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OFFICIAL Biology AQA Year 2 > Topic 6B: Nervous Coordination > Flashcards

Topic 6B: Nervous Coordination Flashcards

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1
Q

What is meant by a resting potential?

A
  • When inside the neurone is more negative than the outside

- membrane is polarised

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2
Q

What is the voltage at resting potential?

A

-70mV (millivolts)

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3
Q

How is resting potential maintained?

A

3 Na ions are actively pumped out of the neurone for every 2 K ions pumped inside the neurone through the sodium potassium pump
-the membrane of the neurone is more permeable to potassium than sodium

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4
Q

If stimulus is big enough…

A

it causes an action potential

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5
Q

Stages of the changes in potential difference during an action potential

A

1) Stimulus
2) Depolarisation
3) Repolarisation
4) Hyperpolarisation
5) Resting Potential

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6
Q

What happens in Stage 1-Stimulus

A
  • excites the neurones cell membrane
  • membrane increases in permeability to sodium
  • V.G sodium channels open
  • sodium diffuses into the neurone
  • down the electrochemical gradient
  • inside of the neurone less negative
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7
Q

What happens at Depolarisation?

A
  • potential difference reaches at -55mV
  • more sodium channels open
  • more sodium ions diffuse rapidly
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8
Q

What happens at Repolarisation?

A
  • M.P is at +40mV
  • V.G sodium ion channels close
  • V.G potassium ion channels open
  • membrane is more permeable to potassium ions
  • potassium ions diffuse out
  • M.P returns to -70mV
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9
Q

What is Hyperpolarisation?

A
  • potassium ion channels are too slow to close so there is a slight overshoot where too many potassium ion diffuses out of the neurone
  • potential difference becomes more negative than the resting potential
  • M.P reaches -90mV
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10
Q

What is the refractory period?

A
  • When ion channels are recovering and cant be opened

- acts as a time delay

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11
Q

The time delay in the refractory period mean…

A
  • action potential doesnt overlap
  • pass along discrete impulses
  • action potential is unidirectional (travel in one direction)
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12
Q

What are the three factors affect the speed of conduction of action potential?

A
  • myelination
  • axon diameter
  • temperature
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13
Q

Why is there in a time delay in the refractory period?

A

-so that the ion channels start to recover and so they cant be made open

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14
Q

When are the sodium and potassium ion closed in a refractory period?

A
  • V.G sodium ion channels closed during repolarisation

- V.G potassium ion channels closed during hyperpolarisation

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15
Q

How does action potential move along the neurone?

A

-the sodium ions that enter the neurone sometimes diffuses sideways
-causes Na ion channels in the next region of the neurone to open
-Na ion diffuses in
-causes a wave of depolarisation that travel along the neurone
-

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16
Q

Once the threshold is reached, an action potential will always fire…

A
  • at the same voltage

- maximal response

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17
Q

The bigger the stimulus….

A

the more times action potentials occur frequently

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18
Q

How does myelination increases the speed of conduction of action potential?

A
  • myelin sheath is an electrical insulator

- It has a faster saltatory conduction

19
Q

What is the saltatory conduction?

A

The neurones cytoplasm conducts enough electrical charge to depolarise the next node so the impluses jump from node to node.

20
Q

What is myelin sheath made out of?

A

Schwann cells in the peripheral system

21
Q

Between the Schwann cells there are tiny patches of bare membrane called…

A

Nodes of Ranvier

22
Q

What are in the nodes of Ranvier?

A

Concentrated in the sodium ion channels

23
Q

In myelinated neurone, depolaristion happens ONLY in the…

A

Nodes of Ranvier

24
Q

How does impluses travel along a non myelinated neurone?

A
  • Travels along the whole length of the axon membrane
  • so depolarisation occurs along the whole length of the membrane
  • therefore slower saltatory conduction
25
Q

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

A
  • bigger diameter
  • less resistance
  • better flow of ions
  • depolarisation reaches quicker
26
Q

How does the temperature affect the speed of conduction of action potential?

A
  • as temp increase
  • conduction speed increases
  • because ions diffuse faster
  • temp higher than 40 degrees = denaturation
27
Q

What is a synapse?

A

a junction between a neurone and neurone OR neurone and effector

28
Q

The tiny gap in synapse is called…

A

synaptic cleft

29
Q

The end of a presynaptic neurone has a…

A

synaptic knob

30
Q

The synaptic knob contains…..

A

synaptic vesicles which contain neurotransmitters

31
Q

Because receptors are only on postsynaptic neurone it means impulses are….

A

unidirectional (moves in one direction)

32
Q

Outline the stages of when ACh transmits across a cholinergic synapse?

A
  • The action potential arrives at the synaptic knob
  • this stimulates the voltage gated calcium ion channels to open
  • Ca ion diffuses into the synaptic knob
  • influx of ca ions causes synaptic vesicles to move to the presynaptic membrane
  • Causes the presynaptic membrane to fuse with synaptic vesicles
  • causes a release in acteylcholine (neurotransmitter) which diffuses across the synaptic cleft
  • ACh bind to complementary cholingeric receptors on the postsynaptic neurone
33
Q

How does the transmission of ACh stimulate a generator potential?

A
  • the cholingeric recptors bind to the receptors
  • causes sodium ion channels to open
  • sodium diffuses in to the postsynaptic membrane
  • causes depolarisation
  • if threshold exceed it causes an generator potential.
34
Q

What happens to ACh after binding?

A
  • It gets broken down by an enzyme called acetylcholinesterase
  • the products are reabsorbed by the presynaptic neurone and is used to make more ACh
35
Q

What are excitatory neurotransmitters?

A

-neurotransmitters that DEPOLARISES the postsynaptic membrane making it fire an action potential if the threshold is reached.

36
Q

Example of excitatory neurotransmitter?

A
  • Acetylcholine is excitatory at cholingeric synapses at the CNS
  • causes an action potential
37
Q

What are inhibitory neurotransmitters?

A

-neurotransmitters that HYPERPOLARISES the postsynaptic membrane preventing it fire an action potential

38
Q

Example of inhibitory neurotransmitter?

A
  • Acetylcholine is inhibitory at cholingeric synapses at the HEART
  • When it binds it causes potassium ion channels to open on the postsynaptic membrane
  • hyperpolarises it
39
Q

What is a neuromuscular junction?

A

A synapse between a motor neurone and a muscle cell

40
Q

How is the neuromuscular junction different cholingeric synapse?

A
  • has lots of folds that form clefts. This is to store the enzyme that breaks down ACh
  • more receptors on the postsynaptic neurone
  • always excitatory so always triggers a response on muscle cells
41
Q

What is summation?

A

Where the effect of neurotransmitter released from many neurones is added together

42
Q

What is Spatial Summation?

A

Many neurones connected to one nerurone

43
Q

What is Temporal Summation?

A

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

44
Q

What does summation allow?

A

it accurately processes information and the response is finely tuned

OFFICIAL Biology AQA Year 2 (15 decks)

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