Overview_Cardiovascular_Physiology_Concepts -...

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Cardiovascular Physiology Concepts In simple terms, the purpose of the cardiovascular system is to distribute blood to the cells of the body in order to provide the cells with sufficient nutrition (glucose, amino acids, fatty acids, oxygen, ions, etc), remove cellular waste (byproducts of metabolism such as carbon dioxide, nitrogen), and permit intercellular communication and regulation via hormones, cytokines and components of immunity. The heart and blood vessels function together to create the required pressures and blood flow to meet these needs. The heart can be considered as a 2 sided pump, i.e. two pumps that are in series with each other. The right side is a low pressure system that pumps blood into the pulmonary circulation. The left side is a high pressure system that pumps blood into the systemic circulation. Thus, the heart receives blood under low pressure, adds energy to it, and pumps it into a high pressure system. The higher pressure in the systemic circulation is necessary for adequate perfusion of the tissues throughout the body. When blood pressure drops too low, as in circulatory shock, tissues are inadequately perfused, and ischemia and infarction may result. The blood vessels have important roles in maintaining blood pressure and blood flow largely through variation in vessel diameter (resistance), and compliance. Alterations in the diameter of blood vessels determine the amount and direction of blood flow, and thus the degree to which a tissue is perfused with blood. Changes in the activity of the cardiac “pump”, and blood vessel “tone” respond to changes in the internal milieu of cellular metabolism as well as to events in the external environment. The coordination of the changing activity of the heart and blood vessels is largely controlled by the autonomic nervous and endocrine systems. In addition, the cardiovascular system interacts with the kidneys and lungs in regulating blood volume, blood gases, electrolytes and pH. The interdependence of the heart, lungs, kidneys, and blood vessels is significant when describing the mechanisms of cardiovascular homeostasis. The primary function of the heart is to generate an arterial blood pressure that is sufficient to perfuse organs. A measure of the heart’s function is cardiac output (CO). Cardiac output is the volume of blood that is ejected from the heart (right or left ventricle) per minute. The normal volume/ min at rest in an adult is from 5-6 L/ minute. Cardiac output will vary with body size, so a volume standardized to body surface area that provides a more accurate comparison between individuals of different size is known as the cardiac index, and in an adult is between 2.6 – 4.2 L/min/m 2 . Cardiac output is dependent on two factors: heart rate and stroke volume. CO = HR x SV
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This note was uploaded on 02/17/2012 for the course MPAS PA 602 taught by Professor Dr.laird during the Fall '10 term at Chatham University.

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Overview_Cardiovascular_Physiology_Concepts -...

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