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A Level Biology > Topic 6B - Nervous Coordination > Flashcards

Topic 6B - Nervous Coordination Flashcards

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1
Q

How is the movement of sodium and potassium ions maintained? What type of transport do they use?

A

Sodium-potassium pump - active transport
Potassium ion channels - facilitated diffusion

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2
Q

Why is the membrane polarised?

A

There is a difference in charge across the membrane

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3
Q

What do sodium potassium pumps do? How does it transport it?

A

Use active transport
Move 3 sodium ions out of the neurone for every 2 potassium ions moved in, using ATP.

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4
Q

What do potassium ion channels do?

A

Allow facilitated diffusion of potassium ions out of the neurone down the concentration gradient.

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5
Q

How is a sodium ion electrochemical gradient produced?

A

Membrane isn’t permeable to sodium ions so cant diffuse back in
More positive Na+ outside of cell than inside

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6
Q

Why do potassium ions diffuse back out through the ion channels?

A

Most channels open at rest
Membrane is more permeable

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7
Q

What is an action potential?

A

Rapid change in potential difference, cell becomes depolarised

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8
Q

What are the 5 stages of an action potential?

A

Stimulus
Depolarisation
Repolarisation
Hyperpolarisation
Resting potential

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9
Q

What happens during the stimulus?

A

Cell membrane excited, causing Na channels to open
Membrane permeable to sodium
Sodium diffuse down sodium electrochemical gradient
Inside of neurone less negative

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10
Q

What happens during depolarisation?

A

If potential difference reaches threshold, more Na channels open
More Na diffuse into neurone causing depolarisation

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11
Q

What happens during repolarisation?

A

Sodium ions channels close and potassium ion channels open
K+ ions diffuse down conc gradient
Begins getting the membrane back to resting potential

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12
Q

What happens during hyperpolarisation?

A

K+ channels slow to close
A few too many K + ions diffuse out of neurone
Potential difference becomes more negative than resting potential

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13
Q

What happens during the resting potential?

A

Ion channels are reset
NaK+ pump returns membrane to resting potential
Does this by pumping Na+ out and K+ in
Maintains resting potential until membrane is excited again

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14
Q

What is the refractory period?

A

Time delay between action potentials
So they dont overlap but pass along as discrete impulses
Potentials are unidirectional and are all closed at the same time

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15
Q

What causes waves of depolarisation?

A

Some Na ions diffuse sideways into neurone
This causes Na ions in next channel of the neurone to open and Na ions diffuse into that part

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16
Q

Why do the waves move away from the parts of the membrane in the refractory period?

A

These parts cant fire an action potential

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17
Q

What is the all or nothing principle?

A

Once the threshold is reached, an action potential will be fired
(Always fires with the same change in voltage, no matter how big the stimulus is)

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18
Q

What will a bigger stimulus cause?

A

More action potentials to occur

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19
Q

What does the myelin sheath do?

A

Electrical impulse insulator

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20
Q

What is the sheath made of in the PNS?

A

Schwann cells

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21
Q

What is between the myelin sheath? What does it do?

A

Nodes of ranvier
Where sodium ion channels are concentrated

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22
Q

Where does depolarisation occur in Saltatory conduction?

A

At the nodes of ranvier

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23
Q

How does an impulse travel in a non-myelinated neurone?

A

Impulse a travels as a wave along a whole length of the axon

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24
Q

How does axon diameter affect conduction?

A

Bigger diameter conduction will work better as there is less resistance
Depolarisation reaches other parts quicker

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25
Q

How does temperature affect conduction?

A

Conduction increases and ions diffuse faster
To an extent - denature at over 40C

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26
Q

What is a synapse?

A

The junction between the neurone membrane and another and an effector cell

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27
Q

What is the synaptic cleft

A

Gap between syanpses

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28
Q

What is the swelling on the presynaptic neurone called?

A

The synaptic knob

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29
Q

What does the synaptic knob contain?

A

Vesciles filled with neurotransmitters

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30
Q

What happens at the end of an action potential?

A

Neurotransmitters are released into the synaptic cleft and diffuse across and attach to the receptor cells on the post synaptic membrane

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31
Q

What do receptors only on the postsynaptic membrane do?

A

Make sure impulses are unidirectional
Remove neurotransmitters so response doesn’t keep happening

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32
Q

What does acetylecholine do?

A

Binds to cholinergic receptors

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33
Q

What happens after the arrival of the action potential? (Cholinergic synapse)

A

Arrives at presynaptic membrane
Stimulates voltage-gated Ca ion channels to open
Ca diffuse into synaptic knob

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34
Q

What occurs during the fusion of vesicles?

A

Influx of Ca ions
Causes synaptic knob to fuse with the presynaptic membrane
Release ACh into synaptic cleft - via exocytosis

35
Q

How does ACh diffuse?

A

Diffuses across cleft and binds to specific cholinergic receptors on postsynaptic membrane
Na channels open

36
Q

Why is ACh removed?

A

To stop the response continuing happening

37
Q

What does the exciters do?

A

Polarise postsynaptic membrane, firing an action potential

38
Q

What does inhibitory do?

A

Hyperpolarise postsynaptic membrane, preventing an action potential from being fired

39
Q

What is inhibitory synapse?

A

Where an inhibitory neurotransmitter is released, following an action potential

40
Q

What is summation?

A

Where the effect of neurotransmitters released from meant neurones is added together

41
Q

What is spatial summation?

A

2 or more presynaptic neurones release their neurotransmitter on the same post synaptic neurone

42
Q

What is temporal summation?

A

2 or more nerve impulses arrive in quick succession from the same presynaptic neurone

43
Q

What do neuromuscular junctions do?

A

Use acetylcholine which binds to chollinergic receptors called nicotine cholinergic response

44
Q

What’s the difference between neuromuscular junctions and cholinergic synapses?

A

Post synaptic membrane has lots of folds that form clefts and store AChE
Has more receptors than other synapses
Always excitatory, so when a motor neurone fires an action potential, it normally triggers a response in a muscle cell

45
Q

Why do some drugs block receptors?

A

So fewer receptors are activated

46
Q

Why do some drugs block enzymes?

A

Less neurotransmitter broken down so that more in the cleft can bind to the receptors and are there for longer

47
Q

Why do some drugs stimulate the release of neurotransmitter?

A

So more receptors can be activated

48
Q

Why do some drugs inhibit the release of neurotransmitter?

A

To the fewer receptors are activated

49
Q

What is smooth muscle?

A

Contracts without conscious control

50
Q

What is cardiac muscle?

A

Contracts without conscious control
Only found in heart

51
Q

What is skeletal muscle?

A

Muscle used to create movement

52
Q

How do skeletal muscles work?

A

Bones of skeleton are incompressible, so they act as levers giving the muscles something to pull

53
Q

What is antagonistic pair?

A

A pair of muscles that work together to move a bone

54
Q

What are the cell membranes of skeletal muscles called?

A

Sarcolemma

55
Q

What are the folds in skeletal muscles called? What do they do?

A

Transverse tubules
Help spread electrical impulses throughout the sacroplasm to reach all parts of the muscle fibre

56
Q

What does sacroplasmic reticulum do?

A

Network of internal membranes that store and release Ca ions needed for muscle contraction

57
Q

What are some qualities of muscles fibres?

A

Lots of mitochondria
Multinucleate
Myofibrils - made of protein highly specialised for contractions

58
Q

What do muscles look like under a microscope?

A

Different colours will stain different parts, the image will either be longitudinal or a transverse cross section

59
Q

What do myofibrils contain?

A

Bundles of thick and thin myofilaments that move past each other to make muscles contract

60
Q

What are thick myofibrils made of?

A

Myosin protein

61
Q

What are thin myofibrils made of?

A

Actin protein

62
Q

What are A bands?

A

Pattern of alternating dark and light bands and some overlapping actin filaments

63
Q

What are L bands?

A

Only light bands - contain only the actin filament

64
Q

What is a myofibrils made of?

A

Short units called sacromeres
End is Z-line
Middle is M-line
Around the M-line is the H-zone

65
Q

What is the sliding filament theory?

A

Myosin and actin filaments slide over each other to make sacromeres contract

66
Q

What causes the actual muscle to contract?

A

Simultaneous contraction of lots of sacromeres means the myofibrils and muscle fibres contract

67
Q

What happens to sacromeres as muscle relaxes?

A

Return to original size

68
Q

What is a myosin filament?

A

Globular heads that are hinged, can move back and forth
Each myosin head has a binding site for actin and a binding site for ATP

69
Q

What is an actin filament?

A

Have an actin myosin binding site.
Protein called tropomyosin is found between actin filaments
Helps myofilaments move past each other

70
Q

What happens to actin-myosin in resting muscle?

A

Binding site is blocked by tropomyosin
Myofilaments can’t slide over each other as myosin heads cant bind to actin filaments

71
Q

What happens when an action potential from a motor neurone stimulates a muscle cell?

A

Depolarises the sarcolemma

72
Q

What does depolarisation cause?

A

Spreads down t-tubules to sacroplasmic reticulum
Causes it to release calcium ions into sacroplasm
In return triggers a muscle contraction

73
Q

What happens when calcium ions bind to tropomyosin?

A

Causes protein to change shape
Pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament

74
Q

What happens when calcium ions bind to a protein attached to tropomyosin?

A

Causes protein to change shape
Pulls the attached tropomyosin out of the actin-myosin binding site on the actin filament

75
Q

What is an actin-myosin cross bridge?

A

The bond formed when a myosin binds to an actin filament

76
Q

What do calcium ions activate?

A

ATP hydrolase
(This hydrolyses ATP into ADP and Pi to provide energy for muscle contraction)

77
Q

What is contraction like in slow twitch muscles?

A

Slow, less powerful

78
Q

What is contraction like in fast twitch muscles?

A

Quicker, more powerful

79
Q

What is movement like in slow twitch muscles?

A

Slow and longer endurance

80
Q

What is movement like in fast twitch muscles?

A

Fast, short endurance and high intensity

81
Q

What respiration occurs in slow twitch muscles?

A

Aerboic

82
Q

What respiration occurs in fast twitch muscles?

A

Anaerboic

83
Q

What colour is slow twitch muscles?

A

Red due to myoglobin and blood vessels

84
Q

What colour is fast twitch muscles?

A

White due to no myoglobin

A Level Biology (20 decks)

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