EK 1001 Bio Question

[eybc20]

#834:
At the neuromuscular junction, neurotransmitters cross the synaptic cleft and depolarize the muscle cell, which opens:

A) Sodium-gated channels
B) Potassium-gated channels
C) Calcium-gated channels
D) Chloride-gated channels

The answer, according to the book, is C.

I'm confused at a couple of points, the first being what "Calcium-gated channel" means. It was my impression that in neurons/muscles we're talking about voltage-gated ion channels, not ligand-gated channels. Am I incorrect here? Calcium binds troponin, but I wouldn't consider troponin as a "calcium-gated channel".

Secondly, I thought that when you stimulate the motor end plate, you're opening voltage-gated sodium channels, which like a neuron, depolarize to an action potential which then allows an influx of calcium from the SR. EK's wording makes it sound like the myofiber is experiencing depolarizations, not an action potential, which would lead me to think the answer would be A over C.

Thanks in advance!

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[Temperature101]

#834:
At the neuromuscular junction, neurotransmitters cross the synaptic cleft and depolarize the muscle cell, which opens:

A) Sodium-gated channels
B) Potassium-gated channels
C) Calcium-gated channels
D) Chloride-gated channels

The answer, according to the book, is C.

I'm confused at a couple of points, the first being what "Calcium-gated channel" means. It was my impression that in neurons/muscles we're talking about voltage-gated ion channels, not ligand-gated channels. Am I incorrect here? Calcium binds troponin, but I wouldn't consider troponin as a "calcium-gated channel".

Secondly, I thought that when you stimulate the motor end plate, you're opening voltage-gated sodium channels, which like a neuron, depolarize to an action potential which then allows an influx of calcium from the SR. EK's wording makes it sound like the myofiber is experiencing depolarizations, not an action potential, which would lead me to think the answer would be A over C.

Thanks in advance!

...............

 

[Manipulator55]

#834:
At the neuromuscular junction, neurotransmitters cross the synaptic cleft and depolarize the muscle cell, which opens:

A) Sodium-gated channels
B) Potassium-gated channels
C) Calcium-gated channels
D) Chloride-gated channels

The answer, according to the book, is C.

I'm confused at a couple of points, the first being what "Calcium-gated channel" means. It was my impression that in neurons/muscles we're talking about voltage-gated ion channels, not ligand-gated channels. Am I incorrect here? Calcium binds troponin, but I wouldn't consider troponin as a "calcium-gated channel".

Secondly, I thought that when you stimulate the motor end plate, you're opening voltage-gated sodium channels, which like a neuron, depolarize to an action potential which then allows an influx of calcium from the SR. EK's wording makes it sound like the myofiber is experiencing depolarizations, not an action potential, which would lead me to think the answer would be A over C.

Thanks in advance!

1) Action potential
2) Ca channels open
3) Ach release cross and bind
4) Na channels open

Seems like a typo

 

[lolcat]

Calcium channels are located on the pre-synaptic terminal and release the synaptic vesicles when activated. But I think it's A also.. Probably a typo. This is why I didn't use this book

 

[pm1]

#834:
At the neuromuscular junction, neurotransmitters cross the synaptic cleft and depolarize the muscle cell, which opens:

A) Sodium-gated channels
B) Potassium-gated channels
C) Calcium-gated channels
D) Chloride-gated channels

The answer, according to the book, is C.

I'm confused at a couple of points, the first being what "Calcium-gated channel" means. It was my impression that in neurons/muscles we're talking about voltage-gated ion channels, not ligand-gated channels. Am I incorrect here? Calcium binds troponin, but I wouldn't consider troponin as a "calcium-gated channel".

Secondly, I thought that when you stimulate the motor end plate, you're opening voltage-gated sodium channels, which like a neuron, depolarize to an action potential which then allows an influx of calcium from the SR. EK's wording makes it sound like the myofiber is experiencing depolarizations, not an action potential, which would lead me to think the answer would be A over C.

Thanks in advance!

I think C might actually be right. Sodium causes the depolarization, it seems like the question is asking what happens after depolarization

Na causes the depolarization, then after that the AP goes through T tubule triggering the release of Ca from the SR.

 

[lolcat]

I think C might actually be right. Sodium causes the depolarization, it seems like the question is asking what happens after depolarization

Na causes the depolarization, then after that the AP goes through T tubule triggering the release of Ca from the SR.

Wow, how did I not see that. Nice

 

[Temperature101]

I think C might actually be right. Sodium causes the depolarization, it seems like the question is asking what happens after depolarization

Na causes the depolarization, then after that the AP goes through T tubule triggering the release of Ca from the SR.

I am not sure C is the correct answer because neurotransmitter leave the presynaptic cleft after Ca++gated channel is open not before. I believe A is the correct answer unless that question is poorly worded.