Cardiovascular unit

Question 1

Role of Na+ in both cardiac myocytes and cardiac pacemaker cells

Answer 1

Cardiac myocytes: Main cause of depolarisation
Pace maker, slowly depolarising pacemaker potential by the funny current channels opening

Question 2

Role of Ca2+ in both cardiac myocytes and cardiac pacemaker cells

Answer 2

Cardiac myocytes: The Plateau phase prolongs the AP
pacemaker: Ca2+ is the main depolariser of AP

Question 3

Molecular mechanism of sympathetic nervous system on the heart

Answer 3

1. NE or EP bind to B2 adrenergic
2. Causes PKA to phosphorylate funny channels and calcium channels
3. Increase the rate of contraction

Question 4

Molecular mechanism of the parasympathetic nervous system on the heart

Answer 4

1. Ach bind to M2R receptor
2. Causes inhibition of adenylyl cycalse
3. Also causes activation of GIRK, causing hyperpolarisation

Question 5

What is a third-degree block?

Answer 5

Top of heart disconnect to the bottom of the heart, more P than QRS

Question 6

Atrial fibrillation ECG patterns

Answer 6

No P waves, irregular QRS

Question 7

Ventricular fibrillation

Answer 7

No P and No QRS

Question 8

What is second degree heart block:

Answer 8

Extra P and normal QRS, slight disconnect between the top and bottom of the heart

Question 9

Steps of cardiac cycle

Answer 9

1. Atria filling (late diastole)
2. Atria systole
3. Isovolumic ventricular contraction (not enough pressure for Aortic valves to open)
4. Ventricular ejection - blood is ejected into aorta
5. Isovolumic ventricular relaxation