Heart

The four chambers are the left atrium, right atrium, left ventricle, and right ventricle. The atria receive blood, while the ventricles pump blood out of the heart to other parts of the body such as the lungs.

Coronary arteries supply the heart muscle itself with oxygenated blood. Blockage of these arteries can lead to coronary heart disease.

Heart activity can be monitored by using an electrocardiogram (ECG) to measure electrical activity, checking pulse rate to measure heart beats per minute, and listening for the sounds of valves closing with a stethoscope.

Physical activity increases heart rate. This is because muscles need more oxygen and glucose, so the heart pumps more blood to deliver these substances more quickly, ensuring cells like those in the quadriceps get enough nutrients.

A balanced diet, low in saturated fats and cholesterol, helps prevent plaque build-up in arteries. Regular exercise strengthens the heart muscle, improves blood flow, and helps maintain a healthy weight, reducing strain on the heart.

Atrioventricular valves (tricuspid and mitral) are located between the atria and ventricles, preventing backflow into the atria when ventricles contract. Semilunar valves (pulmonary and aortic) are located at the exit of the ventricles, preventing backflow into the ventricles when they relax.

The left ventricle pumps blood to the entire body, requiring more force to overcome the higher resistance in the systemic circulation. The right ventricle only pumps blood to the lungs, a shorter distance with lower resistance. Therefore the left ventricle has a thicker and stronger muscle.

The atria only need to pump blood a short distance into the ventricles. Ventricles need to pump blood further, either to the lungs (right ventricle) or the whole body (left ventricle), which requires stronger contractions and thus thicker walls.

The septum is a muscular wall that separates the left and right sides of the heart. This separation prevents the mixing of oxygenated and deoxygenated blood, ensuring that oxygen-rich blood is delivered efficiently to the body.

First, the atria contract, pushing blood into the ventricles. Then, the ventricles contract, pumping blood out to the lungs (right ventricle) and the rest of the body (left ventricle). Valves ensure blood flows in one direction, preventing backflow.

During physical activity, the body needs more oxygen and glucose for respiration in muscle cells. Chemoreceptors detect changes in blood pH, signaling the brain to increase heart rate. This delivers more oxygenated blood to active muscles like the biceps, supporting increased energy production.