaerobic fermentation and aerobic respiration
ATP production limited; without oxygen, produces toxic lactic acid
more ATP produced; requires continuous oxygen supply, produces H2O and CO2
immediate energy needs
short, intense exercise (i.e. 100 m dash); oxygen need is supplied by myoglobin
myokinase transfers Pi groups from ADP to make ATP; creatine kinase transfers Pi groups from...
short term energy needs
glycogen-lactic acid system takes over; produces ATP for 30-40 seconds of maximum activity...
long term energy
aerobic respiration needed for prolonged exercise; produces 36 ATP/glucose molecules; after...
progressive weakness of muscles from prolonged use; ATP synthesis declines as glycogen is consumed;...
ability to maintain high-intensity exercise >5 mins; determined by maximum oxygen uptake
maximum oxygen uptake (VO2 max)
proportional to body size, peaks at age 20, larger in trained athlete and males
used by some athletes; packs glycogen into muscles; adds water at the same time (2.7g h20 with...
heaving breathing after strenuous exercise;
4 purposes oxygen debt used for
replaces oxygen reserves; replenishes phosphagen system, reconverts lactic acid to glucose...
slow oxidative, slow twitch fibers
more mitochondria, myoglobin, and capillaries; adapted for aerobic respiration and resistance...
fast glycolytic, fast twitch fibers
rich in enzymes for phosphagen and glycogen-lactic acid system; SR releases calcium quickly...
weight lifting; stimulates cell enlargement due to synthesis of more myfilaments
aerobic training; produces an increase in mitochondria, glycogen, and density of capillaries
strength of contraction
muscle size and fascicle arrangement; 3-4 kg/cm2 of cross sectional area; size of motor units...
fuisform cells with one nucleus; no striations, sarcomeres, or z discs; thin filaments attach...
Multiunit smooth muscle
largest arteries, iris, pulmonary air passages; terminal nerve branches synapse on myocytes;...
single unit smooth muscle
most blood vessels and viscera as circular and longitudinal muscle layers; electrically coupled...
ability for cell to respond to a stimulus, especially the ability of nerve and muscle cells...
ability to shorten; amount of force that a contracting muscle fiber generates for a given stimulus
where attached to bone, doesn't move
attached to joint, etc, and is moveable
the muscle primarily responsible for a given joint action
muscle that opposes the prime mover/agonist at a joint
holding base solid : ie moving shoulder, fixator muscles allow scapula to stay in place;...
muscle that works with prime mover/agonist to assist