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Lecture

Cardiac Function

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Department
Physiology
Course
PSL201Y1
Professor
Christopher Perumalla
Semester
Winter

Description
← Cardiac Function ← ← The ability of cells to exchange materials with their immediate environment is an absolute requirement in life. Diffusion works well for short distance transport but for humans, diffusion cannot provide cells with all that they need as quickly as they need it since diffusion is efficient but is a slow process. Our body needs a much faster mechanism of transport. ← ← The cardiovascular system can deliver materials throughout the body faster than diffusion could because molecules in the blood move by bulk flow. The most important function of the cardiovascular system is to efficiently transport materials to and from places. ← ← 1. Overview of the cardiovascular system ← ← The cardiovascular system has three components: the heart, blood and blood vessels. The heart is a muscular pump that drives the blood through the blood vessels. The blood is the fluid that circulates around the body carrying materials to and from the cells. The blood vessels are the conduits through which blood flows. ← Transport of substances ← The heart performs sensory and endocrine functions that help regulate the cardiovascular variables such as blood volume and pressure. The blood not only carries nutrients and wastes but also transports hormones from one part of the body to another. Therefore, they serve as a communication link acting in conjunction with the nervous system. The blood vessels are not simply conduits but are also important sensory and effector organs that can regulate blood pressure and distribute blood to various parts of the body. Additionally, regulation of the cardiovascular system requires coopreration with other organ systems including the nervous system, endocrine system and the renal system. ← The main function of the cardiovascular system is the transportation of substances. ← • Blood vessels Arteries: Relatively large, branching vessels that conduct blood away from the heart. Arteries carry oxygenated blood. The aorta is the biggest artery that supplies flesh blood to our body. ← Veins: Relatively large converging vessels that conduct blood to the heart Arterioles: Small, branching vessels with high resistance. Veins carry deoxygenated blood. The biggest vein is called the vena cava Capillaries: Site of exchange between blood and tissue Venules: Small, converging vessels. As blood flows away from the blood, a cycle follows. • The Heart The heart is located in the chest cavity where the diaphragm separates the abdominal cavity from the thoracic cavity. The heart sits just above the diaphragm. It is a muscular organ that is closed within a sac called the pericardium. The function of the pericardium is to lubricate the heart and to decrease its friction but also prevents the heart from overstretching. ← ← ← ← Although the heart is full of oxygenated blood, the heart itself does not draw or use the blood in the chambers to feed itself. Rather, it has a coronary artery that arrives from the aorta. ← ← The heart is divided into the left and the right. The left and the right heart is further divided into the upper chambers of the heart called the atria and the lower chambers of the heart called the ventricles. So, there is four chambers: the right atrium, the left atrium, the right ventricle and the left ventricle. The ventricles are significantly larger than atria and make the bulk of the heart. This is because the ventricles need to generate great pressure to push the blood away from the heart to the arteries. The atria receives blood and transfers it only to the ventricles so the distance traveled is rather limited. The blood goes in one direction, atria to ventricle to the artery. ← ← The atria and the ventricles of the heart are separated by a wall called the interventricular septum that prevents the blood in the left heart from mixing with the blood in the right heart. The septum separating the left and the right atrium is called the interatrial septum. The ventricular muscle is thicker than the atrial muscle. ← ← The left ventricular muscle is much thicker than the right ventricular muscle. This enables the left ventricle to create more pressure and supply more blood to our body. The left heart supplies blood to our body through the aorta while the right heart supplies blood to our lungs only through the pulmonary artery. ← ← ← ← 2. The path and blood flow though the heart and vasculature ← ← The cardiovascular system is often referred to as the circulatory system because the blood flows in an essentially circular path as it travels through the body. The circulatory system consists of two separate divisions: the pulmonary circuit and the systemic circuit. The pulmonary circuit consists of blood vessels within the lungs and those connecting the lungs with the heart. The systemic circuit encompasses the rest of the blood vessels. Both pulmonary and systemic circuits possess a dense network of capillaries where the exchange of nutrients and materials take place. The right heart supplies blood to the pulmonary circuit while the left heart supplies blood to the systematic circuit. ← There is a series flow through the pulmonary and systemic circuits which means that in order to get to one, you must go through the other one. Within the pulmonary or the systemic circuit, there is parallel flow. ← • Oxygenation of blood The exchange between blood and tissue takes place in the capi
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