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A-Level Biology > Nervous Coordination > Flashcards

Nervous Coordination Flashcards

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1
Q

What are nerve cells adapted to do?

A

Rapidly carry electrochemical changes (nerve impulses)

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2
Q

What are dendrites?

A

Extension of the cell body
Carry impulses towards cell body
Increase SA

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3
Q

What is the cell body?

A

Contains nucleus + large amount of RER

So that it can make its own proteins for growth + repair

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4
Q

What is the axon?

A

Collect + carry nerve impulse away from cell body

Spreads nerve impulse

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5
Q

What is the myelin sheath?

A

Multiple cells wrapped around axon

Increase speed of impulse

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6
Q

What are schwann cells?

A

Individual cells
Protect the neurone
Provide electrical insulation
Aid in regeneration of damaged

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7
Q

What are nodes of Ranvier?

A

Gaps where there is no myelination

Increase speed

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8
Q

Describe motor neurone adaptations

A

Lots of dendrites = multiple messages from different places
Attached to muscle
Long axon

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9
Q

Describe sensory neurone adaptations

A

Attached to receptors in skin
Only few dendrites = as only sending one message
Long axon = send message long distance

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10
Q

Describe intermediate neurone adaptations

A

Lots of dendrites on both side
Short axon = no distance
Gathers + transfers lots of info

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11
Q

What is a nerve impulse?

A

Self-propagating wave of electrical disturbance that travels along the surface of axon membrane

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12
Q

What are the two states?

A

Action potential

Resting potential

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13
Q

Resting potential charge

A

Outside + inside of axon have opposite charge
Inside = negative
Outside = positive

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14
Q

What is an action potential?

A

Temporary reversal of charge

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15
Q

How are messages sent?

A

Electrochemically

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16
Q

What controls the movement of Na+ and K+?

A

Phospholipid bi-layer
Intrinsic proteins
Gated channels

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17
Q

How does the phospholipid bi-layer control the movement of ions?

A

Hydrophobic fatty acid tails repel charged molecules

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18
Q

How do intrinsic proteins control the movement of ions?

A

Allow only specific ions to pass through

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19
Q

How does gated channels control the movement of ions?

A

Na+ and K+ open and close to control amount of movement

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20
Q

What is the resting potential voltage?

A

-65mV

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21
Q

How is a resting potential formed?

A

NaK pump = 3Na+ out, 2K+ in
Chemical gradient created
Na+ try to move back in but Na+ gates shut
K+ gates open = K+ diffuses out
= electrical gradient
Some K+ move back down electrical gradient
Until equilibrium is reached
Electrical + chemical gradient = balanced
Both sides of axon = polarised

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22
Q

How is resting potential maintained?

A

Membrane relatively permeable
Na+ actively pumped out by NaK pump
Inside = negative compared to outside

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23
Q

What is the action potential charge?

A

+40mV

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24
Q

What is an action potential?

A

The outside of the membrane is negative, the inside is positive

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25
Q

What is the charge of a hyperpolarised membrane?

A

-70mV

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26
Q

How is an action potential formed?

A

Stimuli causes Na gated channels to open
Na+ diffuses in down electrochemical gradient
More Na channels open until +40mV is reached (depolarised)
At +40mV Na channels close + K gated channels open
Axon repolarised
Movement of K+ out causes an overshoot of electrical gradient (-7mV)
NaK pump restores resting potential = axon repolarised

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27
Q

Describe the passage along the axon

A

One region depolarised + A.P
= acts as stimuli for next
As section becomes depolarised, the previous becomes repolarised = resting potential
A.P passes along axon

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28
Q

Explain how an action potential is passed along an unmyelinated neurone

A

3Na+ out, 2K+ in
Polarised
Influx of Na+ via diffusion = reversal of charge
Act as stimuli for Na channels to open further along
Behind Na channels close, K channels open
Removal of K+ returns membrane back to resting potential

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29
Q

What does the myelin sheath do?

A

Acts as an electrical conductor

prevents action potential from forming

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30
Q

Where can an A.P only occur?

A

Nodes of Ranvier

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31
Q

What is node “hopping” called?

A

Salatory conduction

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32
Q

What is salatory conduction?

A

Action potential propagation along myelinated axons from one node of Ranvier to the next

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33
Q

Why is salatory conduction useful?

A

Speeds up A.P

At each point no energy is lost

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34
Q

Why at each node “hop” is no energy lost?

A

Each A.P is the same size

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35
Q

Describe salatory conduction

A

Stimuli causes Na channels to open
Na+ facilitatedly diffuses in = reversal of charge
Na+ diffuses along conc gradient
Voltage gated Na channels open further along axon
Na+ diffuse in
New A.P occurs
A.P moves along axon

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36
Q

What factors affect the speed of an impulse?

A

Myelination (salatory conduction)
Temperature
Diameter of axon

37
Q

How does an increased temperature speed up an impulse?

A

Particles have more KE so diffuse quicker
Increased enzyme activity
More energy available fort active transport
A.P established quicker

38
Q

How does a smaller axon slow down an impulse?

A

Ions leave easier
= harder to build up ions in axon
= harder to establish electrochemical gradient
Membrane potentials = difficult to maintain
A.P = slower

39
Q

What is the refractory period?

A

The time that it takes for Na+ influx to be possible again

40
Q

What is the refractory period on a graph?

A

The proportion of the graph that leads back to the resting potential

41
Q

What can’t happen during the refractory period?

A

No A.P can occur

42
Q

Because no A.P can occur during the refractory period what about A.P’s does this ensure?

A

One direction
Discrete (separate)
Limited in number at one time

43
Q

How does the refractory period cause the A.P to be in one direction?

A

Area before A.P will be in refractory period

So new A.P must be further along axon

44
Q

How is an A.P discrete?

A

Refractory period takes time so the messages sent to the brain are not muddled

45
Q

Why is the number of A.P’s limited at one time?

A

A.P’s = fixed distance apart
Cannot occur behind one another
Axon fixed length
So only a certain no. of A.P’s will fit

46
Q

Why is it important that it is one direction?

A

Prevents movement backwards

Ensures message towards brain/effector

47
Q

Why is it important that it is discrete?

A

Correct message received/delivered

Correct response coordinated

48
Q

Why is it important that it is in limited numbers?

A

Can respond to different intensities of stimuli

Iniate different responses

49
Q

Explain why the refractory period limits the propagation of an action potential

A

A.P must be at rest (-65mV) for new A.P to be propagated

Due to electrochemical gradient controlling the opening + closing of voltage gated channels

50
Q

What is the synapse?

A

The point where a neurone communicates with the dendrites of another effector

51
Q

What are the organelles of the synapse?

A 
Axon
Myelin sheath
Presynaptic neurone
RER
Mitochondria
Ca2+ channels
Vesicles (containing neurotransmitters)
Synaptic knob
Post synaptic neurone 
Na+ channels
52
Q

What does the synaptic knob contain?

A

Many mitochondria
Large amount of ER
Vesicles with neurotransmitters

53
Q

Why does the synaptic knob contain many mitochondria?

A

Release energy for movement of vesicles

Release energy for protein synthesis

54
Q

Why does the synaptic knob contain large amount of ER?

A

Synthesise chemical messages

55
Q

Why does the synaptic knob contain vesicles with neurotransmitters?

A

Package up neurotransmitter

Move neurotransmitter to membrane

56
Q

What are neurotransmitters?

A

Chemical messages
Specific
Enable synaptic transmission

57
Q

What does the response to the arrival of a neurotransmitter depend on?

A

The cells
The cell’s location
The neurotransmitter involved

58
Q

What is a cholinergic synapse?

A

A synapse that relies on the neurotransmitter acetylcholine

59
Q

What is acetylcholine made of?

A

Acetyl (ethanoic acid)

Choline

60
Q

What does acetylcholine cause?

A

Depolarisation

Generation of A.P

61
Q

Describe synaptic transmission

A 
Depolarisation of presynaptic neuron
Ca channels open
Ca2+ diffuses into presynaptic knob
Vesicles move
Vesicles fuse with phospholipid membrane
Neurotransmitters diffuse across synaptic cleft
Acetylcholine bind to Na channels
Na channels open
Reverse of charge due influx of Na+
Now A.P generated If threshold met
62
Q

What are neuroreceptors?

A

Chemical-gated ion channels in post synaptic neuron membrane

63
Q

Describe neuroreceptors

A

Specific - binding site for neurotransmitter
Usually closed
Undergo conformational change when neurotransmitter binds
Causes influx of Na+

64
Q

Describe acetylcholinesterase

A

Hydrolic enzyme
Located on membrane
Breaks up acetylcholine

65
Q

What happens after hydrolysis of acetylcholine?

A

Acetyl + choline diffuse back across cleft into presynaptic neurone
Neurotransmitters recycled + repackaged
Generation of new A.P prevented

66
Q

Why are chemical synapses useful?

A

Transmit impulses in one direction
Protect system from overstimulation
Single impulse transmitted to multiple neurones
No. of impulses combined at synapse

67
Q

Why does a chemical synapse transmit impulses in one direction?

A

So goes towards effector/ coordinator/ next neuron

68
Q

Why does a chemical synapse protect against over stimulation?

A

Limited number of neurotransmitters released

Prevents fatigue

69
Q

Why does a chemical synapse transmit a single impulse to multiple neurons?

A

One stimuli = multiple responses

eg. Pain = verbal + muscular response

70
Q

Why does a chemical synapse combine a no. of impulses at the synapse?

A

Additive effect

Reach threshold value

71
Q

What is summation?

A

The additive effect of low frequency A.P’s to produce sufficient neurotransmitters to trigger an A.P across synapse

72
Q

What are the two forms of summation?

A

Spatial

Temporal

73
Q

Describe spatial summation

A

Different presynaptic neurones come together to trigger ONE A.P

74
Q

How does spatial summation meet the threshold value?

A

Both neurones need to release neurotransmitters

75
Q

Describe temporal summation

A

Single presynaptic neuron releases neurotransmitters many times over a short period to exceed threshold

76
Q

How does temporal summation meet threshold value?

A

Neurotransmitters released multiple times over short period

High frequency = A.P

77
Q

What factors affect the rate at which acetylcholinesterase works + its effects?

A

Mutations
drugs
Temperature (diffusion)
Inhibitory synapse

78
Q

What is inhibitory synapse?

A

A synapse which the nerve impulse in a presynaptic cell results in a reduced likelihood of an A.P initiation in a post synaptic cell

79
Q

What happens in an inhibitory synapse?

A

Neurotransmitter diffuses across
Causes Cl- channels in post synaptic euro to open
Cl- diffuse across post synaptic membrane
Membrane hyperpolarised
Inhibits further A.P’s generated

80
Q

What are the effect of drugs?

A 
Block receptors so can't be activated by NT
Same shape as NT so mimic action 
Inhibit enzyme that breaks down NT
Stimulate release of NT
Inhibit release of NT
81
Q

What does it mean if drugs are the same shape as NT?

A

More receptors activated

82
Q

What does it mean if drugs block receptors?

A

Fewer receptors can be activated

83
Q

What does it mean if drugs inhibit enzyme?

A

More NT in synaptic cleft to bind to receptors

84
Q

What does it mean if drugs stimulate release of NT?

A

More receptors activated

85
Q

What does it mean if drugs inhibit release of NT?

A

Fewer receptors activated

86
Q

What do serotonin + GABA do?

A

Inhibit nervous responses

87
Q

What is serotonin used for?

A

Antidepressant

88
Q

What is GABA used for?

A

Relieving anxiety, improving mood, reducing PMS + treating ADHD

89
Q

What is the all or nothing principle?

A

The intensity of the stimuli is independent to the strength of the response/A.P

A-Level Biology (21 decks)

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