Circulatory System: Heart Flashcards

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Questions and Answers

Describe the location and position of the heart.

The heart is in the thoracic cavity in the mediastinum between ribs 2-5, about 2/3 on the left side of the body. It is about the size of a fist and weighs 10 ounces.

Describe the internal and external anatomy of the heart.

External includes great vessels, vena cava, pulmonary trunk, aorta, pulmonary veins, coronary vessels, and fat. Internal includes atrium, 4 chambers, 4 valves, left ventricle, chordae tendineae, and papillary muscles.

Describe the structure of the pericardium and heart wall.

The pericardium has a fibrous layer made of dense connective tissue that anchors the heart and a serous layer that provides lubrication. The heart wall consists of the endocardium, myocardium, and epicardium.

Describe the heart valves.

There are 2 AV valves that separate the atria from the ventricles. The fibrous skeleton provides support and insulation, and the semilunar valves do not have tendinous chords. Signup and view all the answers

What is the difference between pulmonary and systemic circulation?

Pulmonary circulation involves the right heart pumping blood to the lungs, whereas systemic circulation involves the left heart pumping blood to the body. Signup and view all the answers

What is the flow of blood in the heart?

The flow is: 1. Superior vena cava, 2. Atrium snaps shut, 3. Out to left pulmonary arteries to the lungs, 4. Pulmonary veins, 5. Left atrium, 6. Aortic valve snaps shut, 7. Aortic valve, 8. Out aorta. Signup and view all the answers

Contrast prenatal heart structure with postnatal heart structure.

The prenatal heart has a foramen ovale (hole between right and left atria) and a ductus arteriosus (passage between pulmonary trunk and aorta). Signup and view all the answers

Name the major vessels of the coronary circulation.

Major vessels originate at the base of the aorta, travel past the superior vena cava (RCA), past the pulmonary trunk to the apex, with veins directed toward the coronary sinus and then to the atrium. Signup and view all the answers

List the special structural and functional characteristics of cardiac muscle tissues.

Cardiac muscle tissues include short branched cells, intercalated discs, many mitochondria, and they do not fatigue. Signup and view all the answers

Describe the structure and function of the electrical conduction systems of the heart.

The heart is coordinated by the SA node, which is the pacemaker. The electrical signal travels to the AV node, then to the Bundle of His, left and right branches, and then to Purkinje fibers. Signup and view all the answers

Contrast the flow of ions underlying each phase of a cardiac pacemaker and a contractile cell action potential.

In a pacemaker cell, there is rapid Na+ influx for depolarization, followed by Ca2+ influx during the plateau phase, and then K+ efflux leading to repolarization. In contractile cells, the depolarization is slower. Signup and view all the answers

Describe how each segment of an ECG corresponds to the electrical activity and contraction of the myocardium.

An ECG records all electrical activity in the heart and is used to determine heart health, regularity, size, position, and damage. Signup and view all the answers

What occurs during the ventricular filling phase?

Ventricles fill mainly passively, with atrial contraction adding about 30%. The end-diastolic volume (EDV) refers to the volume in ventricles after filling. Signup and view all the answers

What happens during isovolumetric contraction?

During this phase, tension is generated but no blood flow occurs. Pressure rises in the ventricles until the AV valves snap shut, while the volume remains constant. Signup and view all the answers

What occurs during isovolumetric relaxation?

The pressure in the part is lower than in the ventricles, causing the SL valves to close. The volume in ventricles stays the same as both sets of valves are closed. Signup and view all the answers

Discuss disorders related to the heart.

Heart disorders include sinus rhythm (normal heartbeat), ectopic focus (another site acts as pacemaker), arrhythmia (abnormal rhythm), bradycardia (slow heart rate), and fibrillation (chaotic electrical activation). Signup and view all the answers

Describe the relationship between heart rate (HR), stroke volume (SV), and cardiac output (CO).

Cardiac output (CO) = HR x SV, demonstrating a direct relationship between these variables. Signup and view all the answers

Explain the regulation of heart rate (HR), stroke volume (SV), and cardiac output (CO).

Increased venous return leads to increased end-diastolic volume (EDV), which increases tension/stretch and the force of contraction, thus increasing SV. Signup and view all the answers

Study Notes

Heart Location and Position

The heart functions as a muscular pump, beating approximately 3 billion times in an 80-year lifespan.
Located in the thoracic cavity within the mediastinum, positioned between ribs 2-5.
Occupies 2/3 of the left side of the body, comparable in size to a fist, and weighs around 10 ounces.

Internal and External Anatomy

External features include major vessels: vena cava, pulmonary trunk, aorta, and pulmonary veins, along with coronary vessels and surrounding fat.
Internally, the heart consists of 4 chambers (atria and ventricles) and 4 valves, with the left ventricle being three times thicker than the right.
Structures include chordae tendineae and papillary muscles.

Pericardium and Heart Wall Structure

The heart is encased in a fibrous layer, which is dense connective tissue providing anchorage.
The serous layer produces lubricating fluid to minimize friction.
Heart wall layers from deepest to superficial include endocardium, myocardium, and epicardium.

Heart Valves

Two atrioventricular (AV) valves separate the atria from the ventricles, supported by the fibrous skeleton to provide insulation.
Semilunar valves differ as they lack tendinous cords.

Circulation Types

Pulmonary circulation involves the right side of the heart pumping blood to the lungs for oxygenation.
Systemic circulation involves the left side pumping oxygen-rich blood to the rest of the body.

Blood Flow Through the Heart

Blood flows from the superior vena cava into the atrium, then through the pulmonary arteries to the lungs, and returns via pulmonary veins to the left atrium, eventually moving out through the aorta.

Prenatal vs. Postnatal Heart Structure

The prenatal heart features include the foramen ovale (a hole between the right and left atria) and the ductus arteriosus (a passage connecting the pulmonary trunk to the aorta).

Coronary Circulation

Major vessels of coronary circulation originate at the base of the aorta, with the right coronary artery (RCA) traveling alongside the superior vena cava and pulmonary trunk to the apex.
Venous blood returns through the coronary sinus to the right atrium.

Cardiac Muscle Tissue Characteristics

Cardiac muscle is composed of short, branched cells connected by intercalated discs, with high mitochondria content and resistance to fatigue.

Electrical Conduction System

The heart's rhythm is managed by the electrical conduction system, with the SA node acting as the pacemaker.
Signals progress from the SA node to the AV node, followed by the Bundle of His, and finally to the Purkinje fibers.

Cardiac Action Potentials

Only depolarizes when stimulated; phases include rapid sodium influx, calcium influx causing a plateau, followed by potassium efflux for repolarization.

ECG and Myocardial Activity

An electrocardiogram (ECG) monitors the heart's electrical activity, helping assess heart health, size, position, and potential damage.

Cardiac Phases: Ventricular Filling

Passive filling occurs primarily due to pressure gradients, with additional volume contributed by atrial contraction.
End diastolic volume (EDV) reflects the total volume in ventricles after filling.

Cardiac Phases: Isovolumetric Contraction

Tension builds in the ventricles with no blood flow; AV valves close producing the "lub" sound.
Blood is ejected once semilunar valves open, with a typical stroke volume of about 70 mL and end systolic volume (ESV) of around 60 mL.

Cardiac Phases: Isovolumetric Relaxation

Pressure in the ventricle drops, leading to the closure of semilunar valves, producing the "dub" sound.
Muscle relaxes with constant volume in the ventricles as all valves remain closed.

Heart Disorders

Sinus rhythm represents a normal heartbeat initiated by the SA node.
Ectopic focus occurs when a different site functions as a pacemaker, leading to arrhythmias (irregular rhythms).
Bradycardia refers to a resting heart rate below 100 bpm, while fibrillation results in chaotic electrical activation preventing effective blood pumping, which can be fatal.

Relationship Between Heart Rate, Stroke Volume, and Cardiac Output

Cardiac output (CO) is directly related to heart rate (HR) and stroke volume (SV) defined by the equation CO = HR x SV.

Regulation of HR, SV, and CO

Increased venous return contributes to greater end diastolic volume (EDV), resulting in enhanced tension/stretch and subsequently stronger contractions, effectively increasing stroke volume (SV).

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Description

Test your knowledge of the heart's location, position, and anatomy with these flashcards. Learn about the heart's role in the circulatory system and its structural features. Perfect for students of biology and health sciences.