Nerve impulse

Question 1

What surrounds neurons?

Answer 1

Plasma membrane

The plasma membrane is impermeable to ions.

Question 2

What allows the movement of some ions in neurons?

Answer 2

Special channels

These channels may be open or closed.

Question 3

What is the concentration of K+ inside a neuron compared to Na+ outside?

Answer 3

↑ [K+] inside; ↑ [Na+] outside

Question 4

What is the resting state of a neuron characterized by?

Answer 4

Polarized membrane

Question 5

What is the typical resting potential of a neuron measured in millivolts?

Answer 5

-70 mV

Question 6

What happens to K+ during the resting state of a neuron?

Answer 6

Moves out due to concentration gradient

Question 7

What causes the interior of a neuron to become more negatively charged?

Answer 7

Movement of K+ out of the cell

Question 8

What initiates depolarization in an action potential?

Answer 8

Nerve stimulation causes Na+ gates to open

Question 9

What occurs during repolarization?

Answer 9

Na+ gates close; many K+ gates open

Question 10

What restores the resting membrane potential?

Answer 10

Na+/K+ pump

Moves 3 Na+ out and 2 K+ in using ATP.

Question 11

What is saltatory conduction?

Answer 11

Action potentials jump from node of Ranvier to node of Ranvier

Question 12

What does the ‘All or None’ response refer to in neurons?

Answer 12

Neurons fire maximally or not at all

Question 13

What does an increase in neuronal stimulation beyond a critical level result in?

Answer 13

No increase in response

Question 14

How do neurons respond to increased stimulation?

Answer 14

By increasing frequency of firing

Question 15

What is the threshold level?

Answer 15

Minimum strength of stimulation required to produce an action potential

Question 16

What is the space called between neurons where communication occurs?

Answer 16

Synapse

Question 17

How is the message transmitted between neurons?

Answer 17

By release of chemical messengers

Question 18

What are neurotransmitters?

Answer 18

Chemicals in the end plates of axons

Question 19

What role does acetylcholine play in synaptic transmission?

Answer 19

Excitatory; makes post synaptic membrane more permeable to Na+

Question 20

What does cholinesterase do?

Answer 20

Destroys acetylcholine

Question 21

What happens when inhibitory neurotransmitters are released?

Answer 21

Post synaptic membrane becomes more permeable to K+

Question 22

What is the result of hyperpolarization in neurons?

Answer 22

Prevents post synaptic neurons from becoming active

Question 23

What is required for the production of an action potential in neuron D?

Answer 23

The sum of two excitatory neurons