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Lab 5: Muscle Physiology
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Biology
Physiology
BY 409L
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68 Terms
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1
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Pi
________ is released and power stroke occurs.
2
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RyR
________ (ryanodine receptor)- gated Ca++ channel on terminal cisternae of sarcoplasmic reticulum.
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DHP receptor
________ (dihydropyridine)- undergoes conformational change in response to action potential, physically attached to RyR.
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Sarcoplasmic Reticulum
________- acts as Ca++ store, Ca++ sequestered inside at rest, Ca++ ATP- ase pump returns Ca++ to SR 3)
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Triad
one t-tubule and 2 flanking terminal cisternae of sarcoplasmic reticulum, closely associated with area of sarcomere where actin and myosin overlap
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Transverse tubules (t-tubule)
invagination of sarcolemma
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DHP receptor (dihydropyridine)
undergoes conformational change in response to action potential, physically attached to RyR
8
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RyR (ryanodine receptor)
gated Ca++ channel on terminal cisternae of sarcoplasmic reticulum
9
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Sarcoplasmic Reticulum
acts as Ca++ store, Ca++ sequestered inside at rest, Ca++ ATP-ase pump returns Ca++ to SR 3)
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Sarcomere
functional unit of myofibril
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Thin filament
composed of actin, troponin and tropomyosin
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Actin
globular protein with active binding site for myosin head, two chains of actin twisted together form main part of thin filament
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Tropomyosin
regulatory protein that blocks myosin binding site on actin at rest
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Troponin
regulatory protein with binding site for Ca++, undergoes conformational change to move tropomyosin when Ca++ is bound
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Myosin
motor protein of sarcomere that binds and breaks down ATP → ADP + Pi
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Titin
elastic protein connecting Z disk to M line, helps align filaments and passively shorten stretched muscle
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Nebulin
inelastic protein associated with thin filament, helps maintain alignment
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Motor Unit
one motor neuron and the muscle cells it innervates
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Fatigue
failure to generate or maintain output
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Central
psychological, can chose to continue
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Peripheral
physiological failure, no choice
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What is released at the axon terminal in a neuromuscular junction?
ACh (acetylcholine)
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At a neuromuscular junction, the motor end plated is lined with ___ receptors.
nicotinic
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What binds to the nicotinic receptors?
ACh (acetylcholine)
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When ACh binds to the nicotinic receptors, they open resulting in ___.
ion flow
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What ion flows in quicker than K+ flows out?
Na+
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What does ion flow initiate?
end-plate potential (EEP)
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How does the end-plate potential initiate an action potential?
it pushes voltage gated channels outside of motor end plate to threshold
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What ends the excitation at motor end plate?
AChE (acetylcholinesterase) breaks down ACh
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What makes up the triad?
one t-tubule and 2 flanking terminal cisternae of sacroplasmic reticulum
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What area is the triad closely associated with?
area of sarcomere where actin and myosin overlap
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What is the function of transverse tubules (t-tubules)?
invagination (folding backwards) of sarcolemma
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Transverse tubules (t-tubules) form a network within a cell that allows ___.
action potential to travel deep
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What receptors line transverse tubules (t-tubules)?
DHP receptors
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DHP receptor (dihydropyridine) will undergo a conformational change in response to ___.
action potential
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DHP receptors are physically attached to ___.
RyR
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RyR (ryanodine receptor) are gated ___ channel on terminal cisternae of sarcoplasmic reticulum.
Ca++
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What is the function of sarcoplasmic reticulum?
acts as Ca++ store
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At rest, Ca++ is inside or outside of cell?
inside
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What pump returns Ca++ to SR?
ATP-ase pump
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What is a functional unit of myofibril?
sacromere
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What composes a sarcomere?
thin filament, myosin, titin, and nebulin
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What composes a thin filament?
actin, troponin, and tropomyosin
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What is actin?
globular protein with active binding site for myosin head, two chains of actin twisted together form main part of thin filament
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What is tropomyosin?
regulatory protein that blocks myosin binding site on actin at rest
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What is troponin?
regulatory protein with binding site for Ca++, undergoes conformational change to move tropomyosin when Ca++ is bound
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What forms the thick filament?
myosin
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What is myosin?
motor protein of sarcomere that binds and breaks down ATP -> ADP + Pi
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Myosin isoforms varies between ___ and speed of contraction varies among isoforms.
muscle cell types
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Binding and breakdown of ATP puts ___ into cocked position.
myosin head
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When myosin head is in cocked position, it is ready to bind to __, while ___ and ___ remain bound.
actin; ADP and Pi
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When binding site is available on myosin head, it binds to ___.
actin
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When Pi is released at myosin head, a ___ occurs.
power stroke
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What occurs during rigor state?
ADP is released but head still bound to actin
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What must bind to myosin head again to release ADP and restart cycle?
ATP
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What is titin?
elastic protein connecting Z disk to M line, helps align filaments and passively shorten stretched muscle
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What is nebulin?
inelastic protein associated with thin filament, helps maintain alignment
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What is excitation-contraction coupling?
EEP -> AP -> DHP receptor conformational change -> RyR opening allowing Ca++ into sarcoplasm as secondary messenger -> Ca++ binds to troponin -> troponin moves tropomyosin exposing myosin binding site on actin -> myosin binds actin performing power stroke
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What detects an AP along sarcolemma?
EMG
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What is a motor unit?
one motor neuron and the muscle cells it innervates
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Number of ___ varies in general relation to size of muscle.
myofibers
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One motor unit can have multiple ___.
myofibers
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What is fine control?
few motor units -> small amount of force added
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What is more efficient force generation?
larger motor units -> large amount of force added
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What occurs to motor units to avoid fatigue?
units cycle in and out during longer muscle contractions
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What is fatigue?
failure to generate or maintain output
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What is central fatigue?
physchological, person can chose to continue
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What is peripheral fatigue?
physiological failure, no choice