Pharmacology

Question 1

what neurotransmitter acts parasympathetically on the cardiac rate?

Answer 1

acetylcholine acting on M2 receptors

Question 2

what does adenylyl cylclase do?

Answer 2

converts ATP into cAMP

Question 3

describe the sympathetic control of cardiac rate and force

Answer 3

noradrenaline binds to B1 adrenoceptors and coupling through Gs proteins causes stimulation of adenylyl cyclase causing an increase in cAMP which ultimately causes an increase in heart rate

Question 4

is contractility increased or decreased in sympathetic system?

Answer 4

it is increased

Question 5

describe the parasympathetic control of cardiac rate?

Answer 5

ACh activates M2 muscarinic receptors coupling with Gi proteins and inhibits adenylyl cyclase, decreases cAMP so ultimately decreases heart rate

Question 6

steps leading to cardiac muscle contraction

Answer 6

1- ventricular AP
2- opening of Ca2+ L type channels during phase 2
3- Ca influx
4- Ca release from sarcoplasmic reticulum
5- Ca binds to troponin in myosin
6- cross bridges form between actin and myosin + ATP causing contraction

Question 7

steps leading to cardiac muscle relaxation

Answer 7

1-repolarisation in phase 3
2-Ca channels close (L-type)
3-Ca influx ceases (Ca efflux via antiport with Na)
4-Ca release from sarcoplasmic reticulum stops
5-Ca dissociates from troponin
6-Cross bridges break (energised by ATP)

Question 8

Ivabradine functions

Answer 8

inhibits HCN channels so decrease pacemaker potential slope

used in angina