Chapter 11: Muscular System Flashcards Preview

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Flashcards in Chapter 11: Muscular System Deck (123)
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31

tropomyosin

blocks the active sites of G actin & prevents myosin from binding when muscles are relaxed

32

troponin

small calcium binding protein on each tropomyosin molecule

33

contractile proteins?

myosin & actin

34

regulatory proteins?

tropomyosin & troponin

35

what happens when calcium is released into the sacroplasm?

Ca binds to troponin which then changes shape and moves tropomyosin from the active site of actin

36

sarcomere

Z disc to Z disc
functional contractile of muscle fiber

37

Which myofilament is free floating?

myosin, it is not anchored like actin

38

A band

dark; overlapping of thick and thin filaments

39

H band

middle of A band (thick filaments ONLY)= bare zone

40

M line

middle of H band

41

I band

light; crosses over 2 sacromeres

42

Z disc

provides anchorage for thin filaments and elastic filaments

43

what myofilaments do muscle fibers contain? (3)

thin, thick, and elastic

44

which band shortens during contraction

H band

45

Why do muscle cells shorten?

because their individual sarcomeres shorten (Z disc pulled closer together)

46

a skeletal muscle never contracts unless stimulated by ______? what happens if this is severed?

a nerve; muscle is paralyzed

47

somatic motor neurons

nerve cells whose cell bodies are in the brainstem & spinal cord that serve skeletal muscles

48

what portion of somatic motor fibers lead to the skeletal muscle?

their axons

49

1 nerve fibers= ______ muscle fiber

several

50

what does an effective contraction require?

the contraction of several motor units (one nerve fiber + muscle fibers) at once

51

average motor unit?

200 muscle fibers for each motor unit

52

small motor units are used for what?

fine degree of control
ex. eye & hand muscles

53

large motor units are used for what?

more strength than control

54

synapse

point where a nerve fiber meets its target cell

55

neuromuscular junction

when target cell is a muscle fiber

56

synaptic knob

swollen end of nerve fiber

57

synaptic cleft

tiny gap between synaptic knob & muscle sarcolemma

58

What is the purpose of Schwann cells?

to isolate & insulate all of the NMJ from surrounding tissue fluid

59

synaptic vesicles undergo ______ releasing ACh into ______

exocytosis; synaptic cleft

60

Lack of ACh receptors leads to?

paralysis in disease