Chapter 5: Membrane potential and Action Potential

Question 1

exist across the membranes ofvirtually all cells of the body

Answer 1

electrical potentials

Question 2

cells that are
capable of generating rapidly changing
electrochemical impulses at their membranes, and
these impulses are used to transmit signals along
the nerve ormuscle membranes

Answer 2

nerve and muscles

Question 3

the potential difference between the inside
and outside, called?

Answer 3

diffusion potential

Question 4

The diffusion potential level across a membrane that exactly opposes the net diffusion of a particular ionthrough the membrane

Answer 4

nernst potential

Question 5

When a membrane is permeable to several different ions,the diffusion potential that develops
depends on three factors:

Answer 5

1. polarity of the electrical charge of each ion
2. the permeability of the membrane to each ion
3. theconcentrations
   of the respective ions on the inside and outside
   of the membrane

Question 6

rapid changes in the
membrane potential that spread rapidly
along the nerve fiber membrane

Answer 6

action potentials

Question 7

RESTING STAGE

Answer 7

This is the resting
membrane potential before the action
potential begins. The membrane issaid to
be “polarized” during this stage because of
the −90millivolts negative membrane potential that is present.

Question 8

potential rising rapidly in
the positive direction

Answer 8

depolarization

Question 9

rapid diffusion of potassium
ions to the exterior re-establishes the
normal negative resting membrane potential

Answer 9

repolarization

Question 10

The necessary actor in causing both depolarization andrepolarization of the nerve
membrane during the action potential

Answer 10

voltage-gated sodium channel

Question 11

also plays an
important role inincreasing the rapidity of
repolarization of the membrane

Answer 11

voltage-gated potassium channel

Question 12

one near the outside of the channel

Answer 12

activation gate

Question 13

one near the outside of the channel

Answer 13

activation gate

Question 14

another near
the inside

Answer 14

inactivation gate

Question 15

Activation of the Sodium Channel

Answer 15

When the membrane potential
becomes less negative than duringthe
resting state, rising from −90 millivolts
toward zero,it finally reaches a voltage—
usually somewhere between−70 and −50
millivolts—that causes a sudden
conformational change in the activation
gate, flipping it all the wayto the open
position.

Question 16

usual voltage activated sodium channels

Answer 16

fast channels

Question 17

central core of the fiber

Answer 17

axon

Question 18

The axon is filled in its center
with ________, which isa viscid intracellular fluid

Answer 18

axoplasm

Question 19

Surrounding the axon is a _________ that is often much
thicker than the axon itself.

Answer 19

myelin sheath

Question 20

About once every 1 to 3 mil-
limeters along the length of the myelinsheathis a

Answer 20

node of ranvier

Question 21

Then the Schwann cell rotates around the axon many times, laying
down multiplelayers of Schwann cell membrane containing the lipid substance

Answer 21

sphingomyelin

Question 22

action potentialsare conducted from
node to node

Answer 22

saltatory conduction

Question 23

the nerve impulse jumps along
the fiber,which is the origin of the term?

Answer 23

saltatory

Question 24

Saltatory conduction is of value for two reasons;

Answer 24

1. causing the depolarization process to jump long intervals along the axis of the nerve fiber
2. conserves energy for the
   axon because only the nodes depolarize