Chapter 48.3

Question 1

Gated Ion Channels

Answer 1

• Changes in membrane potential occur because neurons contain gated ion channels that open or close in response to stimuli

Question 2

Hyperpolarization

Answer 2

• When gated K+ channels open, K+ diffuses out, making the inside of the cell more negative

an increase in magnitude of the membrane potential

Question 3

Depolarization

Answer 3

• Opening other types of ion channels triggers a depolarization, a reduction in the magnitude of the membrane potential

Question 4

Graded Potentials

Answer 4

• Graded potentials are changes in polarization where the magnitude of the change varies with the strength of the stimulus

(Short Distance)

Question 5

Action Potential

Answer 5

• If a depolarization shifts the membrane potential sufficiently, it results in a massive change in membrane voltage called an action potential

Question 6

Voltage-Gated

Answer 6

• Some ion channels are voltage-gated, opening or closing when the membrane potential passes a certain level

Question 7

Refractory Period

Answer 7

• During the refractory period after an action potential, a second action potential cannot be initiated

The refractory period is a result of a temporary inactivation of the Na+ channels

Question 8

Myelin Sheath

Answer 8

• In vertebrates, axons are insulated by a myelin sheath, which causes an action potential’s speed to increase

Made by glia—oligodendrocytes in the CNS and Schwann cells in the PNS

Question 9

Glial Cells

Answer 9

glial cells aid in the maintenance of homeostasis, and form myelin. As a whole, glial cells are the most abundant cells in the central nervous system.

Ex. Oligodendrocytes & Schwann cells

Question 10

Nodes of Ranvier

Answer 10

• Action potentials are formed only at nodes of Ranvier, gaps in the myelin sheath where voltage-gated Na+ channels are found

Question 11

Salatory Conduction

Answer 11

• Action potentials in myelinated axons jump between the nodes of Ranvier in a process called saltatory conduction