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Higher Human Biology 2022 > Unit 3: Neurobiology & Immunology - Key Area 4: The Cells of the Nervous System And Neurotransmitters at Synapses > Flashcards

Unit 3: Neurobiology & Immunology - Key Area 4: The Cells of the Nervous System And Neurotransmitters at Synapses Flashcards

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1
Q

What is the nervous system made up of?

A

A complex network of nerve cells called neurons which receive and transmit electrical signals (nerve impulses), and glial cells which support and maintain the neurons.

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2
Q

What is a neuron made up of?

A

Cell body, nucleus, dendrites, axon, myelin sheath, node and axon ending.

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3
Q

What does the cell body of a neuron contain?

A

The cell nucleus and mitochondria to provide energy.

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4
Q

What are dendrites?

A

Dendrites are nerve fibres that receive nerve impulses and carry them towards the cell body.

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5
Q

What is an axon?

A

An axon is a nerve fibre which carries impulses away from the cell body. Axon ends in many divisions called axon endings/terminals.

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6
Q

What are long axons covered in and what is it’s purpose?

A

A myelin sheath which insulates the axon and increases the speed of impulse conduction.

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7
Q

What is myelin sheath made up of?

A

Fatty tissue

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8
Q

What is the direction that a nerve will always travel in a neuron?

A

Dendrite ➡️ cell body ➡️ axon.

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9
Q

What is myelination?

A

The development of myelin round the axon fibres of individual neurons.

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10
Q

When is myelination not complete by and what does this result in?

A

Myelination is not complete at birth and so nervous control increases over the first 2 years as many more neurons are myelinated. (Myelination continues from birth to adolescence). As a result responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child.

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11
Q

How does multiple sclerosis (MS) work?

A

It is a disease that destroys the myelin sheath causing a loss of co-ordination.

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12
Q

What do sensory neurons do?

A

Carry impulses to the CNS from sense organs.

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13
Q

where are interneurons found and what do they do?

A

Found in the CNS and connect with other neurons.

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14
Q

What do motor neurons do?

A

Carry impulses away from the CNS to effectors such as muscles and glands.

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15
Q

What do glial cells do?

A

Support and maintain the neurons.

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16
Q

How much of the cells in the cerebrum are glial cells?

A

15%

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17
Q

How do glial cells work?

A

They produce the myelin sheath for the axon, the effect of which is to greatly increase the conduction of impulses.

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18
Q

What effect does myelin sheath have on the speed at which the fibre can transmit a nerve impulse?

A

Increase the speed.

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19
Q

Where do neurons connect with other or muscle fibres?

A

At the synaptic cleft

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20
Q

What are synapses?

A

The tiny gaps between two neurons.

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21
Q

Where separates neurons at a synapse?

A

The synaptic cleft.

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22
Q

What is the neuron before the synaptic cleft called?

A

The presynaptic neuron.

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23
Q

What is the neuron after the synaptic cleft called?

A

The postsynaptic neuron.

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24
Q

What do chemicals called neurotransmitters do?

A

Relay messages from neuron to neuron (across the synaptic cleft) within and out with the brain.

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25
Q

What are examples of neurotransmitters?

A

Acetylcholine and noradrenaline

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26
Q

Where are neurotransmitters stored?

A

In vesicles

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27
Q

Where are vesicles situated?

A

In the axon ending of the presynaptic neuron.

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28
Q

Where are neurotransmitters released into and when?

A

They are released into the cleft on arrival of an impulse.

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29
Q

What do neurotransmitters do once they are released?

A

They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron.

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30
Q

What does the fact that vesicles containing neurotransmitters occur on one side of the synapse only mean for nerve impulses?

A

This means nerve impulses travel in one direction only.

31
Q

Between impulses what happens to transmitter molecules to prevent continuous stimulation of post-synaptic neurons?

A

Transmitter molecules are removed from the synaptic cleft.

32
Q

What happens to noradrenaline to prevent continuous stimulation of the post-synaptic neuron?

A

Nor adrenaline is reabsorbed directly into the presynaptic membrane and stored in a vesicle ready for reuse.

33
Q

What happens to acetylcholine to prevent continuous stimulation of the post-synaptic neuron?

A

Acetylcholine is broken down by an enzyme and the non-active products are reabsorbed by the presynaptic neuron and re-synthesised into active transmitter.

34
Q

What do receptors on the post-synaptic membrane do?

A

Determine wether the signal is excitatory or inhibitory.

35
Q

What determines if the signal transmitted by a neurotransmitter is excitatory or inhibitory?

A

The type of receptor.

36
Q

What are the 2 types signals can be?

A

Excitatory or inhibitory.

37
Q

What does an excitatory signal cause?

A

Contraction in muscles. E.g. peristalsis

38
Q

What does an inhibitory signal cause?

A

Inhibitory signal causes the rate and strength of the contraction of heart muscles to reduce.

39
Q

What is the threshold on the post-synaptic membrane?

A

The minimum number of neurotransmitter molecules that must attach to receptors in order to transmit an impulse.

40
Q

What can happen if there is insufficient secretion of neurotransmitter molecules?

A

Synapses can filter out weak stimuli.

41
Q

When is a nerve impulse only transmitted across a synapse?

A

If there is release of enough neurotransmitter.

42
Q

What can a a series of weak stimuli do and what is this process known as?

A

Combine to trigger enough neurotransmitters reach the threshold and fire an impulse in the post-synaptic neuron, a process known as summation.

43
Q

What does summation involve?

A

Several neural pathways.

44
Q

What are the 2 fates of the neurotransmitter once the nerve impulse has been transmitted?

A

Reabsorbed or broken down by enzymes and reabsorbed.

45
Q

What are endorphins?

A

Neurotransmitters that stimulate neurons involved in reducing the intensity of pain.

46
Q

What are increased levels of endorphins connected to other than pain?

A

Food, sex and prolonged euphoria (happiness).

47
Q

What does endorphin production increase in response to?

A

Severe injury, prolonged and continuous exercise, stress and certain foods such as chocolates.

48
Q

What is dopamine?

A

Dopamine is a neurotransmitter that induces feelings of pleasure and reinforces particular behaviour by activating the reward penalty in the brain.

49
Q

What is the reward pathway in the brain?

A

The reward pathway involves neurons which secrete or respond to the neurotransmitter dopamine. The engagement of beneficial behaviours, e.g. eating when hungry.

50
Q

What does dopamine do?

A

Dopamine induces the feeling If pleasure and reinforces particular behaviours.

51
Q

What are the causes of Alzheimer’s?

A

The loss of neurons. The abnormal build up of protein in and around the brain cells.

52
Q

What are the symptoms of Alzheimer’s?

A

Brain degeneration progressively over years. Along with infection, delirium and stroke.

53
Q

What are treatments of Alzheimer’s?

A

Drugs that increase amount of acetylcholine in the body.

54
Q

What are the causes of Parkinson’s?

A

A loss of nerve cells in the part of the brain called substantia nigra.

55
Q

What are the causes of Parkinson’s?

A

Tremors and shaking along with stiffness of muscles and movement.

56
Q

What are the treatments of Parkinson’s?

A

Speech and physiotherapy, medication like dopamine agents and possibly surgery like deep brain stimulation.

57
Q

What are the causes of schizophrenia?

A

The causes are unknown but research suggests a combination of physical, genetic psychological and environmental factor make a person more likely to develop the condition.

58
Q

What are the symptoms of schizophrenia?

A

Changes in behaviour as well as hallucination and confusion.

59
Q

What are the treatments of schizophrenia?

A

Care programs, family therapy, detention and dopamine antagonists.

60
Q

What are the 2 types of drugs used to treat neurotransmitter related disorders?

A

Agonists and antagonists.

61
Q

What are agonists?

A

Chemicals that bind to and stimulate specific receptors mimicking the action of a neurotransmitter at a synapse.

62
Q

What are antagonists?

A

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

63
Q

How do other drugs rather than agonists and antagonists work to treat neurotransmitter related disorders?

A

Other drugs act by inhibiting the enzymes that degrade neurotransmitters or by inhibiting the reabsorption of the neurotransmitter at the synapse, causing an effect.

64
Q

What recreational drugs act as?

A

Agonists and antagonists.

65
Q

How do recreational drugs work?

A

Recreational drugs affect neurotransmission at synapses in the brain altering an individual’s mood, cognition, perception and behaviour.

66
Q

What do recreational drugs alter?

A

An individuals mood, cognition (awareness), perception and behaviour.

67
Q

What part of the brain do most recreational drugs affect?

A

Many recreational drugs affect neurotransmission in the reward pathway of the brain.

68
Q

In what ways can recreational drugs interact with neurotransmitters?

A
  • stimulate the release of neurotransmitters
  • mimic their action (agonist)
  • block their binding (antagonists)
  • inhibit their re uptake
  • inhibit their breakdown by enzymes
69
Q

Why is the definition of drug addiction?

A

A chronic disease that causes the sufferer to compulsively week out and use the drug regardless of the consequences.

70
Q

What is drug addiction caused by?

A

Drug addiction is caused by repeated use of drugs that act as antagonists.

71
Q

How do antagonists work in drug addiction?

A

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

72
Q

Why is drug tolerance caused by?

A

Drug tolerance is caused by repeated use of drugs that act as agonists.

73
Q

How do agonists work in drug tolerance?

A

Agonists stimulate specific receptors causing the nervous system to decrease 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.

Higher Human Biology 2022 (21 decks)

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