The heart: Coronary circulation and conduction system

What is coronary circulation

The flow of blood through the coronary arteries and veins that supply and drain the heart wall

Why doesn’t the heart use blood inside its chambers

The myocardium receives it’s own oxygen and nutrients through coronary circulation

Where do the right and left coronary arteries originate

From the ascending aorta, just superior to the aortic semilunar valve

Where do the coronary arteries travel

Within the coronary sulcus

What is the function of the coronary arteries

Supply the heart wall with oxygen and nutrients

What are the two major branches of the right coronary artery

Right marginal artery and posterior interventricular artery

What does the right marginal artery supply

The right border of the heart

What does the posterior interventricular artery supply

Posterior surfaces of the left and right ventricles

What are the two major branches of the left coronary artery

Anterior interventricular artery (LAD) and circumflex artery

What does the anterior interventricular artery (LAD) supply

Anterior surfaces of the ventricles and interventricular septum

What does the circumflex artery supply

The left atrium and left ventricle

What are the three major cardiac veins

Great cardiac vein, middle cardiac vein, and small cardiac vein

Where do the major cardiac veins drain

Into the coronary sinus, which drains into the right atrium

Which vein runs alongside the anterior interventricular artery

Great cardiac vein

Which vein runs alongside the posterior interventricular artery

Middle cardiac vein

Which vein travels close to the right marginal artery

Small cardiac vein

What is atherosclerosis

Fatty plaque formation within artery walls

How does artherosclerosis affect coronary blood flow

Plaques narrow arteries, decreasing blood supply to the myocardium

What is coronary artery disease

Atherosclerosis of the coronary arteries

How can coronary artery disease affect heart function

Reduced blood supply decreases heart function and may cause angina

What is angina pectoris

Chest pain associated with reduced blood supply to the heart muscle

What are risk factors for atherosclerosis

High blood pressure, smoking, high cholesterol, diabetes, inactivity, and family history

What is myocardial infraction (MI)

Death of cardiac muscle cells, usually following coronary artery blockage

What can happen to the heart muscle after an MI

Non contracting scar tissue may farm, reducing pumping ability

What lifestyle changes reduce heart disease risk

Exercise, reduce fat and cholesterol, eat more fruits and vegetable, and don’t smoke

What treatments are used for coronary artery disease

Clot dissolving enzymes, coronary bypass surgery, angioplasty, and laser surgery

What is autorhythmicity

The heart’s ability to initiate its own heartbeat

What is the function of the cardiac conduction system

Specialized cells initiate and transmit electrical impulses to cardiac muscle cells

What is the heart’s natural placemaker

The sinoatrial (SA) node

Where does the cardiac electrical impulse begin

At the SA node in the right atrium

How often does the SA node normally initiate a heartbeat

Approximately every 0.85 seconds

What happens after the impulse leaves the SA node

It spreads through the atria to the left atrium and atrioventricular (AV) node

Where is the AV node located

On the floor of the right atrium

What is the correct order of ventricular conduction

AV bundle (bundle of His) → right and left bundle branches → purkinje fibers

Where does the AV bundle extend

Into the interventricular septum

Where do purkinje fibers begin

At the apex of the heart

How does the impulse spread through the ventricles

From the apex upward through the ventricular myocardium

What is an ECG/EKG

A graph recording the electrical activity of the cardiac conduction system

What does the P wave represent

Atrial depolarization

What does the QRS complex represent

Ventricular depolarization and atrial repolarization

What does the T wave represent

Ventricular repolarization

What is the purpose of an artificial placemaker

Provides regular electrical signals to trigger heartbeats when conduction fails

What is a cardiac cycle

The time from the beginning of one heartbeat to the beginning of the next

How long does one cardiac cycle last

Approximately 0.85 seconds

What is systole

Contraction of a heart chamber, generating pressure to move blood

What is diastole

Relaxation of a heart chamber, allowing it to fill with blood

During a atrial systole, what happens to the valves

Semilunar valves are close; cuspid valves are open

During stage 1 of the cardiac cycle, what happnes

Atria contract; ventricles relax and receive blood from the atria

How long does atrial systole last

Approximately 0.15 seconds

What happens during stage 2 of the cardiac cycle

Cuspid valves close (lub), semilunar valves open, and ventricles contract

During ventricular systole, which valves are open

Semilunar valves are open; cuspid valves are closed

How long does ventricular systole last

Approximately 0.3 seconds

What happens during stage 3 of the cardiac cycle

Semilunar valves close, cuspid valves open, and all chambers fill with blood

What sound is associated with semilunar valve closure

Dub

What sound is associated with cuspid valve closure

Lub

When the atria contact, what phase are the ventricles in

Diastole (relaxation)

When the ventricles contract, what phase are the atria in

Diastole

How long does simultaneous diastole of all four chambers last

Approximately 0.40 seconds

What is the foramen ovale

An opening between the two atria in the fetal heart

What is the function of the foramen ovale before birth

Allows some blood to bypass the lungs

What happens to the foramen ovale at birth

A flap closes the opening and grows into adjoining tissue

What is the ductus arteriosus

An artery connecting the right pulmonary artery and aortic arch

What is the function of the ductus arteriosus before birth

Allows blood to bypass the lungs and enter systemic circulation

What happens to the ductus arteriosus at brith

Its muscular layer permanently contracts, and its tissue is replaces with connective tissue