2000 : Pathophysiology

Question 1

What is the first phase of the cardiac cycle?

Answer 1

Atrial contraction :
When oxygenated blood enters the left atria (LA), passes through the mitral value and into the left ventricle (LV)
- the pressure in the LA is greater than the LV hence blood flows nicely into LV to reach 80 % pressure filling.
- aortic valve is closed

Question 2

What is the second phase of the cardiac cycle?

Answer 2

Isovolumetric contraction

• once the pressure in the LV exceeds the pressure of the LA the mitral valve closes
• this triggers the LV to being to contract lifting the LV pressure to 79 %
• the LA is still being filled with oxygenated blood

Question 3

What is the third phase of the cardiac cycle ?

Answer 3

Rapid ejection

• LV contracts beyond the pressure of the aorta forcing the aortic valve to be opened (79 - 120 )
• the pressure within goth LV then translates to the aorta
• in the beginning of this phase the aorta expands slightly due to the rapid ejection of the blood within the LV

Question 4

What is the fourth phase of the cardiac cycle ?

Answer 4

Slow ventricular ejection

• the LV is beginning to relax hence blood flow is at a slow pace entering the aorta via the aortic valve

Question 5

What is the fifth phase of the cardiac cycle ?

Answer 5

Isovolumetric relaxation

• LV is relaxed and into a diastole phase
• LV pressure is lower than aortic pressure hence aortic valve closes
• LV pressure is still above LA pressure hence mitral valve is still closed

Question 6

What is phase six of the cardiac cycle

Answer 6

Rapid passive ventricular filling

• pressure in the LV has gone below the pressure in the LA
• mitral valve is open
• oxygenated blood rapidly fills the LV with 80% pressure

Question 7

What is phase 7 of the cardiac cycle ?

Answer 7

Slow passive ventricular filling

• blood is slowing filling the LV from the LA
• aortic valve is still shut
• LA contraction occurs to gain the last 2 % of oxygenated blood from the LA

Question 8

What is EDV

Answer 8

The blood left in the heart after relaxation

Question 9

What is ESV ?

Answer 9

The blood remaining in the heart after contraction

Question 10

Draw a diagram to describe the flow of blood through the heart

Answer 10

SVC + IVC -> RA (tricuspid valve) RV (pulmonary valve) lungs -> LA (mitral valve) LV (aortic valve) aorta

Question 11

What is an ejection fraction? And what is the normal functioning capacity ?

Answer 11

The percentage of the total amount of blood that is pumped out in each heartbeat

65%

Question 12

Ejection fraction equation

Answer 12

EF = SV
——-
EDV

Question 13

Define
- Inotropic
- Chronotropic
- Dromotropic

Answer 13

Inotropic - increasing the force on contractions

Chronotropic - increasing heart rate

Dromotropic - increasing the speed of conduction

Question 14

Why is cardiac output equal on both side but there is a pressure difference for both left and right sides of the heart

Answer 14

When cardiac output is equal on both sides of the heart the pressure of each side is not equal because the right side has to overcome the pressure of the lungs and the left side needs to supply the rest of the body with blood hence pressure is different. Therefore Cardiac workload is not equal in equal sides if the heart

Question 15

What is preload and what can influence it ?

Answer 15

the amount of blood returning to the atria
Influenced by ; GTN, anaphylaxis, dehydration, posture, haemorrhage decrease preload

Question 16

What is afterload and what can it be influenced by ?

Answer 16

pressure the heart has to pump against to get blood back out into the body
Influenced by ; Vasoconstriction, adrenaline, aortic stinosis (thick aorta) will increase after-load

Question 17

The main reason myocardial contractile cells can stimulate depolarization of adjoining cells is via what mechanism?

Answer 17

Gap junctions are bridges between the cell membranes

Question 18

What area of the body does blood flow through ?

Answer 18

Blood flows from areas of high pressure to areas of low pressure

Question 19

What effect would a positive inotrope have on the heart?

Answer 19

It would increase the stroke volume

Question 20

A patient has a heart rate of 150bpm. What effect would a positive chronotrope have?

Answer 20

Reduced preload due to reduced ventricular filling time

Question 21

During isovolumetric contraction the atria are in diastole and the ventricles are in systole

True or False

Answer 21

TRUE

Question 22

How do cells become excitable?

Answer 22

Cells become excitable by the feature that the gap junctions relay allowing the leakage of sodium through one cell into another and so on therefore creating a large cell stimulus.
ONLY IN DEPOL
REPOL DOES NOT HAVE GAP JUNCTIONS

Question 23

they flow like a river from the epicardial surface of the myocardium towards the endocardial surface. What are these rivers called ?

Answer 23

Coronary arteries

Question 24

When will the aortic valve open

Answer 24

The pressure within the left ventricle exceeds the pressure within the aorta

Question 25

Name the four coronary arteries

Answer 25

1. Left coronary artery
2. Circumflex artery
3. Left anterior descending artery
4. Right coronary artery

Question 26

What is cardiac ischaemia ?

Answer 26

It is the lack of blood supply to a certain area, causing the delay in the depolarisation and depolarisation of the cardiac cells.

Can be detected through ST depression and inverted T waves

Question 27

What is cellular infarct ?

Answer 27

Irreversible injury cause it cell death
Can be detected through ST depression and T wave inversion