Cardiovascular Ch 18

Pulmonary circuit

The pathway that carries oxygen-poor blood from the heart to the lungs and back to the heart.

Systemic circuit

The pathway that carries oxygenated blood from the heart to body tissues and back to the heart.

Right side of the heart

Receives oxygen-poor blood from tissues and pumps it to the lungs.

Left side of the heart

Receives oxygenated blood from the lungs and pumps it to body tissues.

Right atrium

Chamber that receives blood returning from the systemic circuit.

Left atrium

Chamber that receives blood returning from the pulmonary circuit.

Right ventricle

Chamber that pumps blood into the pulmonary circuit.

Left ventricle

Chamber that pumps blood into the systemic circuit.

Base of the heart

Leans toward the right shoulder.

Apex of the heart

Points toward the left hip.

Pericardium

A double-walled sac surrounding the heart.

Fibrous pericardium

Protects the heart, anchors it, and prevents overfilling.

Serous pericardium layers

Parietal layer and visceral layer (epicardium).

Pericardial cavity

Fluid-filled space that reduces friction.

Pericarditis

Inflammation of the pericardium causing friction rub.

Cardiac tamponade

Fluid buildup compressing the heart and impairing pumping.

Heart wall layers

Epicardium, myocardium, endocardium.

Myocardium

Cardiac muscle layer responsible for contraction.

Cardiac skeleton

Connective tissue network that anchors muscle fibers and limits action potential spread.

Endocardium

Inner lining of heart chambers and valves.

Interatrial septum

Wall that separates the atria.

Fossa ovalis

Remnant of fetal foramen ovale.

Interventricular septum

Wall that separates the ventricles.

Coronary sulcus

Groove separating atria and ventricles.

Auricles

Appendages that increase atrial volume.

Veins emptying into right atrium

Superior vena cava, inferior vena cava, coronary sinus.

Blood returning to left atrium

Four pulmonary veins.

Trabeculae carneae

Irregular ridges of muscle in ventricles.

Papillary muscles

Muscles that anchor chordae tendineae.

Function of AV valves

Prevent backflow into atria during ventricular contraction.

Right AV valve

Tricuspid valve.

Left AV valve

Mitral (bicuspid) valve.

Chordae tendineae

Fibrous cords that prevent valve flaps from inverting into atria.

Function of semilunar valves

Prevent backflow from arteries into ventricles.

Pulmonary semilunar valve

Located between right ventricle and pulmonary trunk.

Aortic semilunar valve

Located between left ventricle and aorta.

Incompetent valve

Valve that fails to close completely, causing regurgitation.

Valvular stenosis

Stiff valve flaps that restrict blood flow.

Pathway of blood into right atrium

Superior vena cava, inferior vena cava, coronary sinus.

Valve from right atrium to right ventricle

Tricuspid valve.

Valve from right ventricle to pulmonary trunk

Pulmonary semilunar valve.

Pathway of blood into left atrium

Four pulmonary veins.

Valve from left atrium to left ventricle

Mitral valve.

Valve from left ventricle to aorta

Aortic semilunar valve.

Left ventricle thickness reason

Pumps with greater pressure to systemic circuit.

Coronary circulation

Blood supply to the heart muscle itself.

Coronary blood delivery timing

When the heart is relaxed.

Coronary anastomoses

Junctions providing alternate blood flow routes.

Angina pectoris

Chest pain from temporary ischemia.

Myocardial infarction

Heart attack due to prolonged coronary blockage.

Pacemaker cells

Autorhythmic cells that initiate heart depolarization.

Pacemaker potential

Slow Na+ influx causing gradual depolarization.

Ion causing pacemaker depolarization

Calcium (Ca2+).

Ion causing pacemaker repolarization

Potassium (K+).

Normal sequence of excitation

SA node → AV node → AV bundle → bundle branches → Purkinje fibers.

Fibrillation

Rapid, irregular contractions that stop effective pumping.

Purpose of defibrillation

Reset electrical activity to restore normal rhythm.

Plateau phase in contractile cells

Caused by slow Ca2+ channels remaining open.

Why cardiac AP is longer than skeletal muscle

Prevents tetany and ensures full blood ejection.

P wave

Represents atrial depolarization.

QRS complex

Represents ventricular depolarization and atrial repolarization.

T wave

Represents ventricular repolarization.

Systole

Contraction phase of the heart.

Diastole

Relaxation phase of the heart.

EDV

Volume in ventricles at end of diastole.

ESV

Volume remaining after systole.

First heart sound (lub) cause

Closing of AV valves.

Second heart sound (dup) cause

Closing of semilunar valves.

Cardiac output

Heart rate (HR) multiplied by stroke volume (SV).

Stroke volume

Blood pumped per beat.

Preload

Ventricular filling/stretch before contraction.

What increases preload

Exercise, increased venous return, increased blood volume.

Contractility

Strength of contraction at a given muscle length.

What increases contractility

Sympathetic stimulation and Ca2+ availability.

Afterload

Resistance ventricles must overcome to eject blood.

Effect of increased afterload on SV

Decreases stroke volume.

Cardiac reserve

Difference between resting and maximal cardiac output.

Ventricular filling phase

Occurs during mid-to-late diastole when pressure is low and 80% of blood flows passively into ventricles.

Atrial systole contribution

Atrial contraction pushes the remaining 20% of blood into the ventricles.

Isovolumetric contraction

Phase where ventricles begin to contract but all valves are closed.

Ejection phase

Occurs when ventricular pressure exceeds arterial pressure and semilunar valves open.

Isovolumetric relaxation

Early diastole phase when ventricles relax and all valves are closed.

When AV valves open

When atrial pressure becomes greater than ventricular pressure.

When semilunar valves open

When ventricular pressure exceeds pressure in the aorta or pulmonary trunk.

When semilunar valves close

When blood backflows toward the ventricles during relaxation.

Heart murmurs

Abnormal heart sounds caused by turbulent blood flow.

Incompetent valve sound

Swishing sound from blood leaking backward.

Stenotic valve sound

High-pitched or clicking sound from blood forced through a narrow opening.

P–Q interval

Represents atrial systole.

S–T segment

Represents the plateau phase; entire ventricular myocardium depolarized.

Q–T interval

Time from ventricular depolarization to ventricular repolarization.

Depolarization in contractile cells

Caused by rapid Na+ influx through voltage-gated sodium channels.

Plateau phase purpose

Prolongs depolarization to allow sustained contraction and efficient blood ejection.

Repolarization in contractile cells

Caused by K+ efflux when potassium channels open.

Why cardiac muscle cannot tetanize

Long refractory period prevents sustained contractions.

Difference between skeletal and cardiac AP duration

Cardiac AP lasts ~200 ms; skeletal AP lasts 1–2 ms.

Difference between skeletal and cardiac contraction duration

Cardiac contraction lasts over 200 ms; skeletal lasts 15–100 ms.

Effect of respiration on preload

Increased respirations enhance venous return to the heart.

Effect of skeletal muscle pump on preload

Muscle contractions push venous blood back toward the heart.

Why low calcium is dangerous

Low Ca2+ weakens contractility and can lead to cardiac failure.