Cardiovascular System Overview

The rapid electrical depolarization and repolarization of heart muscle cells that enables coordinated contraction and relaxation during the cardiac cycle.

A graphical representation of the heart's electrical activity as it travels through the conduction system.

The normal rhythm of the heart, initiated by the SA node. Characterized by P waves, QRS complexes, and T waves on an ECG.

Represents atrial depolarization, leading to atrial contraction. This phase moves blood from the atria into the ventricles.

Reflects ventricular depolarization and the initiation of ventricular contraction. Consists of three waves: Q wave (septal depolarization), R wave (depolarization of the main ventricular walls), and S wave (depolarization of the Purkinje fibers).

Represents ventricular repolarization, preparing the ventricles for the next cycle of contraction.

The flat section between the end of the QRS complex and the beginning of the T wave. Changes in the ST segment can indicate myocardial ischaemia or necrosis.

The systemic distribution of blood through arteries, veins, and capillaries.

The heart's central organ, responsible for pumping blood throughout the body. It's located in the mediastinum, a central compartment in the thoracic cavity, flanked by the lungs. It's roughly the size of a clenched fist and weighs about 350 grams.

The specialized muscle tissue that makes up the heart, responsible for its contractions.

A double-layered sac that encloses the heart, composed of a fibrous outer layer and a serous inner layer. The serous pericardium further divides into the visceral layer (epicardium) that covers the heart and the parietal layer that lines the fibrous sac.

The heart's electrical control system, responsible for generating and propagating impulses that regulate its rhythmic contractions.

The natural pacemaker of the heart, located in the right atrium. It sets the heart rate at approximately 100 beats per minute in the absence of neural regulation.

Located at the junction of the atria and ventricles, the AV node delays the electrical impulse to allow the atria to finish contracting and fill the ventricles with blood before the ventricles contract. This delay slows the heart rate to about 60 bpm.

A pathway that transmits the electrical impulse from the AV node to the bundle branches in the ventricles, which then carry the impulse through the Purkinje fibers, triggering ventricular contraction.

The process by which the heart's electrical impulses are generated and propagated, leading to rhythmic contractions.

The total resistance to blood flow in the systemic circulation, influenced by blood volume, vessel diameter, and blood viscosity.

Specialized sensory receptors located in the carotid arteries, aortic arch, and right atrium that detect changes in blood pressure, sending signals to the cardiovascular center.

Specialized sensory receptors in the carotid and aortic bodies that respond to changes in blood pH, CO2, and oxygen levels. They contribute to blood pressure regulation by adjusting heart rate and vessel tone.

Sensory receptors in muscles and joints that provide feedback about body position and movement, affecting cardiovascular responses during physical activity.

Heart sounds produced by the closing of heart valves. S1 corresponds to the closure of the atrioventricular valves (mitral and tricuspid), while S2 corresponds to the closure of the semilunar valves (aortic and pulmonary).

Abnormal heart sounds indicating turbulent blood flow within the heart, potentially caused by a stenotic or regurgitant valve.

Sounds heard during blood pressure measurement using a sphygmomanometer, reflecting the resumption of blood flow as cuff pressure is gradually released.

The primary pacemaker of the heart, located in the upper right atrium. It generates electrical impulses that initiate the heartbeat.

Blood viscosity, vessel diameter, and vessel length all directly influence systemic vascular resistance (SVR). Heart rate, however, is not a direct factor in SVR. SVR refers to the resistance to blood flow in the systemic circulation.

The first heart sound (S1) is caused by the closure of the atrioventricular valves (mitral and tricuspid valves). This occurs at the start of ventricular systole, when the ventricles contract and pressure rises, forcing blood against the closed valves.

The baroreceptor reflex is a crucial mechanism for regulating blood pressure. Baroreceptors are specialized sensory cells located in the aorta and carotid arteries. They detect changes in blood pressure and send signals to the brain, which then adjusts heart rate and blood vessel diameter to maintain blood pressure within a normal range.

A myocardial infarction, commonly known as a heart attack, happens when a coronary artery is blocked, preventing blood and oxygen from reaching a part of the heart muscle. This deprivation leads to damage and cell death (necrosis) in the affected area. ST-segment elevation on an electrocardiogram (ECG) is a specific sign that indicates ongoing damage to the heart muscle and is a critical indicator of a heart attack.

Congestive heart failure (CHF) occurs when the heart is unable to pump blood effectively, leading to a buildup of pressure in the circulatory system. This can cause fluid to back up into the lungs, leading to shortness of breath and fatigue. The fluid buildup can also affect the legs and feet, causing swelling. Distended neck veins indicate increased pressure in the right atrium and are another sign of CHF.