1.1 How the Heart Works

Question 1

1. Atrial Systole

Answer 1

• Blood returns to the heart due to action of skeletal and gaseous exchange (breathing muscles as you move and breath)
  
  • Blood under low pressure flows into left and right atria from pulmonary veins and vena cava.
  • Atria fills=pressure of blood against atrioventricular valves and pushes them open and blood begins to leak into ventricles.
  • Atria walls contract, forcing more blood into the ventricles.

Question 2

2. Ventricular Systole

Answer 2

• Ventricles contract from the base of the heart upwards.
  
  • Increasing pressure in the ventricles.
  • Pushes blood up through the arteries.
  • Pressure of blood against the atrioventrcilar vales closes them and prevents blood flowing backwards into the atria.

Question 3

Diastole

Answer 3

• Atria and ventricles relax.
  
  • Elastic recoil of the relaxing heart lowers pressure in the atria and ventricles.
  • Blood under high pressure I the arteries is drawn back towards ventricles and closing semilunar valves and preventing back flow.
  • Coronary arteries fill during diastole.
  • Low pressure in atria: draw blood into the heart from the veins.

Question 4

What is the Cardiac Cycle?

Answer 4

Cardiac Cycle: One complete sequence of filling and pumping blood.