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Physiology > Muscle > Flashcards

Muscle Flashcards

1
Q

how does a message transfer across the neuromuscular junction?

A

release of neurotransmitter acetylcholine into synaptic cleft

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2
Q

where is acetylcholine produced?

A

the nerve terminal

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3
Q

where is acetylcholine stored?

A

synaptic vesicles

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4
Q

what happens after acetylcholine binds to receptors on muscle?

A

triggers end plate potential, which triggers action potentials and muscle contracts

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5
Q

what breaks down acetylcholine?

A

acetylcholinesterase

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6
Q

what is the neuromuscular junction?

A

a chemical synapse

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7
Q

what are the types of skeletal muscle fibers?

A

slow twitch and fast twitch

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8
Q

example of slow twitch muscle fiber

A

postural muscle

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9
Q

example of fast twitch muscle fiber

A

extraocular muscles

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10
Q

differences between slow and fast twitch muscles

A

fast twitch has:

  • less mitochondria
  • less myoglobin
  • some oxidative metabolism
  • more glycolytic metabolism
  • SR highly developed
  • fatigue prone
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11
Q

structure of muscle

A

myofibrils surrounded by sarcoplasm outside myofilaments actin and myosin

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12
Q

where is calcium stored in the muscle

A

sarcoplasmic reticulum

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13
Q

what do T tubules do?

A

spread the muscle action potentials

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14
Q

what is a sarcomere?

A

the contractile unit in skeletal muscle, located in myofibrils

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15
Q

what are the thick and thin filaments in a sarcomere?

A 
myosin = thick
actin = thin
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16
Q

what connects the thick filament to the Z disk?

A

titin

17
Q

what are the protein components of the actin filament?

A

troponin and tropomyosin

18
Q

what happens within a sarcomere when a muscle contracts and relaxes?

A
  • resting: actin and myosin detatched
  • muscle action potential triggers calcium release
  • calcium binds to troponin C
  • myosin crossbridge formed
  • phosphate released = power stroke
  • atp attaches myosin, myosin detaches actin
  • calcium pumped back to SR
19
Q

how do you alter the force of muscle contraction?

A

tetanus or recruitment of motor units

20
Q

what is tetany?

A

a sustained muscle contraction

21
Q

what is a motor unit?

A

an alpha motor neuron and all the muscle fibers innervated by that neuron

22
Q

types of muscle contraction

A

isotonic and isometric

23
Q

what is isotonic muscle contraction?

A

constant tension, muscle length changes, eg moving an object through a distance

24
Q

what is isometric muscle contraction?

A

constant length, tension doesn’t exceed the load, object does not move

25
Q

is cardiac muscle striated?

A

yes

26
Q

what is a pacemaker?

A

sinoatrial node capable of spontaneous depolarization (action potentials)

27
Q

which action potential is longer: cardiac or skeletal?

A

cardiac- stops heart from going into tetany

28
Q

what lies between myocardial cells?

A

gap junctions

29
Q

how does the action potential spread rapidly

A

coupled cells gap junctions

30
Q

why is cardiac muscle “all or nothing” ie all cells behave like one cell

A

it has no motor units

31
Q

composition of smooth muscle

A

no sarcomere, no troponin

poorly developed SR

32
Q

why is extracellular Ca important on smooth muscle

A

the sarcoplasmic reticulum is poorly developed, extracellular Ca must work with SR Ca

33
Q

what is calmodulin?

A

Ca binding protein that activates the enzyme Myosin Light Chain Kinase MLCK

34
Q

what are the types of smooth muscle?

A

single unit and multi unit

35
Q

what is a single unit smooth muscle?

A

many fibers contracting as a single unit, gap junctions important eg digestive tract

36
Q

what is a multi unit smooth muscle?

A

controlled mainly by nerve signals, individual muscle fibers stimulated by individual nerve fibers eg the eye

37
Q

what does activated MLCK do in smooth muscle?

A

activates cross bridge formation and contraction

38
Q

what does myosin phosphatase do in smooth muscle?

A

inactivates myosin cross bridge and relaxes muscle

39
Q

smooth muscle contraction mechanism

A
  1. action potentials cause depolarisation
  2. calcium channels open in plasma membrane
  3. Ca and calmodulin activate MLCK
  4. MLCK activates cross bridge formation and muscle contracts
  5. myosin phosphatase inactivates cross bridge and muscle relaxes

Physiology (7 decks)

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