Cardiac cycle

Question 1

Events in a cardiac cycle

Answer 1

Black = systole

White = diastole

Question 2

Describe the valvular mechanism that regulates bloodflow in the heart chambers

Answer 2

Valve only opens when the pressure in the input chamber exceeds the pressure within the pumping chamber.

As the ventricular wall contracts and relaxes, the chamber’s volume is constantly changing, causing the pressure inside to rise and fall.

Question 3

What are the five stages of valvular action during the cardiac cycle, starting with isovolumetric contraction?

Answer 3

1. Isovolumetric contraction
2. Ventricular ejection
3. Isovolumetric relaxation
4. Ventricular filling
5. Atrial systole

Question 4

When do you hear heart sounds & what are the causes?

Answer 4

• S₁ in isovolumetric contraction
  
  • ​AV valves close
  • Blood vibrates in the closed ventricle
  • Venticle wall vibrates durign contraction
• S₂ in isovolumetric relaxation
  
  • ​Semilunar valves (aortic & pulmonic) close
• S₃ in filling
  
  • ​Vibration of ventricular wall
• S₄ in atrial systole
  
  • ​Blood vibrates during atrial contraction

Question 5

Study this. Where is End-systolic volume and End-diastolic volume?

Answer 5

Question 6

What happens to the pressure-volume curve of the left ventricle if you increase preload (blood in the ventricle right before contraction)?

Answer 6

Wider

Frank-Starling relationship: As this end-diastolic volume increases → stroke volume increases (everything coming in gets pumped out)

Question 7

What happens to the PV curve if you increase afterload (pressure in aorta)?

Answer 7

TALLER & THINNER

To bust open the aortic valve, left ventricular pressure must be higher than the aortic pressure –> taller

Stroke volume decreases because end-systolic volume increases (more blood left in the ventricle after contraction).

Question 8

What happens to the PV curve if you increase contractility?

Answer 8

Taller & wider

Higher contractility means the ventricle can generate more pressure during systole (taller) and stroke volume increases because end systolic volume decreases. (wider).

Question 9

Which is the loudest heart sound?

Answer 9

S1 is the loudest

AV valves close

Question 10

Which is the “atrial heart sound”

Answer 10

S4

Question 11

Why might S₁ have an altered intensity?

Answer 11

High CO states or Tachycardia

Mitral valve probs

Abnormal PR interval

Ventricular hypertrophy

Question 12

What is the normal splitting of S2 ?

Answer 12

A2: Expiration fuses them as one sound

P2: Inspiration separates the two sounds

Question 13

Causes of abnormal splitting of S₂

Answer 13

Bundle branch block

Valvular stenosis

Atrial septal defects

Question 14

The third heart sound (S₃) is typically inaudible except in

Answer 14

Children w/ a thin chest

Patients with left ventricular failure

Question 15

A pathologic S₃ is referred to as a ventricular ______

Answer 15

Gallop

Question 16

Cardiac murmurs (turbulent blood flow) result from

Answer 16

Valve stenosis

Valve regurgitation (incompetency)

Abnormal shunting of blood from high- to low-pressure (e.g. VSD)

Increased flow through regular structures (e.g. anemia)

Ejection into a dilated chamber (aneury

Question 17

Thrill

Answer 17

A murmur that is so severe you can palpate it

Question 18

What might cause a systolic ejection murmur?

Answer 18

Aortic stenosis

Pulmonic stenosis

Question 19

What might cause a pansystolic murmur?

Answer 19

Bicuspid & tricuspid regurgitation

Question 20

What might cause a late systolic mumur?

Answer 20

Mitral valve prolapse

Question 21

What might cuase an early diastolic murmur?

Answer 21

Aortic or pumonic regurgivation

Question 23

What might cause a mid/late diastolic murmur?

Answer 23

Mitral stenosis