Cardiovascular System: Cardiac Function, Anatomy, and Electrical Activity

What are the major components of the cardiovascular system?

The heart, blood vessels, and blood.

What is the primary function of the cardiovascular system?

To transport substances, including oxygen, nutrients, wastes, hormones, immune cells, and clotting proteins.

Where is the heart located and what is its approximate size?

The heart is located in the thoracic cavity, about the size of a fist, weighing between 250 and 350 grams.

What are the four chambers of the heart?

The right atrium, left atrium, right ventricle, and left ventricle.

What are the three layers of the heart wall?

Epicardium (outer layer), myocardium (middle layer), and endothelium (inner layer).

What is the function of heart valves?

To prevent the backward flow of blood and ensure unidirectional flow.

What are the atrioventricular (AV) valves of the heart?

The right AV valve is the tricuspid valve, and

the left AV valve is the bicuspid or mitral valve.

What are the semilunar (SL) valves of the heart?

The pulmonary valve (between the right ventricle and pulmonary trunk) and

The aortic valve (between the left ventricle and aorta).

Describe the path of blood flow through the vasculature.

Heart → arteries → arterioles → capillaries → venules → veins.

What is the pulmonary circuit?

It carries blood from the heart through the lungs and back to the heart.

What is the systemic circuit?

It carries blood from the heart through systemic tissues and back to the heart, including coronary circulation.

What is the role of capillaries in the circulatory system?

Capillaries are the site of exchange for oxygen, nutrients, and wastes between blood and tissues.

What is autorhythmicity in the heart?

The ability of the heart to generate its own rhythm using specialized autorhythmic cells.

What is the function of the sinoatrial (SA) node?

It acts as the pacemaker of the heart, generating a firing rate of 70-80 action potentials per minute at rest.

What is the role of the atrioventricular (AV) node?

It coordinates the electrical signal and has a firing rate of 40-60 action potentials per minute at rest.

What are Purkinje fibers and their function?

They conduct action potentials to contractile cells in the ventricles, causing contraction from the apex upward.

What is the significance of the AV nodal delay?

It ensures that the atria contract before the ventricles, allowing for efficient blood flow.

What is myocardial ischemia?

A condition caused by reduced blood flow to the heart muscle, often leading to chest pain.

What is myocardial infarction?

Commonly known as a heart attack, it occurs when blood flow to a part of the heart is blocked.

What is portal circulation?

A system that features two capillary beds, such as those between the intestines and liver.

What are Autorhythmic Cells responsible for?

They are responsible for the spontaneous depolarization in the heart, driven by Funny channels and T-type Ca2+ channels.

What characterizes the Action Potential in Contractile Cells?

It has a long duration of 250-300 msec and includes distinct phases of depolarization, plateau, and repolarization.

What occurs during Phase 0 of the Action Potential?

Increased permeability to Na+ as voltage-gated Na+ channels open.

What happens during Phase 2 (Plateau) of the Action Potential?

Increased permeability to Ca2+ through L-type Ca2+ channels and decreased permeability to K+.

What is the role of gap junctions in Excitation-Contraction Coupling?

They allow depolarization to spread between cardiac cells.

What is Ca2+-induced Ca2+ release?

It is the process where calcium is released from the sarcoplasmic reticulum after calcium channels in the plasma membrane open.

What is the function of troponin in muscle contraction?

Ca2+ binds to troponin, causing tropomyosin to shift and expose myosin binding sites on actin.

What does an Electrocardiogram (ECG) record?

It records the synchronized electrical activity of the heart from electrodes on the skin.

What does the P wave in an ECG represent?

Atrial depolarization.

What does the QRS complex in an ECG indicate?

Ventricular depolarization and atrial repolarization.

What is Tachycardia?

A fast heart rhythm, defined as a heart rate greater than 100 beats per minute.

What is Bradycardia?

A slow heart rhythm, defined as a heart rate less than 50 beats per minute.

What is a First-degree Heart Block?

It is characterized by slowed conduction through the AV node, resulting in an increased P-Q interval duration.

What occurs during Isovolumetric Contraction?

Ventricles begin contracting, causing ventricular pressure to rise rapidly while all valves remain closed.

What is End-Diastolic Volume (EDV)?

The volume of blood in the ventricle at the end of diastole, typically around 130 mL.

How is Stroke Volume (SV) calculated?

SV is calculated as EDV minus End-Systolic Volume (ESV).

What does the Ejection Fraction (EF) represent?

The fraction of EDV that is ejected during each heartbeat, calculated as SV/EDV.

What happens during the Ventricular Filling phase of the cardiac cycle?

Blood enters the ventricles, and atrial contraction occurs at the end, with AV valves open.

What is the significance of the Dicrotic notch in aortic pressure?

It indicates backflow of blood during isovolumetric relaxation when the aortic valve closes.

What is the role of the aorta during the cardiac cycle?

The aorta acts as a pressure reservoir, expanding during systole and recoiling during diastole to maintain continuous blood flow.

Diastolic Pressure (DP)

the lowest pressure in the arteries, occuring during phases when the SL valve is closed. (RELAXATION)

Systolic pressure (SP)

the highest pressure, occurring during ventricular ejection (CONTRACTION)

sinus rhythm

the normal rhythm generated by the SA node

Relaxation Mechanism

Calcium is actively transported back into the SR and out of the cell, allowing muscle relaxation.

Crossbridge Cycling

myosin heads attach to actin, pulling the filaments together, leading to a muscle contraction.

What happens during Phase 3 (repolarization) of the Action Potential?

K+ channels open, allowing K+ to exit the cell, while Ca2+ channels close, leading to a return to resting membrane potential.

Arteries

Large, branching vessels that carry oxygenated blood away from the heart (except pulmonary arteries).

Arterioles

Smaller vessels with high resistance, regulating blood flow to capillaries

Capillaries

The site of nutrient and gas exchange between blood and tissues.

Veins

Larger vessels that return deoxygenated blood to the heart (except pulmonary veins).