The Cells of the Nervous System and Neurotransmitters at Synapses

Question 1

What are the 3 types of neurons?

Answer 1

Sensory, Inter and Motor

Question 2

What is the basic structure of a neuron?

Answer 2

Cells body, Axon and Dendrites

Question 3

What does the cell body do?

Answer 3

It is the control centre as it contains a nucleus

Question 4

What does the axon’s do?

Answer 4

Its a single nerve fibre that carry’s nerve impulses away from the cell body

Question 5

What does dendrites do?

Answer 5

It passes impulses towards the cell body

Question 6

What is the function of the myelin sheath?

Answer 6

It surrounds the axons with a layer of fatty material that insulates the axon, it greatly increases the speed of impulse conduction

Question 7

What is myelination?

Answer 7

This is the development of myelin and continuous from birth to adolescence

*Responses to stimuli in the first 2 years of life are not as rapid or coordinated as those of an older child or adult

Question 8

What do certain diseases do in relation to the myelin sheath?

Answer 8

They destroy it which causes a loss in coordination

Question 9

What is the function of glial cells?

Answer 9

To produce myelin sheath and support neurons

Question 10

What is the region of functional contraction?

Answer 10

This is between the axon ending of one neuron (pre-synaptic neuron) and a dendrite of another (postsynaptic neuron) is called a synapse with a tiny gap between them known as the synaptic cleft

Question 11

How are messages relayed across the synaptic cleft?

Answer 11

This is done by neurotransmitters stored in vesicles on the presynaptic neuron only, such as acetylcholine and noradrenaline

Question 12

What happens when an impulse passes through the presynaptic neuron?

Answer 12

It stimulates several vesicles to move to the synapse, fuse with the membrane and discharge the neurotransmitters which diffuse across the synaptic cleft and bind to receptors on the membrane of the synaptic neuron

Question 13

To ensure precise control and prevent continuous stimulation, what has to happen?

Answer 13

The postsynaptic neuron must remain excited fir only a brief moment to pass on the impulse, so removal of neurotransmitters by enzyme degeneration (enzyme breaks down neurotransmitters which is then reabsorbed and synthesised into new neurotransmitter) or by reabsorption directly (to be stored in vesicles)

Question 14

The receptors present on the postsynaptic neuron determine what?

Answer 14

Whether the signal is excitatory and inhibitory

Question 15

In order for an impulse to be transmitted, what has to happen?

Answer 15

A certain threshold of neurotransmitter molecules must attach to receptors otherwise they are filtered out due to being weak

However, if a postsynaptic neuron were to receive information via several synapses (convergent pathway), this collective of weak stimuli could be enough to fire an impulse known as summation

Question 16

What are endorphins?

Answer 16

They are neurotransmitters that stimulate neurons involved in reducing intensity of pain by combining with receptors synapses and blocking the transmission of the pain signal

Question 17

Endorphins are produced by what?

Answer 17

The hypothalamus and increases levels are produced in the response to:

Severe injury
Prolonged and continuous exercise
Physical and emotional stress
Certain foods (e.g. chocolate)

Increased levels are linked with feelings of pleasure obtained from activities, such as:

Eating
Sex
Prolonged exercise

Question 18

What is dopamine?

Answer 18

It is a neurotransmitter that induces feelings of pleasure by stimulating the reward pathway which reinforces certain behaviour to satisfy a need that is beneficial such as hunger or thirst

Question 19

What is an Agonist?

Answer 19

It binds to and stimulates specific receptors on postsynaptic neuron mimicking action of naturally occurring neurotransmitters triggering normal cellular response

Question 20

What is an Antagonist?

Answer 20

It binds to specific receptors om postsynaptic neuron and blocking the action of the neurotransmitter inhibiting normal cellular response

Question 21

What do other drugs do (inhibitors)?

Answer 21

They act by preventing the removal of the neurotransmitter (by degrading the enzymes or preventing re-uptake) causing an enhanced effect

Question 22

Recreational drugs act like what?

Answer 22

Agonists and Antagonists

Question 23

What do recreational drugs do?

Answer 23

They affect transmission at synapses in the brain altering an individuals:

• Mood (feels happier, more confident, more aggressive)
• Cognition (cant carry out complex mental tasks such as problem solving and decision making)
• Perception (misinterpretation of stimuli)
• Behaviour (stay awake for longer, talk endlessly about themselves)

Question 24

Many recreational drugs effect what?

Answer 24

The neurotransmitters in the reward circuit of the brain causing them to be overstimulated

Question 25

What is drug addiction caused by?

Answer 25

Repeated use of drugs that act as antagonists. Antagonists block specific receptors causing the nervous system to compensate by increasing both the number and sensitivity of these receptors

This sensitisation leads to addiction where the individual craves more of the drug

Question 26

What is drug tolerance caused by?

Answer 26

Repeated use of drugs that act as agonists. Agonists stimulate specific receptors causing the nervous system to compensate by decreasing both the number and sensitivity of these receptors

This desensitisation leads to drug tolerance where the individual must take more of the drug to get an effect