The Nerve Impluse

Question 1

Absolute Refractory Period

Answer 1

a time when the membrane is unable to produce an action potential

Question 2

Action potential

Answer 2

messages sent by axons

Question 3

All-or-none law

Answer 3

principle that the amplitude and velocity of an action potential are independent of the stimulus that initiated it

Question 4

Axon hillock

Answer 4

a swelling where the axon exits the cell body

Question 5

concentration gradient

Answer 5

difference in distribution of ions across the neuron’s membrane

Question 6

Depolarize

Answer 6

to reduce polarization toward zero across a membrane

Question 7

Electrical gradient

Answer 7

difference in electrical charges between the inside and the outside of the cell

Question 8

graded potentials

Answer 8

a membrane potential that varies in magnitude in proportion to the intensity of the stimulus

Question 9

hyperpolarization

Answer 9

increase polarization across a membrane

Question 10

local anesthetic

Answer 10

drugs that attach to the sodium channels of the membrane, stopping action potentials

Question 11

local neuron

Answer 11

neurons without an axon

Question 12

myelin

Answer 12

a insulating material composed of fats and proteins

Question 13

myelinated axons

Answer 13

axons covered with myelin sheath

Question 14

polarization

Answer 14

difference in electrical charges between the inside and outside of the cell

Question 15

propagation of the action potential

Answer 15

transmission of an action potential down an axon

Question 16

refractory period

Answer 16

time when the cell resists the production of further action potentials

Question 17

relative refractory period

Answer 17

time after the absolute refractory period that requires a stronger stimulus to initiate an action potential

Question 18

resting potential

Answer 18

Difference in voltage in a resting neuron

Question 19

saltatory conduction

Answer 19

the jumping of action potentials from node to node

Question 20

selectively permeable

Answer 20

ability of some chemicals to pass more freely than other through a membrane

Question 21

sodium-potassium pump

Answer 21

mechanism that actively transports sodium ions out of the cell while drawing in two potassium ions

Question 22

threshold of excitation

Answer 22

minimum amount of membrane depolarization necessary to trigger an action potential

Question 23

voltage-gated channels

Answer 23

membrane channel whose permeability to sodium (or some other ion) depends on the voltage difference across the membrane