Unit 2: Synapses

Question 1

What is a synapse?

Answer 1

the junction between two neurones.

Question 2

What is the gap between two neurones called?

Answer 2

the synaptic cleft

Question 3

Action potentials cannot cross the synaptic cleft, how is the nerve impulse continued in the next neurone?

Answer 3

the nerve impulses are carried to the next neurone by neurotransmitters

Question 4

Where are neurotransmitters made?

Answer 4

the presynaptic neurone

Question 5

Where are neurotransmitters stored?

Answer 5

in the synaptic vesicles in the synaptic knob

Question 6

Which two organelles are important for the manufacture of neurotransmitters?

Answer 6

mitochondria and endoplasmic reticulum

Question 7

What are neuroreceptors?

Answer 7

charge gated ion channels that are specific binding sites for the neurotransmitters

Question 8

Where are neuroreceptors found?

Answer 8

on the post synaptic neurone

Question 9

What is the name of the neurotransmitter in a cholinergic synapse?

Answer 9

Acetylcholine

Question 10

What is acetylcholine made up of?

Answer 10

ethanoic acid and choline

Question 11

In which two places do cholinergic synapses occur?

Answer 11

The central nervous system and neuromuscular junctions

Question 12

What happens when an action potential reaches the presynaptic neurone?

Answer 12

the calcium voltage gated channels open, causing calcium to diffuse into the cell down the concentration gradient.

Question 13

What does the influx of calcium ions in the presynaptic neurone cause?

Answer 13

the synaptic vesicles to fuse with the membrane and release acetylcholine into the synaptic cleft via exocytosis

Question 14

What happens after acetylcholine diffuses across the synaptic cleft?

Answer 14

It binds to the receptor sites on the post synaptic neurone which causes sodium ion channels to open. Sodium diffuses into the membrane down the concentration gradient.

Question 15

What happens after the sodium ion channels open in the post synaptic neurone?

Answer 15

It causes depolarisation of the postsynaptic cell membrane called the post synaptic potential which then generates an action potential

Question 16

What is the name of the enzyme that breaks down acetylcholine?

Answer 16

acetylcholinesterase

Question 17

What does acetylcholinesterase do?

Answer 17

hydrolyses the neurotransmitter into acetyl and choline.

Question 18

What happens after acetylcholine has been hydrolysed in the postsynaptic cleft?

Answer 18

Acetyl and choline diffuse back across the synaptic cleft and are absorbed by presynaptic neurone by endocytosis

Question 19

Why does acetylcholine get broken down at the postsynaptic neurone?

Answer 19

To prevent continuously generating an action potential

Question 20

How is acetylcholine reformed in the presynaptic neurone?

Answer 20

ATP made by mitochondria is used to recombine acetyl and choline which is then stored in the synaptic vesicle for future use.

Question 21

What are the five different types of synapses?

Answer 21

Excitatory ion channel synapse, Inhibitory ion channel synapse, non channel synapse, neuromuscular synapse and electrical synapse

Question 22

What are the neuroreceptors for excitatory ion-channel synapses?

Answer 22

sodium channels

Question 23

Why does the excitatory ion-channel synapse make action potentials more likely?

Answer 23

because positive ions diffuse in causing depolarisation

Question 24

What a typical neurotransmitter for an excitatory ion-channel synapse?

Answer 24

acetylcholine

Question 25

What is the neuroreceptor for the inhibitory ion channel synapse?

Answer 25

chloride channels

Question 26

Why is an action potential less likely in an inhibitory ion channel synapse?

Answer 26

because negative ions diffuse in causing hyperpolarisation (more negative inside than usual)

Question 27

What are non channel synapses?

Answer 27

synapses where the neuroreceptors are membrane bound enzymes, not ion channels

Question 28

What type of response do non channel synapses create?

Answer 28

long lasting, slow responses

Question 29

Which type of synapse is a junction between effectors and muscle cells

Answer 29

neuromuscular junctions

Question 30

What is the neurotransmitter for neuromuscular junctions?

Answer 30

acetylcholine

Question 31

Why are electrical synapses different from the other four types of synapses?

Answer 31

They are the only synapses to touch and share proteins. Action potentials pass directly through the neurones without a neurotransmitter

Question 32

Electrical synapses are very rare, in which two places do they occur?

Answer 32

the heart and the eye

Question 33

What is summation?

Answer 33

The process that produces enough neurotransmitters to trigger an action potential in the neighbouring neurone.

Question 34

What are the two different types of summations?

Answer 34

Spatial and temporal

Question 35

What is spatial summation?

Answer 35

where a number of different presynaptic neurones together release enough neurotransmitters to exceed threshold potential and generate an action potential

Question 36

What is temporal summation?

Answer 36

where a single presynaptic neurone releases neurotransmitter many times over a short time period and generate enough to exceed threshold potential and produce an action potential

Question 37

How does a drug that mimics a neurotransmitter affect the synapse?

Answer 37

Stimulates it

Question 38

How does a drug that stimulates the release of neurotransmitters affect the synapse?

Answer 38

stimulates it

Question 39

How does a drug that opens neuroreceptor channels affect the synapse?

Answer 39

stimulates it

Question 40

How does a drug that blocks neuroreceptor channels affect the synapse

Answer 40

inhibits it

Question 41

How does a drug that inhibits the breakdown enzyme affect the synapse?

Answer 41

stimulates it

Question 42

What is the term that describes a drug that stimulates a synapse?

Answer 42

Agonists

Question 43

What is the term that describes a drug that inhibits a synapse?

Answer 43

Antagonists