The Cardiovascular System Chapter 18 The Heart

THE HEART

http://www.youtube.com/watch?v=06iQlVMSB34

The HEART Cardiac muscle tissue Highly interconnected cells FOUR chambers Right atrium Right ventricle Left atrium Left ventricle

INTERNAL http://www.youtube.com/watch?feature=endscreen&NR=1&v=II5RPs1hlGI 1. SA node 2. AV node 3. AV bundle (Bundle of His) 4. Bundle branches 5. Purkinje fibers 6. Pulmonary valve 7. Aortic valve 8. Mitral (bicuspid) valve 9. Tricuspid valve RIGHT side LEFT side

EXTERNAL Right atrium Left atrium Right ventricle Left ventricle Superior vena cava Inferior vena cava Aorta Pulmonary trunk Left pulmonary artery Right pulmonary artery Right pulmonary veins Left pulmonary veins Coronary circulation Apex Ligamentum arteriosum 8. Mitral (bicuspid) valve 9. Tricuspid valve

pulmonary http://www.youtube.com/watch?v=q0s-1MC1hcE

Function of the Heart Valves

Blood Flow Through Heart

Circuits Pulmonary Circulation Systemic Circulation The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart. Systemic Circulation The pathway between the heart and the rest of the body

Coronary Circulation From RIGHT side of heart To outer muscle of heart Back to LEFT side of heart

Size, Shape, Location of the Heart Size of a closed fist Shape Apex: Blunt rounded point of cone Base: Flat part at opposite of end of cone Located in thoracic cavity in mediastinum

Pericardium

Heart Wall Three layers of tissue Epicardium: This serous membrane of smooth outer surface of heart Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting Endocardium: Smooth inner surface of heart chambers

Heart Wall

Systemic and Pulmonary Circulation

Heart Skeleton Consists of plate of fibrous connective tissue between atria and ventricles Fibrous rings around valves to support Serves as electrical insulation between atria and ventricles Provides site for muscle attachment

Cardiac Muscle Elongated, branching cells containing 1-2 centrally located nuclei Contains actin and myosin myofilaments Intercalated disks: Specialized cell-cell contacts Desmosomes hold cells together and gap junctions allow action potentials Electrically, cardiac muscle behaves as single unit

Conducting System of Heart

Electrical Properties Resting membrane potential (RMP) present Action potentials Rapid depolarization followed by rapid, partial early repolarization. Prolonged period of slow repolarization which is plateau phase and a rapid final repolarization phase Voltage-gated channels

Action Potentials in Skeletal and Cardiac Muscle

SA Node Action Potential

Refractory Period Absolute: Cardiac muscle cell completely insensitive to further stimulation Relative: Cell exhibits reduced sensitivity to additional stimulation Long refractory period prevents tetanic contractions

Electrocardiogram Action potentials through myocardium during cardiac cycle produces electric currents than can be measured Pattern P wave Atria depolarization QRS complex Ventricle depolarization Atria repolarization T wave: Ventricle repolarization

Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm Bradycardia: Heart rate less than 60 bpm Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

Alterations in Electrocardiogram

Cardiac Cycle Heart is two pumps that work together, right and left half Repetitive contraction (systole) and relaxation (diastole) of heart chambers Blood moves through circulatory system from areas of higher to lower pressure. Contraction of heart produces the pressure

Cardiac Cycle

Events during Cardiac Cycle

Heart Sounds First heart sound or “lubb” Second heart sound or “dupp” Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole Second heart sound or “dupp” Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer Third heart sound (occasional) Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

Location of Heart Valves

When Things Go Wrong: HEART Complete handout. Then cut & paste into NB.

Effects of Aging on the Heart Gradual changes in heart function, minor under resting condition, more significant during exercise Hypertrophy of left ventricle Maximum heart rate decreases Increased tendency for valves to function abnormally and arrhythmias to occur Increased oxygen consumption required to pump same amount of blood