Year 1 - Nerve Impulses and Synapses

Question 1

What is the charge of the neurone at rest?

Answer 1

Positive on the outside and negative on the inside.

Question 2

What is the charge of the neurone when an impulse passes through?

Answer 2

Positive on the inside and negative on the outside.

Question 3

What is the word that is when a neurone becomes more positive on the inside?

Answer 3

Depolarisation

Question 4

What is the word that is when a neurone going back to its original “resting” charge?

Answer 4

Repolarisation

Question 5

What is an impulse jumping from node of Ranvier to node of Ranvier known as?

Answer 5

Saltatory conduction

Question 6

What is the advantage of saltatory conduction?

Answer 6

The impulse travels faster down the axon

Question 7

What are the cells that form the myelin sheath?

Answer 7

Schwann cells

Question 8

What is the function of the myelin sheath?

Answer 8

Electrical insulation and protection of the axon

Question 9

Impulses never go ________ along neurones or across synapses

Answer 9

backwards

Question 10

What does a stronger stimulus lead to?

Answer 10

A higher frequency of nerve impulses

Question 11

What is a neurotransmitter?

Answer 11

Chemical messenger that allows communication between neurones

Question 12

What is acetylcholine an example of?

Answer 12

Neurotransmitter

Question 13

What is the gap between presynaptic and postsynaptic neurones called?

Answer 13

Synaptic cleft

Question 14

What is the more technical name for a nerve impulse?

Answer 14

Action potential

Question 15

What does the impulse when it arrives at the synaptic knob cause?

Answer 15

It causes calcium ion channels to open, causing calcium ions to flood in to synaptic knob

Question 16

What does calcium ions cause?

Answer 16

Synaptic vesicles to migrate to and fuse with the presynaptic membrane

Question 17

What happens to the synaptic vesicles upon fusing with the presynaptic membrane?

Answer 17

They release their neurotransmitter into the synaptic cleft.

Question 18

What happens whens the neurotransmitter diffuses across the synaptic cleft?

Answer 18

It binds to receptors on the post-synaptic membrane

Question 19

What does the receptors activating and lead to upon binding by neurotransmitter?

Answer 19

The diffusion of sodium ions into the postsynaptic neurone.

Question 20

What is cholinesterase?

Answer 20

An enzyme that breaks down acetylecholine

Question 21

What is the process by which calcium ions are piped out of the synaptic knob?

Answer 21

Active transport (requires energy)

Question 22

What can the neurotransmitter or products of the neurotransmitter breakdown be taken up by?

Answer 22

The synaptic knob to be recycled and repackaged in synaptic vesicles

Question 23

Why do the synaptic knobs contain many mitochondria?

Answer 23

To release enough energy for the active transport of calcium ions out of the knob and repackaged neurotransmitter in synaptic vesicles.

Question 24

Why is the transmission across a synapse unidirectional?

Answer 24

Because neurotransmitter can only be released from the synaptic knob bu the acetylcholine receptors are only found on the postsynaptic membrane.

Question 25

What does unidirectional?

Answer 25

It means occurs in one direction

Question 26

Why are drugs that Inhibit cholinesterase very dangerous?

Answer 26

Because acetylcholine does not break down, leading to excessive impulses to muscles, which go in to permanent contraction (t.g. diaphragm/intercostal muscles, so can’t breathe.)

Question 27

What does it mean that the sodium ions are positively charged?

Answer 27

So if more of these move into a neurone, the more positively charge it becomes inside.