The Heart

This set of 100 flashcards covers the anatomy and physiology of the heart, including blood flow circuits, chamber anatomy, heart wall layers, coronary circulation, the conducting system, ECG components, the cardiac cycle, heart sounds, and factors affecting cardiac output.

Approximately how many times each day does the heart beat?

Approximately $100,000$ times

About how many liters of blood does the heart pump per day?

About $8000$ liters

Which circuit carries blood to and from the gas exchange surfaces of the lungs?

Pulmonary circuit

Where does the pulmonary circuit begin and end?

Begins at the Right Ventricle and ends at the Left Atrium

Which circuit carries blood to and from the rest of the body?

Systemic circuit

Where does the systemic circuit begin and end?

Begins at the Left Ventricle and ends at the Right Atrium

What are the four chambers of the heart?

Right atrium, Right ventricle, Left atrium, and Left ventricle

Which chamber receives blood from the systemic circuit?

Right atrium

Which chamber pumps blood into the pulmonary circuit?

Right ventricle

Which chamber receives blood from the pulmonary circuit?

Left atrium

Which chamber pumps blood into the systemic circuit?

Left ventricle

What is the superior portion of the heart where the great vessels connect?

Base

What is the pointed inferior tip of the heart?

Apex

Where is the heart located in relation to the pleural cavities?

In the mediastinum

What membrane surrounds the heart?

Pericardium

What are the two layers of the serous pericardium?

Outer parietal layer and inner visceral layer (epicardium)

Where is the pericardial cavity located and what does it contain?

Between the parietal and visceral layers; it contains pericardial fluid

What is pericarditis?

Inflammation of the pericardium caused by pathogens, often producing a scratching sound

What is cardiac tamponade?

Restricted movement of the heart due to excess fluid in the pericardial cavity

Which layer of the heart wall consists of cardiac muscle cells?

Myocardium

What is the endocardium?

The innermost layer of the heart wall consisting of endothelium and areolar tissue

What muscular partition separates the atria?

Interatrial septum

What muscular partition separates the ventricles?

Interventricular septum

What is the general function of atrioventricular (AV) valves?

To permit blood flow in one direction and prevent backflow into the atria

What structures tense the chordae tendineae during ventricular contraction?

Papillary muscles

What occurs during Mitral Valve Prolapse (MVP)?

Valve leaflets bulge backward into the left atrium during contraction

Name the two semilunar valves.

Pulmonary and aortic valves

What is Valvular heart disease (VHD)?

A deterioration of valve function often resulting from carditis or rheumatic fever

What are the three main sources of blood for the right atrium?

Superior vena cava, inferior vena cava, and coronary sinus

What is the foramen ovale?

An opening through the interatrial septum in the fetal heart that connects the two atria

What structure does the foramen ovale become after birth?

Fossa ovalis

What are pectinate muscles?

Prominent muscular ridges on the anterior atrial wall and inner surface of the auricle

What is the common name for the right atrioventricular valve?

Tricuspid valve

What is the conus arteriosus?

The pouch-like superior end of the right ventricle leading to the pulmonary valve

Which heart chamber receives blood from the pulmonary veins?

Left atrium

What valve sits between the left atrium and left ventricle?

Mitral valve (also known as the bicuspid or left AV valve)

Which vessel does blood enter after leaving the left ventricle through the aortic valve?

Ascending aorta

What are aortic sinuses?

Saclike expansions at the base of the ascending aorta

How does the wall thickness of the right ventricle compare to the left?

The right ventricle has much thinner walls than the left ventricle

What is the shape of the right ventricle compared to the left?

The right ventricle is pouch-shaped, while the left ventricle is round

What provides the blood supply to the muscle tissue of the heart?

Coronary circulation

Where do the coronary arteries originate?

At the aortic sinuses

What is coronary artery disease (CAD)?

Partial or complete blockage of coronary circulation

What is coronary ischemia?

Reduced circulatory supply resulting from coronary artery blockage

What is angina pectoris?

A temporary ischemia causing chest pressure and pain during exertion or stress

What is a myocardial infarction (MI)?

A heart attack where cardiac muscle cells die from lack of oxygen due to a blockage

What is an infarct?

A nonfunctional area of dead tissue following a myocardial infarction

What is coronary thrombosis?

Thrombus formation at a plaque, the most common cause of an MI

What defines a single heartbeat?

A single cardiac contraction

What are the two types of cardiac muscle cells?

Autorhythmic cells and contractile cells

What is the function of the conducting system?

To initiate and distribute electrical impulses that stimulate heart contraction

Where is the sinoatrial (SA) node located?

In the wall of the right atrium

Where is the atrioventricular (AV) node located?

At the junction between the atria and ventricles

List the sequence of conducting cells through the ventricles.

AV bundle, bundle branches, and Purkinje fibers

What is a pacemaker potential?

A gradual spontaneous depolarization of pacemaker cells

What is the spontaneous depolarization rate of the SA node?

$60\text{--}100$ action potentials per minute

What is the spontaneous depolarization rate of the AV node?

$40\text{--}60$ action potentials per minute

What is the sinus rhythm?

The normal electrical activity of the heart established by the SA node

What does a P wave represent on an ECG?

Atrial depolarization

What does the P-R interval represent on an ECG?

Conduction through the AV node and AV bundle

What electrical event is shown by the QRS complex?

Completion of ventricular depolarization

How long is the impulse delay at the AV node?

$$100\,msec$$

What is bradycardia?

An abnormally slow heart rate

What is tachycardia?

An abnormally fast heart rate

What is an ectopic pacemaker?

Abnormal cells generating high rates of action potentials that bypass the conducting system

What is the resting membrane potential of a ventricular contractile cell?

$$-90\,mV$$

What is the resting membrane potential of an atrial contractile cell?

$$-80\,mV$$

What structures interconnect cardiac contractile cells and transfer contraction force?

Intercalated discs

What two features are found within intercalated discs?

Desmosomes and gap junctions

What ion entry causes rapid depolarization in a cardiac contractile cell?

$Na^+$ (Sodium)

What causes the plateau phase in the action potential of a contractile cell?

$Ca^{2+}$ (Calcium) entry through slow channels

What ion loss causes repolarization in a cardiac contractile cell?

$K^+$ (Potassium) loss through slow channels

How long is the absolute refractory period in a cardiac contractile cell?

$$200\,msec$$

Why is the long action potential duration important in cardiac muscle?

It prevents summation and tetany

What are the two alternating periods of the cardiac cycle?

Systole (contraction) and diastole (relaxation)

At $75\,bpm$, how long does one cardiac cycle last?

$$800\,msec$$

What happens to the cardiac cycle phases when heart rate increases?

All phases shorten, particularly diastole

What is end-diastolic volume (EDV)?

The maximum volume of blood in the ventricles at the end of atrial systole

What is isovolumetric contraction?

The phase of ventricular systole where AV valves close but pressure is insufficient to open semilunar valves

What is stroke volume (SV)?

The amount of blood ejected from the ventricle during systole

What is end-systolic volume (ESV)?

The amount of blood remaining in the ventricle after contraction

What percentage of EDV is typically remaining as ESV?

About $40\%$

What is isovolumetric relaxation?

The period where all heart valves are closed and ventricular pressure drops as the ventricles relax

Which event produces the S1 heart sound?

Closure of the AV valves (the "Lubb" sound)

Which event produces the S2 heart sound?

Closure of the semilunar valves (the "Dupp" sound)

What produces heart murmurs?

Regurgitation of blood through the valves

What is the formula for cardiac output (CO)?

$$CO = HR \times SV$$

What is the formula for calculated stroke volume (SV)?

$$SV = EDV - ESV$$

What is the ejection fraction?

The percentage of EDV ejected during a single contraction

Which brain region contains the cardiac centers for autonomic control?

Medulla oblongata

What is the function of the cardioacceleratory center?

To control sympathetic neurons that increase heart rate

What is the function of the cardioinhibitory center?

To control parasympathetic neurons that slow heart rate

What determines heart rate at the cellular level in pacemaker cells?

The membrane potential and the rate of spontaneous depolarization

What neurotransmitter is released during parasympathetic stimulation to slow the heart rate?

Acetylcholine (ACh)

What neurotransmitter is released during sympathetic stimulation to increase the heart rate?

Norepinephrine (NE)

What is the Bainbridge reflex (atrial reflex)?

The adjustment in heart rate due to an increase in venous return detected by stretch receptors in the right atrium

Define Preload.

The degree of ventricular stretching during ventricular diastole

What is the Frank-Starling Principle?

The principle that as EDV increases, stroke volume also increases

Define Contractility.

The force produced during contraction at a given preload

Define Afterload.

The tension that must be produced by the ventricle to open the semilunar valve and eject blood