Heart (3)

3 layers of the heart

3 layers of the heart

pericardium, myocardium, endocardium

Pericardium

connective tissue outer layer, protecting, anchoring, preventing from overfilling

Myocardium

cardiac muscle tissue

Endocardium

endothelial lining of internal chambers of the heart

4 cardiac chambers

left atrium, right atrium, left ventricle, right ventricle

Atrioventricular (AV) valves

prevent back flow into atria when ventricles contract

Chordae tendineae

anchor for valve flaps to papillary muscles

Semilunar (SL) valves

prevent back flow into ventricles when they relax

Blood flow process

superior/inferior vena cava > right atrium > tricuspid valve > right ventricle > pulmonary semilunar valve > pulmonary trunk > pulmonary arteries > lungs > pulmonary veins > left atrium > bicuspid valve > left ventricle > aortic semilunar valve > aorta > systemic circulation

Excitation process

SA node generates impulses > pause at AV node > AV connects atria to ventricles > Purkinje fibers depolarize cells & ventricles

Contraction differences

depolarization is quicker, repolarization is longer

P wave

depolarization of SA node in atria

QRS complex

depolarization of ventricles, repolarization of atria

T wave

repolarization of ventricles

Tachycardia

abnormally fast heart rate >100bpm

Bradycardia

heart rate slower than 60bpm

Epinephrine

increases heart rate & contractility

Thyroxine

increases heart rate & effects of epinephrine

Systole

contraction phase

Diastole

relaxation phase

End diastolic volume (EDV)

volume of blood in each ventricle at the end of ventricular diastole

End systolic volume (ESV)

volume of blood in each ventricle at the end of ventricular systole

Cardiac output

volume of blood pumped by each ventricle in one minute

Cardiac output formula

heart rate x stroke volume

Heart rate

beats per minute

Stroke volume

EDV - ESV

3 factors affecting stroke volume

preload, contractility, afterload

Preload

degree of stretch of cardiac muscle cells before they contract

Contractility

contractile strength at given muscle length

Afterload

pressure that must be overcome for the ventricles to eject blood