Chapter 1: Nerve Cells and Nerve Impulses Flashcards
When the neuron’s membrane is at rest, where are the sodium ions and potassium ions most concentrated?
Answer: Sodium is mostly outside and potassium is mostly inside.
When the membrane is at rest, what are the forces acting on sodium ions?
Answer: Both the concentration gradient and the electrical gradient tend to move sodium ions into the cell.
When the membrane is at rest, what are the forces acting on potassium ions?
Answer: The concentration gradient tends to move potassium ions out of the cell, and the electrical gradient tends to move them into the cell.
Which direction does the sodium-potassium pump move ions?
Answer: It moves sodium ions out of the cell and potassium ions into the cell
Under what conditions does an axon produce and action potential?
Whenever the membrane’s potential reaches the thershold
If a membrane is depolarized to twice its threshold, what happens?
The neuron produces the same action potential it would at the threshold
To which part or parts of a neuron does the all-or-none law apply?
Axons
During the rising portion of the action potential, which ions are moving across the membrane and in which direction?
Sodium ions move in
After the action potential reaches its peak, the potential across the membrane falls toward its resting level. What accounts for this recovery?
Potassium ions move out because their channels are open and the concentration gradient pushes them out.
What does myelin sheath of an axon accomplish?
It enables action potentials to travel more rapidly.
What causes the refractory period of an axon?
The sodium channels are closed.
About what percentage of the brain does an average person use?
100 percent
