Unit 3 (K4) - Cells of the Nervous System & Neurotransmitters at Synpases

Question 1

What are nerves?

Answer 1

Nerves are bundles of nerve fibres which carry electrical impulses from one part of the body to the other.

Question 2

What are some parts found on a neurone?

Answer 2

1. Cell body
2. Dendrite
3. Axon

Question 3

What does a dendrite do?

Answer 3

They receive nerve impulses and carry them towards the cell body.

Question 4

What does an axon do?

Answer 4

They carry nerve impulses away from the cell body.

Question 5

What direction does a nervous impulse always travel from?

Answer 5

Dendrite > Cell body > Axon

Question 6

What does the myelin sheath do?

Answer 6

1. Insulate the axon
2. Speed up impulse conduction.

Question 7

What is the myelin sheath made up of?

Answer 7

Cells that lie around the fibre.

Question 8

What is myelination?

Answer 8

The development of myelin around axon fibres of individual neurons.

Question 9

What does myelination increase?

Answer 9

Increases the speed of nerve conduction.

Question 10

Give an example of a disease that destroys the myelin sheath

Answer 10

Multiple Sclerosis.

Question 11

What happens when the myelin sheath is destroyed?

Answer 11

It causes a loss of co-ordination.

Question 12

What are the 3 types of neurons?

Answer 12

1. Sensory neuron
2. Inter neuron
3. Motor neuron

Question 13

What is the purpose of glial cells?

Answer 13

1. Providing physical support
2. Production of myelin sheath

Question 14

What is a synpase?

Answer 14

A synapse is a tiny gap between 2 neurons.

Question 15

Where do neurons connect with other neurons?

Answer 15

At the synaptic cleft.

Question 16

How are messages relayed across the synaptic cleft?

Answer 16

By chemicals called neurotransmitters.

Question 17

Where are neurotransmitters stored?

Answer 17

In vesicles in the axon endings of the presynaptic neuron.

Question 18

Where do neurotransmitters bind when they diffuse across the synaptic cleft?

Answer 18

They bind to receptors on the membrane of the postsynaptic neuron.

Question 19

What determines whether a nervous impulse can pass a synpase?

Answer 19

If a certain minimum number of neurotransmitters molecules are released at the synaptic cleft.

Question 20

What is a summation?

Answer 20

This is a series of weak stimuli from many neurons at once which can trigger enough neurotransmitters to fire an impulse.

Question 21

How are transmitter molecules removed from the synaptic cleft?

Answer 21

1. Enzyme degradation
2. Re-uptake

Question 22

Name an example of a neurotransmitter than can affect mood and behaviour

Answer 22

1. Endorphins
2. Dopamine

Question 23

What does endorphins do in the body?

Answer 23

1. Reduce the intensity of pain.

Question 24

How is endorphin production increased?

Answer 24

1. In response to severe injury
2. Prolonged and continuous exercise

Question 25

What does dopamine do?

Answer 25

1. Induces feelings of pleasure
2. Reinforces behaviour by activating the reward pathway in the brain.

Question 26

How is the reward pathway in the brain activated?

Answer 26

When an individual engages in behaviour that is beneficial to them e.g. eating when hungry.

Question 27

What are agonists?

Answer 27

Chemicals that bind and stimulate receptors on the postsynaptic neurons, mimicking the neurotransmitter and triggering an enhanced cellular response.

Question 28

What are antagonists?

Answer 28

Chemicals that bind to specific receptors on the postsynaptic membrane blocking the action of the neurotransmitter at a synapse.

Question 29

What do inhibitory drugs do?

Answer 29

1. They can inhibit the enzymes that degrade neurotransmitters in the synaptic cleft.
2. They can inhibit re-uptake of the neurotransmitter.

Question 30

What do inhibitory drugs result in?

Answer 30

An enhanced effect.

Question 31

How do recreational drugs interact with neurotransmitters?

Answer 31

1. Imitate their action (agonists)
2. Block their binding (antagonists)
3. Inhibit re-uptake/enzyme degradation.

Question 32

What is drug addiction caused by?

Answer 32

Repeated use of drugs that act as antagonists.

Question 33

How does antagonist drugs cause drug addiction?

Answer 33

They block specific receptors causing nervous system to increase both number and sensitivity of these receptors. This sensitisation leads to leads to addiction where individual craves more of the drug.

Question 34

What is drug tolerance cause by?

Answer 34

Repeated use of drugs that act as agonists.

Question 35

How does agonist drugs cause drug tolerance?

Answer 35

They stimulate specific receptors causing the nervous system to decrease both the number and sensitivity of these receptors. This desensitisation leads to drug tolerance where individual needs to take more of the drug to get an effect.