Cardiac cycle





Cardiac Cycle

1.       Heart contracts + relaxes in a rhythmic cycle.

2.     Cardiac cycle consists of alternating periods of :

·        Systole - contraction phase.

·        Diastole - relaxation phase.

3.     Cardiac cycle = one complete sequence of systole + diastole

4.     Resting adult - cardiac cycle repeated 72 times per minute = resting heart rate.

5.     Pulse = causes by elastic recoil of arteries.

6.     Ventricular pressure + aortic pressure + ventricular volume:

• changes (in response to the events that occur)
• at different phases of cardiac cycle.

7.     During diastole:

• pressure↓of heart chambers decreases
• volume↑ increases (as blood is pumped in).

8.     During systole:

• pressure↑of heart chambers increases
• volume↓ decreases (as blood is pumped out).

9.     When aortic pressure > ventricular pressure

à semilunar valves shut + vice versa.

10.  When ventricular pressure > atrial pressure

à AV valves shut + vice versa.

11.   Valves = ensure blood only flows in right direction.

Transport In Animals

1. Human heart : 

• consists of 4 chambers : right atrium, right ventricle, left atrium and left ventricle. 
• pump blood to all parts of the body.
• made up of cardiac muscle. 




Front/venrtral  view of heart

 

2. Superior vena cava
    --> carries deoxygenated blood
    --> from the head + arms
    --> into right atrium.

3. Inferior vena cava
    --> carries deoxygenated blood
    --> from the lower body + legs
    --> into right atrium

4. Right atrium
    --> receives deoxygenated blood
    --> from vena cava
    --> to right ventricle. 

5. Tricuspid (antrioventricular) valves
    --> prevent blood (from right ventricle) flowing backwards
    --> to the right atrium.

6. Right ventricle
    --> pumps blood
    --> to lungs
    --> via pulmonary arteries.

7. Semilunar valves
    --> prevent blood (from pulmonary arteries)
    --> from flowing backwards
    --> into right ventricle.

 




Cross-section of heart

  










8.   Pulmonary artery branches
      --> carries deoxygenated blood
      --> from right ventricle 
      --> to lungs.

9.   Pulmonary vein
      --> carrying oxygenated blood
      --> from lungs
      --> to left atrium.

10. Left atrium
      --> receives oxygenated blood
      --> from lungs 
      --> to left ventricle.

11. Bicuspid (atrioventicular) valves
      -- > prevent blood (from left ventricle) flow backwards to left atrium

12. Left ventricle
      --> pumps oxygenated blood
      --> to body tissue (via aorta).

13. Semilunar/aortic valves
      --> prevent blood (from aorta) flowing backwards (into left ventricle).

14. Aorta
      --> carries oxygenated blood
      --> from left ventricle
      --> to the rest of the body.

15. Septum separates the right and left side of the heart.

Simplified version of heart