Chemical transmission in the CNS Flashcards Preview

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Flashcards in Chemical transmission in the CNS Deck (42):
1

Which receptors does NA act on in the sympathetic NS?

a and b adrenoceptors

2

What is the major NT in the sympathetic NS?

NA

3

What is the major NT in the parasympathetic NS?

Ach

4

Which receptors does Ach act on in the parasympathetic NS?

Muscarinic receptors

5

Which receptors does Ach act on in the somatic NS?

Nicotinic receptors

6

What is the major NT in the somatic NS?

Ach

7

Briefly describe the requirements for chemical neurotransmission?

Synthesis/storage of NTs Release of NTs Inactivation of NTs Receptors for NTs

8

What is required for synthesis and storage of NTs?

Vesicles

9

What is required for release of NTs?

Na and K channels Ca influx

10

What are the two broad mechanisms of NT inactivation?

Reuptake Degradation

11

What are the two major receptor types found at synapses?

Postjunctional and prejunctional

12

What is the trigger for the release of NT from neurons?

Na/K mediated APs > which causes Ca influx > exocytotic release of vesicle

13

How are prejunctional/presynaptic receptors important in transmission?

At high concentrations of NT, NT can bind for reuptake This can act as negative feedback to regulate NT

14

What is the key process for inactivation of NA?

Neuronal uptake

15

What is the secondary mechanisms for inactivation of NA?

Metabolism via MAO Extraneuronal uptake via MAO and COMT

16

Describe the action of cocaine in relation to NA?

Blocks neuronal uptake of NA > increased activation of receptors

17

Describe the action of amphetamine and ephedrine in relation to NA?

Are substrates for carrier and displace NA > reduced reuptake of NA

18

Describe how cocaine differs from amphetamine and ephedrine in its mechanism of action?

Cocaine blocks reuptake receptor Amphetamine and ephedrine act as substrates and displaces NA

19

Which characteristic of cocaine and amphetamines allows them to access their central targets?

Lipid soluble > can cross BBB

20

Which particular functions is NA associated with?

Stimulant effects Mood Appetite Cardiovascular

21

What is the estimate for the number of NTs that act in the CNS?

40

22

Describe the pathway for NA synthesis?

A image thumb
23

What is the precursor for adrenaline synthesis?

NA

24

How do neurons that synthesise adrenaline differ from those that do not?

Presence of enzymes that are able to convert NA to adrenaline

25

Why do some neurons stop at dopamine synthesis, rather than progress on to synthesising NA and adrenaline?

They lack the converting enzymes

26

How do noradrenergic and dopaminergic differ in their distribution in the CNS?

The noradrenergic neurons are more widespread, whereas the dopaminergic neurons are more discrete 

27

How does the importance of dopamine differ in the CNS and PNS?

Very important in multiple CNS pathways

Less important in PNS, mostly a precursor to NA

28

List some of the pathways in which dopamine is involved in the CNS?

Movement

Behaviour

Dependence

Pituitary function

29

Apart from NA, which other NTs can cocaine block reuptake of?

Dopamine

Serotonin

30

Which of the NT actions is linked to the dependence effect of cocaine?

Dopamine

31

Which of the NTs is most strongly linked to the sense of euphoria, wellbeing and appetite effects?

NA

Serotonin

32

Why were the NA and serotonin mechanisms the lead for developing antidepressant drugs?

Linked to sense of wellbeing

33

Why were dopaminergic mechanisms avoided when developing antidepressant drugs?

Linked to dependence 

34

Why can cocaine be used as a local anaesthetic?

Blocks Na channels

35

Can a synapse be both inhibitory and excitatory in the CNS?

No

36

Can NTs in the CNS be both excitatory and inhibitory?

Yes

 

37

How can some NTs be both excitatory and inhibitory in the CNS?

Depends on which receptors are present and which part of the brain you are in

38

Which receptor types are present in the CNS?

Ligand-gated ion channels (eg. nicotinic and GABA A)

GPCRs (muscarinic, a&b adrenoceptors)

39

What are post-synaptic receptors in the dendritic region important in determining?

AP generation and modulation

40

What are pre-synaptic receptors at the axon terminals important regulating?

NT release 

41

What is the predominant role of tyrosine kinase and cytoplamic/nuclear receptors in the CNS?

Neuronal survival, rather than function

42

TAKE HOME MESSAGES

More than one NT usually involved

One NT usually involved in many pathways