Membrane and Action Potentials

Question 0

What are the relative concentrations of K+, Na+, Ca++, and Cl- around a cell

Answer 0

Na+, Ca++, & Cl- more concentrated outside cell

K+ more concentrated inside the cell

Question 1

Describe the components of a typical neuron

Answer 1

Cell body-Houses nucleus, characterized by local potentials, controlled by voltage-gated ion channels
Dendrites-Receive signals, conduct local potentials, controlled by ligand-gated ion channels
Axon-Extension of the cell body opposite the dendrite, carries action potential, covered by axolemma that carries voltage-gated ion channels

Question 2

Diffusion Potential

Answer 2

Caused by ion concentration differences on either side of the membrane

Question 3

Nernst Potential

Answer 3

Amount of energy needed to keep a molecule from crossing the membrane

Question 4

What is the Nernst Equation?

Answer 4

E=z(61.5)+log([ion outside]/[ion inside])

Only used for one ion at a time

Question 5

Donnan-Equilibrium

Answer 5

If equilibrium is to be reached with two permeant ions, electrical potential must exactly balance the concentration gradients of both ions

Question 6

What is the Goldman equation used for?

Answer 6

To find the EMF of more than one ion at a time

Question 7

What are the characteristics of an action potential?

Answer 7

1) Self-propogatting
2) Does not decrease in strength
3) All-or-none principle

Question 8

What are the characteristics of a local potential?

Answer 8

1) Not self propogating
2) Does decrease in strength
3) Not all-or-none

Question 9

Describe the structure of a voltage-gated Na+ channel

Answer 9

Has 4 domains arranged in a circular configuration
Each domain has 6 hydrophobic transmembrane segments
S4 segment has a high + charge
Inactivation gate is associated with a hydrophilic linkage b/w domains 3 & 4

Question 10

When are the 2 gates of a Na+ channel opened and closed during Na+ movement?

Answer 10

Inactivation gate is opened from -90mV to +35mV
Activation gate opens around -70mV to -50mV and remains open until +35mV (both gates are open from -70mV to +35mV)
The inactivation gate is closed and the activation gate is opened from +35mV to -90mV for repolarization

Question 11

How do voltage-gated K+ channels function?

Answer 11

The channels dehydrate the K+ to make it small enough to fit through the small channel