HL Bio - Unit #3.6: The Heart

Veins in the Heart

1. Superior vena Cava

2. Inferior Vena Cava 

3. Pulmonary Veins

Arteries in the Heart

1. Aorta

2. Pulmonary Artery 

3. Right Coronary artery

4. Left Anterior Coronary Artery

5. Left Posterior Coronary Artery

6. Carotid Arteries

Atria

Collection chambers of the heart, where blood is deposited in

Ventricles

Pumping chambers of the heart, where blood enters to be pumped out

the sinoatrial node

Right Atrium: Has the sinoatrial node within its walls

• A small mass of specialised cardiac muscles fibres which act as a pacemaker by generating electrical impulses of the heartbeat at regular intervals

Thickest part of the heart

The left ventricle is the thickest since it needs to pump blood to the whole body

Valves

• Atrioventricular Valves: Open when the pressure is higher in the atrium is higher than that in the ventricles and close when it’s the opposite

  • Tricuspid Valve

  • Bicuspid/mitral Valve

• Semilunar Valves

  • Aortic Valve

  • Pulmonary Valve

Septum

Wall between the left and right ventricles

Cardiac Cycle:

1. Ventricular filling

2. Atrial Contraction

3. Isovolumetric Contraction

4. Ventricular Ejection

5. Isovolumetric Relaxation

6. Atrial Filling

7. Ventricular Filling

Ventricular filling

The ventricles are rapidly filled with the blood accumulated in the atria before the opening of the atrioventricular valves

Atrial Contraction

when contraction of cardiac muscle in the atrium increases pressure, causing additional blood to flow across the tricuspid valve

Isovolumetric Contraction

causes left ventricular pressure to rise above atrial pressure, which closes the mitral valve and produces the first heart sound

Ventricular Ejection

When the heart contracts, it pumps out — ejects — blood from the two lower heart chambers

Isovolumetric Relaxation

When the ventricular pressures drop below the diastolic aortic and pulmonary pressures, the aortic and pulmonary valves close producing the second heart sound

Atrial Filling

When blood re enters the heart and fills the left atrium

Systole

Stage the heart muscle contracts

Atrial Systole

• Passive filling from pulmonary veins & vena cava

• Atria contract, forcing blood into the ventricles.

• Pressure increases slowly, Atrioventricular valves open, semilunar valves remain closed

Ventricular Systole Early

• Contraction of the ventricles

• Pressure rises steeply and this pushes the Atrioventricular valves to close (makes the first sound)

• Semilunar valves are still closed, because pressure in Aorta and pulmonary arteries is still higher than in the ventricles

Late ventricular Systole:

• Ventricular contraction continues

• Pressure in ventricles exceeds the one in the pulmonary artery and aorta so semilunar valves are pushed open and blood is ejected

Diastole

Stage in the cycle where the heart muscle does not contract

Ventricular Diastole Early

• The ventricles relax - pressure in falls rapidly

• Semilunar valves close shut due to lack of blood (makes the second sound)

• Passive ventricular filling starts

Atrial/ventricular Diastole Early

• Continued passive filling of both atria and ventricle through open Atrioventricular valves due to backflow of blood from vena cava inferior/superior, and pulmonary vein.

• Pressure in the aorta is much higher than in the left ventricle, which causes semilunar valves to be closed