lecture 8

Question 1

whats the start of the cardiac cycle

Answer 1

the point of relaxation before the two atria contract again.

Question 2

whats the sequence of events for heart contractions

Answer 2

both atria contract first then both the ventricles contract

Question 3

how do we increase the force of cardiac contraction?

Answer 3

Every cardiomyocyte is activated
during each heart beat, we increase cystolic Ca2+ which will also increase cross bridge formation in cardiac muscle myofibrils.

Question 4

whats the cellular mechanism of cardiac relaxation

Answer 4

Decrease in cytosolic Ca2+ levels.
* Ca2+ pumped back into the SR.
* Cross-bridges release when ATP
binds to myosin.
* Reduction in force means the heart
can relax.
* All cardiac myocytes relax each beat.

Question 5

whats diastole

Answer 5

relaxation and falling pressure

Question 6

whats systole

Answer 6

contraction and rising pressure

Question 7

what are the 5 phases of the cardiac cycle

Answer 7

1: atrial systole
2: isovolumetric ventricular contraction
3: ventricular ejection
4: isovolumetric ventricular relaxation
5: passive filling

Question 8

what happens in isovolumetric ventricle contraction

Answer 8

IVC: ventricle systole and atrial diastole in the background, pressure in the ventricle closes the AV valves. The closing of the AV valves is why we hear the Lubb sound. In this time the ventricle is contracting to create pressure to go through semi lunars, then the semi lunar is opened once enogh pressure is made.

Question 9

what happens in isovolumetric ventricular relaxation

Answer 9

ventricular diastole

Question 10

why is the pressure in the systemic circuit larger

Answer 10

Systemic blood pressure is always higher than the highest pressure of the pulmonary, as they move it round less distance.

Question 11

after what pahses do lubb and dupp happen

Answer 11

between atrial systole and IVC : lubb
between ventricular ejection and IVR: dupp