biology 2

Left is vea caa. Pulmnary veinis right.left ventrucle s thicker ight is only near by lungs. Ventriclesthicker as have t pump bloodout of eart. Sl link ventricles to pumonary artery ad aora. Cords attach av to vetricles to stop them being forced up into atria when atria contract. Whethervakves are open and closed dependx on the relative pressure of the heart chambers. Higher pressure behind valves mean vakves forced open. Higher pressure in frnt of vakvemeans they r forced closed. Myogenic means they contract and elax without recieving signals from nerves. Pattern of contractons controls reg hearbeat. San is in the wall of the right atrium. San is the pacemaker. Its sets ryhtgm of eartbeat. It sends out waves of elecrical activity.t atrial walls) causing right and left atria to contract at sametime. A band of nin conductingcollagen tissue prevents waves of electrical activity from being passed dir from atra to ventricles. Instead waves of elec activity to avn. Avn is resp for passingonto bundle of his there is a slight delay before he avn contracts this makessure atria emptied. Bundle of is is agroup of fibres resp for conduct waves of elec actiity to finer muscles. Called purkyne fibres. They cary elec activity to l and r ventricle walls causing them to contract simultaneouly from  bottom up. Stroke volume is the vol of blood pumped per beat. Cardiac cyce is an ongoing contrac and rekax. Eeps blood continuusly circulating. Pressure changes also occur dueto changes in chamber volume (eg decreasing the volume of the chamber by contraction increases chaber pressure) pushes blood into ventrucles.slight increase in ventricular pressure and chamber vol asventricles recieve ejected blod from contracting atria. The pressure becomes higher in ventricles than atria. Forces av valves shut to prevent backflow. Thepressure in the vent is also hugher than theaorta etc si forced open. Igher pressre in pulmonary etc then closes vales. Blood returns to the heart and atria fill again. Mmhg is the unit pressure. Atheroma forms in endothelium of artery. Ehen damage occurs to endotheliumwhite blood cells and fatty lipids from bloo clump together to firm fatty streaks. Aneuyrsm baloon like swelling. Atheroma plaque damages and weakens artey. Blood travels through weakend arteriesat hp pushes inner lzyers of artey through outer elastic layer to orm an aneurysm. Atheroma plaque can rupture burst through endotheliumdamaging ater wal ad eavingaro suface. Ood clot forms and causes blovkage. Chd is when coronary arteries have lots of atheroma. Damaed walls are at increased ris. Firous plaques. Atheroma formationleads to blood clots leading to myo smoking means feweerantiox and so damage to walls and atheroma form. Anyiox orotect cels from damage. an interventin is a…