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BPLab(Edit1) - The Effect of Extremity Positions During...

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The Effect of Extremity Positions During Rest on Blood Pressure Nolan Chung, Megan Marsh, and Emily Wozobski EXSC 405 (Monday, 11:00 am) 12 October 2009 Introduction
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Blood pressure is very important during rest and exercise, as it is blood pressure that determines the rate at which blood flows through the circulatory path (Brooks, 2005). However, blood pressure is not constant and can be affected by many factors. Innate factors such radius and length of the vessel, blood volume, and viscosity of the blood all affect blood pressure. External influences such as the position of the body in space, exercise, and changes in hormonal levels also cause blood pressure to change (Donovan, 2009). There are two types of blood pressure regulation: short term and long term. Short term regulation is controlled by the sympathetic and parasympathetic nervous systems. Baroreceptors in the aorta monitor and alter the rate of sensory nerve impulses sent to the cardiac and vasomotor control centers in the brain, which adjust blood pressure accordingly (Donovan, 2009). Long-term regulation of blood pressure is accomplished through juxtaglomerular cells in the kidneys, which release certain enzymes and control sodium and water reabsorption (Donovan, 2009). This laboratory experiment specifically examined the way that body position affected blood pressure. During instances where the subject is in a supine position, heart rate is typically lower, and thus cardiac output diminishes. Because cardiac output is a key determinant of blood pressure, it is thus assumed that blood pressure should be lower in a supine position when compared to a standing or sitting position (Brooks, 2005 ). Total peripheral resistance also plays a key role in blood pressure. If one extends their extremities away from the heart, there is a change in the force with which the heart must pump to overcome the push of gravity while distributing blood throughout the body. This increases total peripheral resistance, thus increasing blood pressure. Gravity also affects venous return to the heart. If venous return is lowered, blood pressure is ultimately lowered as well, because venous return has direct relationships with end diastolic volume, stroke volume, and cardiac output (Donovan, 2009). It is important to study the effect of body position on blood pressure because in clinical
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This note was uploaded on 02/03/2010 for the course EXSC 407AL at USC.

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BPLab(Edit1) - The Effect of Extremity Positions During...

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