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Module 202 Neuroscience & behaviour > T1 L7 Chemistry & physiology of the synapse > Flashcards

T1 L7 Chemistry & physiology of the synapse Flashcards

1
Q

What are the 4 main types of transmitters?

A

Amino acids
Monoamines
Acetylcholine
Neuropeptides

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2
Q

What is a ligand?

A

Neurotransmitter

Binds to the channel, changing its conformation to open it & allow ions to flux through the central pore

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3
Q

What is the definition of pharmacology?

A

What transmitter binds to the receptor & how drugs interact with them

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4
Q

What is an agonist?

A

A drug that can combine with a receptor on a cell to produce a physiological reaction

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5
Q

What is an antagonist?

A

A drug that blocks the activity of the agonist or endogenous ligand

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6
Q

What is the definition of kinetics?

A

Rate of transmitter binding & channel gating determine the duration of their effects

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7
Q

What is the definition of selectivity?

A

What ions are fluxed

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8
Q

What is the definition of conductance?

A

The rate of flux helps determine effect magnitude

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9
Q

What do glutamate ionotropic receptors do?

A

Flux Na+

Causes an EPSP depolarising the postsynaptic neuron

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10
Q

What do GABA ionotropic receptors do?

A

Flux Cl-
Causes an IPSP hyper polarising the postsynaptic neuron
Inhibits the neuron from firing unless there is sufficient glutamate stimulation to counteract the hyperpolarisation

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11
Q

What else can activate ionotropic receptors?

A

Acetylcholine
Serotonin
ATP

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12
Q

What activates nicotinic receptors?

A

Acetylcholine

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13
Q

What happens when nicotinic receptors are activated?

A

Excitation & contraction of muscle cells

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14
Q

What 3 types of ionotropic receptors respond to glutamate?

A

NMDA
AMPA
Kainate

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15
Q

What is the agonist & antagonist for NMDA receptors

A

Agonist - NMDA

Antagonist - APV

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16
Q

What is the agonist & antagonist for AMPA receptors?

A

Agonist- AMPA

Antagonist - CNQX

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17
Q

What is the agonist & antagonist for kainate receptors?

A

Agonist - kainic acid

Antagonist - CNQX

18
Q

What is APV?

A

An antagonist to NMDA receptors

19
Q

Describe non-NMDA receptors

A

Fast opening channels permeable to Na+ & K+

Responsible for early phase EPSP

20
Q

Describe the NMDA receptor

A

Slow opening channel
Requires extracellular glycine as a cofactor to open the channel
Gated by membrane voltage

21
Q

Describe the gating of the NMDA receptor

A

Mg2+ plugs pore at resting membrane potential
When membrane depolarises, Mg2+ is ejected from the channel by electrostatic repulsion allowing conductance of other cations, activity-dependent synaptic modification

22
Q

Describe the link between NMDA receptors & schizophrenia

A

NMDA receptors are inhibited by phencyclidine & MK801

Blockade of NMDA receptors in this way produces symptoms that resemble hallucinations associated with Schizophrenia

23
Q

Describe glutamate excitotoxicity

A

Excessive calcium influx into the cell activates calcium-dependent enzymes that degrade proteins, lipids & nucleic acids

24
Q

When does glutamate excitotoxicity cell damage occur?

A

After a cardiac arrest
Stroke
Oxygen deficiency
Repeated intense seizures

25
Q

What are some other examples of ionotropic receptors?

A

Glutamate - excitatory
GABA(A) - inhibitory (brain)
Glycine - inhibitory (spinal cord & brain stem)
Nicotine - excitatory at NMJ. Excitatory or modulatory in CNS
Serotonin - excitatory or modulatory
ATP - excitatory

26
Q

How do metabotropic receptors work?

A

Transduce signals into the cell through activation of a G-protein which triggers a series of intracellular evens

27
Q

Describe G-protein coupled receptors

A

7 transmembrane domain protein
Transmitter binds to extracellular domain & triggers uncoupling of a heteromeric G-protein on intracellular surface
Transduce signal across cell membrane

28
Q

Give the steps of G-proteins

A

1) In resting state the heteromer is bound to GDP
2) on binding of a ligand to the receptor the GDP is switched to GTP & heteromer splits in 2
3) Ga subunit & Gby complex divide & diffuse separately through membrane
4) individual parts are able to stimulate activity of other effector proteins
5) a subunits have intrinsic GTP-GDP enzymatic activity allowing the signal to be transient. The breakdown from GTP to GDP switches off its activity
6) Heteromer recomplexes & awaits activation by ligand binding to another receptor

29
Q

Describe the alpha subunit system

A

Gs stimulates adenylyl cyclase
Gi inhibits adenylyl cyclase
Gq stimulates phospholipase C

30
Q

Describe the By complex system

A

Activate K+ channels directly

Mode of action for muscarinic acetylcholine receptors in heart & GABA(B) receptor

31
Q

Give the steps of the PIP2 second messenger cascade

A

1) Gq activates phospholipase C
2) Converts PIP2 into IP3 & DAG
3) DAG activates PKC
IP3 releases Ca2+ from internal stores which activates Ca2+ dependent enzymes

32
Q

What does protein kinase do?

A

Phosphorylates a protein

33
Q

What is the purpose of amplification of G-protein signalling?

A

Provides a method of amplifying signals between neurons

34
Q

How are G-protein signals amplified

A

1 transmitter bound receptor can uncouple multiple G-protein heteromers
Signal can be amplified at every stage
A weak signal at the synapse can cause an amplified response in the postsynaptic cell

35
Q

What effect do autoreceptors have on presynaptic receptors?

A

Regulate release of transmitter by modulating its synthesis, storage, release or reuptake

36
Q

What effect do heteroceptors have on presynaptic receptors?

A

Regulate synthase and/or release of transmitter

37
Q

How can NE influence the release of ACh?

A

By modulating alpha-adrenergic receptors

38
Q

Give examples of metabotropic receptors

A 
Metabotropic glutamate receptors
GABA(B) receptors
Muscarinic acetylcholine receptors
Dopamine receptors
Noradrenergic & adrenergic receptors
Serotonin receptors
Neuropeptide receptors
39
Q

What are receptor tyrosine kinases?

A

Transmembrane proteins with intrinsic tyrosine kinase activity activated by neurotrophin binding

40
Q

What happens on activation of receptor tyrosine kinases?

A

On activation they autophosphorylate
Phosphorylate intracellular regulatory subunits
Signal transduction cascades

Module 202 Neuroscience & behaviour (39 decks)

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