1. 3. The Heart large muscle large muscle size of your clenched fist size of your clenched fist hollow with 4 chambers hollow with 4 chambers Cardiac Cycle: contracts – blood rushes out contracts – blood rushes out relaxes – rushes in relaxes – rushes in 0.8 s 0.8 s

2. Parts of the Heart Atria (Atrium, sing.) upper chambers, left & right upper chambers, left & right smaller & thin walled smaller & thin walled take in deoxygenated blood from body (lf atria) or oxygenated blood from lungs (rt) take in deoxygenated blood from body (lf atria) or oxygenated blood from lungs (rt)Ventricles lower chambers lower chambers thick walls, muscular thick walls, muscular pumps oxygenated blood out of heart to body (rt) or deox. blood to lungs (lf) pumps oxygenated blood out of heart to body (rt) or deox. blood to lungs (lf)

3. Blood Flow one way only one way only into R atrium from inferior/superior vena cava into R atrium from inferior/superior vena cava R ventricle R ventricle pulmonary artery to lungs to be oxygenated pulmonary artery to lungs to be oxygenated pulmonary veins into L atrium pulmonary veins into L atrium L ventricle L ventricle out aorta to body out aorta to body

4. Valves prevent blood flowing backwards prevent blood flowing backwards atrioventricular valves – b/w atria & vent. atrioventricular valves – b/w atria & vent. pulmonary valve – b/w R vent & pul artery pulmonary valve – b/w R vent & pul artery aortic valve – b/w L vent & aorta aortic valve – b/w L vent & aorta heartbeat is sound of valves opening/closing “lub dub” heartbeat is sound of valves opening/closing “lub dub” lub – atriovent. valve closing lub – atriovent. valve closing dub – pul. & aortic valves closing dub – pul. & aortic valves closing

5. Types of Circulation 1. Systemic Circulation heart to body and return heart to body and return ~ 90% of blood ~ 90% of blood 2. Pulmonary Circulation heart to lungs and return heart to lungs and return ~ 10% ~ 10% 3. Cardiac Circulation blood in heart at any time blood in heart at any time <1% <1%

6. Regulation of Heartbeat avg teen HR (heart rate) 60-100 beats/min (bpm) avg teen HR (heart rate) 60-100 beats/min (bpm) affected by age, fitness, stress… affected by age, fitness, stress… athletes have low HR, babies high athletes have low HR, babies high exercise, stress/fright inc. HR exercise, stress/fright inc. HR pacemaker in wall of R atrium regulates HR pacemaker in wall of R atrium regulates HR

7. Pacemaker sends electrical impulse over the atria to make them contract (blood in) sends electrical impulse over the atria to make them contract (blood in) as atria contract, the impulse reaches the AV node (atrioventricular) on the walls between the ventricles and makes them contract (blood out) as atria contract, the impulse reaches the AV node (atrioventricular) on the walls between the ventricles and makes them contract (blood out) makes heart beat in rhythmic cycle makes heart beat in rhythmic cycle BiologySource BiologySource BiologySource change in voltage is measured by an ECG (electrocardiogram) change in voltage is measured by an ECG (electrocardiogram)

8. Measuring Blood Pressure (BP) sphygmomanometer – pressure cuff to measure BP sphygmomanometer – pressure cuff to measure BP uses mm Hg (standard liquid pressure unit) uses mm Hg (standard liquid pressure unit) 2 numbers ex. 120/70 2 numbers ex. 120/70 1 st # = systolic pressure 1 st # = systolic pressure –pressure in artery when vent. contract 2 nd # = diastolic press. 2 nd # = diastolic press. –pressure in art. when vent. relaxed

9. BP depends on cardiac output & resistance of arteries to blood flow depends on cardiac output & resistance of arteries to blood flow Cardiac Output – amt blood pumped/min Cardiac Output – amt blood pumped/min –as volume inc, so does pressure Resistance due to elasticity of artery walls Resistance due to elasticity of artery walls –if walls don’t expand easily, press inc BP changes with age, fitness, weight… BP changes with age, fitness, weight… avg healthy teen BP 120/80 avg healthy teen BP 120/80