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Pharm Y3S2 > Neuronal Circuits & Dopamine > Flashcards

Neuronal Circuits & Dopamine Flashcards

1
Q

What is the main excitatory neurotransmitter in the brain?

A

Glutamate

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2
Q

What is the main inhibitory neurotransmitter in the brain?

A

GABA

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3
Q

What is the axon?

A

Main conducting unit of a neurone

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4
Q

What occurs at the pre-synaptic terminal?

A

Electrical signal converted to chemical signal via neurotransmitter release

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5
Q

What is the cortex?

A

Darkened region on the edge of the brain

Anything lower than subcortical

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6
Q

What is the resting potential of a neuron?

A

-70mV

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7
Q

What occurs at depolarisation of a neuron?

A

Influx of sodium into cells due to opening of sodium channels

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8
Q

What is the membrane potential after depolarisation?

A

+30mV

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9
Q

What occurs at repolarisation of a neuron?

A

Opening of potassium channels causing efflux

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10
Q

What occurs at hyperpolarisation of a neuron?

A

Brief reduction in membrane potential as potassium channels are slower to close

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11
Q

What is the role of the Sodium-Potassium ATPase in the neuron?

A

Works to return ions back to original position for re-activation

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12
Q

What is the role of ACh in neurotransmission?

A

Binds to both muscarinic and nicotinic receptors on post synaptic membranes

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13
Q

What is the clinical benefit of inhibition of acetyl cholinesterase?

A

Increases synaptic availability of ACh upon release which can be beneficial in dementia

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14
Q

Describe the action of Acetylcholinesterase.

A

Breaks down ACh to form Acetyl coA and choline

50% of choline is then taken up into presynaptic terminal by active transporter

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15
Q

Describe the action of choline acetyltransferase.

A

Forms ACh from acetyl coA and choline, present in neuronal terminal in excess

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16
Q

What are the 5 subunits of nicotinic receptors? How are they made up?

A 
Alpha
Beta
Delta
Epsilon
Gamma
Found in different combinations of types of nicotinic ACh receptors
Found in both muscle and neurons
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17
Q

Describe the activation of a neuromuscular junction.

A

Release of ACh initiated via arrival of action potential in motor neuron
Depolarisation of nerve ending leads to opening of presynaptic calcium channels
Transmitter release via vesicle exocytosis
Postsynaptic ion channels open
Sodium ions influx into muscle cell causing depolarisation
Action potential generates on membrane of skeletal muscle cell

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18
Q

What is myasthenia gravis?

A

Immune system produces antibodies to block/damage muscle ACh receptors
Prevents muscle contraction
Causes lack of contraction and weakening

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19
Q

Which muscles are commonly affected in myasthenia gravis?

A

Eye and facial muscles

Those involved in swallowing

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20
Q

What treatments can be used in myasthenia gravis?

A

AChE inhibitors such as pyridostigmine tend to work best in mild cases
Can improve muscle contractions

21
Q

How is dopamine formed?

A

L-Tyrosine (tyrosine hydroxylase)—> L-dopa (dopa decarboxylase)—-> dopamine

22
Q

What is the rate determining step in dopamine formation?

A

Tyrosine hydroxylase

Normally saturated by substrate

23
Q

What action do D1 dopamine subtypes have?

A

Excitatory

24
Q

What action do D2 dopamine subtypes have?

A

Inhibitory

25
Q

What are the two metabolic enzymes of dopamine?

A

Catechol-O-methyltransferase

Monoamine oxidase

26
Q

What is the pleasure circuit?

A

Projections from the midbrain controlled by dopamine

27
Q

Describe the reuptake of dopamine?

A 
Catecholamines have highly specific active transport mechanisms to remove transmitter from the synapse into the presynaptic terminals
Dopamine transporter (DAT)
28
Q

What effect do drugs of abuse have on the pleasure circuit?

A

Prolong dopamine presence in the synapse
Can cause hallucinations due to blocking DAT
Little effect in frontal lobe as dopamine tends to be broken down via enzymes

29
Q

Where is the nigrostriatal pathway?

A

Substantia nigra to striatum

30
Q

What does the dorsal striatum control? Which pathway is it in?

A

Controls motor control

Nigrostriatal pathway

31
Q

What does the associative striatum control? Which pathway is it in?

A 
Learning
Habituation
Memory
Attention
Motivation
Emotion
Volition
Nigrostriatal pathway
32
Q

What are positive symptoms of schizophrenia associated with?

A

Increased dopamine in associated striatum

33
Q

Where is the mesolimbic pathway?

A

Ventral tegmental area in midbrain to limbic regions

34
Q

What does the mesolimbic pathway control?

A

Reward
Motivation
Affect
Memory

35
Q

Which areas of the brain are involved in the mesolimbic pathway?

A

Ventral striatum (nucleus accumbens)
Amygdala
Hippocampus
Medial pre-frontal cortex

36
Q

Which pathway is involved in cognitive deficits seen in schizophrenia?

A

Mesocortical pathway

37
Q

Where is the mesocortical pathway?

A

Ventral tegmental to frontal cortex

Includes

38
Q

What does the mesocortical pathway control?

A

Cognitive function
Motivation
Emotional response

39
Q

Where is the tuberoinfundibular pathway?

A

Tuberal region to median eminence

Infundibular region at the top of the pituitary stalk

40
Q

How does dopamine act in the tuberoinfundibular pathway?

A

Inhibits prolactin release from pituitary

41
Q

Describe partial agonism in schizophrenia?

A

Recognition of the receptor, does not induce maximal activation
Too much dopamine balanced out without complete inhibition
Does not alter other dopamine pathways as severely as an antagonist. less side effects
i.e. aripiprazole

42
Q

Describe the structure and function of ionotropic receptors?

A

Ligand gated ion channel opened by transmitter
Allows passage of excitatory sodium ions or inhibitory potassium/chloride ions
Involved in fast transmission

43
Q

Give examples of neurotransmitters that are substrates for ionotropic receptors.

A

Acetylcholine
Glutamate
GABA

44
Q

Describe the structure and function of metabotropic receptors?

A

Receptor protein is coupled to effector via G-protein

Cellular effect much slower than ionotropic

45
Q

Give examples of neurotransmitters that are substrates for metabotropic receptors.

A

Dopamine

46
Q

Describe the function of kinase-linked receptors?

A

Slower responses
Endogenous agonists include hormones and GF
Involved in growth and differentiation

47
Q

Describe the function of intracellular receptors?

A

Very slow responses, long lasting

Affect DNA transcription processes

48
Q

Give examples of CNS stimulants.

A

Cocaine
Amphetamines
Nicotine

Pharm Y3S2 (29 decks)

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