Unit 3- Nervous System And Synapses

Question 1

What does a neuron consist of?

Answer 1

Dendrite, cell body, axon, myelin sheath, axon ending.

Question 2

Describe the function of the myelin sheath.

Answer 2

Insulates the axon and increases the speed of the impulse conduction.

Question 3

What is myelination?

Answer 3

Myelination is the development of myelin round axon fibres. It’s not complete at birth and so nervous control increase over the first 2 years.

Question 4

What does myelination being incomplete cause?

Answer 4

Stimuli are not as rapid or coordinated.

Question 5

What’s the function of glial cells?

Answer 5

To physically support neurons and produce the myelin sheath.

Question 6

Neurons at a synapse are separated at what?

Answer 6

The synaptic cleft.

Question 7

What stores neurotransmitters?

Answer 7

Vesicles.

Question 8

What are examples of neurotransmitters?

Answer 8

Acetylcholine, noradrenaline.

Question 9

Describe how an impulse affects the synapse.

Answer 9

Impulse causes vesicles to fuse with the presynaptic neurons membrane and release neurotransmitters into the synaptic cleft.
They diffuse across the cleft and bind to receptors on the postsynaptic membrane.

Question 10

What is needed to trigger the new impulse on the postsynaptic membrane?

Answer 10

A minimum number of neurotransmitter molecules attached to receptors in order to reach the threshold.

Question 11

How are weak stimuli filtered out?

Answer 11

Not enough neurotransmitter molecules reach the postsynaptic neuron.

Question 12

Describe summation.

Answer 12

When a series of weak stimuli can release enough neurotransmitter to trigger an impulse.

Question 13

What are the types of signals?

Answer 13

Excitatory, inhibitory.

Question 14

What does an excitatory signal cause.

Answer 14

Contraction in muscle.

Question 15

What does an inhibitory signal cause?

Answer 15

Reduces the rate and strength of heart muscle contraction.

Question 16

How are neurotransmitters removed?

Answer 16

Enzyme (acetylcholine) or re-uptake (noradrenaline).

Question 17

What are endorphins?

Answer 17

Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.

Question 18

What causes increased levels of endorphins?

Answer 18

Eating, Sex, prolonged exercise.

Question 19

What causes increased levels of endorphins production?

Answer 19

Severe injury, prolonged and continuous exercise, stress, certain foods.

Question 20

What neurotransmitter involves the reward pathway?

Answer 20

Dopamine.

Question 21

What does dopamine do?

Answer 21

Induces feelings of pleasure and rewards particular behaviour.

Question 22

What are the 3 types of drug?

Answer 22

Agonist, antagonist, inhibitor.

Question 23

What is the role of agonists?

Answer 23

Agonists bind to and stimulate receptors mimicking the neurotransmitter.

Question 24

What is the role of antagonists?

Answer 24

Antagonists bind to specific receptors blocking the action of the neurotransmitter.

Question 25

Describe sensitisation (drug addiction).

Answer 25

Caused by the repeated use of drugs that act as antagonists. This blocks specific receptors causing the nervous system to increase the number and sensitivity of these receptors. Leading to addiction.

Question 26

Describe desensitisation (drug tolerance).

Answer 26

Drug tolerance is caused by repeated use of drugs that act as agonists. This causes the nervous system to decrease the number and sensitivity of these receptors. Leading to drug tolerance.