Anatomy and PhysiologyChapter 20: The Heart

Introduction

•Heart beat 100,000X / day ( moves 8000L)•Muscle is never at rest•Pulmonary circuit goes to heart from

lungs•Systemic circuit goes to heart from body•Arteries (afferent) – away from the heart•Veins (efferent) – toward the heart•Capillaries – exchange vessels

20.1 Anatomy of the Heart

•Tilts to left of sternum•Between intercostal spaces 3 and 5•Associated with lots of fatty tissue•Pericardial sac – protects and lubricates

(fluid)•Myocardium = heart muscle•Coronary arteries = supply blood to heart

muscle itself ( these are “bypassed”)

Chambers and vessels KNOW THIS•Superior vena cava – blood from

head/neck/limbs to RA•Right Atrium – receives blood from body•Right ventricle – pump * / to lungs•Left Atrium– from lungs•Left ventricle – pump * / to body through;

thicker more muscular side… to whole body•Aorta • Inferior vena cava – receives blood from the

trunk to RA•* RV and LV pump at same time, same amount

Important information

•Be able to label the diagrams at end of ch. 20 on page 705 – there will be a heart diagram to label on the test, like the ones you colored and the one on pg 705. You will have a word bank.

Chambers, vessels and valves•RA and RV separated by tricuspid valve•Cusps anchored to chordae tendineae that

tug flaps down to prevent backflow•LA receives blood through mitral valve•LV is associated with semilunar valve

20.2 Generation of Action Potentials

•Muscle cells in conducting system coordinate beat

•Contractile cells contract to propel blood•Electrocardiograph (ECG, EKG) shows

electrical events of heart beat •App called cardiograph

• Sinoatrial (SA) node in RA▫Spontaneous depolarization without neural or

hormonal▫80 – 100 action potentials per minute▫Pacemaker cells

• Atrioventricular (AV) node between A and V▫50 msec from SA to AV▫Delay at AV node so atria finish contracting

before ventricles• Conducting cells with internodal pathways do

not have stable resting potential; drift toward threshold

• Purkinje fibers ▫Rapid conduction of action potentials ventricular

myocardium

Summary of gates and Action Potential in Cardiac Muscle•1. rapid deploarization

▫Opening of fast Na channels•2. plateau

▫Slow Ca channels•3. repolarization

▫Slow P channels

Energy

•Heart muscles have lots of mitochondria that break down both fatty acids and glucose (stored as glycogen)

•Have heme units (part of hemoglobin) stored as myoglobin so they can have access to lots of O2 – very aerobic

•Calcium ions are very important to the conduction of action potentials in the cardiac muscle cells