L10 & L11 - drugs affecting the SNS

Question 1

what are ganglia

Answer 1

clusters of cell bodies

Question 2

what does SNS stimulate

Answer 2

increased HR 
vasoconstriction
bronchodilation 
pupils dilate 
decrease smooth muscle contraction

Question 3

where is SNS ganglia

Answer 3

close to spinal cord

Question 4

what does disynaptic mean?

Answer 4

there are 2 synapses along the pathway (pre and post ganglionic ) compared to one synapse in somatic motor neurons

Question 5

describe adrenal medulla (what is it)

Answer 5

modified post ganglionic neuron

Question 6

is there ganglia in the pathway from CNS to adrenal medulla?

Answer 6

no, the adrenal medulla is modified ganglia

Question 7

what cells release NA and A

Answer 7

chromaffin cells

Question 8

describe the entire process of adrenaline synthesis

Answer 8

phenylalanine — tyrosine — L DOPA — Dopamine — Noradrenaline — adrenaline

Question 9

what enzyme converts phenylalanine to tyrosine

Answer 9

phenylalanine hydroxylase

Question 10

what enzyme converts tyrosine to L-DOPA

Answer 10

tyrosine hydroxylase

Question 11

what enzyme converts L-DOPA to dopamine

Answer 11

DDC

Question 12

what enzyme converts dopamine to noradrenaline

Answer 12

dopamine B hydroxylase

Question 13

what enzyme converts noradrenaline to adrenaline

Answer 13

PNMT

Question 14

where does synthesis of the catecholamines (dopamine/NA/A) occur?

Answer 14

adrenal medulla

postganglionic SNS neurons

Question 15

where can drugs act in the synthesis of catecholamines and give examples

Answer 15

inhibit tyrosine hydroxylase
by a-methyl-P-tyrosine

carbidopa inhibit DDC (L-DOPA - dopamine)

Question 16

where is dopamine converted to NA/A

Answer 16

in vesicles

Question 17

what is VMAT and what does it do

Answer 17

vesicular monoamine transporter

packages free NA/dopamine in presynaptic membrane into vesicles

Question 18

what does reserpine do?

Answer 18

blocks VMAT
leads NT being broken down
leads to block of SNS transmission

Question 19

what does guanethidine do

Answer 19

prevents catecholamine exocytosis

Question 20

what does carbidopa do

Answer 20

blocks DDC preventing L-DOPA to dopamine

Question 21

what is uptake 1

Answer 21

uptake back into presynaptic neuron

main transmission terminator (80% re uptake)

Question 22

what is uptake 2

Answer 22

breakdown of NT by enzymes in cleft / diffusion of NT away from cleft

Question 23

what is the effect of uptake 1 blockers

Answer 23

enhance transmission

Question 24

give example of uptake 1 blocker

Answer 24

cocaine

Question 25

what degrades NA/A in the presynaptic nerve terminal

Answer 25

monoamine oxidase

Question 26

what uptake mechanism is adrenaline most likely to be taken up by

Answer 26

uptake 2

Question 27

how can SNS transmission be stopped by negative feedback and what receptors are involved

Answer 27

a2 adrenoreceptors on the presynaptic membrane 1. when [NA] in cleft is high it will bind to a adrenoreceptors on the presynaptic membrane 2. these inhibit NA release

Question 28

list the drugs that inhibit SNS transmission presynapticly

Answer 28

1. a-methyl-P-tyrosine 2. carbidopa 3. reserpine 4. guanethidine

Question 29

define indirect sympathomimetics

Answer 29

drugs that provoke SNS effect by causing release of NA/A but dont act on adrenoreceptors

Question 30

what are the 2 mechanisms of indirect sympathomimetics?

Answer 30

1. enter sym nerve and displace NT from vesicles | 2. inhibit NT reuptake (uptake 1)

Question 31

what is the name of the transporter for NA uptake 1

Answer 31

NET

Question 32

describe the primary actions of amphetamine | indirect sympathomimetics

Answer 32

primary mechanism 1. 'hijacks' uptake 1 then displaces NA from vesicles 2. NA will be broken by MAO / leak into cleft 3. increase in neurotransmission

Question 33

describe the secondary actions of amphetamine (indirect sympathomimetics)

Answer 33

can inhibit MAO when concs high enough

Question 34

side effects of imipramine

Answer 34

anti histamine sodium channel blocker anti muscarinic

Question 35

put these in order of their effectiveness on smooth muscle adrenaline noradrenaline isoprenaline

Answer 35

noradrenaline > adrenaline > isoprenaline

Question 36

put these in order of their effectiveness on cardiac muscle adrenaline noradrenaline isoprenaline

Answer 36

isoprenaline > adrenaline > noradrenaline

Question 37

what type of receptors are adrenoreceptors

Answer 37

G protein coupled

Question 38

where are B1 receptors found

Answer 38

post synaptic - mainly heart

Question 39

where are B2 receptors found

Answer 39

non synaptic sites eg airways

Question 40

where are a1 receptors found

Answer 40

post synaptic - most tissues except heart

Question 41

where are a2 receptors found

Answer 41

pre synaptic - everywhere

Question 42

does NA have a greater effect on a or B receptors

Answer 42

a

Question 43

does NA have a greater effect on B1 or B2

Answer 43

B1

Question 44

what receptors does isoprenaline act on

Answer 44

B only

Question 45

does adrenaline have greater effect on a or B

Answer 45

B

Question 46

effect of α1 agonist?

Answer 46

1. contracts vascular smooth muscle | 2. increase in TPR and MABP - reflex decrease in HR

Question 47

effect of B agonist

Answer 47

1. increase HR & contractility 2. relax vascular smooth muscle 3. decrease TPR (increase CO to balance)

Question 48

side effects of B blockers?

Answer 48

1. fatigue 2. reduced B.P to extremities 3. bronchoconstriction 4. risk of cardiac failure