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AS Psychology > Bio - Neurons and synaptic transmission > Flashcards

Bio - Neurons and synaptic transmission Flashcards

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1
Q

What is most of the brain made up of?

A

Cells called glial cells and astrocytes. Among the cells are neurons.

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2
Q

What are among the cells that make up our brain?

A

Neurons

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3
Q

What are neurons?

A

Specialised cells whose function is to move electrical impulses to and from the CNS.

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4
Q

What is the function of neurons?

A

Move electrical impulses to and from the CNS.

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5
Q

How many neurons does the brain contain?

A

Somewhere in the region of 100 billion neurons with each neuron connected to 1000 other neurons.

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6
Q

What is each neuron in the brain connected to?

A

1000 other neurons.

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7
Q

Describe action potential:

A

Neurons must transmit information both within the neuron and from one neuron to the next. The dendrites of neurons receive information from sensory receptors or other neurons. This information is then passed down to the cell body and on to the axon. Once the information has arrived at the axon, it travels down its length in the form of an electrical signal known as an action potential.

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8
Q

How narrow can a neuron be?

A

As narrow as 0.004 centimetres in diameter.

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9
Q

How long is the longest neuron in the body?

A

About 1 metre.

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10
Q

What is the rate of neural growth during foetal development in utero?

A

250000 neurons per minute.

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11
Q

How much more oxygen does the brain use compared to the rest of the mass of the body?

A

10x as much.

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12
Q

What are the 3 types of neurons?

A

Sensory
Relay
Motor

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13
Q

What makes up a neuron?

A

A cell body, dendrites and an axon.

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14
Q

What do dendrites do?

A

Receive signals at one end of the neuron from other neurons or from sensory receptors.

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15
Q

What are dendrites connected to?

A

The cell body.

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16
Q

What is the cell body in a neuron?

A

The control centre of the neuron.

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17
Q

From the cell body, where is the impulse carried in a neuron?

A

Along the axon.

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18
Q

What happens after the impulse has been carried along the axon in a neuron?

A

It terminates at the axon terminal.

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19
Q

What forms around an axon in many nerves including those in the brain and spinal cord?

A

An insulating layer - the myelin sheath.

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20
Q

What does the myelin sheath allow?

A

Allows nerve impulses to transmit more rapidly along the axon.

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21
Q

What happens if the myelin sheath is damaged?

A

Impulses slow down.

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22
Q

By how much does the length of a neuron vary?

A

The length can vary from a few millimetres to up to one metre.

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23
Q

Where in the body are sensory receptors found?

A

Various locations such as in the eyes, ears, tongue and skin.

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24
Q

What happens when impulses from sensory neurons reach the brain?

A

They are translated into sensations of for example, visual input, heat, pain, etc., so that the organism can react appropriately.

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25
Q

Does all sensory information reach the brain?

A

No as some neurons terminate in the spinal cord allowing reflex actions to happen quickly without the delay of sending impulses to the brain.

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26
Q

What type of neuron is most common?

A

Relay.

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27
Q

What do relay neurons allow?

A

Sensory and motor neurons to communicate with each other.

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28
Q

Where are relay neurons found?

A

Lie wholly within the brain and spinal cord.

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29
Q

What are relay neurons also known as?

A

Interneurons.

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30
Q

What does the term motor neuron refer to?

A

Neurons located in the PNS that project their axons outside the PNS and directly or indirectly control muscles.

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31
Q

What do motor neurons form with muscles?

A

Synapses.

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32
Q

What does the motor neuron release when stimulated?

A

Neurotransmitters.

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33
Q

What do neurotransmitters released by motor neurons do?

A

Bind to receptors on the muscle and trigger a response which leads to muscle movement.

34
Q

What happens when the axon of a motor neuron fires?

A

The muscle with which it has formed synapses with contracts.

35
Q

What does the strength of the muscle contraction caused by a firing neuron depend on?

A

The rate of firing of the axons of motor neurons that control it.

36
Q

What is muscle relaxation caused by in terms of neurons?

A

Inhibition of the motor neuron.

37
Q

What must an action potential cross when it has arrived at the terminal button at the end of the axon?

A

A gap between the presynaptic neuron and and the postsynaptic neuron. The synapse.

38
Q

What does a synapse include?

A

The end of the presynaptic neuron, the membrane of the postsynaptic neuron and the gap inbetween.

39
Q

What is the gap between the pre- and postsynaptic cell membranes called?

A

The synaptic gap.

40
Q

What is at the end of the axon of the nerve cell?

A

A number of sacs known as the synaptic vesicles.

41
Q

What do the synaptic vesicles contain?

A

The chemical messengers that assist in the transfer of the impulse, the neurotransmitters.

42
Q

What happens to the synaptic vesicles as the action potential reaches them?

A

It causes them to release their contents through a process called exocytosis.

43
Q

How does the neurotransmitter travel across a synapse?

A

It diffuses across the gap between the pre- and postsynaptic cell, where it binds to specialised receptors on the surface of the cell that recognise it and are activated by that particular neurotransmitter.

44
Q

What do specialised receptors on the surface of a cell after a synapse do once they have been activated by a neurotransmitter?

A

The receptor molecules produce either excitatory or inhibitory effects on the postsynaptic neuron.

45
Q

How long does synaptic transmission take?

A

A fraction of a second.

46
Q

What is the process by which the effects of the molecule produced by the receptors on the postsynaptic neuron are terminated at most synapses?

A

‘Re-uptake’.

47
Q

During reuptake, what is the neurotransmitter taken up by?

A

Again by the presynaptic neuron.

48
Q

What happens to the neurotransmitter once it has been taken up again by the presynaptic neuron?

A

It is stored and made available for later release, (a sort of recycling programme).

49
Q

What determines how prolonged a nerve impulse effect will be?

A

How quickly the presynaptic neuron takes back the neurotransmitter from the synaptic cleft.

50
Q

Finish this:

The quicker the neurotransmitter is taken back by the presynaptic neuron…

A

The shorter the effects on the postsynaptic neuron.

51
Q

What do some antidepressant drugs do (in terms of neurotransmitter action)?

A

Prolong the action of the neurotransmitter by inhibiting the re-uptake process, leaving the neurotransmitter in the synapse for longer.

52
Q

What is special about a neurotransmitter/what can they do?

A

Be ‘turned off’ after they have stimulated the postsynaptic neuron.

53
Q

When can neurotransmitters be ‘turned off’?

A

After they have stimulated the postsynaptic neuron.

54
Q

How can a neurotransmitter be ‘turned off’ after they have stimulated the postsynaptic neuron?

A

Takes place through the production of enzymes produced by the body, which makes the neurotransmitters ineffective.

55
Q

Where do neurotransmitters carry signals to and from?

A

From the pre-synaptic cell across the synaptic gap to the receptor site on the postsynaptic cell.

56
Q

What can neurotransmitters be classed as?

A

Excitatory or inhibitory.

57
Q

What are examples of excitatory neurotransmitters?

A

Acetylcholine and noradrenaline.

58
Q

What do excitatory neurotransmitters do?

A

They are the nervous system’s ‘on switches’.

They increase the likelihood that an excitatory signal is sent to the postsynaptic cell, which is then more likely to fire.

59
Q

What are examples of inhibitory neurotransmitters?

A

Serotonin and GABA.

60
Q

What do inhibitory neurotransmitters do?

A

They are the nervous system’s ‘off switches’.

They decrease the likelihood of a neuron firing.

61
Q

What are inhibitory neurotransmitters generally responsible for?

A

Calming the mind and body, including sleep, and filtering out unnecessary excitatory signals.

62
Q

What does an excitatory neurotransmitter binding with a postsynaptic receptor cause?

A

An electrical charge in the membrane of that cell, resulting in an excitatory post-synaptic potential (EPSP).

63
Q

What causes and EPSP (excitatory post-synaptic potential)?

A

An excitatory neurotransmitter binding with a postsynaptic receptor causes an electrical charge in the membrane of that cell, resulting in an excitatory post-synaptic potential (EPSP).

64
Q

If an EPSP is caused, what is more/less likely to happen?

A

The postsynaptic cell is more likely to fire.

65
Q

What does an inhibitory neurotransmitter binding with a postsynaptic receptor cause?

A

An inhibitory postsynaptic potential (IPSP), making it less likely that the cell will fire.

66
Q

If an IPSP is caused, what is more/less likely to happen?

A

The postsynaptic cell is less likely to fire.

67
Q

What can a nerve cell receive at the same time?

A

Both EPSPs and IPSPs.

68
Q

How is the likelihood of the cell firing determined?

A

By adding up the excitatory and the inhibitory synaptic output. The net result of this calculation (known as summation) determines whether or not the cell fires.

E.g. more + then - then the cell is likely to fire.

69
Q

How can the strength of EPSP be increased?

A

In spatial summation, a large number of EPSPs are generated at many different synapses on the same postsynaptic neuron at the same time.

In temporal summation, a large number of EPSPs are generated at the same synapse by a series of high-frequency action potentials on the presynaptic neuron.

70
Q

What is the rate at which a particular cell fires determined by?

A

What goes on in the synapses.

71
Q

What is the rate of firing like if excitatory synapses more active?

A

Cell fires at a high rate.

72
Q

What is the rate of firing like if inhibitory synapses more active?

A

Cell fires at a much lower rate, if at all.

73
Q

What type of synapse would be more active if a cell fires at a high rate?

A

Excitatory synapses more active.

74
Q

What type of synapse would be more active if a cell fires at a much lower rate, if at all.

A

Inhibitory synapses more active.

75
Q

What do motor neurons do?

A

Form synapses with muscles and control their contractions.

76
Q

What is a neurotransmitter?

A

A chemical substance that plays an important part in the workings of the nervous system by transmitting nerve impulses across a synapse.

77
Q

What are relay neurons and what do they do?

A

Most common type of neuron in the CNS. They allow sensory and motor neurons to communicate with each other.

78
Q

What do sensory neurons do?

A

Carry nerve impulses from sensory receptors to the spinal cord and the brain.

79
Q

What is a synapse?

A

The conjunction of the end of the axon of one neuron and the dendrite or cell body of another.

80
Q

What is synaptic transmission?

A

Refers to the process by which a nerve impulse passes across the synaptic cleft from one neuron (the presynaptic neuron) to another (the postsynaptic neuron).

AS Psychology (69 decks)

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