Anatomy & Physiology 34B
Chapter 14 – Autonomic Nervous System
I.
Overview
A. Two divisions of the Peripheral Nervous System (_____)
1. ________________ (voluntary) NS consists of
a. Motor cranial and spinal nerves from the CNS to _________ muscle
b. Sensory nerves from _______________ of the skin, muscles, bones, and joints to the
CNS
2. __________________ (involuntary) NS consists of
a. Motor output from the CNS to the _________, _________ and ______ muscle
b. Receives sensory input from ______________ of the internal viscera to the CNS
II. Introduction to the ANS
A. The autonomic nervous system (ANS) is the general __________ _________ division of
the PNS, and contains two subdivisions
1. _______________ N.S. – involved in “fight or flight” responses; prepares the body for
physical activity
2. ___________________ N.S. – involved in “rest & digest” activities; this division is in
control the majority of the time
B. Involuntary effectors (smooth & cardiac _________ and _______) are regulated by
autonomic motor impulses via the ANS
C. The autonomic motor pathway involves 2 types of _____________ neurons (recall that
the somatic motor pathway had 1 type of motor neuron):
1. _______________ (presynaptic) neurons - have their cell bodies in the gray matter of
the _________ or spinal cord; release ______ neurotransmitter; their axon terminals
synapse with
2. _________________ (postsynaptic) neurons - extend from autonomic ganglia and
synapse with an effector organ
3. Autonomic _____________ are located in the head, neck, & abdomen, and on each
side of the spinal cord (paravertebral)
III. Sympathetic (____________) division - preganglionic neurons exit the spinal cord lateral
horns from ____ to ___ and lead to the sympathetic chain (_______________) ganglia
A. In the thoracolumbar region, each paravertebral ganglion is connected to a spinal nerve by
two branches called ____________
________
1. _________ communicating rami consist of ___________ ____ganglionic fibers
exiting a ventral root to the ganglion
2. _________ communicating rami consist of ______________ ______ganglionic
neurons leaving the ganglion to spinal nerves en route to their target organs
B. After they end in the ganglion, the _______ ___ganglionic neurons may follow several
courses
1. Some synapse in the ganglion with ___________ postganglionic neurons, leading to
_____ __________ of several organ systems
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2. Some ___________ up and down the chain, then synapse with postganglionic neurons
in ganglia at other levels
3. Some pass through the chain without synapsing and continue as ______________
nerves
4. ______ _____ganglionic neurons exit the paravertebral ganglia via three routes
a. Spinal nerve route – from gray ramus to a ________ nerve or its subdivisions; route
to ______ glands, arrector ____ muscles, and blood ___________ of the skin and
skeletal muscles
b. Sympathetic nerve route – along ____________ nerves to the heart, lungs,
esophagus, and ______________ blood vessels
c. Splanchnic nerve route – originates from spinal nerves ___-____; preganglionic
fibers pass through the ganglia to form the __________ nerves, which lead to the
collateral (__________) ganglia (in the abdominal aortic plexus) from which
postganglionic fibers emerge to innervate ________________ organs
5. ____________ glands – sit on top of the kidneys and consist of an outer cortex and an
inner ____________, which secretes the hormones epinephrine (____________) &
norepinephrine
IV. Parasympathetic (_____________) division -preganglionic neurons exit from the midbrain,
brain stem and _________ (cranial nerves III, VII, IX, & X also participate)
A. ______ preganglionic neurons leave the pons, medulla oblongata, and S2-S4 of the
spinal cord and synapse with ____ postganglionic neurons in ____________ ganglia in
or near the target organs
B. Each preganglionic neuron synapses with only about _____ postganglionic neurons; thus
parasympathetic effects are more ______________; no mass activation of organs occurs
C. Parasympathetic fibers leave the brain via four __________ nerves
1. ______________ nerve (CN III) fibers control the ciliary muscle, which controls the
_____, and the pupillary constrictor muscle, which narrows the ________
2. _________ nerve (CN VII) fibers regulate the secretion of tears, __________, and nasal
secretions
3. ___________________ nerve (CN IX) fibers regulate salivation by the ___________
salivary gland
4. ______ nerve (CN X) – carries about __% of all parasympathetic preganglionic fibers;
the vagus travels down the neck and forms
a. Cardiac plexus, which innervates the ________
b. Pulmonary plexus, which innervates the bronchi and blood vessels into the ______
c. Esophageal plexus, which regulates __________
d. ___________, which pass through the diaphragm and contribute to the abdominal
aortic plexus and pelvic __________ nerves that affect the _________________ organs
V. _________________ of the ANS
A. Neurotransmitters & Receptors
1. The parasympathetic NS is called ____________ because both its preganglionic and
postganglionic neurons secrete ____
2 The sympathetic NS is called ___________ because although its preganglionic neurons
secrete ____, most of its _____ganglionic neurons release norepinephrine (___)
3. Cholinergic receptors on target tissues bind _____
4. Adrenergic receptors on target tissues bind ______________
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5. Target tissues that respond to both parasympathetic and sympathetic influences have
both __________ and __________ ___________ in their cell membranes
B. __________ Receptors include 2 types of receptors that bind ACh
1. ________________ receptors bind nicotine, as well as ACh and other drugs that
resemble nicotine (e.g., curare)
a. These receptors are found on all ______ganglionic neurons, in the adrenal
__________, and on __________ muscle fibers
b. When ACh binds to these receptors, excitatory postsynaptic potentials (______s) are
produced
2. ______________ receptors bind muscarine, a mushroom poison, in addition to ACh
and other drugs that resemble muscarine (e.g., atropine)
a. These receptors occur on all ______, ________ muscle, and _________ muscle cells
that receive cholinergic innervation
b. When ACh binds to these receptors, the effect may be either excitatory or inhibitory
(e.g., ______s in intestinal smooth muscle, but inhibitory postsynaptic potentials
_______s in cardiac muscle)
C. __________ Receptors are G protein-linked and function by means of ______
_________ ; they include 2 main types plus several subclasses
a. _____ receptors - found in smooth muscle of the skin blood vessels and abdominal
_____________; NE binding causes vasoconstriction and dilates eye pupil
b. _____ receptors – found in adrenergic axon terminals and pancreas; NE binding
____________ NE release from axons and insulin secretion from pancreas
2. _________ adrenergic receptors – NE binding to these receptors is usually inhibitory,
with some exceptions. Subclasses are
a. _____ receptors - found in ___________ muscle and kidneys; NE and epinephrine
binding increases heart rate and strength, and renin release by kidneys.
b. _____ receptors are not associated with sympathetic neurons, and respond more to
_____________; found in lung bronchi, and blood vessels of heart, liver and skeletal
muscle; allows ______________ in blood vessels and bronchioles
3. Different ______________ on target cell membranes can allow different effects when
stimulated by ACh or NE
a. NE binding to ___________ adrenergic receptors in many blood vessels (e.g., to
digestive organs) causes vaso_______________
b. NE binding to __________ adrenergic receptors in heart and skeletal muscle blood
vessels causes vaso___________
D. ______ Innervation - both sympathetic & parasympathetic divisions innervate most of
the _____ organs, causing antagonistic or cooperative effects (see comparison table in text)
1. _______________ effects oppose each other (e.g., sympathetic stimulation _____ up
the heart, parasympathetic ______ it down)
2. _____________ (agonistic) effects occur when the two divisions act on different
effectors to produce a ___________ overall effect (e.g., for salivation parasympathetics
stimulate salivary gland ______ cells, while sympathetics stimulate salivary ______
cells)
3. Examples of _________________ (“fight or flight”) responses:
a. Dilates _________
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b. Stimulates _______ glands
c. Vaso__________ blood vessels to glands and internal organs
d. Dilates ____________ and blood vessels to heart & skeletal muscles
e. Stimulates adrenal ____________ to secrete epinephrine & norepinephrine into the
blood stream
f. Increases _______ _______ and force of contraction, as well as blood pressure
g. Stimulates break down and release of __________ from liver and lipids from fat
cells to supply __________ to blood stream
4. Examples of _________________________ (“rest & digest”) functions
a. Pupils are _____________
b. Glands are stimulated to __________
c. Heart rate is _________ and steadied
d. Blood vessels to heart and bronchioles are vaso__________
e. Smooth muscle of bladder and digestive organs are contracted, promoting
_______________.
E. Control Without Dual Innervation
1. Certain organs, such as the adrenal medulla, arrector pili muscles, sweat glands, and
many blood vessels receive only _____________ fibers
2. Sympathetic fibers to a blood vessel have a baseline firing frequency called
_____________ tone
a. This keeps the vessels in a partial state of constriction called ____________ tone
b. An increase in firing frequency causes vaso_____________ by increasing smooth
muscle contraction
c. A decrease in firing frequency causes vaso____________ by allowing the smooth
muscle to relax
d. In this manner the _____________ NS can _____ blood flow from one area to
another according to the needs of the body
F. ANS functions are also regulated by four regions of the _____
1. Cerebral ______, especially the ____________ part of the emotional brain exerts
autonomic effects through the hypothalamus and the ANS
2. _______________ – contains important nuclei for many visceral functions and is
involved in __________ and drives that act through the ANS. Fight or flight
responses begin here
3. _______________ formation – contains centers for cardiac, vasomotor, and
__________________ function, and receives visceral input via the ______ nerve. It
can integrate and respond to this input without the rest of the brain
4. _________________ – can integrate autonomic responses, such as defecation and
urination reflexes, without brain involvement
G. Autonomic agonists and antagonists are important tools in research and _____________
1. ______________ are molecules that bind to a receptor and mimic the effect of the
receptor’s normal ligand. Examples:
a. _____________ binds to nicotinic receptors and mimics ACh
b. _____________ (a mushroom chemical) binds to muscarinic receptors and mimics
ACh
2. ________________ are molecules that bind to a receptor and block the receptor’s normal
neurotransmitter action. Examples:
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a. ______________, a poison, binds to nicotinic receptors and blocks ACh; paralysis
results because the nerve impulse cannot be transmitted to postganglionic neurons or
muscle tissue
b. ______________ (bella donna) is a poison that binds to muscarinic receptors and
blocks parasympathetic responses
3. Many ___________ used to treat depression act either on
a. Membrane _______________ for neurotransmitters (e.g., selective serotonin reuptake
inhibitors, “_________s,”allow serotonin to remain in synapses longer) or
b. ________________ of the neurotransmitters (e.g., monoamine oxidaze “______”
inhibitors )
4. Discovery of α and β adrenergic receptors led to the development of drugs that block only
_________ of the receptor types
a. Beta blockers prevent high blood pressure by blocking _____ receptors on the heart
and kidneys