Chapter 12 - Nervous System

Question 1

Initiation of the action potential usually occurs _______ of the neuron.

A. in the cell body

B. on the dendrites

C. at the axon initial segment

D. on the axon

Answer 1

C. at the axon initial segment

Question 2

For a hormone to elicit a specific response from a cell, the cell must possess __________.

A. a synapse

B. a cell body

C. dendrites specific to the hormone

D. receptor proteins specific to the hormone

Answer 2

D. receptor proteins specific to the hormone

Question 3

Which statement about the startle response of the cockroach is true?

A. Vibrations of hairs generate nerve impulses in sensory neurons.

B. Sound waves or air currents synapse with the filiform hairs.

C. Sensory neurons synapse with and excite the dorsal hollow spinal cord.

D. At the metathoracic ganglion, the interneurons synaptically inhibit leg motor neurons.

Answer 3

A. Vibrations of hairs generate nerve impulses in sensory neurons.

Question 4

Which statement about glial cells is true?

A. They integrate cell membrane potentials to enhance or inhibit action potentials.

B. They decrease the velocity of nerve-impulse propagation.

C. They help supply metabolic substrates to neurons.

D. They act as metabolic intermediaries between epithelial cells and neurons.

Answer 4

C. They help supply metabolic substrates to neurons.

Question 5

In a cell, the difference in ion concentration between the intracellular and extracellular fluids results from _________.

Answer 5

both active ion transport and passive diffusion of ions

Question 6

According to the Nernst equation, which change will depolarize Vm, the membrane potential?

A. A decrease in temperature

B. An increase in the valence of the ion species involved

C. A decrease in the concentration of anions inside the membrane

D. A decrease in the electromotive force of the ion

Answer 6

C. A decrease in the concentration of anions inside the membrane

Question 7

Which statement regarding the ions in intracellular and extracellular fluids in a standard animal cell is true?

A. Na+ leaks into the cell rapidly because its electrochemical gradient is large.

B. K+ leaks out of the cell slowly because the electrochemical gradient is small.

C. Cl– leaks into the cell rapidly because its electrochemical gradient is large.

D. Negatively charged proteins leak out of the cell slowly because their electrochemical gradient is small.

Answer 7

B. K+ leaks out of the cell slowly because the electrochemical gradient is small.

Question 8

According to the Goldman equation, the contribution of each ion to the membrane potential depends most on ___________.

Answer 8

its membrane permeability

Question 9

Which structure is most responsible for the all-or-none property of the action potential?

Answer 9

Voltage-gated Na+ channels

Question 10

For an axon at resting membrane potential, the K+ leak channel is _______, the voltage-gated Na+ channel is _______, and the voltage-gated K+ channel is _______.

A. open; inactivated; closed

B. closed; inactivated; closed

C. open; inactivated; open

D. open; closed; closed

Answer 10

D. open; closed; closed

Question 11

What is a neuron?

Answer 11

A specialized cell that generates electrical signal (an action potential). It conveys information over long distances and it is fast and addressed.

Question 12

Where does input occur on neuron?

Answer 12

Dendrites

Question 13

Where does integration occur on the neuron?

Answer 13

The nucleus in the cell body.

Question 14

Where does conduction occur on the neuron?

Answer 14

On the axon.

Question 15

Where does output occur on the neuron?

Answer 15

Axon terminals.

Question 16

How do neurons function to cause an action?

Answer 16

The nervous system consists of neurons that are specialized cells involved in fast and addressed electrical signaling. It can transmit 100+ impulses a second, and directly sends the signal to the post-synaptic cell (target cell).

Question 17

How do hormones function to cause an action?

Answer 17

The endocrine system has hormones that are released into the blood stream and bathe the organs. It is a slow and broadcast approach for eliciting a response. In order for an action to occur the hormone must reach the hormone receptor.

Question 18

What body tissue is under both neural and endocrine control?

Answer 18

Skeletal muscle system illustrates the relationship of dual control.
The nerve innervates the muscle and the muscle needs ATP to move (insulin taking in glucose).
The nerve sends message to the brain, the brain sends message to the endocrine system so it can release hormone(s) necessary to elicit a psychical movement in the muscle.

Question 19

All cells respond to electrical currents but NOT all cells ________ action potentials.

Answer 19

generate

Question 20

When and how did scientists first start studying the axon?

Answer 20

In the 1930s the squid axon that have been used to show how the movement of ionic charges across a cell membrane causes an electrical signal which travels through nerve fibers.

Question 21

How does a membrane’s selective permeability to ions produce a membrane potential?

Answer 21

At the membrane, K+ ions tend to diffuse OUT down their chemical concentration gradient.

• The (+) charge has left the cell, (-) ions attempt to follow BUT the membrane is not permeable to them
• So instead, the (-) charged ions tend to accumulate inside the cell membrane while K+ ions tend to accumulate on the outside of the cell membrane
• This net charge separation develops & produces a membrane potential

Question 22

What is the Nernst equation and what does it measure?

Answer 22

E=RT/ZF*ln(Cout/Cin)

It measures the relationship between concentration differences of a permeating ion across a membrane and the membrane potential at equilibrium.

The LARGER the concentration difference across the membrane, the LARGER the membrane potential.

Question 23

What is the equilibrium potential for K+ in our system as we have defined it?

Answer 23

-58 mV, value of membrane potential at which K+ ions are at electrochemical equilibrium

Question 24

What TWO factors affect membrane potentials?

Answer 24

1. membrane permeabilities

2. concentration gradient of several ion species

Question 25

Is the Na+/K+ pump electroneutral or electrogenic?

Answer 25

It is electrogenic, it transports 3 Na+ ions OUT for each 2 K+ ions transported IN.

Electrogenic pumps generate a current tha makes a small, direct contribution to Vm, changes concentration to offset leaks.

Electroneutral pumps have no change in charge, BUT the concentration of the ions may change.

Question 26

Does increasing stimulation also increase the membrane potential?

Answer 26

No, the cell can only be so positive (cannot exceed 40.0 mV).