SNS antagonists and false transmitters

Question 1

SNS adrenoreceptor subtypes

Answer 1

a1- vasoconstriction and relaxes gut

a2- inhibits NA release

B1- increases contractility+ HR and renin release from kidney NOT BLOOD VESSELS

B2- bronchodilation, vasodilation (of muscles) and hepatic glycogenesis

Question 2

adrenoreceptor antagonists

Answer 2

non selective- carvedilol (alpha 1 and beta 1), phentolamine (alpha 1 and 2), prazosin (alpha 1), propanolol (beta 1 and 2), and atenolol (beta 1)

Question 3

organs involved in hypertension ie targets for treatment

Answer 3

heart (controls CO), CNS (controls heart and BP setpoint), blood vessels (arterioles) and kidneys (both control TPR-compreises of blood volume and vascular tone)

also SNS nerves, as they release NA

Question 4

danger of hypertension and goal of treatment

Answer 4

it is pressure above 140/90- biggest risk factor for stroke (affects CNS), also affects heart failure, kidney disease, so treatment of hypertensions reduces deaths for CVS/renal events

Question 5

targets for beta blockers and effects

Answer 5

block B1 receptors in heart and kidney- lower HR+ SV (less cAMP due to less activation of G protein) and lowers renin= lower ANG 11 and aldosterone

also block SNS nerves releasing NA and CNS (both have B1/2 receptors)- B adrenoreceptors in post synaptic membrane is blocked

NOT ARTERIOLES (alpha 1)

Question 6

types of beta blockers and receptors blocked

Answer 6

propanolol- equal affinity for beta 1 and 2

atenolol- more selective for beta 1

carvedilol- additional benefits from alpha blockage as well

Question 7

side effects of beta blockers

Answer 7

lungs- causes bronchconstriction ( bad for asthmatics/COPD)

heart- someone with heart failure needs SNS drive for heart

liver- less glycogen breakdown= increased risk of hypoglycaemia for diabetics particularly

fatigue (lower CO and less muscle perfusion), coldness (less vasodilation) and bad dreams (CNS)

Question 8

benefit of atenolo over propranolol

Answer 8

less hypoglycaemia and bronchoconstriction

Question 9

benefit of carvedilol over atenolol and propranolol

Answer 9

not only kidney and heart effects, but also vasodilatory effects

Question 10

alpha blockers

Answer 10

phentolamine blocks alpha 1 receptors (less IP3 thus Ca2+ via G protein and alpha 2 receptor (not needed)= vasodilation

prazosin selective for alpha 1- trets phaeochromocytoma induced hypertension (medulla releases adrenaline)- however prazosin for some reason is less powerful than phentolamine

Question 11

side effects of alpha blockers

Answer 11

GI motility increases= diarrhoea

Question 12

why do alpha 2 and baroreceptors reduce effectiveness of phentolamine and prazosin

Answer 12

blocks alpha 2, so less - feedback, so more NA released

baroreceptors respond to lower pressure so fire less, so SNS increases to compensate

Question 13

false transmitter methyldopa- mechanism

Answer 13

methyldopa covnverted into false transmitter alpha noradrenalne- less active at beta 1/alpha 1, but binds well to alpha 2

unlike NA, it is not well broken down MAO, so uptake back into synapse less, so accumulates and more likely to displace NA

thus used as antihypertensive, improving blood flow

Question 14

side effects of methyldopa

Answer 14

hypotension as so powerful

causes dry mouth due to less saliva production from SNS

Question 15

treating arrhythmias using beta blockers

Answer 15

abnormal heart beats eg atrial fibrillation- often problem with contraction, SNS just gives heart less time to contract and makes arrythmia worse- beta blockers (propranolol) gives heart more time to contract

Question 16

treating angina using beta blockers with side effect

Answer 16

chest pain on EXERTION due to atherosclerosis narrowing coronary vessels- beta blockers reduce HR/CO, so heart has less demand for O2 and thus blood - side effect is cannot exercise effectively

Question 17

treating glaucoma using beta blockers

Answer 17

decreases production of aqueous humour as ciliary body produces less bicarbonate ions, so less aqueous humour formation

Question 18

anti hypertensive drugs

Answer 18

ABCD- ace inhibitors, beta blockers, calcium channel blockers, diuretics