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muscle contraction Flashcards

1
Q

what is the function of myoepithelial cells

A

expel secretions from glandular acini

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2
Q

what are pericytes

A

smooth muscle like cells that surround blood cells

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3
Q

what are myofibroblasts

A

cells with a contractile role in addition to secreting collagen. important following tissue damage during the process of healing and repair, leading to the formation of a scar

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4
Q

what is atrophy

A

decrease in the size of an organ

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5
Q

what are myocytes

A

muscle cells

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6
Q

what does the sarcolemma do

A

make t tubules that project downward to the centre of the muscle fibre

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7
Q

what is the functional unit of myocytes

A

sarcomere

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8
Q

what is the sarcoplasm

A

the cytoplasm of a myocyte

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9
Q

what does the sarcoplasmic reticulum do

A

stores calcium and runs parallel to t tubules

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10
Q

what is found within the sarcoplasm

A

myofibrils that consist of contractile proteins and regulatory proteins

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11
Q

what do contractile proteins consist of

A

thick myosin and thin actin filaments

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12
Q

what is thick myosin

A

hundreds of myosin proteins

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13
Q

what are actin filaments

A

small globular proteins made from g actin

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14
Q

what is found on each g actin that forms the actin filaments

A

an active site that the myosin heads bind to during contraction

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15
Q

what do g actin form

A

a filament that looks like a long helix structure

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16
Q

what is f actin

A

the long helix structure formed by the combination of g actin

17
Q

which proteins are found on f actin

A

troponin and tropomyosin

18
Q

what are troponin and tropomyosin

A

regulatory proteins found on f actin

19
Q

what is tropomyosin

A

string like protein that wraps around g actin and covers the active sites so the myosin heads cant bind

20
Q

what is troponin

A

a protein with three subunits - t subunit, i subunit and c subunit. each one binds to something different

21
Q

what does the t subunit of troponin bind to

A

tropomyosin

22
Q

what does the i subunit of the troponin bind to

A

f actin

23
Q

what does the c subunit of troponin bind to

A

calcium ions

24
Q

what is the m line

A

the centre of the sarcomere

25
Q

what is the m line made up of

A

myomesin proteins

26
Q

what are the borders of sarcomeres called

A

the z discs

27
Q

what are the s discs made up of

A

alpha actin proteins

28
Q

where do thick filaments attach on sarcomeres

A

m line

29
Q

where do thin filaments attach on sarcomeres

A

z discs

30
Q

how many thin filaments are there for each thick

A

two

31
Q

what is the i band

A

the only thin filaments region

32
Q

where are i bands found on each sarcoemere

A

there are two half i bands at either end

33
Q

what is the a band of a sarcomere

A

the region with thick filament and thin filament

34
Q

what happens to the lines of sarcomeres when the muscle contracts

A

the thick filaments pull the thin filaments up and below it toward the m line.
z discs are pulled toward m line.
whole sarcomere is shorter
a band does not change as it is the length of the thick filament
h and i band shortens

35
Q

what is the h zone

A

the region with only thick filament

36
Q

what is maximal contraction

A

when there is almost complete overlap of thick and thin filament, and the h and i bands are almost completely gone

37
Q

describe the process of muscle contraction

A
  • action potential travels along the sarcolemma and reaches the t tubule
  • DHP receptors stimulated
  • these receptors are connected to the ryanodine receptor on the SR
  • when DHP is stimulated and changes shape, it causes the ryanodine receptor to open
  • this allows calcium to flow into the sarcoplasm from the SR
  • these float to the thin filament and bind to C subunit of troponin
  • this subunit changes shape
  • this moves tropomyosin out of the way, allowing myosin head to bind to the g actin proteins on f actin
  • before myosin can bind to actin, it must power up.
  • the myosin head is an ATPase and releases energy to cock the head backward
  • it then binds to an active site
  • this is cross bridge formation, which is the trigger to release stored energy in the myosin head
  • when this happens the myosin head launches toward the m line
  • actin is pulled along with it
  • this is the power stroke
  • once the action potential ends the calcium ions are pumped back into the R and the subunit is no longer bound to the calcium, so the tropomyosin covers the actin once more.
38
Q

what leads to the sliding of the thin filament over the thick filament

A

combined power strokw

39
Q

what is the myosin head

A

an ATPase

Revision (48 decks)

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