physio lab 3 - Introduction The cardiovascular system which...

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Introduction The cardiovascular system, which encompasses the heart, blood vessels and blood, functions in the transport of respiratory gases, nutrients, wastes and hormones, as well in body temperature regulation. The human heart is described as a pump that is responsible for the flow of blood throughout the body, and it consists of four chambers, which includes two upper atria and two lower ventricles. The blood moves in a circular path in the body and it is always contained in a vessel or the heart, therefore, it is considered a closed system. Blood travels away from the hearth through vessels called arteries, whereas blood travels to the heart through veins. Capillaries, the site of diffusion for oxygen and nutrients into the tissues and for waste and carbon dioxide into the blood, serve as the connection between arteries and veins. In the closed system, blood is pumped through two separate circuits: the systemic circuit (the body) and the pulmonary circuit (the lungs). Deoxygenated blood is carried from the right ventricle of the heart to the lungs of the pulmonary circuit for oxygenation. On the other hand, oxygenated blood is taken from the longs to the left atria and them pumped to the systemic circuit The complete pathway of blood in the human body is as follows: vena cavae, right atria, right ventricle, pulmonary blood flow, left atria, left ventricle, and systemic circulation. The movement of blood through the heart is one complete heartbeat, which has both a ventricular contraction (systole) and ventricular relaxation (diastole), is considered the cardiac cycle. The systolic blood pressure (140 or below) is the pressure during contraction and the diastolic pressure (90 or below) is the pressure during relaxation. Blood pressure itself is described as the force the blood exerts against vessel walls. Using the diastolic and systolic blood pressures, the mean arterial pressure (MAP) can be 1
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calculated through the following formula: MAP= diastolic BP + (systolic BP – diastolic BP) /3. MAP represents the average arterial pressure of one entire cardiac cycle and shows the driving pressure of blood as it travels through the body. When blood flows into the heart, it is termed as the venous return due to blood pressure in the veins. The amount of blood delivered in venous return is directly proportional to the ventricular ejection (cardiac output) or the amount of blood leaving the ventricles. The cardiac output (L/min) is the rate in which blood is pumped through the left ventricle. Cardiac output, also known as Q, depends on the heart rate (number of beats per minute) and the stroke volume (amount of blood pumped by the left ventricle with each beat). Therefore Q=HR x SV. At resting conditions, Q is measured, as 5.0 L/min. Any change in a person’s heart rate or stroke volume will cause a change in the cardiac output. Influences of Q are: the end diastolic volume, peripheral resistance, and the strength of contraction. The end diastolic volume is the amount of blood left in the
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This note was uploaded on 04/07/2008 for the course APK 2105 taught by Professor Brooks during the Fall '07 term at University of Florida.

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physio lab 3 - Introduction The cardiovascular system which...

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