A&p Study Guide Apk Exam 3

Front 1

Outside the central nervous system, clusters of neuron cell bodies are called

Back 1

ganglia

Front 2

Outside the central nervous system, axons travel together in bundles called

Back 2

nerves

Front 3

The resting membrane potential of a cell is produced by ion movements through

Back 3

Ion movements through leak channels, which are not gated (that is, they remain open continuously), produce the resting membrane potential of all cells, including neurons.

Front 4

In neurons that generate many action potentials, why don't the ion gradients across the neuron's cell membrane dissipate?

Back 4

Not many ions move across the membrane during an action potential. Those that do are pumped back across the membrane by the Na+/K+ ATPase. Leak channels remain open at all times, even during an action potential.

Front 5

The types of channels that can be found in excitable cells such as neurons include

Back 5

Nonexcitable cells only have leak channels. Excitable cells like neurons may have all three types of channels: ligand-gated, leak, and voltage-gated

Front 6

In contrast to almost all other cell types in the body, neurons

Back 6

Unlike other cell types, an excitable cell such as a neuron can alter its membrane potential by opening or closing gated ion channels, thereby altering membrane permeability.

Front 7

The resting membrane potential depends directly or indirectly on

Back 7

the Na+ and K+ ATPase, the ion permeability of the cell membrane, the concentration gradients of ions across the cell membrane

Front 8

Put the following events of the action potential in the correct order, starting with depolarization: a. Na+ permeability > K+ permeability b. K+ permeability > Na+ permeability c. Vm approaches EK+ d. Vm approaches ENa+ (Vm = membrane potential; EK+ = equilibrium potential for potassium; ENa+ = equilibrium potential for sodium)

Back 8

At the threshold for an action potential, Na+ permeability begins to exceed K+ permeability. At the peak of the action potential, the membrane potential approaches ENa+. During the downsweep phase, the permeability of the cell to K+ is greater than that for Na+, and increases until the membrane potential approaches EK+.
a,d,b,c

Front 9

Refractory periods contribute to which of the following properties of action potentials?

Back 9

Once an action potential propagates in one direction, it cannot "go backwards" because the patch of membrane that the action potential just passed through will be in the refractory period. The length of the refractory period in a neuron also helps to determine how many action potentials can be initiated per unit time, i.e., action potential frequency. Also, refractory periods prevent the overlap of action potentials, so they cannot summate the way graded potentials can.

Front 10

Graded potentials and action potentials are similar in that

Back 10

Only action potentials show an all or none response to a stimulus. Graded potentials decrement over distance and change their amplitude depending on stimulus strength.

Front 11

Sensory neurons are also called ______ neurons because they transmit information toward the central nervous system

Back 11

Afferent neurons transmit information to the central nervous system; efferent neurons transmit information away from the central nervous system.

Front 12

dendrites

Back 12

input area; receives signals from other neurons

Front 13

soma (cell body)

Back 13

input area; main nutritional and metabolic area

Front 14

axon

Back 14

conductive region; generates an action potential

Front 15

The area where the axon emerges from the soma

Back 15

axon hillock

Front 16

the action potential is generated from the

Back 16

axon hillock

Front 17

what support cell forms the myelin sheath?

Back 17

shwann cells

Front 18

myelin is found around which part of the neuron?

Back 18

axon

Front 19

the tightly wound cell membrane around the axon forms the myelin sheath and acts as a

Back 19

conductor

Front 20

the most common central nervous system neuron is called a _________ neuron.

Back 20

sensory (afferent)

Front 21

neurons have _____ axon(s)

Back 21

only one

Front 22

axons are ____ branched

Back 22

frequently

Front 23

Dendrites have _____ branch(es)

Back 23

many

Front 24

Neurons that innervate smooth muscle, such as the lining of blood vessels or the GI tract, belong to the __________ nervous system.

Back 24

peripheral, autonomic

Front 25

Glial cells ________.

Back 25

constitute 90% of the cells in the nervous system

Front 26

Interneurons

Back 26

are located entirely within the CNS

Front 27

Schwann cells

Back 27

are located in the peripheral nervous system, are a type of glial cell

Front 28

Action potentials propagate down the axon

Back 28

like a row of falling dominoes, by current flow through the intra- and extracellular fluid around sequential areas of the axonal membrane, by current flow through electrotonic conduction

Front 29

The neurotoxin called tetrodotoxin, or TTX,

Back 29

blocks voltage-gated sodium channels

Front 30

at the resting membrane potential,

Back 30

sodium is leaking into the cell, potassium is leaking out of the cell

Front 31

If the Na+/K+ ATPase was turned off, the membrane potential would eventually become equal to _______.

Back 31

zero mV

Front 32

Graded potentials

Back 32

spread through electrotonic conduction, can summate, and can be depolarizing or hyperpolarizing

Front 33

In sodium channels at the resting membrane potential,

Back 33

the activation gate is closed and the inactivation gate is open

Front 34

The positive feedback loop during the depolarization phase of the action potential is "turned off" during repolarization because

Back 34

Na+ channels inactivate, K+ channels open

Front 35

The amplitude of the peak of the action potential depends on

Back 35

the relative sizes of the electrochemical gradients for Na+ and K+, the differences in Na+ and K+ permeability

Front 36

During the after-hyperpolarization phase of the action potential,

Back 36

potassium channels are closing

Front 37

A suprathreshold stimulus can

Back 37

inc the frequency of action potentials

Front 38

Effector organs

Back 38

are muscles, are glands, may be controlled by the somatic nervous system, may be controlled by the autonomic nervous system

Front 39

Action potentials

Back 39

propagate faster in larger diameter axons, cannot go backward over a previously depolarized patch of membrane, can propagate in only one direction

Front 40

In myelinated axons,

Back 40

action potentials propagate by electronic conduction, minimal current leaks across the membrane between nodes, currents must reach the next node before the membrane potential falls below threshold

Front 41

During an action potential, what changes significantly?

Back 41

the membrane potential

Front 42

Action potential conduction velocity is the slowest in

Back 42

small unmyelinated axons