Human Heart Anatomy and Function

Heart Anatomy and Function

• The ventricles are the chambers that expel blood from the heart.
• The heart is located in the thoracic cavity, between the lungs.

Pericardium Function

• The pericardium is a sac that surrounds and protects the heart, reducing friction between the heart and surrounding structures.

Blood Vessels

• Veins are the blood vessels that always carry blood back to the heart.

Heart Layers

• Fluid is found between the visceral pericardium and the epicardium, the innermost and outermost layers of the heart.

Septa Function

• The septa are partitions that separate the heart into left and right sides, ensuring that oxygenated and deoxygenated blood do not mix.

Cardiac Output

• The formula for calculating cardiac output is heart rate (HR) x stroke volume (SV).
• For a 150 lbs. individual, the normal stroke volume is approximately 70 mL.

Heart Rate Regulation

• The vagus nerve is responsible for decreasing heart rate.
• The ejection fraction represents the proportion of blood pumped out of the ventricles with each heartbeat.

Substances Affecting Heart Rate

• Caffeine and nicotine increase heart rate.

Emotional Influence on Heart Rate

• The adrenal gland, which releases cortisol, influences heart rate based on emotions.

Valves

• The semilunar valves prevent backflow from arteries back into ventricles.

Papillary Muscles

• Papillary muscles, located in the ventricles, contract to tighten the chordae tendineae and prevent the cusps of the atrioventricular valves from prolapsing.

SA Node

• The sinoatrial (SA) node, located in the right atrium, is the natural pacemaker of the heart.

EKG Reading

• The QRS complex on an electrocardiogram (EKG) reading represents ventricular contraction.

Action Potential

• The action potential (electrical current) in cardiac muscle cells is caused by the movement of ions across the cell membrane.

Cardiac Muscle Structure

• The intercalated discs are structures that hold cardiac muscle cells together.

Conducting Cells

• Conducting cells in the heart, such as the AV node and bundle of His, transmit electrical signals to coordinate heartbeats.