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Biology > The nervous system > Flashcards

The nervous system Flashcards

1
Q

What is the stimulus?

A

A change in the envirnoment

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2
Q

What is the receptor?

A

A specialised cell which detects the change in environment

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3
Q

If the stimulus is visible light, what is the receptor and what is the sense?

A

Receptor is the retina and the sense is sight

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4
Q

If the stimulus is sound what is the receptor and sense?

A

Receptor is the inner ear and the sense is hearing

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5
Q

If the stimulus is temperature what is the receptor and sense?

A

Receptor is dermis of skin and the sense would be heat/temp

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6
Q

If the stimulus is gravity what is the receptor and sense?

A

Receptor is middle ear and the sense is balance

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7
Q

If the stimulus is heavy pressure what is the receptor and sense?

A

Receptor is deeper dermis of skin and the sense is pain

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8
Q

If the stimulus is pressure what is the receptor and sense?

A

Receptor is dermis of skin and the sense is touch

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9
Q

If the stimulus is chemical what is the receptor and sense?

A

Receptor could be nose/tongue and the sense could be smell/taste

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10
Q

What comprises the CNS?

A

The brain and spinal cord which are surrounded by meninges

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11
Q

What comprises the peripheral nervous system?

A

Pairs of nerves and their branches which originate at the brain or spinal cord

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12
Q

What is the pathway from a stimulus to a response involving the cns?

A

Stimulus - receptor - sensory neurone - CNS - motor neurone - effector - response

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13
Q

What is an effector?

A

A gland or a muscle

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14
Q

What is white matter and what is it mainly made of?

A

Nerve fibres surrounded by myelin sheath

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15
Q

What is myelin sheath?

A

A phospholipid material that cells produce to cover the axon.

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16
Q

Why is myelin sheath good?

A

Because its a phospholipid its a good insulator for impulses.

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17
Q

What is grey matter and what is it mainly made of?

A

Made mostly of the nerve fibres of relay neurons and cell bodies of relay neurons and motor neurons

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18
Q

What is the autonomic nervous system?

A

Unconscious control of the functions of internal organs, e.g. heartbeat.
Does not need any help from CNS or PNS

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19
Q

Draw an a-level diagram of a nerve and label.

A

pg 254 in textbook

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20
Q

What is the reflex arc?

A

Rapid, involuntary responses where your muscle contracts.
Brain is not involved however a small part of the spinal cord is

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21
Q

What is the pathway from stimulus to effector involving the reflex arc?

A

Stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector

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22
Q

What is the dorsol root ganglion?

A

Swelling in the pathway of a reflex arc.
The swelling will be where the sensory neurone is located

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23
Q

What organisms have nerve nets?

A

Hydra, like jellyfish, coral or sea anemones

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24
Q

Describe nerve nets

A

Have a simple pattern
Can be manipulated easily in labs
They regenerate rapidly so lost regions regrow fast like a leg
They have no brain or spinal cord

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25
Q

Where are the nerve nets found?

A

In the ectoderm which is the outer layer of the body

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26
Q

What are the responses hydra can produce?

A

Contraction of tentacles, hunting and feeding

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27
Q

What are the difference between nerve nets and the human nervous system

A

Nerve nets have 2 cells, human has many
Nerve nets have no myelin sheath, humans do
Nerve nets do not have a CNS, human do
Nerve nets respond to a limited number of stimuli
Nerve nets impulses travel in all directions, humans only travel in one

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28
Q

What are the 3 types of neurons and what do they do?

A

Sensory- carries impulses from sense receptors to CNS
relay- receive impulses from sensory neurones and transmits them to motor neurons
motor- carries impulses from CNS to effector

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29
Q

What is a neuron?

A

A specialised nerve cell which is adapted to rapidly carry impulses to parts of the body

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30
Q

What is the role of the Nissl granules?

A

Cytoplasmic granules containing ribosomes from the RER.
In nerve cell body,for protein transport/synthesis

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31
Q

What is the role of the dendrite?

A

Branches which carry impulses to the cell body

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32
Q

What is the role of the axon?

A

To transmit/conduct the impulse away from the cell body

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33
Q

What is the role of schwann cells?

A

They surround and support the nerve fibres and in vertebrate embryos they drain their cytoplasm to become myelin sheath.

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34
Q

What is the role of myelin sheath?

A

Insulates the axon and allows impulses to be conducted node to node

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35
Q

What is the role of the nodes of ranvier?

A

1 micrometre gaps between the schwann cells, they make transmission of the impulse faster

36
Q

What is the synaptic end bulb?

A

A swelling of an axon near the end in which a neurotransmitter is synthesised.

37
Q

What is the role of the axon terminal/ending?

A

It secretes neurotransmitter which transmits the impulse to adjacent neurone

38
Q

What can skin cells not do that neurones can do?

A

Change their resting potential

39
Q

What is the resting potential?

A

The potential difference across the membrane of a cell when there is no nervous impulse being conducted

40
Q

What is the rate of the resting potential?

A

-70mV

41
Q

On the nerve membrane what ion is highest on the inside and what ion is highest on the outside?

A

High conc of k+ and low Na+ on the inside of axon.
Low conc of k+ and a high conc of Na+ outside of axon

42
Q

Why is there different concentrations on either side of the membrane?

A

So that potassium will always want to diffuse out and sodium will always want to diffuse in.
DOWN THEIR CONC GRADIENT

43
Q

What do the ions flow through?

A

Voltage gated channel proteins

44
Q

Why is there more potassium ions on the inside of the membrane?

A

Because the axon membrane is more permeable to potassium as there are more voltage gated channel proteins that are permeable/open to potassium than there are voltage gated channel proteins for sodium.

45
Q

What is the sodium potassium pump?

A

It pumps potassium back into the inside of the axon against its conc gradient.
It also pumps sodium back to the outside of the axon against its conc gradient.

46
Q

What enzyme does the sodium potassium pump use?

A

ATPase

47
Q

Why is the resting potential -70mV

A

Because 3 sodium ions are pumped out of the membrane faster than 2 potassium ions can be pumped in for every ATP hydrolysed with active transport. which leaves the inside of the cell with a negative potential.
There are also more negative ions like pyruvate and ATP-4.

48
Q

What is the potential difference at active potential?

A

+40mV

49
Q

Describe the oscilloscope graph

A

voltage gated sodium channels open causing an influx of sodium to diffuse inside the axon down their conc gradient. This stage is called depolarisation and the charge inside the axon becomes 40mV.
Once 40mV is reached the voltage gated sodium channel closes.
Now the voltage gated potassium channel opens allowed potassium to diffuse down their conc gradient, this is called repolarisation.
More potassium diffuses out than sodium diffused in which causes the inside of the axon to become more negative than -70, this is hyperpolarisation.
To fix this the sodium potassium pump pumps potassium back inside and sodium back out AGAINST their conc gradient.

50
Q

What type of protein is the sodium potassium pump?

A

A trans-membrane protein.

51
Q

How many sodium ions and potassium ions are pumped out/in for 1 ATP hydrolysed?

A

3 sodium ions and 2 potassium ions

52
Q

What is a nerve?

A

A bundle of neurones or nerve fibres

53
Q

What does the nervous system do?

A

Detects stimuli inside the body and in environment
Initiates response
Processes and stores info

54
Q

What is an excitable cell?

A

One which can change its potential, e.g. a neurone

55
Q

What is a nervous impulse?

A

The transmission of a change in potential along a nerve fibre in response to the movement of sodium ions.

56
Q

What is an oscilloscope graph and what is it used for?

A

A graph which shows how the voltage across the membrane changes over time/action potential.
It is used to measure the magnitude and speed of transmission of an impulse.

57
Q

On a diagram of the pathway of a reflex arc how could you tell where the motor neurone and sensory neurone would be?

A

The sensory neurone would be located where there is swelling/dorsal root ganglion
The motor neurone would be located by the ventral root.

58
Q

What is synapse?

A

The gap between the nerve cells

59
Q

What is the all or nothing law?

A

If the stimulus is below the threshold for depolarisation no action potential will be initiated.
If the stimulus is above the threshold for depolarisation an action potential will be initiated.

60
Q

What affects the speed of conduction of an impulse across the axon?

A

Temperature, Diameter of axon and myelination.

61
Q

How does the temperature affect the speed of conduction?

A

Sodium and potassium ions will have more kinetic energy and therefore move faster between the voltage gated channels causing nerve impulses to travel faster.

62
Q

How does the diameter of the axon affect the speed of conduction?

A

A bigger diameter will allow more movement of ions so faster nerve impulses

63
Q

How does myelination affect the speed of conduction?

A

Myelin insulates the axon which speeds up conduction.

64
Q

What is saltatory conduction?

A

This only occurs when the axon is myelinated, the nerve impulse is propagated from node to node.

65
Q

If the stimulus is large what does it do to the action potential?

A

The action potential frequency increases.
It always stays at +40mV

66
Q

What are some properties of synapse?

A

Conducts impulse in one direction
Prevents overstimulation
Filters low level stimuli as a threshold has to be reached to achieve depolarisation.

67
Q

What is Temporal summation?

A

This is where depolarisation builds up overtime in order to reach the threshold and initiate an action potential

68
Q

What is spatial summation?

A

This is where several pre-synaptic neurones conduct an impulse/synapse with the same post-synaptic neurone so that depolarisation builds up and the threshold is reached.

69
Q

What is electrical synapse?

A

Where the synapse is very small so impulses can pass neurone to neurone without a neurotransmitter

70
Q

What is chemical synapse?

A

Where the synapse is large so neurotransmitters are needed to pass an impulse

71
Q

Describe the whole process of chemical synapse

A

Electrical impulse arrives at pre-synaptic bulb which alters the permeability of the membrane, calcium channels open and Ca+ ions flow to the end of the bulb. The movement of Ca+ causes synaptic vesicles to move to the pre-synaptic membrane and fuse.
They release Acetylcholine via exocytosis into the synaptic cleft.
Acetylcholine diffuses to the post-synaptic membrane where is binds to x2 receptor sites on an intrinsic protein. The protein changes shape and opens allowing Na+ to flow down its conc gradient into the post-synaptic bulb from the synaptic cleft.
This causes the post-synaptic neurone to be depolarised and an action potential is initiated.

72
Q

If there wasn’t enough Acetylcholine bound to the intrinsic protein what would happen?

A

No action potential would be initiated because depolarisation wouldn’t be reached.

73
Q

Why must acetylcholine be removed from the synaptic cleft?

A

So that action potentials are not constantly produced.

74
Q

What are the methods of removing acetylcholine from the cleft?

A

Immediate uptake of Acetylcholine by post-synaptic nerve.
Active transport of Ca+ so less Acetylcholine is released.
Acetylcholinesterase which hydrolyses acetylcholine in the cleft.

75
Q

What are the products of the hydrolysis of acetylcholine and where do they go?

A

Products are ethanoic acid and choline.
They diffuse back into the pre-synaptic bulb to regenerate acetylcholine.

76
Q

What is the enzyme that hydrolyses acetylcholine?

A

Acetylcholinesterase

77
Q

What is the neurotransmitter used in chemical synapse?

A

Acetylcholine

78
Q

What does the movement of Ca+ trigger?

A

Triggers the movement of synaptic vesicles to the pre-synaptic membrane where they fuse.

79
Q

How does alcohol affect the nervous system?

A

It inhibits the nervous system, creating fewer action potentials in the post synaptic neurone by reducing the neurotransmitter transmissions.

80
Q

What is alcohol?

A

A sedative

81
Q

How does cocaine or coffee affect the nervous system?

A

They stimulate the nervous system producing more action potentials in the post synaptic neurone.

82
Q

What is coffee/cocaine?

A

A stimulant

83
Q

How do drugs mimic in the nervous system?

A

The drug may have the same shape as acetylcholine and bind to the intrinsic proteins, so depolarisation threshold is reached therefore more action potentials are initiated.

84
Q

What do organophosphates do?

A

They inhibit acetylcholinesterase,.

85
Q

What is the effect of organophosphates?

A

Because they inhibit acetylcholinesterase acetylcholine is not hydrolysed and remains in the synaptic cleft. This causes repeat firing of the post synaptic neurone.

86
Q

What does caffeine do?

A

It is a stimulant that increases the metabolic rate in the pre-synaptic cells, therefore ATP production is increased so more neurotransmitter is synthesised.

87
Q

What does myelin sheath allow?

A

Insulates the axon and allows saltatory conduction, this means action potentials are conducted faster

Biology (26 decks)

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