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Physiology I

Propagation of Action Potentials - Test 3

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.
Created by: Tri 2



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