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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:
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
(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
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.
- Winter '13