The heart and cardiac cycle

Septum

Separates oxygenate and deoxygenated blood

Features of the cardiac muscle

Layers of the heart wall are the pericardium→ myocardium→ endocardium

Rich in myoglobin which is a respiratory pigment with high affinity for oxygen

Why is there fluid in between the pericardium and the myocardium

To reduce friction

What is the blood pressure before and after the valve when it is closed

Low BP before

High BP after

What is the blood pressure before and after the valve is open

High BP before

Low BP after

What is the foramen ovale

It is a gap in the septum at birth which closes later on

Atrial systole (0.1s)

Atria contract forcing blood into the ventricles

AV valves open and semilunar valves closed

Ventricular systole (0.3s)

Ventricles contract forcing blood into the pulmonary artery and the aorta

AV valves close and semilunar valves open

Diastole (0.4s)

Whole heart relaxes and refills with blood

Semilunar valves close and AV valves open

What creates the lub sound

AV valves close

What creates the dub sound

Semilunar valves close

how is the heart myogenic

It initiates its own contractions

Sinoatral node (SAN) , right atrium

Sets of a wave of electrical excitation that spreads across both atria making them contract

Atrioventricular node (AVN), lower section of the right atrium

Picks up the impulse from SAN with slight delay and then passes it down to the Bundle of His and out through the Purkyne fibres in the ventricles

Where is the Bundle of His

On the bottom of the heart

How does the impulse travel in the ventricles

From the base upwards

Cardiac output formula

Stroke volume • Heart rate