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A-Level Biology > Nervous Coordination > Flashcards

Nervous Coordination Flashcards

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
What is the charge of a hyperpolarised membrane?
-70mV
26
How is an action potential formed?
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
27
Describe the passage along the axon
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
28
Explain how an action potential is passed along an unmyelinated neurone
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
29
What does the myelin sheath do?
Acts as an electrical conductor | prevents action potential from forming
30
Where can an A.P only occur?
Nodes of Ranvier
31
What is node "hopping" called?
Salatory conduction
32
What is salatory conduction?
Action potential propagation along myelinated axons from one node of Ranvier to the next
33
Why is salatory conduction useful?
Speeds up A.P | At each point no energy is lost
34
Why at each node "hop" is no energy lost?
Each A.P is the same size
35
Describe salatory conduction
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
36
What factors affect the speed of an impulse?
Myelination (salatory conduction) Temperature Diameter of axon
37
How does an increased temperature speed up an impulse?
Particles have more KE so diffuse quicker Increased enzyme activity More energy available fort active transport A.P established quicker
38
How does a smaller axon slow down an impulse?
Ions leave easier = harder to build up ions in axon = harder to establish electrochemical gradient Membrane potentials = difficult to maintain A.P = slower
39
What is the refractory period?
The time that it takes for Na+ influx to be possible again
40
What is the refractory period on a graph?
The proportion of the graph that leads back to the resting potential
41
What can't happen during the refractory period?
No A.P can occur
42
Because no A.P can occur during the refractory period what about A.P's does this ensure?
One direction Discrete (separate) Limited in number at one time
43
How does the refractory period cause the A.P to be in one direction?
Area before A.P will be in refractory period | So new A.P must be further along axon
44
How is an A.P discrete?
Refractory period takes time so the messages sent to the brain are not muddled
45
Why is the number of A.P's limited at one time?
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
Why is it important that it is one direction?
Prevents movement backwards | Ensures message towards brain/effector
47
Why is it important that it is discrete?
Correct message received/delivered | Correct response coordinated
48
Why is it important that it is in limited numbers?
Can respond to different intensities of stimuli | Iniate different responses
49
Explain why the refractory period limits the propagation of an action potential
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
What is the synapse?
The point where a neurone communicates with the dendrites of another effector
51
What are the organelles of the synapse?
``` Axon Myelin sheath Presynaptic neurone RER Mitochondria Ca2+ channels Vesicles (containing neurotransmitters) Synaptic knob Post synaptic neurone Na+ channels ```
52
What does the synaptic knob contain?
Many mitochondria Large amount of ER Vesicles with neurotransmitters
53
Why does the synaptic knob contain many mitochondria?
Release energy for movement of vesicles | Release energy for protein synthesis
54
Why does the synaptic knob contain large amount of ER?
Synthesise chemical messages
55
Why does the synaptic knob contain vesicles with neurotransmitters?
Package up neurotransmitter | Move neurotransmitter to membrane
56
What are neurotransmitters?
Chemical messages Specific Enable synaptic transmission
57
What does the response to the arrival of a neurotransmitter depend on?
The cells The cell's location The neurotransmitter involved
58
What is a cholinergic synapse?
A synapse that relies on the neurotransmitter acetylcholine
59
What is acetylcholine made of?
Acetyl (ethanoic acid) | Choline
60
What does acetylcholine cause?
Depolarisation | Generation of A.P
61
Describe synaptic transmission
``` 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
What are neuroreceptors?
Chemical-gated ion channels in post synaptic neuron membrane
63
Describe neuroreceptors
Specific - binding site for neurotransmitter Usually closed Undergo conformational change when neurotransmitter binds Causes influx of Na+
64
Describe acetylcholinesterase
Hydrolic enzyme Located on membrane Breaks up acetylcholine
65
What happens after hydrolysis of acetylcholine?
Acetyl + choline diffuse back across cleft into presynaptic neurone Neurotransmitters recycled + repackaged Generation of new A.P prevented
66
Why are chemical synapses useful?
Transmit impulses in one direction Protect system from overstimulation Single impulse transmitted to multiple neurones No. of impulses combined at synapse
67
Why does a chemical synapse transmit impulses in one direction?
So goes towards effector/ coordinator/ next neuron
68
Why does a chemical synapse protect against over stimulation?
Limited number of neurotransmitters released | Prevents fatigue
69
Why does a chemical synapse transmit a single impulse to multiple neurons?
One stimuli = multiple responses | eg. Pain = verbal + muscular response
70
Why does a chemical synapse combine a no. of impulses at the synapse?
Additive effect | Reach threshold value
71
What is summation?
The additive effect of low frequency A.P's to produce sufficient neurotransmitters to trigger an A.P across synapse
72
What are the two forms of summation?
Spatial | Temporal
73
Describe spatial summation
Different presynaptic neurones come together to trigger ONE A.P
74
How does spatial summation meet the threshold value?
Both neurones need to release neurotransmitters
75
Describe temporal summation
Single presynaptic neuron releases neurotransmitters many times over a short period to exceed threshold
76
How does temporal summation meet threshold value?
Neurotransmitters released multiple times over short period | High frequency = A.P
77
What factors affect the rate at which acetylcholinesterase works + its effects?
Mutations drugs Temperature (diffusion) Inhibitory synapse
78
What is inhibitory synapse?
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
What happens in an inhibitory synapse?
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
What are the effect of drugs?
``` 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
What does it mean if drugs are the same shape as NT?
More receptors activated
82
What does it mean if drugs block receptors?
Fewer receptors can be activated
83
What does it mean if drugs inhibit enzyme?
More NT in synaptic cleft to bind to receptors
84
What does it mean if drugs stimulate release of NT?
More receptors activated
85
What does it mean if drugs inhibit release of NT?
Fewer receptors activated
86
What do serotonin + GABA do?
Inhibit nervous responses
87
What is serotonin used for?
Antidepressant
88
What is GABA used for?
Relieving anxiety, improving mood, reducing PMS + treating ADHD
89
What is the all or nothing principle?
The intensity of the stimuli is independent to the strength of the response/A.P

A-Level Biology (21 decks)

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