1. Chapter 18 Autonomic Nervous System
Co 18
Chapter 18 Autonomic Nervous System

2. Somatic Nervous System
Fig. 18.1
Somatic Nervous System
Somatic Nervous System
Sends stimuli from vision, hearing, equilibrium, smell, taste, touch, proprioception to CNS
Carries voluntary (conscious and unconscious) nerve impulses for skeletal muscle control
Posterior root ganglion
Somatic sensory neuron detects stimuli and transmits nerve impulses from skin, skeletal muscle, joints, and special senses (vision, hearing, etc.).
Anterior root
Somatic motor neuron
sends nerve impulses to
skeletal muscle.
Skeletal muscle
Sensory receptor
in skin
(a)

3. Autonomic Nervous System
Fig. 18.1
Autonomic Nervous System
AKA visceral nervous system
Works reflexively and without awareness
Visceral sensory components sense stimuli from blood vessels and internal organs
Autonomic motor components transmit nerve impulses to cardiac muscle, smooth muscle, and glands
Autonomic Nervous System
Autonomic
ganglion
Preganglionic autonomic motor neuron transmits nerve impulses to a ganglionic motor neuron.
Ganglionic autonomic
motor neuron transmits
nerve impulses to smooth
muscle, cardiac muscle,
and glands.
Visceral sensory
neuron detects
stimuli within blood
vessels and smooth
muscle in the
viscera.
Smooth muscle
in trachea
Sensory receptor
in viscera
(b)

4. Fig. 18.2 Lower Motor Neurons of Autonomic Nervous System
Preganglionic neuron extends from brainstem or spinal cord, axon exits CNS in cranial or spinal nerve
Autonomic ganglion is where pre- and post-ganglionic neurons synapse; houses ganglionic neuron cell body
Ganglionic neuron cell body attached to postganglionic axon
Autonomic ganglion
Postganglionic axon
Preganglionic axon
Preganglionic neuron cell body
Ganglionic neuron cell body
Spinal cord
Effector organ (e.g., cardiac
muscle, smooth muscle, or
gland)
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5. Two-neuron system enables more complex signaling and better control
Page 540 1
“Preganglionic” flight from Indianapolis
to Chicago (autonomic ganglion)
Chicago
Indianapolis
Miami 2
“Postganglionic” flight
from Chicago to Miami
(effector organ)
Two-neuron system enables more complex signaling and better control
Neuronal convergence and neuronal divergence

6. Sympathetic vs. Parasympathetic Divisions of Autonomic Nervous System
Fight-or-flight response
increased heart rate and blood pressure, decreased digestion
Rest-and-digest response
decreased heart rate and blood pressure, increased digestion

7. Overview of Parasympathetic Pathways
Parasympathetic division aka craniosacral div—conservation of energy and replenishment of nutrient stores (“rest-and-digest”), most active during times body must process nutrients, conserve energy, attempt to return to homeostasis = lack of extensive divergence in preganglionic axons prevents mass activations as seen in symp
Structurally simpler than symp div; pregang neurons housed within nuclei in brainstem & within lateral grey matter of S2-S4 spinal cord segments
Ganglionic neurons in parasym found in either terminal ganglia (located close to target organ) or intramural ganglia (located within wall of target organ)
CN III oculomotor, VII facial, IX glossopharyngeal = convey parasympathetic innervation to the head
(diff post gang axons CNIII innerv results in lens accommodation- more rounded so can see close-up objects, and pupil constriction from bright light)
(CN VII – control production/secretion of tears, nasal secretions, saliva – part of why your moth salivates when you smell an aromatic meal)
(CN IX – also causes increase in saliva – from diff salivary glands than VII)
CN X vagus= parasympathetic stimulation for thoracic and most abdominal organs, plus gonads – almost 80% parasym pregangl axons are transmitted through this nerve
(vagus = wanderer, wandering pathway of vagus nerve as projects inferiorly thru neck and throughout trunk)
(thoracic cavity: increased mucous production, decreased diameter in airways, decrease heart rate and force of heart contractions
Abdominal cavity: increased smooth muscle motility-muscle contraction- and secretory activity in digestive tract organs)
Remaining pregang parasym axons originate from pregang neuron cell bodies within later gray matter of S2-S4 spinal cord segments – branch to form the pelvic splanchnic (“splangknik”: visceral) nerves, contribute to hypogastric plexus then project from there to gangl neurons eithin either terminal or intramural ganglia; targets innervated: distal portion large intestine, rectum, most reproductive organs, urinary bladder, distal part of ureter – causes smooth muscle motility and secretory activity in digestive organs, muscle contraction in bladder, erection of clitoris & penis
Figure 18.5

8. Overview of Sympathetic Pathways
Sympathetic trunk ganglia
Sympathetic division aka thoracolumbar div—preparation of body for emergencies (“fight-or-flight”); much more complex than parasym div anatomically/functionally
sym preganglionic neuron cell bodies housed in lateral horn of T1-L2 segments of spinal cord
travel with somatic motor neuron axons to exit spinal cord and enter the anterior roots and then the T1-L2 spinal nerves – then shortly after that enter into the left and right sympathetic trunks immediately lateral to vert column (look like pearl necklaces – string = bundles of axons, “pearls” = symapthetic trunk ganglia aka paravertebral or chain ganglia, house symp ganglionic neuron cell bodies)
One trunk ganglion associated with each spinal nerve (approx), cervical portion of each sympathetic trunk partitioned into 3 symp trunk ganglia (vs 8 cervical spinal nerves): superior cerv ganglion = postgang symp neuron cell bodies with axons distributed throughout head and neck, innerv sweat glands there, smooth muscle in blood vessels, dilator pupillae muscle, muscle to elevate eyelid (middle and inferior extend to thoracic viscera)
Figure 18.6