Synapses 1 Flashcards

1
Q

What is a cholinergic synapse?

A

A synapse that uses acetylcholine as its neurotransmitter.

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2
Q

What is a neurotransmitter?

A

A chemical used as a signalling molecule between two neurones in a synapse.

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3
Q

What is a synapse?

A

A junction between two or more neurones, where one neurone can communicate with, or signal to, another neurone.

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4
Q

What is the name of the small junction at the synapse?

A

The synaptic cleft.

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5
Q

What is the swelling called at the end of the pre-synaptic neurone?

A

The pre-synaptic bulb.

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6
Q

Why does the pre-synaptic bulb contain mitochondria?

A

It indicates that an active process needing ATP is involved.

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7
Q

Why does the pre-synaptic bulb contain a large amount of smooth endoplasmic reticulum?

A

They package the neurotransmitter into vesicles.

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8
Q

What does the post-synaptic membrane contain?

A

Specialised sodium ion channels that can respond to the neurotransmitter.

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9
Q

What happens when acetylcholine is present in the synaptic cleft?

A

It binds to the receptor sites on the sodium gated channels on the post-synaptic bulb.

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10
Q

Describe the structure of the receptors of the sodium-gated channels.

A

Five protein subunits make up the sodium channel. Two of these polypeptides have a special receptor site that is specific to acetylcholine.

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11
Q

What happens when an action potential arrives at the synaptic bulb?

A

The voltage-gated calcium ion channels open. This causes the calcium ions to diffuse into the synaptic bulb.

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12
Q

What does the influx of calcium ions cause?

A

The synaptic vesicles to move to, and fuse with, the pre-synaptic membrane.

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13
Q

What is contained/released by the vesicles?

A

Acetylcholine

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14
Q

What happens once the acetylcholine binds to the receptors on the post-synaptic membrane?

A

The sodium-gated channels open. Sodium ions diffuse across the post-synaptic membrane into the post-synaptic neurone.

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15
Q

What happens as a result of the influx of sodium ions?

A

A generator potential or excitatory post-synaptic potential is created.

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16
Q

What happens when enough generator potentials are created?

A

If sufficient generator potentials combine then the potential across the post-synaptic membrane reaches the threshold potential. A new action potential is created in the post-synaptic neurone.

17
Q

What is the role of acetylcholinesterase?

A

It is an enzyme found in the synaptic cleft. It hydrolyses the acetylcholine to ethanoic acid (acetic acid) and choline. It stops the transmission of further action potentials.