Nervous System Overview and Action Potentials 2 Flashcards
What is the absolute refractory period?
during this time, it is impossible for the cell to fire another action potential
-Na+ have a closed inactivation gate
What is the relative refractory period?
during this time, a larger-than-normal EPSP can elicit an action potential
-begins once the VG Na+ channels start to rest to the resting state
What is hyperkalemia?
it is an increase in extracellular potassium levels
What does an ECF potassium concentration of 3.5 < K < 6 mM cause?
increase membrane excitability
-depolarize Vm moving closer to threshold
What does an ECF potassium concentration > 6 mM cause?
reduce membrane excitability
-depolarize membrane and cause inactivation of voltage gated Na+ channels
What is hypokalemia and what does it cause?
decrease in ECF potassium
-reduces membrane excitability
-hyperpolarizes membrane further from threshold
What does hypercalcemia cause?
reduce membrane excitability
What does hypocalcemia cause?
increase membrane excitability
Where does the action potential begin?
at the axon hillock
What causes the action potential to only be able to move in one direction down the neuron?
the inactivation gate of the Na channels
What causes the action potential to move down the neuron?
the Na diffuses and depolarizes the membrane at the next segment of the axon
What is saltatory conduction of AP?
when the action potential jumps from internode to internode jumping over the nodes of Ranvier
What does myelin do?
works as an insulator and speeds up the conduction velocity of action potential
-conserve axon energy
What are the two things that increase the velocity of the AP?
myeline and increases the diameter of the axon
What disease can cause demyelination of the CNS?
multiple sclerosis
