Synapses (7)

Question 1

____ neurons do not touch each other. There is a small ____ separating them.

Answer 1

Adjacent Gap

Question 2

What forms a synapse?

Answer 2

The gap between the neurons or synaptic cleft plus the adjacent membranes.

Question 3

What is a synapse?

Answer 3

It is the junction across which a nerve impulse passes from an axon terminal to a neuron, a muscle cell or a gland cell.

Question 4

What is in the cytoplasm of the synaptic knobs?

Answer 4

There are hundreds of small vesicles filled with molecules of a neurotransmitter such as the chemical acetylcholine.

Question 5

Define neurotransmitter.

Answer 5

A chemical substance released from axon terminals at a synapse to carry impulses across the gap.

Question 6

How do impulses travel across synapses? (2)

Answer 6

As neurons do not touch, impulses have to cross the gap to continue their path through the nervous system. -When nerve impulses reach the terminal branches of axons, they cause vesicles in the pre-synaptic membrane of a synaptic knob to burst, releasing neurotransmitters which diffuse across the synaptic gap -The neurotransmitters carry impulses across the gap - a chemical process which stimulates receptors in the post-synaptic membrane to initiate nerve impulses

Question 7

What happens during general anaesthetic?

Answer 7

The impulse being generated in post-synaptic membranes are temporarily inhibited.

Question 8

The synapse between the terminal branches of a motor neuron and a muscle is called a ____ synapse.

Answer 8

Myoneural

Question 9

Why are synapses important? (3)

Answer 9

• They make sure that the flow of impulses is in one direction only as the vesicles containing the transmitter are only in the axon terminal knobs, so impulses can only be transmitted from the one side.
• They allow the dispersal of impulses to many other neurons as the neurotransmitter can stimulate several post synaptic membranes.
• They allow the filtering out of continual, unnecessary or unimportant stimuli. If a neuron is constantly stimulated (eg. clothes touching the skin) the synapse will not be able to renew its supply of transmitter fast enough to continue passing the impulse across the cleft, so these stimuli are filtered out