Chapter 15 Cardiovascular

System

THE HEART

LAYERS OF THE HEART• Pericardium

• Outer layer; protects heart• Pericardial fluid between pericardium and

epicardium reduces friction• Epicardium

• Attached to the surface of the heart• Myocardium

• Cardiac muscle fibers, involuntary, striated, connected by intercalated discs

• Endocardium• Squamous epithelium lines inside of myocardium• Covers valves of heart and tendons

Chambers of the HeartThe human heart contains 4 chambers.This varies in other animals. The number of chambers directly relates to how efficient the oxygenation process is.The human heart is divided by the interatrial septum in the atria and the interventricular septum in the ventricles.This ensures no blood mixing.

VALVES• Atrioventricular (AV) lie between atria and

ventricles with blood pushed through by pressure• Tricuspid on right side• Bicuspid (mitral) on left side

• Semilunar prevent blood from flowing back into the heart so blood flows from ventricles to arteries• Pulmonary – between right ventricle and pulmonary

trunk• Aortic – between left ventricle and aorta

Vocabulary Words

4 layers of the heartHeart chambersVena cava-superior and inferiorCoronary sinusPulmonary arteryaorta

BLOOD SUPPLY TO THE HEART

• Coronary arteries• Feed the myocardium• Originate from ascending aorta• Right feeds right side (largest)• Left feeds left side• Deoxygenated blood collects in coronary sinus

Conduction•1% of heart cells generate action potential (ap)

–Pacemaker sets rhythm for heart–Conducting system propagates action potentials throughout the heart1. Excitation at sinoatrial node (SA) to both atria which contract

2.Also excites atrioventricular node (AV) where ap slows for atria to empty

Conduction3. Action potential enters AV bundle in ventricular septum

4. To Purkinje fibers and ventricles contract

–The SA node generates action potentials 100 times per minute, faster than any other region so this is the pacemaker for the heart.

Vocabulary Words

Tricuspid valveChordae tendineaePapillary musclesBicuspid (mitral) valvePulmonary valveAortic valve

ElectrocardiogramP wave

-depolarization

-spreads from SA node

-contraction of atria

ElectrocardiogramQRS complex

-onset of ventricular

depolarization

-spreads through the

ventricles

ElectrocardiogramT wave

-ventricular repolarization

occurs before

ventricles relax

Cardiac Cycle

relaxation contraction relaxation

• Two atria contract while ventricles relax and visa-versa

• Relaxation period• all 4 chambers in diastole• ventricle pressure drops and

AV valves open• T wave

• Atrial systole (contraction)• atria contract• last of blood into ventricles• P wave

• Ventricular systole (contraction)

• contraction of ventricles• AV valves close and Semilunar

valves open• QRS complex

• Heart Sounds: • Lubb – AV valves closing• Dubb – SLV valves closing; short;

sharp sound

REGULATION OF HEART RATE• Autonomic

• Originates in medulla oblongata

• sympathetic • conduction system, and

chambers• parasympathetic

• vagus nerve• neuro and

chemoreceptors

• Chemical• hormones: epinephrine

and norepinephrine• ions: Na+, K+, Ca2+

Vocabulary Words

Sinoatrial node (SA)Atrioventricular node (AV)Atrioventricular bundle (Bundle of His)Purkinje fibersEKG or ECGDiastoleSystole