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BIOL 4510 Lecture 1-3-2012.pdf

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BIOL 4510
Peter Backxx

BIOL4510/KINE4510 Lectures 1-3: Cardiac Physiology Peter Backx, 2012 Consider reading: Berne & Levy. Cardiovascular Physiology Chapters 1-4 Circulatory system In small single cell organisms or animals < 1 mm in diameter, movement of molecules can occur easily by diffusion or cell transport from the external environment. However, with larger multicellular organisms, diffusion is inadequate to provide the necessary nutrients, gases, salts or removal of waste. Required for cell-to-cell communication (transport hormones, deliver drugs etc) Required to regulate temperature Major components of a circulatory system: a plumbing system 1) a pump 2) a conduit or vascular system 3) blood/fluids Closed Circulatory System Circulatory systems is nearly closed. This means that to a good approximation fluids/blood stay in the cardiovascular system…although this is not quite true…example given later Other facts  vertebrates and some invertebrates  blood flows in a continuous circuit  small volume (5-10% of the body volume)  high pressure  can alter velocity and distribution of blood flow rapidly All closed circulatory systems are comprised of:  Heart: pressurizes blood to provide propulsion to “force” blood to flow in the pipes  Arteries or arterial system takes blood away from heart and distributes to body. Act as storage bin for high pressure blood  Capillaries: micro-vessels that are very small <5-6mm. They allow blood to flow from arteries to vein. Almost every cells of the body is adjacent to at least one capillary.  Veins or venous system returns blood to heart from the capillaries and serves as a major blood storage reservoir for low pressure blood  Pressure of the blood drops as it flows from arteries to veins due to viscosity of blood (by definition viscous fluids require energy to flow). Movement of blood  force imparted by rhythmic contraction of the heart  elastic recoil of arteries following filling by cardiac contraction  squeezing of blood vessels during body movement  peristaltic contractions of the smooth muscle surrounding blood vessels 1 Mammalian Circulatory System The heart is important for circulating oxygenated blood to the body, and to deliver venous blood to the lungs. STRUCTURE AND FUNCTION OF THE HEART Anatomy of the Heart Anterior View Posterior View 2 Overview of structure and function (ADULT HEART) - heart functions to provide the mechanical energy required to cause blood to flow - heart works as an ideal pump which (in conjunction with blood vessels) maintains blood pressure in order to ensure continuous perfusion of the blood throughout the body - "simple" hollow organ designed to work as a pump (Figure 1) - pumps deoxygenated blood (dark) to lungs to be oxygenated and delivers oxygenated blood (bright red) to the entire body - also delivers nutrients, metabolic waste products, hormones, biochemical regulators and heat to the cells of the body - 4 chambers: 2 atria 2 ventricles - atria = thin walled sacs act as "pump primers" and reservoirs for blood - ventricles = thick walled sacs provide energy for pumping blood ("motor") - 2 separate pumps; left and right each with 1 atrium (atr) + 1 ventricle (vtr) - pumps separated by septum: coupled primarily through the blood flow - left side = pressure pump; forces blood flow through the entire body (oxygenated) - right side = volume pump; blood forced to lungs (deoxygenated) - vtr and atr separated by atrioventricular valves (right = tricuspids; left = mitral) - valve acts prevent "backflow of blood" (see below); allows one-way blood flow - valves = connective tissue flaps: swing shut when blood flows backwards - heart connected to body by major vessels: aorta---left vtr, pulmonary artery---right vtr vena cava---right atr pulmonary vein---left atr - blood flow: body to right atr. to right vtr. to lungs to left atr. to left vtr. to body to... - major vessels and heart ventricular chambers separated by semilunar valves (flaps) right = pulmonic valves ; left = aortic valves 3 - no "physical valve" exists between atr and their corresponding vessels (veins) but there is a "physiological valve" (i.e. blood still flows one-way). How this is achieved will be mentioned in lcass Pericardium Pericardium is a fibrous, fluid-filled (serous) sac that surrounds the myocardium. In the mediastinum (chest cavity), it is anchored by connective tissue. The main function of the pericardium is to restrict heart movement and prevents the heart from overfilling with blood. Fibrous pericardium is the outer layer is comprised of tough and dense connective tissue, which is attached to both the sternum and the diaphragm The serous pericardium is a thin, double-layered serous membrane composed of the • parietal layer • visceral layer 4 Coronary Vessels Left and right coronary arteries travel in the coronary sulcus or the atrioventricular groove. Arterial Circulation Venous Circulation The right coronary artery typically branches into the:  right marginal artery which supplies the right border of the heart  posterior interventricular artery which supplies both the left and right ventricles Left coronary artery (also called the left anterior descending artery) typically branches into the:  Anterior interventricular artery which supplies the anterior surface of both ventricles and most of the interventricular septum  Circumflex artery supplies the left ventricular free wall. Coronary veins drain the myocardium from: From the anterior interventricular area through the great coronary vein or coronary vein From the right atrial area through the small coronary vein From the posterior interventricular area through the middle coronary vein. All of these veins come together to form the coronary sinus which drains directly into the right atrium. 5 Heart Muscle The heart wall is comprised of three distinctive layers: 1) ___________________________ 2) ___________________________ 3) ___________________________ The _____________________is the outermost heart layer, and is also known as the visceral layer of serous pericardium. It is composed of simple squamous epithelium underlined by fat As we age, more fat is deposited in the epicardium and this layer becomes thicker and more fatty. The ____________________is the middle layer of the heart wall composed primarily of cardiac muscle tissue, and is the thickest of the three heart wall layers. The ____________________covers internal surface of the heart and the external surfaces of the heart valves. It is composed of a thin endothelial layer of cells and areolar connective tissue under the endothelium 6 Heart Valves Ensure blood flows in proper direction Left A-V valve (bicuspid, mitral) between left atrium and left ventricle; valve opens when ______________________ Right A-V valve (tricuspid) between the right atrium and right ventricle; valve opens when Aortic semilunar valve between left ventricle and aorta; valve opens when ________________________ 7 Pulmonary semilunar valve between right ventricle and pulmonary artery; valve opens when ________________________ 8 Cardiac Cycle 9 Cardiac Electrical Activity
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