Support Us

If you found our community helpful, your small donation will help us reach more students around the globe. You may also like us on Facebook or follow us on Twitter.
New Topic  
harpo10
wrote...
4 years ago
A) What is an example of a possible depolarizing event.
B) Explain the cause of the rapid change in membrane potential during the period in which it increases after the depolarizing event.
C) Explain how the membrane potential reestablishes the starting value at the resting membrane potential, in a period of rapid decreasing of membrane potential.
  • Read 975 times
  • 1 Reply
replies
wrote...
*
*
Posts: 16058
Credits: 3546
4 years ago
A) What is an example of a possible depolarizing event.

An axon becoming more positive inside when sodium ions enter the cell during an action potential.

B) Explain the cause of the rapid change in membrane potential during the period in which it increases after the depolarizing event.

Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane. These channels are shut when the membrane potential is near the resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold value. When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential. This then causes more channels to open, producing a greater electric current, and so on. The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential. The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, and the ion channels then rapidly inactivate. As the sodium channels close, sodium ions can no longer enter the neuron, and they are actively transported out the plasma membrane. Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state.

C) Explain how the membrane potential reestablishes the starting value at the resting membrane potential, in a period of rapid decreasing of membrane potential.

As the sodium channels close, sodium ions can no longer enter the neuron, and they are actively transported out the plasma membrane. Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, called the refractory period, due to additional potassium currents. This is the mechanism which prevents an action potential traveling back the way it just came.
✓ Why won't you follow us on Twitter? Small Smiley
New Topic      
This topic is currently locked from adding new posts. Only administrators and moderators can reply. If you'd like to contribute to this topic, start a new thread and make reference to this one. Otherwise, contact a moderator for more options.

Control Panel

Click to ask a question. 305 Students and 17 members are standing by to answer all your science and biology homework problems, free. So far today, 182 guests have joined.
Dictionary
Search Images
Related Images
Views
1121
Rating

Views
366
Rating

Views
493
Rating