A. Includes a powerful pump (heart) and extensive system of tubes (blood vessels) B. Functions to transport oxygen, nutrients, and wastes. A. Size 1. Varies with body size - average adult 9 cm x 14 cm B. Location 1. Nearly centered in the thoracic cavity, with the distal end toward the left side.

Superior vena cava Left ventricle Right ventricle Heart covered by visceral pericardium Pericardial cavity - serous fluid aorta C. Coverings of the heart 1. Pericardium outer layer 2. Visceral pericardium (inner layer) 3. Parietal pericardium (middle layer)

1. Pericardium outer layer 3. Parietal pericardium (middle layer) 2. Visceral pericardium (inner layer)

D. Wall of the Heart 1. endocardium 2. myocardium 3. epicardium a. serous membrane a. thick cardiac muscle layer a. epithelial and connective tissue b. specialized muscle fibers - Purkinje fibers

E. Heart Chambers and Valves 1. chambers a. right atrium - receives returning blood from body b. right ventricle - pumps blood to lungs c. left atrium - receives blood from lungs d. left ventricle - pumps blood throughout body A B C D A C D B Interventricular septum

2. Valves a. tricuspid valve* - allows blood from right atrium to right ventricle b. pulmonary valve # - allows blood to leave right ventricle c. bicuspid (mitral) valve* - allows blood from left atrium to ventricle d. aortic valve # - prevents blood from flowing back into the left ventricle after contraction - located at base of aorta. = three cusps to valve= two cusps to valve 3. Skeleton of heart a. connective tissue provide firm attachment points for valves, muscles Prevent atria & ventricles from dialating *=AV valve # = semi lunar valve

4. Path of Blood Through the Heart - a. aorta & branches b. capillary beds of all body tissues where gas exchange occurs c. superior and inferior vena cavae d. pulmonary arteries e. capillary beds of the lungs where gas exchange occurs a. b. c. d. e. f. pulmonary veins f.

5. Blood Supply to Heart a. coronary arteries - i. Supply blood to heart tissue ii. Feed into many capillaries of myocardium iii. Small alternative branches (anastomoses) b. cardiac veins - i. Drains blood to coronary sinus on hearts posterior surface - empties into right atrium

A. Cardiac Cycle - (the coordinated contractions / relaxation of heart) 1. Atria - relaxed (atrial diastole) a. blood flows in b. pressure increases - A-V valves open blood flows into ventricle 2. Atria - contracted (atrial systole) a. atrial pressure rises - forcing remaining blood into ventricle 3. Ventricles contract (ventricular systole) a. A-V valve closes - partially extends into atrium b. papillary muscles contract pulling on chordae tendineae reducing valve extension back into atria. c. A-V valve remains closed as atria refills - pressure increases d. ventricle pressure increases opening semi-lunar valves e. Blood leaves ventricles

4. Ventricles relax (ventricular diastole) a. A-V valve opens blood flows into ventricle - atria pressure drops b. ventricle pressure low while filling - increases slightly with atria contraction c. semi-lunar valves close

B. Heart Sounds 1. Lubb - first part - when ventricles contract A-V valves are closing 2. Dubb - second sound - when ventricles relax - semi-lunar valves close C. Cardiac muscle Fibers 1. Cardiac muscle fibers in branching networks a. stimulation to part - impulses to all - contracts as a unit i. unit is functional syncytium Atrial syncytium and ventricular syncytium Separated by fibrous skeleton D. Cardiac Conduction System 1. Sinoatrial node (S-A node) a. self initiating impulses travel to atrial syncytium b. right and left atria contract simultaneously c. impulse passes to atrioventricular node (A-V node) via junctional fibers (JF)

2. A-V node a. JF fibers small diameter conduct impulses slowly - delays impulse b. A-V node further slows impulse - allows for atrium to empty before ventricle contracts 3. A-V bundle - (bundle of His) a. from A-V node impulse travels along A-V bundle - through interventricular septum 4. Purkinje Fibers (PF) a. PF arise from A-V bundle b. spread into papillary muscles c. branch into small fibers contacting cardiac muscle fibers 5. Whorls of muscle fibers in ventricles contract in a twisting motion squeezing blood from ventricle

E. Regualation of the Cardiac Cycle 1. Parasympathetic fibers contacting S-A, A-V node - continuous a. acetylcholine release decreases S-A and A-V node activity 2. Sympathetic fibers contact S-A, A-V nodes and other areas a. norepinephrine released - increases rate and force of contraction 3. Monitored by medulla oblongata (MO) a. Baroreceptors - monitor blood pressure i. Increase pressure - slows down heart rate (HR) b. Cerebrum and hypothalmus - influence MO c. Temperature i. Decrease - decrease HR d. Ions i. K + - decrease HR ii. Ca +2 - increase HR

S-A node Atrial syncytium Junctional fibers A-V node A-V bundle bundle branches Purkinje fibers Ventricular syncytium

F. Electrocardiogram (ECG) or (EKG) 1. A recording of electrical changes in the myocardium during a cardiac cycle - (waves or deflections) 2. S-A node triggers - atrial fibers depolarize - P wave recorded 3. When ventricular fibers depolarize - QRS complex recorded a. Q wave b. R wave c. S wave Depolarization of ventricular fibers just prior to contraction 4. Ventricular fibers repolarizing produce T wave 5. repolarizing of atria mask by ventricle depolarizing

A. Arteries 1. Elastic vessels - carry blood away from heart 2. Branch into smaller arterioles - capillaries 3. Structure - a. three layers i. Tunica interna ii. Tunica media Endothelium cells smooth surface, Smooth muscle encircle tube. Elastic connective tissue iii. Tunica externa Connective tissue with elastic and collagenous fibers

B. Capillaries 1. Smallest diameter BV 2. Connect arterioles with venules 3. Thin walls for O 2, CO 2, nutrient and waste exchange with blood 4. Density varies with need - muscles, endocrine glands, SI, increased numbers 5. Precapillary sphincters - open and close off capillaries as needed 6. Exchanges of substances a. diffusion - high to low concentration. b. filtration - high pressure in arteriole end of capillary forces out molecules c. osmosis - water tends to enter toward venous end of capillary.

C. Veins 1. Return blood to heart 2. Smaller branches - venules 4. Valves prevent back flow 5. Collapse when empty 3. Three layer walls similar to arteries

A. A measure of force exerted on inner walls of blood vessels. 1. Systolic pressure - high end of the measured pressures 2. Diastolic pressure - low end of measured pressures B. Factors influencing blood pressure (BP) 1. Heart action - (cardiac output) - determines how much blood enters arterial system. a. Cardiac output = stroke volume x heart rate. 2. Blood volume - 3. Peripheral resistance - friction between blood and walls of blood vessels 4. Blood viscosity - ease at which fluid molecules move past one another C. BP control 1. Regulation of cardiac output and peripheral resistance