Anatomy and Physiology Answer Key

Preganglionic fibers are short and release

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Unformatted text preview: anglionic fibers are long and postganglionic fibers are very short. All parasympathetic fibers (pre- and postganglionic) are cholinergic and liberate acetylcholine. The parasympathetic NS is more active in conserving energy and replenishing energy reserves ('feed or breed' or 'rest and digest'). 2. Autonomic nervous system controls visceral motor functions through reflex activity. Examples: Pupil reflex: Cranial reflex to light. Stimulation of the eye by bright light causes reflex constriction of the pupil mediated through the parasympathetic nervous system. Control of heart rate: Increase in arterial pressure causes reflex stimulation of the cardioinhibitory centre through the parasympathetic division, slowing heart rate and decreasing arterial BP to normal. If BP falls, reflex acceleration of the heart takes place: the baroreceptors do not stimulate the cardioinhibitory centre, and the accelerator centre (sympathetic) is free to dominate. A similar reflex (the Bainbridge or right heart reflex) operates in response to increased venous return. Increased return of blood to the heart causes reflex stimulation of the accelerator centre, causing heart rate to increase (sympathetic). 3. Bladder emptying is under reflex control and is stimulated by stretching of the bladder wall. Stretching causes both a conscious desire to urinate and an unconscious reflex contraction of the bladder wall and relaxation of the internal urethral sphincter. The conscious part of the brain also sends impulses to Nervous Regulatory Systems (page 70) 1. 2. (a) The sensory receptors receive sensory information (information about the environment) and respond by generating an electrical response (message). (b) The central nervous system (CNS) processes the sensory input and coordinates an appropriate response (through motor output). (c) A system of effectors bring about an appropriate response. Note: Together these systems function to bring about appropriate (adaptive) responses to the environment so that homeostasis is maintained. (a) an...
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This document was uploaded on 01/28/2014.

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