13. Muscle conduction to contraction Flashcards Preview

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Flashcards in 13. Muscle conduction to contraction Deck (38)
1

Muscle contraction - steps

neurotransmitter release --> postsynaptic ligand --> depolarization --> Ca2+ release from saecoplasmatic reticulum --> tropoinin C to tropomyosin system --> displacement of myosin on the actin filament --> myosin binds and hydrolyses ATP

2

muscle contraction - neurotransmitter release is caused by

action potential depolarization opens presynaptic voltage - gated Ca2+ channels, inducing neurotransmitter release

3

muscle contraction - post synaptic ligand leads to

muscle cell depolarization in motor end plate

4

muscle contraction - depolarization process

it starts from ligand binding --> depolarization travels along muscle cell and down the T- tubule

5

muscle contraction - depolarization result to -->

depolarization of the voltage - sensitive dihydropyridine receptor, mechanically coupled to the ryanodine receptor on the sarcoplasmic reticulum --> conformation change --> Ca2+ release from sarcoplasmic reticulum

6

muscle contraction - Ca2+ action ( and mechanicals changes )

released Ca2+ binds to troponin C causing a conformation change that moves tropomyosine out of the myosin-binding groove on actin filaments

7

muscle contraction - myosin action

myosin release bound ADP and inorganic PO4(3-) --> displacement of myosin on the actin filament ( power stoke) --> binding a new ATP causes detachment of myosin head from actin filament --> hydrolysis ---> high energy position ( cocked) for the next cycle

8

sarcomere anatomy - M line

M line : middle line

9

sarcomere anatomy - H band

myosin between myosin heads ( in the middle of the sarcomere)

10

sarcomere anatomy - A band

all mysosin ( in the same sarcomere ) ( thick filaments

11

sarcomere anatomy - I band

from the end of the myosins of the one sarcomere to the end of the myosins of the next sarcomere

12

sarcomere anatomy - Z lines

the lines of sarcomere

13

transverse (T) tubules ?

extensions of plasma membrane part of juctaposed with terminal cisternae ( part of sarcoplasmic reticulum )

14

Terminal cisternae are

enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules

15

T tubules and Terinal cisternae - numbers

in skeletal muscle : 1T +2 terminal cisternae ( triad) in cardiac muscle : 1T + 1 terminal cisternae ( diad )

16

contraction - appearance of bands

- shortening of H band + I band + sarcomere
-A band remains the same length

17

H band after contraction

shorter

18

A band after contraction

same

19

I band after contraction

shorter

20

sarcomere band after contraction

shorter

21

muscle contraction - post synaptic ligand binding leads to muscle cell depolarization in the

motor end plate

22

muscle depolarization travels muscle cell and down the

T-tubule

23

muscle cells - T - tubule receptor

dihydropyridine receptor

24

muscle cells - sarcoplasmic reticulum receptor

ryanodine receptor

25

• At the synapse of a neuromuscular junction, which ion influx into the axon triggers the release of neurotransmitter?

Calcium, through voltage-gated channels

26

• After presynaptic neuron neurotransmitter release, postsynaptic ligand binding leads to the depolarization of which membrane?

The motor end plate of the muscle cell (postsynaptic membrane)

27

• As an action potential travels along a muscle cell, it goes down into invaginations in the membrane called what?

T tubules

28

• A new drug inhibits the ryanodine receptor. What ion will not be released from the sarcoplasmic reticulum as a result?

Calcium

29

• During skeletal muscle contraction, what is the result of calcium binding to troponin C?

A conformational change that allows tropomyosin out of the myosin-binding groove on actin filaments

30

• During skeletal muscle contraction, which bands of the sarcomere shorten in length?

H band and I band between the Z lines (HIZ shrinkage)

31

• Ryanodine receptors on the ____ surface are coupled with ____ receptors on the cell membrane.

Sarcoplasmic reticulum; dihydropyridine

32

• In a sarcomere, the M line is the site of ____ (actin/myosin) attachment and the Z line is the site of ____ (actin/myosin) attachment.

Myosin, actin

33

• What happens during a power stroke in a myocyte?

Myosin releases ADP and inorganic PO43- and is displaced on the actin filament

34

• A poison affects the release of certain molecules, such that myosin cannot be displaced on the actin filament. What molecules are these?

ADP and inorganic PO43-

35

• In a sarcomere, why does the A band remain the same length during contraction?

The A band represents myosin, which is fixed relative to sarcomere contraction between the Z lines

36

• What happens when ATP binds to a myosin head that is attached to the actin filament?

It triggers its release; subsequent hydrolysis of the ATP to ADP places myosin in a cocked position for the next contraction cycle

37

• What are T-tubules, and what is their relation to the muscle?

T-tubules are extensions of plasma membrane juxtaposed with terminal cisternae and are part of the sarcoplasmic reticulum

38

• What are the differences between skeletal muscle T-tubules and cardiac muscle T-tubules?

Skeletal muscle T-tubules = 1 T-tubule & 2 terminal cisternae (triad), cardiac muscle T-tubules = 1 T-tubule & 1 terminal cisterna (diad)

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