NervousSystem1I - Nervous System I: The Action Potential 1....

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1 Nervous System I: The Action Potential 1. a. The action potential changes the membrane potential from -70 mV (resting) to +30 mV and back again to the resting membrane potential. b. This results from a change in membrane permeability Frst to Sodium then to potassium due to the opening of what type of ion channels? voltage gated ion channels 2. a. Where is the density of voltage-gated Na channels the greatest? They are located throughout the neuron more densely in the axon and in greatest density in the axon hillock b. What areas of the neuron generate signals that open these voltage- gated channels? The Axon is the transmitter of the signal that orginates in the Axon hillock c. Opening of these channels causes the membrane to depolarize (voltage change). 3. a. If the membrane reaches the trigger point, known as threshold , what electrical potential will be generated? Action potential b. During the depolarization phase, voltage-gated sodium channels open and Sodium ions enter the cell. 4. What are the two processes that stop the potential from rising above 30 mV? a.sodium permeability decreases rapidly, reducing the in±ow of sodium b.potassium permeability increases, Potassium then moves down it’s electro chemical gradient to return cell to resting level 5. a. The opening of voltage-gated K_ channels cause the membrane to repolarize. b. Does K_ move into or out of the cell? into the cell c. If the membrane potential becomes more negative than _70 mV, this is called Hyperpolarization . 6. a. After an action potential, the neuron cannot generate another action potential because sodium channels are inactive. This period is called the refractory
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2 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. the diameter of the axon
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This note was uploaded on 02/15/2011 for the course BIOLOGY 2240 taught by Professor Borek during the Spring '11 term at Georgia State University, Atlanta.

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NervousSystem1I - Nervous System I: The Action Potential 1....

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