T3 L18: Molecular control of the heart

Question 1

What is the difference between extrinsic and intrinsic regulation of force contraction in the heart?

Answer 1

Intrinsic is at the cellular level, extrinsic involves compounds from other cells and making the cross bridge formation stronger

Question 2

What does greater overlap of sarcomeres cause?

Answer 2

Stronger force of contraction

Question 3

How quick is the isolated/denervated heart rate?

Answer 3

100 beats per minute

Question 4

Why is the normal resting heart rate lower than the isolated denervated heart rate?

Answer 4

Normal heart rate is toned by parasympathetic stimulation

Question 5

What effect does noradrenaline have on the funny current?

Answer 5

It increases the funny current. The pacemaker potential will increase via beta-receptors

Question 6

What do pacemaker cells do?

Answer 6

Control the rate of contraction of cardiomyocytes

Question 7

What does an increase in Ca2+ do to cardiomyocytes?

Answer 7

Increases force of contraction

Question 8

What does an increase in K+ do to cardiomyocytes?

Answer 8

It shortens the action potential so allows a faster heart rate

Question 9

When do HCN channels open and what do they do?

Answer 9

They open when the membrane becomes negative and they help control the slope of the pacemaker potential

Question 10

What do alpha-1 adrenergic receptors do?

Answer 10

Work using the Gq pathway to increase Ca2+ and cause vasoconstriction

Question 11

What do alpha-2 adrenergic receptors do?

Answer 11

Work using Gi pathway to increase glucagon and decrease insulin

Question 12

What do beta-receptors do?

Answer 12

Work using the Gs pathway to increase heart contractility, heart rate, bronchodilation

Question 13

What type of stimulation does the vagus nerve carry?

Answer 13

Parasympathetic

Question 14

What effect does vagal stimulation have on heart rate and how?

Answer 14

It releases ACh to increase K+ which hyperpolarises the membrane and slows down heart rate

Question 15

What does atropine do?

Answer 15

It blocks vagal stimulation so heart rate can increase

Question 16

What ion is involved in delayed rectifier channels in the heart?

Answer 16

K+

Question 17

What ion is involved in inward rectifier channels in the heart?

Answer 17

K+

Question 18

What is E-C coupling?

Answer 18

The link between excitation and the consequent huge influx in cytosolic Ca2+

Question 19

What do RyR do?

Answer 19

Release Ca2+ from the sarcoplasmic reticulum

Question 20

What does SERCA do?

Answer 20

Pumps Ca2+ back into the sarcoplasmic reticulum

Question 21

What can Ca2+ overload cause?

Answer 21

Ectopic beats and arrhythmias because Ca2+ spill out of the SR

Question 22

What does the drug Amlodipine do and what is it used for?

Answer 22

Its a Ca2+ blocker used to treat angina and arrhythmias

Question 23

What does the drug Verapamil do and what is it used to treat?

Answer 23

Ca2+ blockers used for arrhythmias because it slows down nodal rate

Question 24

What does the drug Diltiazem do and what is it used to treat?

Answer 24

A Ca2+ blocker used to treat angina and arrhythmia because it slows down nodal rate and reduces workload

Question 25

What does the drug Digoxin do?

Answer 25

It increases stroke volume and contractility so is used for heart failure. It works by inhibiting Na+/K+ channels and by stimulating the vagus nerve

Question 26

What is the preferred treatment for heart failure?

Answer 26

Beta-blockers because there a lower mortality rate compared to Digoxin

Question 27

Where is NO released from?

Answer 27

The endothelium

Question 28

What 2 things does the endothelium detect?

Answer 28

Stretch and plasma proteins

Question 29

Which protein initiates VSMC (vascular smooth muscle cell) contraction?

Answer 29

Myosin light chain kinase (MLCK)

Question 30

How does MLCK work?

Answer 30

It phosphorylates mysoin at its light chain

Question 31

What is MLCK activated by?

Answer 31

Calcium calmodulin (Ca2+ bound to protein)

Question 32

What is the drug Glyceryl Trinitrate (GTN) used for?

Answer 32

For vasodilatation because it degrades to NO within the body but tolerance can be built so its taken in pulses

Question 33

What does Bradykinin do?

Answer 33

It vasodilates but constricts bronchi and GI tract smooth muscle

Question 34

Which drugs prevent degradation of bradykinin?

Answer 34

ACE inhibitors. They cause a dry cough when the bradykinin accumulates

Question 35

When would Troponin (Tn) be released?

Answer 35

Released from cardiomyocytes during necrosis

Question 36

What increases Creatine Kinase (CK)?

Answer 36

Released from cardiomyocytes during necrosis

Question 37

Wat increases C reactive protein (CRP)?

Answer 37

Increases during inflammation