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BIOMED > chemical synaptic transmission SEM1 > Flashcards

chemical synaptic transmission SEM1 Flashcards

1
Q

what is the criteria that define a neurotransmitter

A

A)Presence at Synapse: Must exist in the synapse with pathways for its synthesis.

B)Calcium-Dependent Release: Released upon stimulation (like a pre-synaptic action potential) through a mechanism dependent on calcium ions.

C)Specific Receptors: Must have specific receptors on the post-synaptic cell

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2
Q

what is end plate potential (EPP)

A

the conversion of an electrical signal in the nerve into a mechanical response in the muscle resulting in muscle contraction

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3
Q

what do NMJ function with

A

high safety factor

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4
Q

what does the safety factor at the NMJ ensure

A

ensures the end plate potentials (EPPs) are much larger than required for reliable muscle action potential generation

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5
Q

what is the normal response of calcium entering a neuron

A

action potential triggers chain reaction => calcium enters neuron => promotes release of acetylcholine => imitating muscle contraction

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6
Q

what occurs if tetrodotoxin blocks the initial action potentials in neuron

A

chain reaction leading to calcium entering neuron is halted preventing muscle contraction

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7
Q

what are the 4 main steps of calcium induced vesicle fusion and neurotransmitter exocytosis at a synapse

A

1)vesicle docks
2)SNARE complex formation
3)calcium entry
4)membrane fusion and neurotransmitter release

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8
Q

what occurs during vesicle docking during Ca2+ induced vesicle fusion

A

neurotransmitter vesicles attach to presynaptic membrane with SNARE proteins (e.g syntaxin and SNAP-25)

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9
Q

what occurs during SNARE complex formation during Ca2+ induced vesicle fusion

A

SNARE proteins tightly bind together pulling the vesicle and presynaptic membrane close for fusion

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10
Q

what occurs during calcium entry during Ca2+ induced vesicle fusion

A

voltage-gated calcium channels open due to incoming action potential, allows Ca2+ ions to enter and bind to synaptotagmin on vesicle

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11
Q

what occurs during membrane fusion and neurotransmitter release during Ca2+ induced vesicle fusion

A

calcium-bound synaptotagmin triggers fusion of vesicle w/ presynaptic membrane => release of neurotransmitters into synaptic cleft to signal next neuron

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12
Q

what is the function of SNARE proteins

A

mediate the fusion of vesicles containing neurotransmitters, hormones etc w cell membranes to release their contents

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13
Q

what is the process of vesicular exocytosis and recycling at a synaptic terminal

A

1)brief stimulation of presynaptic terminal
2)washing away extracellular HRP
3)formation of clathrin-coated pits
4)recycling and reformation of synaptic vesicle
5)continuous cycle of endo and exocytosis

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14
Q

At the NMJ what does acetylcholine bind to

A

Binds to post-synaptic nicotinic acetylcholine receptors (nAChR)

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15
Q

What are nicotinic acetylcholine receptors (nAChR)

A

nAChR are ligand-gated ion channels

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16
Q

How is acetylcholine cleared from the synaptic cleft

A

By the enzyme acetylcholinesterase

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17
Q

What does the enzyme acetylcholinesterase do

A

Hydrolyses acetylcholine to choline and acetate

18
Q

What are combined together to synthesise acetylcholine

A

Acetyl CoA and choline are combined by the enzyme choline acetyltransferase (ChAT)

19
Q

What are the two types of synaptic communication

A

Electrical and chemical synapse

20
Q

what is Dale’s law

A

the same neuron uses the same set of neurotransmitters at all of its synapses

21
Q

what occurs at the axon hillock

A

low threshold action potentials originate here

22
Q

What is the process of synthesis and release of glutamate in the brain

A

1)synthesis of glutamate
2)storage and release
3)reuptake and recycling
4)modulation

23
Q

What is L-glutamate

A

Major ‘fast’ excitatory neurotransmitter in the mammalian CNS

24
Q

What is glutamate

A

Amino acid

25
Q

How is glutamate synthesised

A

Synthesised from glutamine (Gln) by the enzyme-phosphate-activated glutaminase (PAG) in the presynaptic neuron

26
Q

Where is glutamate stored and released

A

Stored in the synaptic vesicle within the presynaptic neuron and released into the synaptic cleft

27
Q

What can glutamate do once released

A

Bind to receptors on the postsynaptic neuron to propagate the neural signal

28
Q

How is glutamate recycled

A

Excess glutamate taken up by neurons and glial cells through plasma membrane transporters to be recycled or broken down

29
Q

What are ionotropic glutamate receptors (iGluRs)

A

Membrane ion channels that are gated by glutamate

30
Q

What are metabotropic glutamate receptors (mGluRs)

A

Seven transmembrane domain proteins that couple to G proteins

31
Q

What are gamma amino-butyric acid (GABA) and glycine

A

Inhibitory amino acid neurotransmitters

32
Q

What do GABA and glycine mediate

A

Mediate fast synaptic inhibition through activation of ionotropic receptors

33
Q

How is GABA synthesised

A

GABA synthesised in the presynaptic neuron from glutamate by the enzyme glutamic acid decarboxylase (GAD)

34
Q

Where is is GABA stored and released

A

Stored in synaptic veiscle within presynaptic terminal and released into synaptic cleft

35
Q

What is the action of GABA at the postsynaptic receptor

A

Binds to GABA receptors on postsynaptic neuron and leads to opening of ion channels resulting in hyperpolarisation of the neuron => inhibiting neuronal activity

36
Q

What is the process of the reuptake of GABA

A

Removed by reuptake into neurons and glial cells via GABA transporters (GAT) - reuptake terminates inhibitory signal

37
Q

How is GABA broken down/recycled

A

Broken down by enzymes or recycled back into glutamate

38
Q

What usualy causes an increased influx which causes hyperpolarisation inside a neuron

A

Typically increased influx of chloride ions

39
Q

What are properties of glycine receptors

A

Ionotropic
Conduct CL- ions

40
Q

What are properties of GABAa receptors

A

Ionotropic
Conduct Cl- ions

41
Q

What are properties of GABAb receptors

A

Metabotropic
Coupled to G-proteins

BIOMED (24 decks)

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