Transportin-Humans

The Heart Cardiac muscle that contracts and relaxes rhythmically. Has its own blood supply for glucose and oxygen. Vessels are called coronary arteries and veins. Blockage of these vessels with cholesterol results in coronary heart disease which leads to myocardial infarction (heart attack). Diagram of the heart: center339090001173480413004000 1285240425323000 4743450135890(Bicuspid valve) 00(Bicuspid valve) 487997587630Septum 00Septum 38906455334000 Parts of the heart Aorta Main artery which carries blood to the rest of the body. Pulmony artery / vein Takes blood to the lungs / Takes blood from the lungs. Superior / Inferior Vena Cava Takes blood from the head / Takes blood from the body. Heart beat Called a cardiac cycle Volume in one cycle = stroke volume Volume in one minute = stroke volume x beats per minute = cardiac output General diastole Both atria relax and blood flows into all four chambers. Bicuspid and tricuspid valves open. Semi-lunar valves are closed. Artrial systole Both atria contract, squeezing blood into the ventricles and raising the pressure in the ventricles. Bicuspid and tricuspid valves still open. Semi-lunar valves still closed Ventricular systole Ventricles contract, squeezing blood into the arteries to lungs and the rest of the body. Bicuspid and tricuspid valves close. Semi-lunar valves open. 1355725-381000 -190506286500 Heart valves Tendons support the valves and ensure that they do not collapse in the wrong direction. Tricuspid valve (Atrioventricular valve) Between RIGHT atrium and RIGHT ventricle. Bicuspid valve (Atrioventricular valve) Between LEFT atrium and LEFT ventricle. Semi-lunar valves Between RIGHT ventricle and PULMONARY artery Between LEFT ventricle and AORTA. Control of the heartbeat Specialized muscle cells can conduct electrical impulses and give the heart the signal to start beating. Most important patch of these cells is the sino-atrial node (pacemaker) which is found in the right atrium. Other patches: Atrioventricular node which is lower down in the right atrium. Pukyne fibres in the bundle of His, which is near the bottom of the septum. Signals of the heartbeat: First electrical impulse from the sino-atrial node, after which both atria contract. Signal then moves to the atrioventricular node, which delays the conduction for the atria to relax. Signal then moves to the Purkyne fibres, after which both ventricles contract. Role of the brain: Sends nerve impulses to the sino-atrial node to speed up or slow down heart rate according to the body’s metabolic needs (According to CO2 and O2 concentrations as well as energy being used). If the sino-atrial node stops working, an artificial pacemaker may be inserted into the heart to keep the heart beating regularly. Diseases of heart and arteries (Cardiovascular diseases) Atherosclerosis Caused by the hardening of the arteries which is usually due to the build up of cholesterol in the lining. Very common in the coronary arteries around the heart, causing them to narrow This is called Coronary Heart Disease or CHD. Coronary Heart Disease (CHD) Can lead to the blockage of the blood flow to a section of the heart. When this occurs the heart cannot get glucose or oxygen and a myocardial infarction (heart attack) occurs. This may be fatal. Risk Factors: Genetic predisposition High-cholesterol diet Obesity Stress Smoking tobacco Little/no exercise Blood vessels 514350-190500133350362331000 2733675-296545Diagram of cross-section of artery or vein: (Thickness of layers differ) 00Diagram of cross-section of artery or vein: (Thickness of layers differ) Arteries 251396538735Connective tissue made up mainly of elastic fibres Smooth muscle and elastic fibres Epithelium One cell thick lining 00Connective tissue made up mainly of elastic fibres Smooth muscle and elastic fibres Epithelium One cell thick lining Away from the heart/organ etc. No valves Elastic for smooth blood flow Strong walls High pressure Pulses Veins To the heart/organs etc. Semi-lunar valves Blood is pushed steadily through by the contraction of surrounding muscles If no movement, blood clots, which can then shoot up into the brain and death is imminent. Low pressure Wider lumen 168275063500 3009265100965Endothelial cell 00Endothelial cell 259334023876000Capilaries One cell thick Very thin walls Penetrate entire body Carry materials to and from cells in the bod Efficient exchange between blood and tissues Circulation Humans have a double circulatory system This means that blood flows through the heart twice per one cycle through the body. The double circulatory system consists of: Pulmonary circuit – from the heart to the lungs and then back to the heart. Systemic circuit – from the heart to the rest of the body and back to the heart. 39814509144000This is represented on the diagram alongside: Blue – Deoxygenated blood -171450166497000Red – Oxygenated blood -438150995045Superior 00Superior -4381502443480Inferior 00Inferior Important arteries and veins: