3.6.2.2 synaptic transmission Flashcards

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1
Q

What is the myelin made up of?

A

Schwann cells

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2
Q

What is saltatory conduction?

A

In myelinated neurones, depolarisation can only occur at the nodes of Ranvier, so the impulse ‘jumps’ from node to node.

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3
Q

What are the nodes of Ranvier?

A

Bare areas of neurones that are not insulated with myelin.

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4
Q

Give three factors that affect the speed of conduction of action potentials.

A
  1. Axon diameter
  2. Myelination
  3. Temperature
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5
Q

Why does increasing temperature increase the speed of transmission?

A

Ions diffuse faster when temperature increases.

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6
Q

Give one function of the refractory period

A

It produces discrete impulses that are unidirectional.

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7
Q

What is a synapse?

A

The junction between a neurone and the next cell.

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8
Q

What ensures that impulses cross the synapse in one direct only?

A

Neurotransmitter is released from the presynaptic knob.

Receptors for the neurotransmitter is only found on the post synaptic membrane.

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9
Q

What are Cholinergic synapses?

A

Synapses that use acetylcholine.

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10
Q

What happens to the neurotransmitter once they have attached to the receptors on the post synaptic membrane?

A

They are broken down by enzymes and their products are taken back into the neurone.

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11
Q

What stimulates the synaptic vesicles to move towards the presynaptic membrane in a cholinergic synapse?

A

Calcium ions diffuse into the synaptic knob causing the synaptic vesicles to move towards the presynaptic membrane.

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12
Q

What happens when the acetylcholine bind with the receptors on the post synaptic membrane?

A

Sodium channels open and sodium flood in. If the threshold is reached and action potential is generated.

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13
Q

How is acetylecholine removes from the synaptic cleft?

A

Acetylcholinesterase breaks acetylcholine and the products are reabsorbed to make more acetylcholine.

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14
Q

What is temporal summation?

A

It is where there are two or more nerve impulses that arrive in quick succession from the same presynaptic membrane and action potential is more likely to occur..

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15
Q

What is spatial summation?

A

When many neurones connect to one neurone. The small amount of neurotransmitter released from each of these neurones can be enough to reace the threshold value.

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16
Q

ATP is an energy source used in many cell processes. Give two ways in which ATP is a suitable energy source for cells to use.

A
  1. Releases relatively small amount of energy / little energy lost as heat;
  2. Releases energy instantaneously;
  3. Phosphorylates other compounds, making them more reactive;
  4. Can be rapidly re-synthesised;
  5. Is not lost from / does not leave cells.
17
Q

Describe how calcium ions are involved in synaptic transmission.

A

(Nerve impulse causes) Ca2+ to enter presynaptic neurone/membrane;

(Ca2+ entry) causes fusion of vesicles with presynaptic membrane /
causes exocytosis / release of transmitter;

18
Q

Describe how a nerve impulse causes the release of neurotransmitter from the vesicles in the presynaptic knob

A
  1. (Nerve impulse/depolarisation of membrane) causes Ca2+channel (proteins) to open;
  2. Ca2+enter by (facilitated) diffusion;
  3. Causes (synaptic) vesicles to fuse with (presynaptic) membrane;
19
Q

GABA causes negatively charged chloride ions to enter post synaptic neurones - How does this inhibit post synaptic neurones?

A
  1. neurone becomes more negative/hyperpolarised
  2. not enough sodium ions enter (to reach threshold)
  3. for depolarisation to take place