KA4 The cells of the nervous system

Question 1

What do neurones do?

Answer 1

Neurones receive and transmit electrical impulses, and provide the body with a rapid means of communication and control

Question 2

What are the 3 types of neurones?

Answer 2

Sensory, inter and motor

Question 3

What 3 structures do each neuron have?

Answer 3

Dendrites, a cell body and an axon

D—C—A

Question 4

What is the function of the myelin sheath?

Answer 4

The layer of fatty material that insulates an axon and increases the speed of impulse conduction

Question 5

When does myelination continue from?

Answer 5

Myelination continues from birth to adolescence

Responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child or adult

Question 6

What causes the myelin sheath to break down?

Answer 6

Certain diseases cause the myelin sheath to break down, causing a loss of coordination in the sufferer

Question 7

What is the function of glial cells?

Answer 7

Glial cells produce the myelin sheath and support neurons

Question 8

Where do neurons connect with other neurons?

Answer 8

At a synaptic cleft

Question 9

What is the transmission at a synapse?

Answer 9

Neurotransmitters are stored in vesicles in the axon endings of the presynaptic neuron
The neurotransmitters are released into the synaptic cleft on arrival of an impulse
They diffuses across the cleft and bind to receptors on the membrane of the postsynpatic neuron.

Question 10

Why must neurotransmitters be rapidly removed after the impulse has been transmitted?

Answer 10

They must be removed by enzymes or reuptake as soon as the impulse has been transmitted to prevent continuous stimulation of post synaptic neurone

Question 11

How is acetylcholine removed?

Answer 11

It is broken down by an enzyme

Acetylcholine—enzyme—non active products

Question 12

How is noradrenaline broken down?

Answer 12

It is directly reabsorbed

Question 13

What determines whether a signal is excitatory or inhibitory?

Answer 13

Receptors

Question 14

What does excitatory mean?

Answer 14

Excitatory signals increase the chance of the impulse being transmitted

Question 15

What does inhibitory mean?

Answer 15

Inhibitory signals reduce the chance of the impulse being transmitted

Question 16

What does noradrenaline do?

Answer 16

It is sympathetic
It increases activity in heart and lungs
It decreases activity in digestive system

Question 17

What does acetylcholine do?

Answer 17

It is parasympathetic
It slows activity in heart and lungs
It increases activity in digestive system

Question 18

What is a threshold?

Answer 18

For a nerve impulse to be transmitted, a minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the post synaptic membrane

Question 19

What happens if the threshold is not met?

Answer 19

The stimulus is too weak and is filtered out by synapse.

Question 20

What is a summation?

Answer 20

A series of weak stimuli added together can release enough neurotransmitter to fire a nerve impulse.
Convergent neural pathways can do this

Question 21

What are endorphins?

Answer 21

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

Question 22

What do endorphins increase in respond to?

Answer 22

Stress
Severe injury
Prolonged and continuous exercise
Certain foods eg chocolate

Question 23

What are increased levels of endorphins linked to?

Answer 23

Feelings of pleasure obtained from activities such as eating, sex and prolonged exercise

Question 24

What is the function of dopamine?

Answer 24

Dopamine is a neurotransmitter that incudes feelings of pleasure and reinforces particular behaviour by activating the reward pathway

Question 25

What is the reward pathway and when is it activated?

Answer 25

The reward pathway involves neurons which secrete or respond to dopamine
The reward pathway is activated when an individual engages in a behaviour that is beneficial to them, eg eating when hungry

Question 26

What are the drugs used to treat neurotransmitter- related disorders?

Answer 26

Agonists or antagonists

Question 27

What are agonists?

Answer 27

Agonists are chemicals that bind to and STIMULATE specific receptors mimicking the action of a neurotransmitter at a synpase

Question 28

How do other drugs treat neurotransmitter- related disorders?

Answer 28

Other drugs act by inhibiting the enzymes that degrade neurotransmitters (acetylcholine) or by inhibiting the reuptake of the neurotransmitter (noradrenaline) at the synapse causing an enhanced effect

Question 28

What are antagonists?

Answer 28

Antagonists are chemicals that bind to specific receptors BLOCKING the action of a neurotransmitter at a synapse.

Question 29

What do recreational drugs affect?

Answer 29

Recreational drugs affect neurotransmission at synapses in the brain altering an individuals mood, cognition, perception and behaviour
Many recreational drugs affect neurotransmission in the reward pathway of the brain

Question 30

What is drug addiction caused by?

Answer 30

Repeated use of drugs that act as ANTAGONISTS
They block specific receptors which causes the nervous system to increase the number and sensitivity of receptors
This sensitisation leads to addiction- where the individual craves more of the drug

Question 31

What causes drug tolerance?

Answer 31

Repeated use of drugs that act as AGONISTS
They stimulate receptors which causes the nervous system to decrease both the number and sensitivity of receptors
This desensitisation leads to drug tolerance - where the individual must take more of the drug to get an effect