Nervous System I: The Action Potential - Self Test

NOTE: This quiz is designed to be completed using the InteractivePhysiology CD that you used in the Muscle Lab.  However, you should be able to answer most of the questions without the CD by using your class notes and your textbook.

1. The action potential changes the membrane potential from _-70___ mV (resting) to _+30___ mV and back again to the resting membrane potential.

 This results from a change in membrane permeability first to __Na+_____ then to __K+_____ due to the opening of what type of ion channels? ___Voltage-gated channels___________________

 

2. a. Where is the density of voltage-gated Na+ channels the greatest? ___Axon hillock/Initial segment________

   b. What areas of the neuron generate signals that open these voltage-gated channels? __Dendrites, Cell body_______

   c. Opening of these voltage-gated Na+ channels causes the membrane to _depolarize_______ (voltage change).

 

3. a. If the membrane reaches the trigger point, known as __Threshold_____, what is the name of the electrical potential that is generated? ______Action Potential____________________________________

   b. During the depolarization phase, voltage-gated __Na+________ channels open and _Na+______ enters the cell.

 

    4. What are the two processes that stop the potential from rising above 130 mV?

   a. Inactivation of voltage-gated Na+ channels

   b. Activation (opening) of voltage-gated K+ channels

 

5. a. The opening of voltage-gated K+ channels cause the membrane to __Repolarize after a depolarization_______.

   b. Does K+ move into or out of the cell? ___OUT_______________

   c. If the membrane potential becomes more negative than -70 mV, this is called _hyperpolarization________.

   d. This potential is caused by what characteristic of K+ permeability? ___slow closing of K+ channels_________.   

6. a. After an action potential, the neuron cannot generate another action potential because __Na+_____ channels are inactive. This period is called the _Absolute Refractory__ period.

   b. During the __Relative Refractory______ period, the cell can generate another action potential but only if the membrane is ____More_______ (more or less) depolarized.

 

    7. a. Conduction velocity along the axon is increased by what two characteristics?

    1. _Diameter of the axon___________

    2. _Myelination of the axon________

   b. Conduction along a myelinated axon is called __Saltatory________________________
   conduction.