The Heart

And how it works…

Heart Beats

Heat BeatsStep 1: Enter Atrium

Right Side- Deoxygenated blood

enters the right atrium through 2 large veins - Superior vena cava:

upper half of the body

- Inferior vena cava: below the diaphragm

Left Side- Oxygenated blood

(from the lungs) enters the left atrium through the pulmonary vein- Comes from the lungs

Heart BeatsStep 2: Contract Atrium

• Blood flows from the atrium into the ventricle

• The atrioventricular (AV) valve allows for a one-directional flow

• The AV valve closes once the ventricle is full - LUB

Heart BeatsStep 3: Contract Ventricle

• Right ventricle contracts

• Blood flows through the semilunar valve into the left pulmonary artery – DUB

• Blood flows towards the lungs

• Left ventricle contracts

• Blood flows through the semilunar valve into the right pulmonary artery

• Blood flows out towards the body

Path of Blood through the Heart

Heart Sounds

• Two normal heart sounds– Lub: closure of the AV valves (beginning of

ventricular contraction - systole)– Dub: closure of the semilunar valves (end of

ventricular systole – diastole)

• Other sounds– Heart murmur: turbulent blood flow

Heart Murmur: back flow

Overview: Blood Flow

• Blood in body• Into heart via vena cava (vein)• Right atrium• Right Ventricle• Left pulmonary artery (deoxygenated)• Lungs (becomes oxygenated)• Pulmonary vein• Left atrium• Left ventricle• Arteries (oxygenated towards body tissue)

Connecting the Heart to the Lungs & the Body

Setting the Heart’s Tempo

• Heart muscles contract without being stimulated by external nerves (myogenic muscles)

• Heart muscle does not all contract at the same rhythm when separated

• Heart rhythm is set by the sinoatrial (SA) node – specialized nerve cells

• Nerve impulses travel to a second node AV node which sends the message toward the ventricles

Normal Sinus Rhythm

• P wave followed by a ventricular response

Atrial Fibrilation

• Most common arrhythmia

• Result of hypertension

AV Block

• Delay in the AV node

• Caused by many things but could be decreased levels of Oxygen in the blood

Ventricular Fibrilation

• The ventricles are not contracting as a unit

• There is no clear cardiac output

• Commonly known as a Heart Attack

Flatline:

• Asystole: no cardiac electrical activity (no contractions or blood flow) – cannot be treated with defibrillation