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Flashcards in Synapses Deck (26)
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1
Q

Does mylination or axon diameter have a greater effect on speed of an impulse?

A

Myelination.

2
Q

What are the two types of synapse?

A

Electrical synapses and chemical synapses.

3
Q

What are the differences between the two types of synapse?

A

Electrical synapses have pre and post synaptic neurones that are directly connected by gap junctions, whereas chemical synapses are physically separated by a space.
electrical synapses allow local currents from arriving APs to flow directly across the junction, very rapid

4
Q

What are axodendritic synapses?

A

Between the axon of one neurone and the dendrites of another.

5
Q

What are axosomatic synapses?

A

Between the axon terminals of one and the cell body of another.

6
Q

What are axoaxonal synapses?

A

Between two axons.

7
Q

What are the two types of neurotransmitter receptors?

A

Ligand-gated ion channels and G-protein coupled receptors.

8
Q

How are ligand-gated channels opened?

A

The neurotransmitter binds to the receptor, activated resulting in a conformational change such that it forms an open channel

9
Q

How are G-protein coupled receptors opened?

A

A neurotransmitter binding to a receptor that contains and G-protein attached that then binds to an effector protein that sends intracellular messages to a voltage-gated ion channel so that it opens.

10
Q

Where does Ach act?

A

Muscarinic or nicotinic receptors. Muscarinic are G-protein coupled and nicotinic receptors are ion channel receptors.

11
Q

What enzyme synthesises Ach?

A

Choline acetyl transferase.

12
Q

What enzyme breaks down Ach?

and where?

A

acetylcholinesterase, in the cleft

13
Q

How is ACh formed?

A

Choline and acetyl CoA combining.

14
Q

What are the breakdown products of ACh?

A

Choline and acetic acid.

15
Q

Why are neuromuscular junctions used as a model synapse?

A

They are easy to experiment with and study - they are simple as there is only one input and one output.

16
Q

What is temporal summation?

A

Adding together of action potentials that occur at the same synapse but at different times.

17
Q

What is spatial summation?

A

Adding together of potentials that occur at different sites on the neurone.

18
Q

How are APs generated in the presynaptic neurone

A

by graded potentials

19
Q

common features of all synapses

A

presynaptic terminals have vesicles arranged in active zones, with the others dispersed
post membrane is specialised and contains clusters of neurotransmitter receptors and signalling molecules

20
Q

what defines a neurotransmitter

A

present in axon terminals along with synthetic material for making it
released in response to depolarisation (calcium dependent exocytosis)
specific receptors in post membrane
mechanism for removal

21
Q

where are nicotinic receptors found?

A

at neuromuscular junctions of skeletal

22
Q

process of release of neurotransmitter by exocytosis

A
  • vesicles docked at active sites
  • arrival of AP causes VGCC to open, calcium ions flow in and allow docked vesicles to fuse with the membrane (some completely fuse and some are recycled by endocytosis)
23
Q

a drug might:

A

increase leakage of neurotransmitter from a vesicle
increase transmitter release into cleft
inhibit transmitter synthesis
block transmitter uptake
bind to receptor on post-synaptic membrane to block neurotransmitter (agonist)
inhibit or stimulate secondary messenger in post synaptic cell

24
Q

glutamate- excitatory or inhibitory?

A

generates excitatory postsynaptic potential (EPSP)

25
Q

GABA

A

Y-aminobutyric acid

generates inhibitory postsynaptic potential (IPSP)

26
Q

What is needed for action potentials to occur?

A

Graded potentials to reach above the threshold.