Cardiology: The Cardiovascular System

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.

The heart muscle, making up 99% of the heart's tissue. Responsible for the heart's contractions.

A double-layered sac that encloses the heart. Consists of a fibrous outer layer and a serous inner layer.

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

Located at the junction between the atria and ventricles. Delays the electrical impulse to allow the atria to complete their contraction and fill the ventricles with blood before the ventricles contract.

Transmits the electrical impulse from the AV node to the bundle branches in the ventricles, which then carry the impulse through the Purkinje fibres to the ventricular myocardium, triggering ventricular contraction.

The system that generates and propagates electrical impulses to control the heart's rhythmic contractions.

The heart's ability to pump blood throughout the body, providing tissues with nutrients and oxygen while removing waste products.

The electrical activity of the heart muscle, allowing coordinated contraction and relaxation.

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

The normal rhythm of the heart, initiated by the SA node.

Represents atrial depolarisation, leading to contraction and moving blood from the atria to the ventricles.

Represents ventricular depolarisation, initiating ventricular contraction. Consists of three waves: Q (septal depolarization), R (main ventricle walls), and S (Purkinje fibres).

Represents ventricular repolarisation, preparing the ventricles for the next contraction.

The flat section between QRS complex and T wave, indicating potential heart issues.

The process of blood being distributed throughout the body, carried through arteries, veins, and capillaries.

SVR, or total peripheral resistance (TPR), is the overall resistance to blood flow in the systemic circulation. It's affected by several factors: blood volume, vessel diameter, and blood viscosity.

Baroreceptors are stretch-sensitive receptors located in the carotid arteries, aortic arch, and right atrium. They sense blood pressure changes and send signals to the cardiovascular center in the brain to adjust heart rate and blood vessel diameter accordingly.

Chemoreceptors are found in the carotid and aortic bodies. They are sensitive to changes in blood pH, CO2 levels, and oxygen levels. When these levels change, they send signals to the cardiovascular center to regulate heart rate and blood vessel tone.

Proprioceptors are found in muscles and joints. They provide information about body position and movement, which helps regulate cardiovascular responses during physical activity. For example, they signal the heart to pump faster during exercise.

Heart sounds, like S1 and S2, are produced by the closing of heart valves. S1 occurs when the AV valves (mitral and tricuspid) close, and S2 occurs when the semilunar valves (aortic and pulmonary) close.

Murmurs are abnormal heart sounds that can indicate turbulent blood flow through a heart valve. They can be either systolic (during ventricular contraction) or diastolic (during ventricular relaxation) and classified based on their intensity.

Korotkoff sounds are the sounds heard during blood pressure measurement using a sphygmomanometer. They're caused by the resumption of blood flow as the cuff pressure is gradually released. They help determine the systolic and diastolic blood pressures.

Systemic vascular resistance (SVR) is the resistance that the heart must overcome to pump blood throughout the body. It is influenced by factors such as blood viscosity, vessel diameter, and vessel length. However, heart rate does not directly influence SVR.

The first heart sound (S1) is produced by the closure of the atrioventricular valves (mitral and tricuspid valves). This happens when the ventricles contract, forcing blood out of the heart and closing the valves.

The baroreceptor reflex is a negative feedback mechanism that regulates heart rate in response to changes in blood pressure. Baroreceptors, located in the carotid arteries and aortic arch, detect changes in blood pressure and send signals to the brainstem, which adjusts heart rate via the autonomic nervous system.

A myocardial infarction (MI), or heart attack, occurs when the blood supply to a part of the heart is blocked by a blood clot. This blockage causes heart muscle tissue to die due to lack of oxygen. ST-segment elevation on an ECG indicates ongoing myocardial injury, which can lead to permanent heart damage.

Congestive heart failure (CHF) is a condition where the heart cannot pump blood effectively, leading to an accumulation of fluid in the lungs and peripheral tissues. Causes include myocardial damage (like from a heart attack), high blood pressure, or valve dysfunction. The symptoms of shortness of breath and leg swelling are due to fluid accumulation, while distended neck veins indicate increased central venous pressure.

Blood viscosity refers to the thickness of blood. Higher viscosity means it is harder for the heart to pump blood, increasing resistance (SVR).

The diameter of blood vessels significantly influences SVR. Smaller vessels create more resistance to blood flow, raising SVR.

Longer blood vessels increase SVR. The farther the blood has to travel, the more resistance it encounters.