Chapter 3

Question 1

resting potential:

Answer 1

a difference in electrical potential across the membrane of a nerve cell during an inactive period

Question 2

electrostatic pressure/electrical gradient:

Answer 2

the propensity of charged molecules or ions to move, via diffusion, toward areas with the opposite charge

Question 3

sodium-potassium pump:

Answer 3

the energetically expensive mechanism that pushes sodium ions out of a cell, and potassium ions in

Question 4

equilibrium potential:

Answer 4

the point at which the movement of ions across the cell membrane is balanced, as the electrostatic pressure pulling ions in one direction is offset by the diffusion force pushing them in the opposite direction

Question 5

threshold:

Answer 5

the stimulus intensity that is just adequate to trigger an action potential at the axon hillock

Question 6

refractory phase:

Answer 6

temporarily unresponsive or inactivated. 2 types: 1) absolute refractory phase – a brief period of complete insensitivity to stimuli; 2) relative refractory phase – a period of reduced sensitivity during which only strong stimulation produces an action potential

Question 7

saltatory conduction:

Answer 7

the form of conduction that is characteristic of myelinated axons, in which the action potential jumps from one node of Ranvier to the next

Question 8

postsynaptic potential:

Answer 8

a local potential that is initiated by a stimulation at a synapse, which can vary in amplitude, and spreads passively across the cell membrane, decreasing in strength with time and distance

Question 9

spatial summation:

Answer 9

the summation of postsynaptic potentials that reach the axon hillock from different locations across the cell body

Question 10

temporal summation:

Answer 10

the summation of postsynaptic potentials that reach the axon hillock at different times; the closer in time the potentials occur, the more complete the summation is

Question 11

transporters:

Answer 11

specialized receptors in the presynaptic membrane that recognize transmitter molecules and return them to the presynaptic neuron for reuse

Question 12

epilepsy:

Answer 12

a brain disorder marked by major, sudden changes in the electrophysiological state of the brain that are referred to as seizures

Question 13

seizures are caused by:

Answer 13

too much glutamate