Cardiac Physiology 1: Heart as a pump

Question 1

How are metabolites/blood pumped around the body? Why?

Answer 1

-By creating a pressure gradient for BULK FLOW to capillaries .. short diffusion distance with cells and capillaries

Question 2

What is Darcys law used to explain?

Answer 2

• Flow = P/R
  Basic mechanism of bulk flow > To create flow we need to increase pressure gradient

Question 3

The heart must play a dual role to effectively pump blood. What does this mean?

Answer 3

Question 4

Describe the Cardiac cycle.

Answer 4

1. Deoxygenated blood from body would enter the Right Atrium via the SVC/IVC/ Coronary sinus
2. Right atrium
3. Tricuspid Valve
4. Right Ventricle
5. Pulmonary Valve
6. Pulmonary Artery
7. Pulmonary Circulation
8. Oxygenated blood enters left side of heart via Pulmonary VEINS
9. Left Atrium
10. Bicuspid valve
11. Left Ventricle
12. Aortic Valve
13. Aorta
14. Through into the body

Question 5

What happens in diastole part 1?

Answer 5

1. RAPID VENTRICULAR FILLING
   >Elastic recoil of ventricles increases ventricular volume so lowers ventricular pressure > increasing pressure gradient for ventricular filling from veins

Question 6

What happens in diastole part 2?

Answer 6

2. DIASTISIS
   > Once the ventricles have fully relaxed, blood pressure gradient between veins and ventricles is reduced, slowing filling down

Question 7

What happens in atrial systole?

Answer 7

-ATRIAL SYSTOLE
> Atrial contraction decreasing volume of atria this increases atrial pressure, facilitating blood flow into ventricles. Increases ventricular volume by only ≈10%.

Question 8

What happens after atrial systole?

Answer 8

-ATRIOVENTRICULA VALVES CLOSE
>Atrial contraction cease. Ventricular pressure exceeds atrial pressure. Atrial ventricular pressure closes

Question 9

What happens after the atrioventricular valves close? Part 1

Answer 9

1-ISOVOLUMETRIC VENTRICULAR CONTRACTION
>Ventricles start to contract – this causes a large increase in ventricular pressure until…..

Question 10

What happens after the atrioventricular valves close? Part 2

Answer 10

2- EJECTION
>Ventricular pressure exceeds Aortic pressure (or pulmonary artery). This causes the respective valves to open allowing ejection of blood from the ventricles

Question 11

What happens after ventricular systole?

Answer 11

-DIASTOLE > SEMI-LUNAR VALVES CLOSE
>As blood is ejected and the ventricles start to relax, the pressure in the ventricles begin to decrease. When aortic pressure exceeds ventricular pressure, the semilunar valves close

Question 12

What happens after semi-lunar valves close?

Answer 12

-ISOVOLUMETRIC RELAXATION
>The elastic recoil of the relaxing ventricles cause the ventricular pressure to rapidly fall. When atrial pressure exceeds ventricular pressure…
>….. Atroventricular valves open, bringing us back to where we began!

Question 13

What does the heart sounds S1 and S2 correspond to ?

Answer 13

-The turbulence in blood flow elicited by the backflow of blood which is caused by the closing of the atrioventricular and semilunar valves closing respectively

Question 14

What maintains flow of blood throughout the whole cardiac cycle?

What causes dicrotic notch?

Answer 14

-Elastic recoil of the arteries

-Backflow of blood at valve closure causes dicrotic notch

Question 15

What must the outputs of the left and right ventricle be?

Answer 15

• Matched
  > Blood volume contained within each circulation stays constant

Question 16

Define :
-Preload
-Afterload
-EDV
-ESV
-SV

Answer 16

> Preload = the force that stretches the cardiac muscle prior to contraction
Afterload= the amount of resistance the heart must overcome to open aortic valve
EDV = amount of blood that is in the ventricles before the heart contracts (increased preload causes increased EDV)
ESV= the volume of blood in the left or right ventricle at the end of the systolic ejection
SV = volume of blood pumped from the left ventricle per beat.
(EDV-ESV)

Question 17

What happens when right side of the heart pumps faster than left?
>Frank sterling mechanism

Answer 17

Question 18

What happens when right side of the heart pumps faster than left? Full explanation
>Frank sterling mechanism

Answer 18

Question 19

What would happen in the absence of Frank - Starling mechanism?

Answer 19

1. Increased output from right side not matched by left
   - Leading to accumulation of pressure in pulmonary circulation
   → The development of pulmonary oedema
   → Hypoxaemia

2.- Increased output from left side not matched by right
-Increase in venous pressure of peripheral circulation
→ Lead to development of peripheral oedema
→ Risk tissue hypoxia