13 - Blood, Heart, Circulation

Cardiac Cycle: Pressure Changes

SYSTOLE 1. Isovolumetric contraction: -- the ventricles about to contract -- increase in vent pressure --> av valves to close = lub sound -- sl valves still closed bc vent pressure isn't high enough to open them -- vent still filled with blood and not yet eject blood 2. Ejection -- as vent increases and greater than arteries -- sl opens -- blood ejected into arteries

blood vessels

arterioles = small branches of arteries that leads to capillaries venules = small branches of veins that drain into larger veins capillaries = only blood vessels that are involved in exchange between tissues and blood --- only contain 1 layer (tunica interna) to allow allow easy exchange between gas and tissues

heart arrhythmia

bradycardia = normal in endurance athletes (for them resting heart rate = 40 - 60 bpm) tachycardia = normal while someone is exercising --- if at rest & tachycardic --> abnormal fibrillation: due to contracting of different myocardial cells at different times

electrical activity of heart

cardiac muscles are short and branched -- fibers are connected by gap junctions (intercalated discs) -- allow cardiac muscles to transmit signal from cell to cell

Veins

contains most of the circulating blood in body bc further from heart = function under lower pressure bc bp is low in veins & blood returning to heart (venous return) is flowing against gravity = modified to ensure blood returning is equal to original cardiac output - lumen is larger than arteries = less resistance to blood flow - valves = prevent backflow - when skeletal muscles contract & relax, blood is squeezed thru veins, resulting in blood flowing towards heart - act of breathing = help return blood to heart --> flattening of diaphragm at inhalation increases abdominal cavity pressure in relation to thoracic pressure and moves blood toward heart varicose veins are structural defects due to incompetent valves -- problem in ppl who are obese and ppl who stand a long time -- blood can pool in feet and legs, ineffecient blood return to heart due to inactivity or pressure in veins = cause valves to be overworked and give way

lymphatic system

lymphatic vessels = first 2 functions lymphoid tissues and organs = last function --- contain phagocytic cells and lymphocytes, which are important for body defense and resistance to disease

atherosclerosis

plaque buildup on artery wall thrombi = blood clots these insults cause insults/injuries to the endothelium --- remember: intact endothelium act as a smooth physical barrier by release of chemical regulators --- risk factors disrupt this protective mechanism --- regular exercise = helps improve and maintain proper endothelium protection