Sympathetic and Parasympathetic Tone

Sympathetic and Parasympathetic Tone -...

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Sympathetic and Parasympathetic Tone  With few exceptions, the vascular system is entirely innervated by sympathetic fibers that keep  the blood vessels in a continual state of partial constriction. When faster blood delivery is  needed, these fibers cause the vessels to constrict and blood pressure to rise. When blood  pressure is to be decreased, the vessels are allowed to dilate.  Drugs (phentolamine) that interfere with the activity of these vasomotor fibers are often used to  treat hypertension.  During circulatory shock or when more blood must be provided to meet the increased needs of  working skeletal muscles, blood vessels serving the skin and abdominal viscera are strongly  constricted. This "blood shunting" helps to maintain circulation to vital organs or enhance blood  delivery to skeletal muscles.  The parasympathetic effects normally dominate the heart and smooth muscles of the digestive  and urinary tract organs. The parasympathetic division prevents unnecessary heart acceleration 
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This note was uploaded on 11/22/2011 for the course BSC BSC1085 taught by Professor Sharonsimpson during the Fall '10 term at Broward College.

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Sympathetic and Parasympathetic Tone -...

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