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Physiology I
Propagation of Action Potentials - Test 3
| Question | Answer |
|---|---|
| Does degradation or decrement occur during the action potential? | No |
| Is there a change in shape of wave form during the action potential? | No |
| True or false, the action potential is an all or none response? | True |
| True or false, the action potential is a self reinforcing signal? | True |
| Action Potential propagation is dependent upon:? | Properties of the voltage gated channel and Cable properties of the cell |
| What are cable properties of the cell? | 1. Resistance (ie. Cell membrane, Ion concentrations, and Cell Diameter) 2. Capacitance |
| What is the threshold determined by? | The protein structure of the voltage gated channel |
| How many ions move per a protein cycle? | 5-6 ions |
| True or False, the action potential at one location can act as a stimulus for production of an action potential at an adjacent region of the membrane? | True |
| What is the generation of a new action potential at each site referred to as? | Self Reinforcing Signal |
| True or false, Nerve and muscle cells have the properties of an electrical cable? | True |
| In nerve and muscle cells the plasma membrane act as what? | Insulation |
| In nerve and muscle cells the cytoplasm act as what? | A core conductor |
| True or false, the cytosolic resistance is greater than the membrane resistance? | False, Rm is greater than Rc |
| True or False, Membane resistance has a direct relationship to membrane permeablity? | False, Rm is inveersely related to membrane permeablity |
| Why do ions have difficulty penetrating the membrane? | Because the membrane is nonpolar |
| What is Ri or Rc? | Cytoplasmic Resistance - the resitance of ions to flow in the cytoplasm |
| What determines the velocity of propagation? | Space and Time constants |
| Velocity equals? | Space Constant / Time Constant |
| Define the space constant? | It is a measure of the distance it takes for the initial depolarization voltage to decline by 1/e or about 63%. |
| Define the Time Constant? | It is a measure of the time it takes for the initial action potential voltage to decline by 1/e or about 63%. |
| True or false, If the space constant is large - the potential will spread a greater distance along the axon and bring distant regions to threshold sooner? | True |
| True or False, If a time constant is large - the action potential will be initiated sooner and velocity of the propagation is faster? | False, Small time = faster |
| True or False, it is desireable to have axons with high propagation velocities? | True |
| How does compression of a nerve effect its ability to conduct a nerve impulse? | Compression alters the velocity of conduction by decreasing the cell diameter and in turn decreases the space constant, thus decreasing the propagation velocities |
| What causes saltatory conduction? | Schwann cells |
| What is saltatory conduction? | The conduction of the action potential that jumps from node to node that allows the impulse to travel at great speeds |
| How does Saltatory conduction effect the Velocity of Conduction. | Remember, Velocity is dependent upon the Space Constant and the Time Constant. So the space constant is increased and the Time constant is decreased. |
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Tri 2
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