Heart

What is the size and shape of the heart in the thorax?

The heart is roughly the size of a fist, cone-shaped, located in the thoracic cavity between the lungs in the mediastinum, and it is oriented with the apex pointing to the left side.

What are the functions of the heart and blood vessels?

The heart pumps blood; arteries carry blood away from the heart; arterioles regulate blood flow; capillary beds facilitate exchange; venules return blood to the heart; veins carry blood back to the heart.

What are the pericardial layers?

The pericardial layers include the fibrous pericardium and the serous pericardium, which is divided into the parietal layer and the visceral layer.

What are the three layers of the heart wall and their functions?

1. Epicardium: protective outer layer; 2. Myocardium: muscular middle layer responsible for contraction; 3. Endocardium: inner lining of the heart chambers.

Name the four heart chambers and their great vessels.

1. Right Atrium - receives deoxygenated blood from the body via the Superior/Inferior Vena Cava; 2. Right Ventricle - pumps blood to the lungs via the Pulmonary Arteries; 3. Left Atrium - receives oxygenated blood from the lungs via the Pulmonary Veins; 4. Left Ventricle - pumps oxygenated blood to the body via the Aorta.

Describe pulmonary and systemic circulation. Why do humans have two separate circulations?

Pulmonary circulation moves blood between the heart and lungs for oxygenation, while systemic circulation moves blood between the heart and the rest of the body. Two circulations are necessary to efficiently separate oxygenated and deoxygenated blood.

What are the heart valves and their functions?

The heart valves include the Tricuspid Valve (between Right Atrium and Right Ventricle), Pulmonary Valve (out of Right Ventricle), Mitral Valve (between Left Atrium and Left Ventricle), and Aortic Valve (out of Left Ventricle). They ensure unidirectional blood flow and are called 'passive flap valves' because they open/close based on pressure changes.

What is the role of coronary arteries?

Coronary arteries supply blood to the heart muscle itself, providing necessary oxygen and nutrients for cardiac function.

How do skeletal muscle and cardiac muscle compare?

Skeletal muscle is striated, voluntary, and multinucleated, whereas cardiac muscle is striated, involuntary, branched, and has intercalated discs.

What are the components of the electrical conduction system of the heart?

The system includes the Sinoatrial (SA) Node, Atrioventricular (AV) Node, Atrioventricular Bundle (Bundle of His), and Purkinje Fibers.

What does an ECG show?

An ECG (electrocardiogram) shows the electrical activity of the heart with waves representing depolarization and repolarization of the heart chambers.

What is heart block?

Heart block is a condition where the electrical impulses are partially or completely blocked as they move through the heart, affecting its rhythm.

What causes the heart sounds?

Heart sounds are caused by the closure of heart valves during the cardiac cycle: the 'lub' sound is from the closing of AV valves, and the 'dub' sound is from the closing of semilunar valves.

What is systole and diastole?

Systole is the phase of contraction of the heart muscles, while diastole is the phase of relaxation between contractions.

What is cardiac output?

Cardiac output is the volume of blood the heart pumps per minute; it is calculated as Heart Rate (HR) times Stroke Volume (SV).

How do changes in heart rate affect cardiac output?

Increasing heart rate generally increases cardiac output; however, an excessive heart rate may decrease stroke volume and thus cardiac output.

Trace the pathway of blood starting from the left ventricle.

Blood flows from the Left Ventricle -> Aorta -> Arteries -> Arterioles -> Capillaries (exchange) -> Venules -> Veins -> Superior/Inferior Vena Cava -> Right Atrium.

What is an action potential in cardiomyocytes?

An action potential in cardiomyocytes is a rapid change in membrane potential that leads to contraction; it differs from a neuron's action potential by having a longer plateau phase.

What are the phases of the cardiac cycle?

atrial systole, ventricular systole, atrial diastole, and ventricular diastole

What is the cardiac output equation?

Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV). Each part indicates the rate of beats per minute and the volume of blood per beat, respectively.