Muscle Excitation and Contraction

Question 1

FOr control of skeletal muscle contraction….

innervation is from…..

neurotransmitter is……

receptor on muscle is…..

Answer 1

innervation from motor neurons

acetylcholine is the NT

acts on nicotinic receptors

Question 2

Describe the steps of the signal transduction in muscle.

Answer 2

1. acetylcholin acts on nicotinic receptors
2. nicotinic receptors are Na+ channels that causes the membrane to depolarize
3. depolarization opens VG calcium channels
4. calcium enters the muscle cell
5. the VG channels are physically connected to ryanodine receptors on the sarcolasmis reticulum, which opens and releases intracellular Ca++
6. the elevated intracellular Ca++ initiates contraction

Question 3

what is the average ratio of nerve to muscle fibers?

Answer 3

1:23

Question 4

Again, the acetylcholin nicotinic receptor is a ____ channel.

Answer 4

a sodium

Question 5

What are the voltage gated calcium channels called?

Answer 5

L channels

Question 6

THe L channels are physically coupled to the ___ receptors on the _____.

Answer 6

the ryanodine receptors on the sarcoplasmic reticulum

Question 7

Intracellular calcium concentration must reach ___ to trigger contraction.

Answer 7

1 micomolar (or 10-6 M)

Question 8

How does calcium cause contraction?

Answer 8

It binds to TnC in the troponin complex to cause a conformational change in tropomyosin, revealing the actin binding sites for myosin to bind to.

Question 9

the A band has ___ fibers

the I band has ____ fibers

Answer 9

A = myosin

I = actin

Question 10

Which are the dihydropyridine receptors?

Answer 10

the L calcium channels

Question 11

What molecule needs to be present in order for contraction to occur besides Ca++?

Answer 11

ATP - that’s where the energy comes from