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UNIT 9 The Nervous System
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Name __________________________________
Date _________________ Period _____
Part 3 - Membrane Potential
1. Every cell has a voltage, much like a battery has a voltage (between it’s two terminals). Voltage is a
measure of how much a charge (positive or negative) “wants” to flow. The voltage across the cells of your
body is the:
2. The inside (cytoplasm or cytosol) is _______________ compared to the outside of the cell (extracellular
fluid) which is ______________.
3. When a neuron is at rest (not being stimulated) it maintains a _____________ _____________.
4. The average resting potential of many vertebrate neurons is: ________ millivolts (mV).
5. The sodium-potassium pump is the main contributor to the resting membrane potential of most cells. Fill
in the general process of how it maintains this resting potential.
6. What is the second main contributor to the resting membrane potential, and which channel is more
abundant?
7. Describe what an electrochemical gradient is, in your words so that you’ll be able to explain it on a test,
hint hint!
8. The inside of a cell has a higher concentration of _____ ions and the outside has a higher concentration of
_____ ions.
9. Describe the two types of polarization events that occur and label them with a simple graph.
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UNIT 9 The Nervous System
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Part 4 - The Action Potential
10. Action potentials (or nerve impulses) are created when the membrane is depolarized to about _____
millivolts (mV).
11. Where on the neuron does the action potential originate? ____________________________________
12. A threshold potential is:
13. Graded potentials are the result of activated gated ion channels whereas action potentials are caused by
___________________________________.
14. What are the two channels that are used to create action potentials?
15. What are the three phases of an action potential?
16. Fill in the sequence of events that occur during an action potential.
17. Describe the nature of action potentials.
18. Draw a myelinated neuron and show how action potential travel down the axon at the nodes of Ranvier.
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