Synapses

Question 1

What is a synapse?

Answer 1

The junction between two neurones (or a neurone and an effector).

Question 2

What are neurotransmitters?

Answer 2

Chemicals used to transmit impulses across the synapses.

Question 3

What is the synaptic cleft?

Answer 3

The gap which separates the axon of one neurone from the dendrite of her next neurone.

Question 4

What is a presynaptic neurone?

Answer 4

The neurone along which the impulse has arrived.

Question 5

What is the postsynaptic neurone?

Answer 5

Neurone that receives the neurotransmitter.

Question 6

What is the synaptic knob?

Answer 6

The swollen end of the presynaptic neurone.

Question 7

What are synaptic vesicles?

Answer 7

Vesicles containing neurotransmitters.

Question 8

What are neurotransmitter receptors?

Answer 8

Receptor molecules which the neurotransmitter binds to in the postsynaptic membrane.

Question 9

What are the two types of neurotransmitter?

Answer 9

Excitatory and inhibitory.

Question 10

What do excitatory neurotransmitters do?

Answer 10

Result in the depolarisation of the postsynaptic membrane.

Action potential can be triggered.

Question 11

What do inhibitory neurotransmitters do?

Answer 11

Result in the hyperpolarisation of the postsynaptic membrane.
Action potential is prevented from being triggered.

Question 12

Describe in steps the mechanism of transmission of impulse across synapses.

Answer 12

1) AP reaches end of presynaptic neurone.
2) Calcium ion channels triggered to open.
3) Calcium ions diffuse into synaptic knob.
4) Synaptic vesicles fuse with membrane, neurotransmitter is released.
5) Neurotransmitter diffuses across synaptic cleft and binds to receptors.
6) a Sodium ion channels open.
7) Sodium ions diffuse into postsynaptic neurone.
8) AP is triggered in postsynaptic neurone.

Question 13

What are the three main roles of the synapse?

Answer 13

To ensure impulses are unidirectional.
To allow an impulse from one neurone to be transmitted to a number of neurones.
To allow a number of neurones to feed into the same synapse.

Question 14

What is summation?

Answer 14

When the amount of neurotransmitter builds up sufficiently to reach the threshold so much that an action potential is triggered.

Question 15

What are the two ways in which summation can occur?

Answer 15

Spatial summation and Temporal summation.

Question 16

When does spatial summation occur?

Answer 16

When many presynaptic neurones connect to one postsynaptic neurone. Builds up to a high enough level in the synapse.

Question 17

When does temporal summation occur?

Answer 17

When a single presynaptic neurone releases neurotransmitter several times over a short period. Builds up in synapse until amount is sufficient.

Question 18

Do drugs that stimulate the nervous system create more or fewer action potentials?

Answer 18

More, which results in an enhanced response.

Question 19

Do drugs that inhibit the nervous system create more or fewer action potentials?

Answer 19

Fewer, which results in a reduced response.

Question 20

Drugs that stimulate the nervous system work by…(3 ways)

Answer 20

1) Mimicking the shape of a neurotransmitter.
2) Stimulating the release of more neurotransmitter.
3) Inhibiting the enzyme responsible for breaking down the neurotransmitter

Question 21

Drugs that inhibit the nervous system work by….(2 ways)

Answer 21

1) Blocking receptors

2) Binding to specific receptors to cause a change in shape causing more neurotransmitter to bind.