Cardiac 2

Question 1

What forms the right border of the heart?

Answer 1

right atrium

Question 2

What forms the inferior border of the heart?

Answer 2

primarily the right ventricle

Question 3

What mainly forms the left border of the heart?

Answer 3

left ventricle( and in part the left atrium/auricle)

Question 4

Which part of the pericardium lines the fibrous pericardium?

Answer 4

parietal pericardium

Question 5

What type of cell is pericardium made out of?

Answer 5

thin layer of squamous mesothelial cells

Question 6

which part of the pericardium attaches to the heart wall?

Answer 6

visceral pericardium

Question 7

cardiac tamponade

Answer 7

Cardiac tamponade happens when extra fluid builds up in the pericardium. This fluid puts pressure on the heart and prevents it from pumping well. This is a medical emergency.

Question 8

what ring is absent in the fibrous skeleton of the heart?

Answer 8

pulmonary ring

Question 9

Which ring is incomplete in the fibrous skeleton of the heart?

Answer 9

tricuspid ring

Question 10

the conduction system of the heart

Answer 10

Cells in SA( sinoatrial) node depolarize randomly( pacemaker potential)-> when pacemaker potential reaches threshold AP is triggered->AP propagates through both atria via gap junctions-> 2 atria contract at the same time->AP reaches the AV( atrioventricular) node-> AP slows in AV ( the delay provides time for atria to empty the blood into ventricles-> AP propagates through AV bundle-> AP enters both R and L bundle branches->the bundle branches extend through interventricular septum toward the apex-> Purkinje fibers conduct AP to the remainder of ventricular myocardium-> ventricles contract pushing the blood out.

Question 11

Why is the rise in pressure in the atria small during contraction?

Answer 11

• the atrial muscle layer is thin

- no valves where pulmonary veins enter the atrium-> nothing to prevent backflow of blood into the veins

Question 12

Stage of the cardiac cycle

Answer 12

• Ventricular filling: pressure in the ventricles drops below that in the atrium
• Atrial contraction: Atria contract to complete the filling of the ventricle
• Isovolumetric ventricular contraction( systole)- ventricles begin to contract. Blood within it lifts backward towards the atrium and the atrioventricular valves(tricuspid and mitral) close. Ventricular pressure is still below that of the aorta and pulmonary artery so aortic & pulmonary valves stay closed. For this brief period, both inlet and outlet valves are closed.
• Ventricular ejection. Systole continues, but now ventricular pressure exceeds aortic and pulmonary pressure, so aortic and pulmonary valves open. Blood leaves the ventricle. The pressure in the aorta and the ventricle continues to rise, but then level off and begins to decrease.
• Isovolumetric ventricular relaxation. The ventricles relax, ventricular pressure drops suddenly, the flow reverses in the aorta/pulmonary artery and the outlet valves close. The inlet valves are closed because the ventricular pressure still exceeds the atrial pressure. Both inlet and outlet valves are closed again.d

Question 13

what is the function of fibrous skeleton?

Answer 13

• insulate the ventricular myocardium from the electrical activity in the atria apart from the AV node
• provide structural support for the high-pressure valves of the heart

Question 14

what is the function of the AV node?

Answer 14

• it is a slow conducting electrical pathway between the atria and ventricles
• It causes a delay of the wave of action potentials traveling through the muscle of the heart, allowing time for the atria to contract (as the mechanical contraction is a slower process than the electrical activation) and top up the volume of the ventricles, prior to ventricular contraction.

Question 15

what is the function of the AV node?

Answer 15

• it is a slow conducting electrical pathway between the atria and ventricles
• It causes a delay of the wave of action potentials traveling through the muscle of the heart, allowing time for the atria to contract (as the mechanical contraction is a slower process than the electrical activation) and top up the volume of the ventricles, prior to ventricular contraction.
• Without this delay, the action potential propagates at such a speed that the ventricles and atria would contract almost simultaneously.

Question 16

what is the volume of right and left ventricle

Answer 16

120 ml

Question 17

In what phase of the cardiac cycle does the 2nd heart sound occur?

Answer 17

At the end of ventricular ejection and the beginning of isovolumetric ventricular relaxation

The second heart sound is caused by the closing of the aortic and pulmonary valves in quick succession. These valves close when the arterial pressure exceeds the ventricular pressure, which signals the start of isovolumetric ventricular relaxation.

Question 18

When does the 1st heart sound occur?

Answer 18

The first heart sound (S1) represents closure of the atrioventricular (mitral and tricuspid) valves as the ventricular pressures exceed atrial pressures at the beginning of systole (point a). S1 is normally a single sound because mitral and tricuspid valve closure occurs almost simultaneously.

Question 19

What is the longest phase of cardiac cycle?

Answer 19

(Passive) Ventricular filling ~ 0.4 sec
As heart rate increases, relaxation time and therefore filling time reduces, while contraction time reduces only slightly

Question 20

In which phase of the cardiac cycle does the pressure in the aorta increase and decrease?

Answer 20

Ventricular ejection.

The pressure in the aorta initially increases as the rate of entry into the artery is greater than the rate that it can drain. This then levels out when the rate of filling equals the rate of emptying. Finally, this then decreases as the rate of blood entering the aorta is lower than the rate of blood that is draining into systemic arteries. This is the rate of ejection of blood is much higher at the beginning of systole than the end. The more the cardiac muscle fibers in the ventricle are stretched, the greater force they produce. This means early in systole the ventricle can generate enough force to fill the artery faster than it can drain. The force of ejection decreases as the volume in the ventricle decreases and the muscle fibers reduce in length.