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Old 04-29-2012
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Question Calcium uptake and the action potential?

The flow of calcium into the cell is an important component of the upstroke phase of action potentials in which of the following?

Cardiac ventricular muscle
Intestinal smooth muscle
Skeletal muscle fibers
Nerve cell bodies
Presynaptic nerve terminals
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presynaptic nerve terminals
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Originally Posted by Hope2Pass View Post
presynaptic nerve terminals
you think nerve terminal same as cell ?
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Originally Posted by Kabutar111 View Post
you think nerve terminal same as cell ?

Well the questions asking about a cell where influx of Calcium generates an upstroke phase (depolarization) and results in an action potential -

By elimination method -
-Cardiac ventricular muscle = Na+
-Intestinal smooth muscle ...no idea
-Skeletal muscle fibers = Na+
-Nerve cell bodies = Na+
-Presynaptic nerve terminals = Ca+

If there was an option for SA or AV nodal cells then I would've gone with that. Is that the right answer or do I need a long break from my studies ?
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Originally Posted by Hope2Pass View Post
Well the questions asking about a cell where influx of Calcium generates an upstroke phase (depolarization) and results in an action potential -

By elimination method -
-Cardiac ventricular muscle = Na+
-Intestinal smooth muscle ...no idea
-Skeletal muscle fibers = Na+
-Nerve cell bodies = Na+
-Presynaptic nerve terminals = Ca+

If there was an option for SA or AV nodal cells then I would've gone with that. Is that the right answer or do I need a long break from my studies ?
i am little confused with this one so lets, give others a run at it
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Default Im sure on this one..!!!!

The answer is intestinal smooth muscle.....i read about this while answering some offline questions and i got around 3-4 stems related to this concept...so guys u can count on me...........
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Originally Posted by anomali View Post
The answer is intestinal smooth muscle.....i read about this while answering some offline questions and i got around 3-4 stems related to this concept...so guys u can count on me...........
so all smooth muscle CA for upstroke ?
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so all smooth muscle CA for upstroke ?
Yeah..In all smooth muscles the upstroke of action potential is caused by calcium....ill post the explanation in a while..searching for the same....
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Default Here is the explanation......

In intestinal smooth muscle, the upstroke of the action potential is caused by the flow of calcium into the cell. In cells of the cardiac ventricular muscle, the plateau phase of the action potential, but not the upstroke, is accompanied by the flow of calcium into the cells. Skeletal muscle fibers resemble nerve fibers. In both of these cells, the upstroke of the action potential is caused by the flow of sodium into the cell....
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Quote:
Originally Posted by anomali View Post
The answer is intestinal smooth muscle.....i read about this while answering some offline questions and i got around 3-4 stems related to this concept...so guys u can count on me...........
I'm confused with this question...

I would exclude:
- cardiac ventricle muscle - Ca++ is relevant in 2 phase not in the upstroke phase
- skeletal muscle fibers - Na+
- nerve cell bodies
- presynaptic nerve terminals - Ca increase allows e.g. neurotransmitter release but is not responsible for the upstroke phase...

smooth muscle????
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I opened the reply window a while ago so I missed your answer anomali - THANK YOU for your input!

OMG! I didn't know that! Where's this question from? Is it mentioned in KLN?
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I opened the reply window a while ago so I missed your answer anomali - THANK YOU for your input!

OMG! I didn't know that! Where's this question from? Is it mentioned in KLN?
pre test
its kind of mentioned in kaplan but not in straight sense
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Yeah..In all smooth muscles the upstroke of action potential is caused by calcium....ill post the explanation in a while..searching for the same....
Can you please explain your answer, I know the other answers are not right. But in BRS it says:
Mechanism of slow wave production-->is the cyclic opening of Ca2+ channels (depolarization) followed by opening of K+ channels (repolarization)..But it also says in "bold" letters that slow waves are *not action potentials, although they determine the pattern of action potentials. However when I searched online what causes smooth muscle depolarization..it said "acetylcholine" causes smooth muscles to depolarize making them more likely to fire and cause action potential.
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Can you please explain your answer, I know the other answers are not right. But in BRS it says:
Mechanism of slow wave production-->is the cyclic opening of Ca2+ channels (depolarization) followed by opening of K+ channels (repolarization)..But it also says in "bold" letters that slow waves are *not action potentials, although they determine the pattern of action potentials. However when I searched online what causes smooth muscle depolarization..it said "acetylcholine" causes smooth muscles to depolarize making them more likely to fire and cause action potential.
http://www.vivo.colostate.edu/hbooks...slowwaves.html a look at this link

He says there are two types of electrical activity in smooth muscle cells- slow waves and spike potentials. Slow waves cause the formation of spike potentials in the presence of neurotransmitters released in the vicinity of smooth muscle cells by neurons....spike potentials cause the depolarisation above the threshold level and initiate the contraction wave. I guess the calcium is responsible for the upstroke of the depolarisation caused by spike potentials......

hope this supports my answer and clear things for u..........
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Quote:
Originally Posted by anomali View Post
http://www.vivo.colostate.edu/hbooks...slowwaves.html a look at this link

He says there are two types of electrical activity in smooth muscle cells- slow waves and spike potentials. Slow waves cause the formation of spike potentials in the presence of neurotransmitters released in the vicinity of smooth muscle cells by neurons....spike potentials cause the depolarisation above the threshold level and initiate the contraction wave. I guess the calcium is responsible for the upstroke of the depolarisation caused by spike potentials......

hope this supports my answer and clear things for u..........
i do remember reading something of short in guyton but , i can't open that book nomore ,will eat my whole day
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