BIOLOGY NOTES BIOLOGY CARDIOVASCULAR SYSTEM HUMAN HEART see book for model Pump of CV system o Cardiac muscle o Blood vessels that supply blood to heart muscle 4 chambers o 2 atria atrium o 2 ventricles 4 valves o 2 between atria and ventricles o 2 between ventricles and arteries o Valves keep the blood moving in one direction Left atrium and ventricle o Pump oxygenated blood to all parts of body except lungs o More muscular Right atrium and ventricle o Pump de oxygenated blood to the lungs CIRCULATION OF BLOOD Blood is pumped through the body in a circuit o One way route Pulmonary circulation to lungs o Right atrium and ventricle pump de oxygenated blood white to lungs o O2 gained and CO2 released in lungs o Oxygenated blood gray returns to left atrium o See book for model Systemic circulation body o Left atrium and ventricle pump oxygenated blood gray to all parts of body except lungs Systemic circulation o Tissues use O2 and produce CO2 o De oxygenated blood white returns to right atrium o See book for model Note blood pressures throughout circuit see model Q When they work correctly the valves in the heart Ensure that blood moves in only one direction CARDIAC CYCLE ELECTRICAL Contraction of heart must be highly coordinated to pump blood effectively Model in book Atrial excitation A V nodal delay Ventricular excitation begins Ventricular excitation complete Electrocardiogram ECG or EKG Electrical activity of heart measured outside the body Q The sinoatrial SA node in the right ventricle is also called the heart s Pacemaker CARDIAC CYCLE MECHANICAL DIASTOLE Heart is relaxed Atria and ventricles fill with blood o Valves open between atria and ventricles o Valves closed between ventricles and arteries SYSTOLE Heart contracts Atria pump blood into ventricles o Valves open between atria and ventricles Ventricles eject blood into arteries o Valves closed between atria and ventricles o Valves open between ventricles and arteries CARDIAC OUTPUT CO the volume of blood pumped by the heart in a minute Two components o Stroke volume the volume of blood pumped by one heartbeat o Heart rate HR the number of beats per minute CO SV x HR CO changes when either component changes CARDIAC CYCLE CONTROL OF HEART RATE Nervous system is important for acute beat to beat changes in heart rate through modulation of SA node protons o When exercising your body detects reductions of O2 and increases in CO2 and o The nervous system releases norepinephrine noradrenaline and epinephrine adrenaline to increase SA node activity The neurochemicals that modulate electrical activity in the SA node influences the rate of cardiac contraction Hormones can also influence HR and cardiac contraction over longer time frame VASCULATURE THE TUBES All the blood vessels collectively throughout the body that blood moves through Three portions o Arterial blood vessels o Capillaries o Venous blood vessels Blood leaving the heart enters the arterial vasculature then capillaries and returns to heart via the venous vasculature From the right side of the heart deoxygenated blood enters the pulmonary artery travels to capillaries in the lungs where it is re oxygenated and returns to the pulmonary veins to the left side of the heart Left side oxygenated blood enters the aorta travels to capillaries in some major tissue or organ of the body other than the lungs then the deoxygenated blood returns through veins to the right side of the heart Structure of each vasculature made of three parts o Smooth muscle o Connective tissue o Endothelium ARTERIAL VASCULATURE Carries blood away from the heart towards capillaries in tissues o Blood leaving the heart enters a large diameter artery which subdivides into smaller diameter arteries Subdivide even further into arterioles which branch into capillaries Blood in an artery does NOT distinguish if blood is oxygenated pulmonary artery carries DEOXYGENATED blood from the right side of the heart to the lungs Blood leaves left ventricle at high systolic pressure the aortic valve ensures that arterial blood pressure remains high during diastolic phase blood pressure medical exam o BP in pulmonary artery not as high in aorta because there is less cardiac muscle in the right ventricular wall compared to the left o Blood pressure drops as arteries branch into arterioles Kidneys are the exception blood enters through the renal arteries which are connected to the main branch of the aorta Structure of arteries especially aorta reflects higher pressure of blood pumped by ventricles Endothelium is a thin wall of cells that form the inner lining of the arterial vasculature and can influence homeostasis and health CAPILLARIES Smallest diameter blood vessels Located throughout the body Site of exchange for gasses and other small molecules between blood and vascularized cells in tissues The central component of the circuit that blood flows through when pumped from a cardiac ventricle to the atrium on the other side of the heart o Receive blood from arterial vasculature o Blood exits capillaries into venous vasculature BP is lower than in AV o More capillaries than arterioles greater some total area for blood distribution o RBCs temporarily deformed due to small diameter Structure a single layer of endothelium o Short distance for diffusion of molecules between blood and tissue cells o Diffusion the net movement of molecules from regions of high concentration to low concentration by the random motion of molecules colliding with other molecules Smooth muscle cells also located in some capillary beds VENOUS VASCULATURE Receives blood from capillaries and returns to the atria of the heart Blood from capillaries comes together in large diameter venules then into veins BP in VV is lower than capillaries lowest in the circuit Veins contain valves that keep blood moving in a single direction Skeletal muscles act as a secondary pump that aids blood flow through the veins Structure o Connective tissue o Smooth muscles o Thin layer of endothelial cells that from an inner lining Much thinner than arterial because there is less connective tissue and smooth muscle Can sometimes contribute to disease progression ie tumor growth ANGIOGENESIS GROWTH OF NEW BLOOD VESSELS CARDIOVASCULAR DISEASES ATHEROSCLEROSIS BLOOD VESSEL BLOCKAGE Leading cause of death for men and women in the US and the developed world Thickening of an arterial wall due to buildup of fats like cholesterol o LDL platelets and some blood cells can contribute
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