Physiology Clements-Jewery Action Potentials

Front 1

All neuronal information is carried and encoded in the form of __________ __________

Back 1

action potentials

Front 2

A cell must be depolarized to the point of its __________ for an action potential to be generated

Back 2

threshold

Front 3

Action potentials vary in amplitude depending on the size of the stimulus (True/False)

Back 3

False (action potentials are all-or-none) (digital) (action potential FREQUENCY can be altered by the size and duration of a stimulus)

Front 4

What sets the limit on the frequency of action potentials?

Back 4

The absolute refractory period

Front 5

Na+ conductance is highest during what phase of an action potential?

Back 5

depolarization

Front 6

gNa is __________ (greater than, equal to, less than) gK at the peak of an action potential

Back 6

equal to

Front 7

During an action potential, there is ____________ (inward/outward) Na+ conductance and _________ (inward/outward) K+ conductance

Back 7

inward, outward

Front 8

During an action potential, the extracellular concentration of Na+ decreases and extracellular K+ increases, and the concentrations must be returned to normal by the Na/K ATPase before the next action potential can occur. (True/False)

Back 8

False (the amount of ions exchanged in order to depolarize the membrane is not significant enough to affect the ion concentrations. Even without the Na/K ATPase, the cell could depolarize thousands of times before the concentrations would be significantly affected.

Front 9

Label

Back 9

Front 10

Voltage-gated Na+ channels open under a ________ _________ process

Back 10

positive feedback

Front 11

What must the voltage-gated Na+ channels overcome in order to initiate an action potential?

Back 11

The K+ efflux

Front 12

hyperparathyroidism leads to __________calcemia which leads to __________ excitability which leads to muscle ___________

Back 12

hyper, deceased, weakness

Front 13

What are the two main factors that prevent a membrane potential from reaching the nernst potential of Na+ during an action potential?

Back 13

Decreased driving force of Na+ at the peak of the action potential and the closing of innactivation gates on the voltage-gated Na+ channels cause the Na+ influx to be brief and only depolarize the membrane to ~+30mV

Front 14

During repolarization the activation gate on the Na+ channel is __________ and the inactivation gate is ___________

Back 14

closed, closed

Front 15

During the peak of an action potential the activation gate on the Na+ channel is __________ and the inactivation gate is ___________

Back 15

open, closed

Front 16

During depolarization the activation gate on the Na+ channel is __________ and the inactivation gate is ___________

Back 16

open, open

Front 17

The Na+ activation gate swings ________ with depolarization and the inactivation gate swings _________

Back 17

open, shut

Front 18

What causes the refractory period?

Back 18

The refractory period is caused by the recovery period of the membrane from Na+ gate innactivation. The membrane must have enough innactivation gates re-open in order for a Na+ influx significant enough to trigger the next action potential

Front 19

What effect would a drug have that prolongs the time of recovery of Na+ inactivation channels?

Back 19

It would cause a prolonged absolute refractory period

Front 20

Hyperkalemia causes __________

Back 20

inexcitability (high levels of extracellular K+ make the membrane potential more positive, thus closing the innactivation gates before the activation gates open)

Front 21

Which channels account for the high K+ permeability at rest?

Back 21

The "inward rectifier" channels

Front 22

Action potential duration is dependent on the magnitude of ____ currents

Back 22

K+

Front 23

Smaller K+ currents trigger ________ action potential duration

Back 23

longer

Front 24

What is responsible for the plateau in a cardiac action potential

Back 24

The Ca++ influx

Front 25

decreased internal resistance will result in a _________ space constant and __________ conduction velocity

Back 25

increased, increased

Front 26

Myelination increases _________ resistance thereby increasing conduction velocity

Back 26

membrane