Membrane Potentials and Action Potentials

Question 1

what are the basic structures in a neuron

Answer 1

cell body
dendrites
axon

Question 2

what does the cell body do

Answer 2

houses the nucleus and other typical cell organelles

Question 3

what do dendrites do

Answer 3

they are cellular extensions of the neuron and characterized by the presence of ligand (neurotransmitter) gated ion channels. They also conduct local potentials

Question 4

what is an axon

Answer 4

extension of the cell body and is typically opposite the side of the cell body where dendrites are located (covered by the plasma membrane).
* characterized by the presence of voltage-gated ion channels and the ability to conduct an action potential

Question 5

define diffusion potential

Answer 5

caused by an ion concentration difference on either side of a membrane

Question 6

define nernst potential

Answer 6

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

Question 7

define electrical dipole layer

Answer 7

dichotomous distribution of ions on either side of the membrane represents a voltage change

Question 8

what assumptions are made when using the Nernst equation

Answer 8

• equation can only be used for one ion at a time
• membrane must be completely permeable to that ion
• ion must be at equilibrium

Question 9

what are characteristics of action potential propagation

Answer 9

• it is all or none
• it is self-propagating: each region of depolarization serves to generate action potentials on either side
• it is non-decremental: it does not decrease in strength

Question 10

what is the difference between ligand and voltage gated channels

Answer 10

ligand involves the attachment of a chemical messenger while voltage involves a change in the membrane potential

Question 11

steps for action potential propagation

Answer 11

1. resting stage (-90mV)
2. Depolarization stage (membrane becomes permeable to Na+ and may overshoot large axons)
3. repolarization stage (Na+ channels close, K+ channels open more than normal)
4. Sodium and Potassium conductance

Question 12

difference between orthodromic and antidromic direction

Answer 12

orthodromic direction is the direction normally taken while antidromic is the opposite directions

Question 13

what is the principle lipid found in myelin sheaths

Answer 13

sphingomyelin

Question 14

what does dendrites mean

Answer 14

branches

Question 15

what is axolemma characterized by

Answer 15

it is a plasma membrane characterized by the presence of voltage-gated ion channels and the ability to conduct an action potential

Question 16

what does the cell membrane function to maintain

Answer 16

separate intracellular and extracellular environments

Question 17

what are ways to increase the propagation of an action potential?

Answer 17

increasing the diameter of the axon and increasing the membrane resistance of the axon