Action Potential Flashcards
(39 cards)
What happens during the Rising/Depolarization stage
Na+ channels open
Na+ rushes into cell
Makes cell membrane less negative
What happens during Overshoot stage
Na+ channels close
results in repolarization
makes cell membrane more negative
What happens during Falling stage
K+ channels open
K+ rushes out of cell
results in repolarization
makes cell membrane more negative
What happens in Undershoot stage
K+ channels close
hyperpolarization
Na+ channel resting state
Activation gate is close
Inactivation gate is open
Na+ can’t pass through channel
Na+ channel activation state
Activation gate is open
Inactivation gate is open
Na+ can pass through channel
Na+ channel inactivation state
Activation gate is open
Inactivation gate is closed
Na+ can’t pass through channel
Given the same membrane potential, which channel is MORE likely to open
Na+ channel
What is the K+ channel responsible for
repolarization
Threshold
- enough depolarization to trigger an action potential
- inward flow of Na+ is greater than outward flow of K+
Factors that affect speed of action potential
axon diameter
myelination
Larger axon diameter results in
faster AP
Larger axon diameter results in
saltatory conduction which is faster
How does hypocalcemia affect threshold
increases chances of it being met
How does hypercalcemia affect thrershold
decreases chances of it being met
Symptoms of hypocalcemia
neuropsych
neuromuscular irritability
Chvostek’s sign
Trousseau’s sign
Symptoms of hypercalcemia
mental confusion fatique muscle weakness diminished reflexes coma
Lowered Na+ ECM concentration has what affect
decreases chances of threshold bieng met
reduces peak amplitude
MS
affects CNS
damages oligodendrites
causes demylination
Guillan Barre
affects PNS
damages peripheral myline
causes demylination
absolute refractory period
second action potential not possible during this period of time, regardless of strength
Relative refractory period
second action potential possible, but it “costs” more
How does local anesthesia work
LA blocks Na_ channels, inhibits action potential generation, reduces pain sensation
Ouabain
causes Na/K pump to stop pumping. However the chem. conc. gradients take time to degrade and thousands of APs can go out
