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Quiz 2 > Q2-MB6/Muscle Structure and Contraction > Flashcards

Q2-MB6/Muscle Structure and Contraction Flashcards

1
Q

what are the 3 types of muscle

A

skeletal smooth cardiac

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2
Q

what is the most abundant type of muscle found in body?

A

skeletal

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3
Q

where is smooth muscle mostly found?

A

in the linings of organs such as blood vesssels, stomach, and intestines

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4
Q

2 classification systems of muscles

A

appearance and innervation

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5
Q

2 sub classes of appearnace of muscles

A

striated and unstriated

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6
Q

2 types of innervation

A

voluntary and involuntary

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7
Q

what is the endomysium

A

surrounded muscle fiber

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8
Q

what does smooth muscle control?

A

it controls the movement of contents of the organ

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9
Q

which types of muscles are unstriated?

A
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10
Q

which types of muscles are striated?

A
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11
Q

which types of muscles are voluntary?

A
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12
Q

which types of muscles are involuntary?

A
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13
Q

what is the endomysium?

A

it is a connective tissue sheath that surrounds skeletal muscle cells

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14
Q

what is a group of skeletal muscle cells called?

A

fasicle

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15
Q

what is the lining that surrounds a fascicle?

A

perimysium

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16
Q

what is a group of fascicles called?

A

a muscle

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17
Q

what is a muscle surrounded by?

A

the epimysium

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18
Q

label this diagram

A
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19
Q

what type of structure do muscle fibers have?

A

multinucleate, syncytial

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20
Q

A sarcomere starts and ends at what?

A

starts at the z line and ends at the next z line

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21
Q

what is the I band bisected by?

A

the Z line

22
Q

what is the H zone bisect?

A

the A band

23
Q

What does the M line bisect?

A

the H zone

24
Q

What is the M line and what is it made out of?

A

the M line is the middle line and it is made out of proteins called myomesin

25
Q

What is the H zone?

A

the H zone is where there is no actin filaments, but it does contain the M line

26
Q

What is the A band?

A

The area where we find the whole thick filament/myosin

27
Q

What is the I band?

A

It is where one thick filament ends and the next thick filament begins, there is only actin and the Z line there

28
Q
A
29
Q

What is this in a sarcomere?

A

I band, thin filaments only

30
Q

What is this in a sarcomere?

A

H zone, thick filaments only

31
Q

What is this in a sarcomere?

A

M Line, thick filaments with accessory proteins

32
Q

What is this in a sarcomere?

A

Outer edge of A band, thick and thin filaments overlap

33
Q

What is the main job of accessory proteins in a sarcomere?

A

to maintain structure

34
Q

What is alpha-actinin?

A

it is an accessory protein that maintains the actin lattice

35
Q

What is dystrophin?

A

it is an accessory protein that anchors actin filaments to the sarcomere

36
Q

What is the sarcoplasmic reticulum?

A

it is modified smooth ER that helps with the control of Calcium ion levels

37
Q

What are T tubules?

A

they are inward extensions of the sarcolemma (PM of muscle cell) that bring action potentials into the interior of the muscle fiber

38
Q

Where are triads located?

A

they are at the junction of the A band and I band

39
Q

Where is the terminal cisterna?

A

it is where the sarcoplasmic reticulum meets the T tubule

40
Q

What is stored in the sarcoplasmic reticulum?

A

calcium ions

41
Q

explain how a thin filament is made with actin, tropomyosin, and troponin

A

actin molecules come together to form a helical strucutre known as an actin helix.

_(_each actin molecule has a myosin binding site.)

tropomyosin is a protein that binds to the actin and blocks the myosin binding site.

we see the function of troponin during muscle relaxation and contraction.

in muscle relaxation, troponin binds to the actin and tropomyosin to stabilize the actin filament. in muscle contraction, troponin binds to calcium, which displaces tropomyosin, and allos actin and myosin to bind together.

42
Q

what is the thick filament made out of?

A

myosin

43
Q

what is a myosin molecule made up of?

A

it contains 2 identical subunits with intertwined tails

44
Q

what helps with flexibility in a myosin molecule?

A

hinge region

45
Q

What do the head regions on a myosin molecule form with each other?

A

they form cross bridges

46
Q

What is located on the head of a myosin molecule?

A

an actin binding site and a Myosin ATPase site

47
Q

how are myosin filaments oriented?

A

they are oriented in opposite directions from the central M line

48
Q

Explain the process of muscle contraction and relaxation.

A
  1. at the axon terminal, neurotransmitters are released into the synaptic cleft and attached to Ach receptors on the sarcolemma.
  2. when the Ach binds to its receptors, this causes a net entry of Na+.
  3. this starts the action potential which then moves along the sarcolemma towards the T tubules.
  4. once the AP reaches the T tubules, the AP activates voltage gated receptors, which then triggers a calcium release from the terminal cisternae of the sarcoplasmic reticulum into the cytosol of the muscle cell.
  5. the calcium ions then bind to troponin which changes its shape. when the troponin’s shape is changed it cant stay binded to the tropomyosin, which means that tropomyosin cant block that actin active sites anymore, leaving the actin active sites exposed.
  6. once the actin active sites are exposed, the myosin heads attach to the actin, pulling the actin filaments towards the center of the sarcomere. (this is powered by ATP) - CONTRACTION
  7. once the AP ends, calcium is removed by active transport and taken to the sarcoplasmic reticulum.
  8. when the calcium is removed, tropomyosin can again block the actin active sites from myosin. - RELAXATION
49
Q

what is the sliding filament theory hypothesis of huxley?

A

muscle shortens by interdigitation of actin and myosin

50
Q

what happens to the sarcomere, I band, H zone, and A band according to the sliding filament hypothesis?

A
51
Q

how does the sliding filament hypothesis work?

A

when calcium binds to troponin, it changes its shape, which moves tropomyosin from the active site of actin.

the myosin heads can now attach to the actin filament, forming a cross bridge.

the breakdown of ATP releases energy, which allows the myosin to pull the actin filament inwards. when the ATP molecule binds to the myosin head, the myosin detaches from the actin filament and the cross bridge is broken.

when the ATP gets broken down again, the myosin is again able to attach to an actin binding site further along the actin filament.

this process keeps repeating.

https://www.youtube.com/watch?v=nTZnBdeIb5c - 2 minutes

Quiz 2 (18 decks)

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