Lecture 4 - Skeletal Muscle Contraction Flashcards Preview

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Flashcards in Lecture 4 - Skeletal Muscle Contraction Deck (24)
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1

What is connective tissues surrounding the entire muscle?

Epimysium

2

What is made up of multiple fascicles?

Muscle

3

What is connective tissue surrounding individual fascicle?

Perimysium

4

What is a bundle of myofibers?

Fascicle

5

What is delicate connective tissue around each myofiber?

Edomysium

6

What is the cell membrane of each muscle fiber called?

Sarcolemma (=plasmalemma)

7

What is an individual multinucleated muscle cell called?

Myofiber

8

What is a chain of sarcomeres within a myofiber?

Myofibril

9

What is actin and myosin filaments that make up a sarcomere called?

Myofilament

10

What anchor actin filaments and are located at the end of a sarcomere?

Z discs (Z lines)

11

What are composed entirely of actin and change their width during contraction?

I bands

12

What are composed of actin and myosin and do not change their width during contraction?

A bands

13

What are composed entirely of myosin and change their widths during contraction?

H bands

14

What are responsible for the banding pattern characteristic of striated muscle?

Sarcomeres alignment

15

Describe the sequences LEADING UP TO the sliding filament mechanism.

1) Action potential arrives
2) Voltage gated calcium channels open
3) Ach released into synaptic cleft
4) Opening of ligand gated sodium channels
5) Action potential occurs
6) Voltage gated T-tubules interact with ryanodine receptors on SR membrane
7) Opening of Ryanodine-sensitive calcium ion release channels
8) Ca2+ increases in cytosol
9) activation of sliding filament mechanism

16

Describe the sequences after Calcium has been released in the cytosol to muscle contraction.

1) Calcium ions bind to troponin
2) Tropomyosin uncovers myosin binding sites on actin.
3) ATPase heads of myosin molecules split ATP and bind to actin.
4) Stored energy in myosin head causes deformation such that thick and thin filaments slide past one another.
5) A second ATP binds to myosin and causes it to release actin
6) process is repeated
7) contraction stops when ATP-dependent calcium pump sequesters calcium ions into SR.

17

What causes conformational changes in the ryanodine receptors and are located on the sacrolemma T-tubules?

Dihydropyridine receptors (DHP)

18

What open in response to conformational changes in the DHP receptors and allow calcium to flow into the cytosol from the SR?

Ryanodine receptors (RyRs or Ca2+ release channels)

19

How many heads does each myosin molecule contain?

2

20

Where is ATP required for muscle contraction? (3)

1) sliding filament mechanism (most)
2) pumping calcium from sarcoplasm back into SR
3) pumping sodium and potassium ions through the sarcolemma to reestablish resting potential.

21

What type of contraction occurs when there is an increase in tension but not in length?

Isometric

22

What type of contraction occurs when there is a change in muscle length? (2)

Isotonic contraction. Eccentric - lengthens, Concentric - shortens.

23

What type of muscle has fewer mitochondria, primarily uses anaerobic respiration, and has a larger concentration of ATPase?

Fast(white), contract rapidly but have less endurance. Example: gastrocnemius

24

What type of muscle has more mitochondria, primarily uses aerobic respiration, has more myoglobin, and smaller concentration of ATPase?

Slow(red), slow twitch fibers contract more slowly but have more endurance. Example: soleus