Skeletal muscle part 2

Question 1

Describe the events which occur on the neuromuscular junction

Answer 1

1. ) action potential will cause Ca2+ voltage gated ion channels to be opened
2. ) this will cause Ca2+ to go down their electrochemical gradient from the cytosol
3. ) the Ca2+ increase in the cell will signal the synaptic vesicle containing Ach to be released via exocytosis on (as they fuse to the presynaptic membrane)
4. ) the Ach will be released to the synaptic cleft
5. ) Ach will bind to ligand gated receptors which will enable Na+ and K+ ions to pass through (Na+ innflux, K+ efflux) depolarizing the muscle cell
6. ) the depolarization will travel to the myofibrils
7. ) this will trigger the opening of voltage gated Ca2+ channels to open on the SR
8. ) this will release Ca2+ down their electrochemical gradient, increasing the Ca2+ concentration in the cytoplasm
9. ) as Ca2+ binds to troponin, changing the conformation of tropomyosin, thus a exposing myosin binding sites on the actin molecule

Question 2

When Ca2+ is low in the SR, active transporters mediate Ca2+ back via the expense of an ATP? true/false

Answer 2

true

Question 3

Are the ligand gated ach channels always open?

Answer 3

no, as Ach is immediately converted to acteyl and choline, by an enzyme called acteylcholineesterase

Question 4

excitation contraction coupling?

Answer 4

when a motor neuron, innervates muscle fibres

Question 5

What is isotonic contraction?

Answer 5

a contraction where the tension developed by the muscle remains almost constant while the muscle changes lenght

Question 6

what is isometric contraction?

Answer 6

a contraction where the tension developed does not exceed the resistance of object and there is no change in muscle length

Question 7

What is a motor unit?

Answer 7

consists of a motor neuron and all the skeletal muscles it innervates

Question 8

What is a muscle twitch?

Answer 8

the brief contraction in all the muscle fibres in a motor unit in response to a single action potential

Question 9

How is muscle contraction controlled?

Answer 9

frequency of stimulation

recruiting additional motor units

Question 10

list in order temporal summation

Answer 10

(force of contraction vs time (msec))
single twitch
wave summation
unfused wave summation
fused wave summation

Question 11

How does elasticity increase the amount of force generated?

Answer 11

as it twitches, it does not have enough time to contract back during temporal summation, thus the force generated after will increase

Question 12

What are the types of skeletal muscle fibres?

Answer 12

SO (slow oxidative) type 1
FOG (fast oxidative-glycolitic) type 2B
FG (fast glycolitic) type 2A

Question 13

What are SO composed of?

Answer 13

red color
a lot of myoglobin and mitochondria
they use