Cardiovascular System: Heart Anatomy, Physiology, and Disorders

A&P II - Chapter 3 FULL

What is the approximate size of the heart?

About the size of a fist.

Where is the heart located?

In the mediastinum between the second rib and the fifth intercostal space, two-thirds to the left of the midsternal line.

What is the apex of the heart?

The bottom part of the heart that points to the left hip.

What is the pericardium?

A double-walled sac enclosing the heart, covered by an epithelial membrane called serosa.

What are the two layers of the pericardium?

Visceral and parietal layers.

What is the function of the pericardial cavity?

Filled with fluid for lubrication to reduce friction.

What are the three layers of the heart?

Epicardium, myocardium, and endocardium.

What is the epicardium?

The outer layer of the heart, also known as the visceral layer of the serous pericardium.

What is the myocardium?

The middle layer of the heart, containing spiral bundles of cardiac muscle and a fibrous skeleton.

What is the function of the fibrous skeleton of the heart?

Anchors muscle fibers, supports vessels and valves, and limits the spread of action potentials.

What is the endocardium?

The inner layer of the heart that covers the inside of the heart walls and is continuous with the endothelial lining of blood vessels.

What are the two types of chambers in the heart?

Atria (receiving chambers) and ventricles (pumping/discharging chambers).

What structures are included in the right atrium?

Superior vena cava, inferior vena cava, and coronary sinus.

What structures are included in the left atrium?

Pulmonary veins.

What are the semilunar valves?

Aortic and pulmonic valves that prevent backflow into the ventricles when they relax.

What are the atrioventricular valves?

Tricuspid and bicuspid valves that prevent backflow of blood into the atria from the ventricles.

What are chordae tendineae?

Structures that ensure blood moves unidirectionally and prevent backflow in the heart valves.

What are the four chambers of the heart?

Two atria and two ventricles.

What is the coronary circulation?

A smaller system that supplies blood to the heart itself.

What are the major arteries of coronary circulation?

Coronary (right and left), marginal, circumflex, and interventricular arteries.

What is a functional syncytium in cardiac muscle?

A condition where all muscle fibers work as one big cell due to gap junctions allowing action potentials to conduct between fibers.

What are the unique characteristics of cardiac muscle?

Cardiac muscle is branched, forms a 3D network, and has intercalated discs that prevent separation during contraction.

How does cardiac muscle differ from skeletal muscle in terms of mitochondria?

Cardiac muscle has many more mitochondria than skeletal muscle.

What are the three ion channels involved in cardiac muscle physiology?

Calcium (Ca++), Sodium (Na+), and Potassium (K+).

What initiates the depolarization of the sarcolemma in cardiac muscle?

The opening of sodium (Na+) channels.

What is the membrane potential during the peak of depolarization in cardiac muscle?

+20 mV.

What causes the prolonged depolarization in cardiac muscle action potential?

Calcium (Ca++) enters from the sarcoplasmic reticulum.

What is the role of troponin in cardiac muscle contraction?

Calcium binds to troponin, which opens the myosin binding site.

What is the intrinsic conduction system of the heart?

It consists of autorhythmic cells that generate spontaneous action potentials.

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

It acts as the pacemaker, creating a sinus rhythm of 90-95 action potentials per minute.

What happens at the atrioventricular (AV) node?

It slows down transmissions by 0.1 seconds and generates 40-60 action potentials per minute.

What is the cardiac cycle?

All events associated with blood flow through the heart during one complete heartbeat.

What occurs during ventricular filling in the cardiac cycle?

AV valves are open, allowing 80% passive filling and 20% from atrial contraction.

What is isovolumetric contraction?

It occurs after AV valves close and before semilunar valves open, with no blood flow.

What is the ejection phase in the cardiac cycle?

Pressure in the ventricles exceeds that in the aorta and pulmonary artery, causing semilunar valves to open.

What are heart sounds associated with?

Turbulent flow after valves close, with 'LUB' after AV valves close and 'DUB' after semilunar valves close.

What is cardiac output?

The volume of blood pumped by each ventricle in one minute, calculated as CO = HR x SV.

What factors affect stroke volume?

Preload, contractility, and afterload.

What is preload in cardiac physiology?

The degree of stretch of cardiac muscle cells before they contract, following the Frank-Starling law.

What are positive inotropic agents?

Factors that increase contractility, such as increased calcium influx and hormones like epinephrine.

What is afterload?

The pressure that must be overcome for the ventricles to eject blood.

What are positive chronotropic factors?

Factors that increase heart rate, such as dopamine and epinephrine.

What is the role of the parasympathetic nervous system in heart rate regulation?

It opposes sympathetic effects and decreases heart rate by hyperpolarizing pacemaker cells.

What is angina pectoris?

Severe chest pain that can spread to the shoulders, arms, and neck, often an early sign of a heart attack.

What is a common cause of heart disease?

Arteriosclerosis, which leads to the hardening and narrowing of arteries.

What is an atrial septal defect?

A hole in the interatrial septum of the heart.

What is tachycardia?

A heart rate of more than 100 beats per minute.

What is congestive heart failure?

A condition where the heart cannot pump blood fast enough, leading to pulmonary or leg edema.