Nervous System 2
Supplemental Instruction
Iowa State University
SI Session
Leader:
Course:
Instructor:
Date:
Lauren R
AnS 214
Dr. Selsby
2/11/16
1. The resting membrane potential of a cell is _____________________.
2. What creates a membrane potential? Describe where these substances are in a neutral cell.
3. What is depolarization and how does it affect the possibility of a nerve impulse occurring?
Hyperpolarization?
4. What happens at threshold?
5. Fill in the missing labels for diagram (a).
6. A resting neuron has a high concentration of
____________ ions inside its soma. This ion has a
________________charge. The extracellular fluid, on
the other hand has a high concentration of
________________ ions, the charge is
________________. Given the opportunity,
________________ would diffuse down its
concentration gradient OUT of the cell, while
________________ would diffuse down its concentration gradient INTO the cell. This balance of ions is
maintained by a structure called the __________________________, which exchanges
________________ Na ions from the cytoplasm in return for ________________ K ions from the
extracellular fluid. When combined with the high (-) charged protein concentration within the cell, this
mechanism maintains resting membrane potential at ________________.
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7. When a stimulus causes some of the Na channels of a cell to open at the axon hillock, what happens
to the ion balance?
What effect does this have on resting potential?
This corresponds to what number on diagram (a)?
8. As the cell depolarizes, what critical value does it have to hit, in order to stimulate all Na channels
to snap open?
This is an example of what sort of feedback?
At what point do the Na channels close? This corresponds to what number on diagram (a)?
9. What other channels are being activated as the cell is depolarized?
How does this affect membrane potential?
This corresponds to what number on diagram (a)?
10. What is responsible for the phenomenon of
hyperpolarization?
What counteracts this phenomenon to return the cell
to resting membrane potential?
11. Fill in the blanks of the diagram at right.
Define absolute refractory period.
Define relative refractory period.
12. Fill in the diagram with lines representing the opening and closing of Na and K channels responsible
for the observed changes in membrane potential.
13.
Using the graph of an action potential, match the green numbers with their corresponding
events. Place the number on the line next the correct phrase:
_____ Membrane depolarizes to threshold. Voltage-gated Na+ channels open and Na+ enters the
cell.
_____ The cell returns to resting ion permeability and resting membrane potential.
_____ K+ moves from the cell to the extracellular fluid (the cell is repolarizing).
_____ Rapid Na+ entry depolarizes the cell.
_____ Resting membrane potential.
_____ Na+ channels close and slower K+ channels open.
_____ Depolarizing stimulus.
_____ K+ channels remain open and additional K+ leaves the cell, hyperpolarizing it.
Myelination
15. Explain the role of myelination in signal conduction.
16. What type of myelination is found in the central nervous system?
17. What type of myelination is found in the peripheral nervous system?