Skeletal Muscle Physiology I Flashcards

1
Q

sliding filament mechanism

A

a) Muscle relaxed
b) Partially contracted muscle
- actin move toward each other, sarcomere shortens
- I band and H zone narrow
c) Maximally contracted muscle
- actin ends overlapp
- H zone disappears

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2
Q

Cross Bridge Cycle

A
  1. Exposure: Ca2+ binds to troponin, exposes active site. Myosin heads in active state (ADP energy stored, ADP+phosphate bound)
  2. Cross bridge forms: myosin binds to active sites, phosphate released
  3. Power stroke: myosin head toward M line, pulls actin. When bent, ADP released.
  4. Release: ATP binds to head, releases myosin from actin
  5. Re-energize: ATPase on head turns ATP to ADP and phosphate, cycle starts again
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3
Q

rigor mortis

A

Stiff muscles in dead bodies
Myosin head stays bound to actin because no ATP being produced to release it

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4
Q

difference between skeletal muscle and nervous resting membrane potential

A

membrane potential larger in skeletal muscles
- greater K leak channels in

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5
Q

what is a branch of a somatic motor neuron called

A

branch from somatic motor neuron

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6
Q

neurtotransmitter released in somatic motor neurons

A

Acetylcholine

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7
Q

portion of sarcolemma that contains neuromuscular junction

A

motor end plate

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8
Q

function of neuromuscular junction

A
  • AP arrives at presynaptic terminal, opens VG Ca2+ channels
  • Ca2+ releases Ach from synaptic vesicles into synaptic cleft via exocytosis
  • Ach diffuses across cleft, binds to ligand gated Na+ channels on motor end plate
  • chanels open, Na+ into cell
  • depolarization
  • VG channels right beside continue AP
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9
Q

EPSP or IPSP in muscles?

A

alwasy EPSP

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10
Q

difference between neuron and skeletal muslce

A

In muscle ligand gated channels located close to VG channels on postsynaptic membrane

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11
Q

how to stop muscle contraction from continually occuring

A
  • Ach constantly broken down by ACETYLCHOLINEESTERASE into choline and acetic acid
  • choline recycled (paired with acetic acid in presynatpic terminal), acetic acid reused by other cells
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12
Q

excitation-contraction coupling

A
  1. muscle AP propagated along sarcolemma and into t-tubules
  2. Ca+ channels in the SR open and calcium is released into sarcoplasm
  3. Ca+ binds to troponin, movement of tropomyosin off of myosin binding site
  4. Heads of myosin can bind active sites on actin, cross-bridge forms
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13
Q

how does calcium release from troponin?

A

via SERCA pumps
- an ATPase

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14
Q

3 places where ATP is needed for skeletal muscle contraction

A
  1. Na+ K to reestablish resting membrane potential
  2. for myosin heads: stored energy and to detach from actin
  3. calcium pumps
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