Membrane potentials and action potentials

Question 1

What is the axon?

Answer 1

An extension of the neural cell that transmits action potentials.

Question 2

What is the axolemma?

Answer 2

membrane of the axon; it has voltage-gated ion channels and conducts an action potential.

Question 3

What is the function of the plasmalemma?

Answer 3

to mainain separate intracellular and extracellular environments. It is permeable to specific ions.

Question 4

What is a diffusion potential?

Answer 4

potential caused by an ion concentraiton difference on either side of the membrane.

Question 5

what is the nernst potential?

Answer 5

the diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ion through a membrane.

Question 6

What is the formula for the nernst potential?

Answer 6

E = z61.5(log[iono/ioni]); E = difference in electrical potential between inside and outside the neuron.

Question 7

What is the charge of an inner membrane at resting potential?

Answer 7

negative

Question 8

What is the charge of an outer membrane at resting potential?

Answer 8

positive

Question 9

equilibrium potential

Answer 9

equilibrium is reached when the electrical force driving ions out of one compartment is equal to the concentrational force driving ions out of the other compartment.

Question 10

What is the principle of electrical neutrality?

Answer 10

The sum of concentrations of cations within any compartment must be equal to the sum of concentrations of anions in that compartment.

Question 11

What is donan gibbs equlibrium?

Answer 11

the electrical potential across a cell membrane must exactly balance the concentration gradients for both ions. The equilibrium for both ions must be equal.

Question 12

What are the three characteristics of an action potential?

Answer 12

It is all or note, it is self-propagating and it doe snot decrease in strength.

Question 13

What are ion channels?

Answer 13

Channels that allow the passage of ions from one side of the membrane to the other. They are selective.

Question 14

What are voltage gated sodium channels?

Answer 14

Channels that involve a change in membrane potential; they have an activation/inactivation gate.

Question 15

When is the inactivation gate opened?

Answer 15

resting potential (-90 mV), -90 to +35 mV

Question 16

When is the activation gate opened

Answer 16

-90 to +35 mV, -70 to - 50 mV, +35 to -90 mV

Question 17

Why are both gates opened from -90 to +35 mV?

Answer 17

Because both gates have to be opened to allow ions to pass through.

Question 18

What are the steps of action potential propagation?

Answer 18

resting, depolarization, repolarization, and sodium & potassium conductance.

Question 19

How can an action potential be increased?

Answer 19

increasing the diameter of the axon (more cross sectional area), increasing the membrane resistance of the axon (myelin), smaller diameter fibers (less resistance)

Question 20

What is saltatory conduction?

Answer 20

The jumping of current flow at the nodes of ranvier during an action potential.

Question 21

What direction is orthodromic?

Answer 21

from the cell body to the synapses

Question 22

What direction is antidromic?

Answer 22

from the synapses to the cell body

Question 23

Do action potentials occur at the myelin or the nodes of ranvier?

Answer 23

nodes of ranvier

Question 24

What is the absolute refractory period?

Answer 24

period during which a second action potential cannot be elicited even with a strong stimulus; energy is derived from ATP; most Na ions in this period are open or inactivated.

Question 25

Wnat is the relative refractory period?

Answer 25

When a stronger than normal stimulus can cause an action potential; the mechanism is an elevated potassium conductance. It occurs during repolarization.