Cardiac Cycle

Question 1

Define the 2 types of blood vessels in the body

Answer 1

Resistance vessls- restrict blood flow to drive supply to hard to perfuse areas of the body. Can reduce their diameter

Capacitance vessels- enable system to vary amount of blood pumped around the body as they can store blood in the system to determine flow

Question 2

Define Systole

Answer 2

Contraction and ejection of blood from ventricles

Question 3

Define Diastole

Answer 3

Relaxation and filling of ventricles

Question 4

Describe the Conduction System

Answer 4

1. Pacemaker cells in SA node generate action potential
2. Atrial systole- activity spreads over atria
3. Reaches AV node, delayed for 120ms
4. Excitation spreads down septum
5. Then spreads through ventricular myocardium from endocardial to epicardial surface
6. Ventricles contract from apex up

Question 5

What are the 7 phases of the Cardiac Cycle

Answer 5

1. Atrial Contraction
2. Isovolumetric Contraction
3. Rapid Ejection
4. Reduced Ejection
5. Isovolumetric Relaxation
6. Rapid Filling
7. Reduced Filling

Question 6

How long are Systole and Diastole and what happens to their lengths when the heart rate increases?

Answer 6

Systole is 0.35s

Diastole is 0.55s

Increased heart rate decreases the length of diastole while systole stays the same length

Question 7

Name and label the diagram

Answer 7

Wiggers diagram

30- Dicrotic notch

31- X descent

32- Y descent

Question 8

During which phases are the Mitral/Tricuspid Valves open

Answer 8

Phase 1: Atrial Contraction

Phase 6: Rapid Refilling

Phase 7: Reduced Filling

Question 9

During which phases are the Aoritc/Pulmonary valves open

Answer 9

Phase 3: Rapid Ejection

Phase 4: Reduced Ejection

Question 10

During which phases are all valves closed

Answer 10

Phase 2: Isovolumetric Contraction

Phase 5: Isovolumetric Relaxation

Question 11

Describe and name Phase 1

Answer 11

Atrial Contraction:

P wase (ECG) signifies atrial depolarisation

A wave due to atrial systole where atrial pressure rises

Atrial contraction which accounts for the final 10% of ventricular filling (Atrial Kick)

Question 12

Describe and name Phase 2

Answer 12

Isovolumetric Contraction:

QRS complex- ventricular depolarisation

Ventricular pressure rises due to ventricle contraction, this also closes the mitral valve and causes the C wave in atrial pressure

No change in ventricular volume => isovolumetric

Question 13

What is responsible for the first and second heart sounds

Answer 13

1st heart sound due to mitral and tricuspid valves closing

2nd heart sound due to the aortic and pulmonary valves closing

Question 14

Describe and name Phase 3

Answer 14

Rapid Ejection:

Ventricular pressure greater than aortic causing aortic valve to open and ejection begins.

Rapid decrease in ventricular volume

X descent on atrial pressure graph due to atrial base being pulled downward as ventricles contract

Question 15

Describe and name Phase 4`

Answer 15

Reduced Ejection:

Ventricles repolarise producing T wave

Repolarisation leads to decline in tension and rate of ejection decreases

Atrial pressure rises due to venous return from lungs producing V wave

Question 16

Describe and name Phase 5

Answer 16

Isovolumetric Relaxation:

When intraventricular pressure falls below aortic there is brief backflow of blood that closes the aortic valve

Volume in ventricle remains constant => isovolumetric

Dicrotic notch seen in aortic pressure due to closure of valve

Question 17

What is Stroke volume

Answer 17

Volume of blood ejected per beat

Stroke volume = EDV - ESV

Question 18

Describe and name Phase 6

Answer 18

Rapid Filling:

Intraventricular pressure falls below atrial, opening the mitral valve and rapid ventricular filling begins

Y-descent seen as atrial pressure decreases after mitral valve opening

Blood is sucked into the ventricles from the atria

Question 19

Describe and name Phase 7

Answer 19

Reduced Filling:

Rate of filling slows (diastasis) as ventricle reaches inherant relaxed volume

90% full by end of phase 7

Question 20

Name two types of abnormal valve function

Answer 20

Stenosis

Regurgitation

Question 21

What is aortic valve stenosis

Answer 21

Where there is narrowing of the aortic valve

Causes:

• Degenerative- senile calcification/fibrosis
• Congenital- bicuspid form of the valve
• Chronic rheumatic fever- causes inflammation and then commissural fusion of the vavle leaftlets

Effects:

• Less blood can get through valve causing:
  
  • Increased LV pressure leading to LV Hypertrophy
  • Left sided heart failure causing syncope and/or angina

Question 22

What is aortic valve regurgitation

Answer 22

Condition where aortic valve does not close all the way so there is back leakage when valve should be closed

Causes:

• Aortic root dilation- leaflets pulled apart
• Valvular damge

Results in blood flowing back into LV during diastole causing:

• Increased stroke volume
• Increased systolic and decreased diastolic pressures
• Bounding pulse- head bobbing and Quincke’s sign
• LV hypertrophy

Question 23

What is mitral valve regurgitation

Answer 23

Where mitral valve doesn’t shut properly so blood flows back in during systole

Causes:

• Damage to papillary muscle after MI
• Left sidede heart failure leading to LV dilation and stretching of the valve
• Rheumatic fever leading to leaflet fibrosis, disrupting seal formation
• Myxomatous degeneration weaking tissue leading to prolapse

Can result in LV hypertrophy as preload increases due to blood leaking back into LA

Question 24

What is mitral valve stenosis

Answer 24

Where the mitral valve doesn’t open enough

Main cause is Rhuematoid fever causing commissural fusion of leaflets making it harder for blood to flow into LV from LA

Results in an increased LA pressure causing:

• LA dilation
  
  • Atrial fibrillation causing thrombus formation
  • Oesophagus compression and dysphagia
• Pulmonary oedema, Dyspnea, Pulmonary hypertension
  
  • RV hypertrophy