Drugs modifying cardiac rate and force - heart rate

Question 1

What is the transmitter and the hormone for the sympathetic system and which receptor is activated?

Answer 1

Noradrenaline is the transmitter and adrenaline is the hormone and beta 1 adrenoceptors are activated

Question 2

In the sympathetic system what happens through G coupling?

Answer 2

Adenylyl cyclase is activated which increases cAMP which causes a positive chronotopic effect (increase in heart rate) this is mediated by the SA node and due to an increased slope of the pacemaker potential

Question 3

In the parasympathetic system which is the transmitter and what receptors are activated?

Answer 3

Acetylcholine and M2 muscarinic cholinoceptors are activated

Question 4

What happened in the sympathetic system through G protein coupling?

Answer 4

Decreased activity of adenylate cyclase which decreases cAMP also potassium channels are opened to cause hyper polarisation of the SA node. Negative chronotopic effect

Question 5

What is If - they funny current?

Answer 5

It is an inward curve activated by hyper polarisation - it is carried by sodium

Question 6

What happens if If is blocked?

Answer 6

Decreases the slope of the pacemaker potential and decreases the heart rate

Question 7

What can block If?

Answer 7

Acetylcholine

SBAs such as aniline and ivabradine (selective blocker of HCN channels that is used to slow heart rate in angina)

Question 8

What two drugs regulate If and how?

Answer 8

Isoprenaline is a beta adrenergic agonists and it signals via cAMP to increase heart rate
ACh is a muscarinic agonist and decreases cAMP therefore reducing the heart rate
Thyroid hormones increase the heart rate
Other neurotransmitters increase the hr
Adenosine decreases the heart rate
Nitric oxide increases the heart rate