3.4.14 Kin 470 class notes- Introductiono A major challenge to homeostasis posed by exercise is the increased demand for exerciseo During heavy exercise, need for oxygen may increase 15- to 25-foldo Two major adjustments to meet increased oxygen demand: 1. Increase cardiac output (CO; blood pumped per min) 2. Redistribute blood flow- pulmonary and systemic circulationso systemic circuits left side of the heart pumps oxygenated blood through arteries returns deoxygenated blood to the right heart via veinso pulmonary circuit right side of the heart pumps deoxygenated blood to the lungs via pulmonary arteries returns oxygenated blood to the left heart via pulmonary veins- 1. Blood flow is faster in vessels with larger diameters- 2. Resistance is greater in vessels with smaller diameters- 3. All of the exchange of oxygen and waste in the tissues occurs in the capillaries- structure of the hearto 2 pump system; 2 atrium-ventricle pairso 1 way valves prevent backflowo 2 circuits: pulmonary and systemico body  right atria  right ventricle  lungs  left atria  left ventricle muscle around left ventricle, need to create high pressure to pump out to body long distance runner would look different – larger in volume, thickening around walls, healthy hypertrophy (physiological), also happens during pregnancy various forms of heart failure – pathological hypertrophy, interventricular septum thickens, pathological- myocardiumo epicardiumo myocardium cardiac muscle tissue separated by connective tissues and including blood capillaries, lymph capillaries, and nerve fibers function; provides muscular contractions that eject blood from hearts chamberso endocardium characteristics; protective subendothelial layer- cardiac muscle has specialized structureso cousin of skeletal muscleo myosin and actino contract same way – sliding filamento cardiac muscle: high density of mitochondria well designed for endurance beats for 80 years jam packed with mitochondria different than skeletal muscle intercalated discs; leaky membranes, rapid electrical transmission internal conduction system- heart doesn’t need nervous input- it contracts without input- mutated muscle fibers- along spectrum of nervous tissue- heart has its own “nervous system”- comparison of cardiac and skeletal muscleo cardiac muscle is much smaller than skeletal muscle 1/10 of the sizeo skeletal muscle has many nucleio both striatedo both have actin and myosino skeletal muscle has no cellular junctionso functional comparisons: heart is aerobic beast, won’t do anaerobic energy production only time is during a heart attack (blockage)- deprive of oxygen neural control- heart is uncontrollable – get nervous, HR rises heart disease/heart attack- no regeneration potential in heart- design flaw- when you have a heart attack – the vessel gets plaque in it. Tissue dies and is damaged, never get back that tissue– not true for skeletal muscle- lifting weights will damage the muscle but after a week or two the muscle will be restored- the cardiac cycleo systole contraction phase ejection of blood 2/3 blood is ejected from ventricles per beato diastole relaxation phase filling with bloodo at rest, diastole longer than systoleo during exercise, both systole and diastole are shorter- pressure changes during the cardiac cycleo diastole pressure in ventricles is low filling with blood from atria- AV valves open when ventricular P < atrial Po Systole Pressure in ventricles rises Blood ejected in pulmonary and systemic circulation- Semilunar valves open when ventricular P > aortic P Heart sounds- First: closing of AV valves- Second: closing of aortic and pulmonary valves Lub, dub- Pressure, volume, and heart sounds during the cardiac cycleo Isovolemic contraction phaseo Haven’t exceeded pressure exerted by valveso Transition to open valves, pressure keeps going up but volume is dropping rapidly- Blood pressureo Pulse pressure = systolic – diastolico mean arterial pressure (MAP) average pressure in the arteries determines rate of systemic blood flow MAP = diastolic + 1/3 ( pulse pressure)- Arterial Blood Pressureo Expressed as systolic/diastolic Normal is 120/80 or 110/75 High is 140/90 125/85 is prehypertensiveo systolic pressure pressure in the arteries generated during ventricular contraction (systole)o diastolic pressure (bottom number)- measurement of arterial blood pressure- mean arterial pressure at resto blood pressure = 120/80 mm Hgo MAP = 80 mm Hg + .33 (120-80)= 93 mm Hg- During exerciseo Blood pressure = 180/80- Mean arterial pressure important measureo Volume of blood pumped by heart per mino Resistance of the vesselso Directly proportionalo MAP = CO * total peripheral resistance- Facors that influence arterial blood pressureo Cardiac output- Regulation of BPo Short term SNS Baroreceptors sense changesin pressureo Long term Kidneys- Regulate blood volume- Hypertensiono Resting BP above 140/90o Primary hypertension Cause unknown 90% of caseso secondary some other condition or disease risk factors for:- left ventricular hypertrophy- atherosclerosis and heart attack- kidney damage-