Download Chapter 15 ()

Anatomy Lecture Notes
Chapter 15
ANS = general visceral motor portion of PNS
sympathetic
"fight or flight"
prepares body for emergencies and intense
division
muscular activity
parasympathetic "rest and digest" maintains body, conserves and stores energy
division
both divisions innervate cardiac m., smooth m., and glands (dual innervation)
divisions usually cause opposite effects in effector organs
A. ANS pathway has 3 components
1. preganglionic neuron - CNS to ganglion
2. ganglion (autonomic motor)
3. postganglionic neuron - ganglion to effector
B. anatomical comparison
1. origin (location of preganglionic neuron cell bodies)
S: lateral gray horn, thoracic and lumbar spinal cord
P: brain stem and sacral spinal cord
Strong/Fall 2008
page 1
Anatomy Lecture Notes
Chapter 15
2. relative length of pre- and postganglionic neurons
sympathetic
parasympathetic
preganglionic
postganglionic
3. location of ganglia
a. sympathetic
paravertebral (sympathetic chain) ganglia - chain lateral to spinal column
prevertebral (collateral) ganglia - ventral body cavity
b. parasympathetic
terminal (intramural) ganglia in effector organs
cranial ganglia
4. divergence of preganglionic neurons
a. sympathetic - extensive
b. parasympathetic - minimal
Strong/Fall 2008
page 2
Anatomy Lecture Notes
Chapter 15
C. neurotransmitters
cholinergic neurons - acetylcholine (Ach)
adrenergic neurons - norepinephrine (NE)
preganglionic
sympathetic
parasympathetic
* except in skeletal blood vessels and sweat glands
postganglionic
D. parasympathetic outflow
1. cranial nerves
a. oculomotor
preganglionic neurons in midbrain
ganglion = ciliary ganglion
postganglionic neurons innervate intrinsic muscles of eye: ciliary and iris
b. facial nerve
preganglionic neurons in pons
ganglia = pterygo-palatine and submandibular
postganglionic neurons innervate :
submandibular & sublingual salivary glands
lacrimal gland
nasal mucus glands
c. glossopharyngeal nerve
preganglionic neurons in medulla oblongata
ganglion = otic
postganglionic neurons innervate parotid gland
d. vagus nerve
preganglionic neurons from medulla via plexuses
ganglia = intramural
postganglionic neurons innervate most visceral organs of thorax and
abdomen
2. sacral
preganglionic neurons in S2-S4
pelvic splanchnic nerves
ganglia = intramural
postganglionic neurons innervate pelvic organs
Strong/Fall 2008
page 3
Anatomy Lecture Notes
Chapter 15
E. sympathetic outflow
1. preganglionic neuron cell bodies in lateral gray horn of segments T1-L2
axons leave spinal nerve in white ramus
2. pathways of preganglionic neurons
a. synapse with postganglionic neuron in paravertebral ganglion; return to
spinal nerve in gray ramus
same segment
inferior or superior segment
b. pass through paravertebral ganglia to synapse with postganglionic neuron in
a prevertebral ganglion
splanchnic nerves
Strong/Fall 2008
page 4
Anatomy Lecture Notes
Chapter 15
F. adrenal medulla
specialized sympathetic ganglion
chromaffin cells are modified postganglionic cells without axons
secrete norepinephrine and epinephrine into circulation
G. control of ANS
1. reticular formation contains vital reflex centers that control organs via autonomic
nerves
2. hypothalamus integrates both ANS divisions and links ANS to limbic system
3. cerebral cortex can be used to indirectly and temporarily control some autonomic
functions
H. visceral sensory neurons
general visceral sensory neurons monitor viscera for pain, temperature, chemicals,
stretch
neuron cell bodies are in dorsal root ganglia
axons project to thalamus and cerebral cortex
Strong/Fall 2008
page 5