Action Potentials Flashcards
What is the absolute refractory period?
During this time it is impossible for the cell to fire another action potential.
What causes the absolute refractory period?
Due to all-or-none activation & the voltage-gated Na+ channels’ closed inactivation gates
What is the relative refractory period?
During this time a larger-than-normal EPSP can elicit an action potential. Begins once the voltage-gated Na+ channels start to reset to the resting state, and ends when they are all reset
What is the purpose of the refractory period?
Keeps the Action Potential flowing (propagating) in one direction
What does a modest increase in potassium do to neuron excitability?
Increases membrane excitability
Depolarizes Vm moving closer to threshold
What does a large increase in potassium do to neuron excitability?
Reduces membrane excitability
Depolarizes membrane and cause inactivation of voltage gated Na+ channels
What does a large decrease in potassium do to neuron excitability?
Reduces membrane excitability
Hyperpolarizes membrane further from threshold
What does a large decrease in calcium do to neuron excitability?
Increases membrane excitability
What does a large increase in calcium do to neuron excitability?
Reduces membrane excitability
How do potassium concentrations changes neuron excitability?
Changes excitability of neurons and other excitable tissue
How do calcium concentrations changes neuron excitability?
Ca++ binds to external surfaces of Na+ channel setting their excitable state
Where is the action potential initiated?
Axon hillock
Is an action potential propagation non-decremental?
Yes
What does myelin do?
Functions as insulator; Speeds up Conduction Velocity of Action Potential; Conserves Axon energy
What is “Saltatory COnduction of AP”?
AP jumps from nodes node
