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Chapter 15

Anatomy and Physiology HAP101 Chapter Notes - Chapter 15: Otic Ganglion, Pterygopalatine Ganglion, Renal Plexus

Anatomy and Physiology
Course Code
Anatomy and Physiology HAP101
Tania Killian

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HAP101 Chapter 15: The Autonomic Nervous System
LO 15.1: Compare the sympathetic and parasympathetic divisions of the ANS
Includes both sensory and motor neurons
o Sensory neurons convey input from receptors for somatic senses (tactile, thermal, pain, and proprioceptive
sensations) and from receptors for the special senses (sight, hearing, taste, smell, and equilibrium). These neurons
are consciously perceived
o Motor neurons innervate skeletal muscles and produce both reflexive and voluntary movements. When this type of
neuron stimulates the muscle, it contracts; the effect always is excitation. If the neurons cease to stimulate a muscle,
the result is a paralyzed, limp muscle that has no muscle tone
Main input to the ANS comes from autonomic (visceral) sensory neurons. These neurons are associated with interoceptors,
which are sensory receptors located in blood vessels, visceral organs, muscles, and the NS that monitor conditions in the
internal environment
Input that influences the ANS also includes some sensations monitored by somatic sensory and special sensory neurons.
Autonomic motor neurons regulate visceral activities by either increasing (exciting) or decreasing (inhibiting) ongoing
activities in their effector tissue. Unlike
Most autonomic responses cannot be consciously altered to any great degree. Thus, some autonomic responses are the basis
for polygraph testing. Yet, there are some techniques (e.g. medication) that may help in regulating at least some autonomic
Conscious control can be learnt through the use of biofeedback, monitoring devices that display information about a body
Comparison of Somatic and Autonomic Motor Neurons
Autonomic motor pathways consist of two motor neurons, in which one follows the other
o The first neuron (preganglionic neuron). This neuron has its cell body in the CNS and its myelinated axon extends
from the CNS to an autonomic ganglion (ganglion is a collection of neuronal cell bodies in the PNS).
o The second neuron (postganglionic neuron) has its cell body in that same autonomic ganglion. Its unmyelinated
axon extends directly from the ganglion to the effector.
The output part of the ANS has two divisions:
o The Sympathetic Division: often referred to as the “fight – or flight” division because its stimulation leads to an
increased alertness and metabolism
o The Parasympathetic Division: often referred to as the “rest – and digest” division because it stimulation leads to
a decrease in most bod activity
Somatic Nervous System
Autonomic Nervous System
Sensory Input
From somatic sense and special senses
Mainly from interoceptors; some from somatic sense ad special
Control of Motor
Voluntary control from cerebral cortex,
with contributions from basal ganglia,
cerebellum, brain stem, and spinal cord
Involuntary control from hypothalamus, limbic system, brain
stem, and spinal cord; limited control from cerebral cortex
Motor Neuron
One-neuron pathway: somatic motor
neurons extending from CNS synapse
directly with effector
Usually two-neuron pathway: preganglionic neurons extending
from CNS synapse with postganglionic neurons in autonomic
ganglion, and postganglionic neurons extending from ganglion
synapse with visceral effector.
NTs and
All somatic motor neurons release only
acetylcholine (Ach)
All sympathetic and parasympathetic preganglionic neurons
release Ach. Most sympathetic postganglionic neurons
norepinephrine; those to most sweat glands release Ach. All
parasympathetic postganglionic neurons Ach.
Skeletal muscle
Smooth muscle, cardiac muscle, and glands
Contraction of skeletal muscle
Contraction or relaxation of smooth muscle; increased or
decreased rate and force of contraction of cardiac muscle;
increased or decreased secretions of glands
LO 15.2: Describe preganglionic and postganglionic neurons of the ANS
Each division of the ANS has two motor neurons.
o Preganglionic Neuron: its cell body is in the brain or spinal cord; its axons exist the CNS as part of a cranial or
spinal nerve. Its axon is a myelinated and small in diameter, extending to an autonomic ganglionic.
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