Heart

What is the general shape of the heart?

Cone-shaped/inverted pyramid; approximately the size of a closed fist.

Where is the heart located?

In the mediastinum, between the two lungs, resting on the diaphragm.

Which direction does 2/3 of the heart point?

Toward the left of the body's midline.

What is the base of the heart?

The broad posterior-superior portion, directed toward the right.

What is the apex of the heart?

The pointed anterior-inferior end, directed toward the left.

What is the pericardium?

A fibrous connective-tissue sac enclosing the heart.

What are the functions of the pericardium?

Protects the heart from trauma and infection.

What are the 2 layers of the pericardium?

Fibrous pericardium and serous pericardium.

What is the fibrous pericardium?

The outermost layer; prevents overstretching and anchors the heart in the mediastinum.

What are the layers of the serous pericardium?

Visceral and parietal serous pericardium.

What is another name for the visceral serous pericardium?

Epicardium.

Where is pericardial fluid located?

Between the visceral and parietal serous pericardium.

What is the normal amount of pericardial fluid?

About 50 mL.

What causes a pericardial friction rub?

Decreased pericardial fluid, as seen in pericarditis.

What happens in cardiac tamponade?

Increased pericardial fluid.

What is the anterior surface of the heart also called?

Sternocostal surface.

What mainly forms the anterior surface?

Right atrium and right ventricle, with the right ventricle being most anterior.

What is the posterior surface also called?

Base surface.

What forms the posterior surface?

Right and left atria.

What is the inferior surface called?

Diaphragmatic surface.

What forms the inferior surface?

Both ventricles; the left ventricle forms the apex.

What are the atria called?

Receiving chambers.

Why are the anterior walls of the atria rough?

Because of pectinate muscles.

What divides the right and left atria?

Interatrial septum.

What is the fossa ovalis?

An oval depression that is the remnant of the fetal foramen ovale.

What is the foramen ovale?

An opening in the fetal interatrial septum that normally closes after birth.

What are the ventricles called?

Pumping chambers.

What are trabeculae carneae?

Ridges of cardiac muscle fibers within the ventricles.

What are papillary muscles?

Cone-shaped structures of trabeculae carneae where chordae tendineae attach.

What divides the right and left ventricles?

Interventricular septum.

What are the atrioventricular valves?

Tricuspid and bicuspid/mitral valves.

Which AV valve is on the right?

Tricuspid valve.

Which AV valve is on the left?

Bicuspid/mitral valve.

What are the semilunar valves?

Pulmonic and aortic valves.

What are AV valves also called?

Inlet valves.

What are semilunar valves also called?

Outlet valves.

Trace blood flow through the heart.

SVC/IVC → RA → tricuspid valve → RV → pulmonary valve → pulmonary artery → lungs → pulmonary veins → LA → mitral/bicuspid valve → LV → aortic valve → aorta → systemic circulation.

Which side of the heart has higher pressure?

Left side.

Which side has lower pressure?

Right side.

What produces S1?

Closure of the AV valves.

What is S1 commonly called?

Lub.

What produces S2?

Closure of the semilunar valves.

What is S2 commonly called?

Dub.

What causes S3?

Rapid ventricular filling.

What is S3 called?

Ventricular gallop.

S3 is associated with what condition in the reviewer?

CHF.

What causes S4?

Atrial systole.

S4 is associated with what conditions?

MI and hypertension.

What are S3 and S4 detected with?

Phonocardiogram.

What does sympathetic stimulation do to cardiac contraction?

Increases contraction.

What does parasympathetic stimulation do?

Decreases contraction.

What is the SA node?

The primary pacemaker of the heart; initiates depolarization.

Where is the SA node located?

Right atrium/superior septal wall, just below and slightly lateral to the SVC opening.

What is another name for the SA node?

Sinus node.

Where is the AV node located?

Behind the tricuspid valve.

What is the most common site of heart block?

AV node.

Where is the Bundle of His located?

Interventricular septum.

Where are Purkinje fibers located?

Surrounding the two ventricles.

What is the function of the coronary arteries?

Supply blood to the heart.

What does the RCA primarily supply?

RA, most of RV, minor LV, and SA node.

What does the LCA primarily supply?

LA, most of LV, and minor RV.

What are major branches of the LCA?

LAD and circumflex artery.

What does the LAD supply?

Anterior and apical walls.

What does the circumflex artery supply?

Lateral and inferior walls of the LV.

What is MI?

Myocardial infarction/heart attack.

RCA occlusion mostly affects what?

SA node.

LCA occlusion mostly affects what?

Left ventricle.

What is the resting membrane potential?

−85 mV.

What occurs during Phase 0?

Depolarization; inward Na+ current.

What occurs during Phase 1?

Initial repolarization; decreased Na+ influx and outward K+ current.

What occurs during Phase 2?

Plateau; maintained depolarization with inward Ca+ current.

What occurs during Phase 3?

Repolarization; decreased Ca+ influx and outward K+ current.

What occurs during Phase 4?

Resting membrane potential returns to −85 mV.

Is cardiac muscle voluntary or involuntary?

Involuntary.

Why does cardiac muscle depend on extracellular Ca+?

It has relatively little Ca+ in the sarcoplasmic reticulum.

What is diastole?

Ventricular relaxation.

What is systole?

Ventricular contraction.

What happens during rapid ventricular filling?

S3 may occur; about 75% of blood enters the ventricles passively during the first third.

What happens during the middle third of diastole?

Continuous blood flow occurs.

What happens during the last third of diastole?

The atria deliver the final 25% of blood—the atrial kick.

Which valves are open during diastole?

AV valves.

Which valves are closed during diastole?

Semilunar valves.

What happens during isovolumic contraction?

Ventricular pressure rises while both AV and semilunar valves are closed.

What is afterload?

The ventricular force required to open the semilunar valves.

What happens during ventricular ejection?

Semilunar valves open and blood is ejected into the pulmonary artery and aorta.

Approximately what percentage of blood is ejected during the first third of ejection?

70%.

What happens during isovolumic relaxation?

Ventricular pressure decreases and both valve groups are closed initially.

Normal systolic BP?

120 mmHg.

Normal diastolic BP?

80 mmHg.

What is pulse pressure?

SBP − DBP.

Normal pulse pressure?

40 mmHg.

What is EDV?

Blood remaining in the ventricles after diastole; normal ≈120 mL.

What does EDV represent mechanically?

Preload/initial stretching of the heart.

What is ESV?

Blood remaining after systole; normal ≈50 mL.

Increased ESV is associated with what?

CHF.

What is stroke volume?

Blood pumped by the ventricles per contraction.

Normal stroke volume?

70 mL.

Formula for SV?

SV = EDV − ESV.

What is cardiac output?

Blood pumped by the ventricles per minute.

Normal resting cardiac output?

4–6 L/min.