Regulation and Integration of the Body
Parasympathetic eﬀects are highly localized and
Control of Autonomic Function
Autonomic function is controlled at several levels: (1) Te spinal
cord and brain stem (particularly medullary) centers mediate
reﬂex activity. (2) Hypothalamic integration centers interact
with both higher and lower centers to orchestrate autonomic,
somatic, and endocrine responses. (3) Cortical centers inﬂuence
autonomic function via connections with the limbic system.
Conscious control of autonomic function is rare but possible, as
illustrated by biofeedback training.
Homeostatic Imbalances of the ANS
Most autonomic disorders reﬂect problems with smooth muscle
control. Abnormalities in vascular control, such as hypertension,
Raynaud’s disease, and autonomic dysreﬂexia, are most
Developmental Aspects of the ANS
Preganglionic neurons develop from the neural tube;
postganglionic neurons develop from the embryonic neural crest.
Te eﬃciency of the autonomic nervous system declines in
old age, as reﬂected by decreased gland secretion, reduced
gastrointestinal motility, and slower sympathetic vasomotor
responses to changes in position.
The Effects of Drugs
Drugs that mimic, enhance, or inhibit the action of ANS
neurotransmitters are used to treat conditions caused by
excessive, inadequate, or inappropriate ANS function. Some
drugs bind with only one receptor subtype, blocking or
enhancing speciﬁc ANS-mediated activities.
Interactions of the Autonomic Divisions
Most visceral organs are innervated by both parasympathetic
and sympathetic divisions. Te divisions interact in various
ways but usually exert a dynamic antagonism. Antagonistic
interactions mainly involve the heart, respiratory system, and
gastrointestinal organs. Sympathetic activity increases heart
activity, dilates bronchioles, and depresses gastrointestinal
activity. Parasympathetic activity reverses these eﬀects.
Most blood vessels are innervated only by sympathetic ﬁbers and
exhibit vasomotor tone. Parasympathetic activity dominates the
heart and muscles of the gastrointestinal tract (which normally
exhibit parasympathetic tone) and glands.
Te two ANS divisions exert cooperative eﬀects on the external
Roles unique to the sympathetic division are regulating blood
pressure, shunting blood in the vascular system, regulating
body temperature, stimulating the kidneys to release renin, and
Activation of the sympathetic division can cause widespread,
long-lasting mobilization of the ﬁght-or-ﬂight response.
(Some questions have more than one correct answer. Select the best
answer or answers from the choices given.)
All of the following characterize the ANS except
presence of nerve cell bodies in the CNS,
presence of nerve cell bodies in the ganglia
Relate each of the following terms or phrases to either the
division of the autonomic
short preganglionic, long postganglionic ﬁbers
otic and ciliary ganglia
generally short-duration action
increases heart rate and blood pressure
increases gastric motility and secretion of lacrimal,
salivary, and digestive juices
innervates blood vessels
most active when you are relaxing in a hammock
active when you are running in the Boston Marathon
Preganglionic neurons develop from
neural crest cells,
neural tube cells,
alar plate cells,
Te white rami communicantes contain what kind of ﬁbers?
Collateral sympathetic ganglia are involved with innervating
all of these.
Short Answer Essay Questions
Brieﬂy explain why the following terms are sometimes used to
refer to the autonomic nervous system: involuntary nervous
system and emotional-visceral system.
Describe the anatomical relationship of the white and gray rami
communicantes to the spinal nerve, and indicate the kind of
ﬁbers found in each ramus type.
Indicate the results of sympathetic activation of the following
structures: sweat glands, eye pupils, adrenal medullae, heart,
bronchioles of the lungs, liver, blood vessels of vigorously
working skeletal muscles, blood vessels of digestive viscera,
Which of the eﬀects listed in response to question 8 would be
reversed by parasympathetic activity?
Which ANS ﬁbers release acetylcholine? Which release
Describe the meaning and importance of sympathetic tone and
List the receptor subtypes for ACh and NE, and indicate the
major sites where each type is found.
Which area of the brain is most directly involved in mediating
Describe the importance of the hypothalamus in controlling the
autonomic nervous system.
Describe the basis and uses of biofeedback training.