Download Thoracic Viscera -> by following Cardiopulmonary splanchnic nerve

Autonomic Nervous System
Monday, February 2, 2015
9:29 AM
ANS is divided into two parts
- Sympathetic
○ Fibers originate in Throacolumbar SC levels
○ Active during stress, competition, fear, excitement
○ Functions are Catabolic in nature
- Parasympathetic
○ Fibers originate in cranial and sacral levels
○ Active during relaxation, digestion, calm
○ Functions are anabolic in nature
Primary functions of ANS
Neuroanatomy Page 1
-Even though urination/defecation is via parasympathetic, incontinence during stressful events can be
caused by an overshoot of sympathetic stimulation being corrected by parasympathetic
-Important notes:
- Skin has NO PARASYMPATHETIC Stimulation -> NO BLOOD VESSELS/SWEAT
GLANDS/ARRECTOR PILI MUSCLE innervation
- Even though sympathetic stimulation causes vasoconstriction, it actually causes DILATION
in CORNARY arteries.
- Heart has intrinsic ability to beat -> ANS controls heart RATE and Contractility not the
actual ability to beat
General ANS Organization
- Remember that somatic motor neurons have monosynaptic neurons in anterior horn and
synapse directly onto the muscle
- ANS has Pre-ganglionic (PrG) and Post-ganglionic (PoG) neurons
○ PrG are in CNS and project out to synapse onto PoG
○ The PoG then leaves its respective ganglia and synapses on effectors
 Effectors include Glands, Cardiac Muscle, smooth muscle, and adipose
 Most effectors are dual innervated by sympathetic and parasympathetic =>
antagonistic effects on effectors
- ANS PrG axons are MYELINATED
○ Parasympathetic system has LONG PrG axons and synapse at ganglia near
effector(target) organs
○ Sympathetic system has SHORT PrG axons and synapse at ganglia near spinal cord
Sympathetic Division
- ANS fibers leave SC via VENTRAL root
- PrG cell bodies for sympathetic are located in intermediolateral cell column of T1-L2/L3
- PoG cell bodies are located in one of two ganglia, named for where they are anatomically
○ Paravertebral Ganglia = sits lateral to vertebral column
 C1-C4 => Superior Cervical Ganglion
□ How sympathetic fibers reach head
 C5-C6 => Middle Cervical
 C7-C8 => Inferior Cervical
□ If fused at C7-T1 => Stellate Ganglion
 Thoracic/Lumbar/Sacral Ganglion
 Ganglion impar (where both chains meet near coccyx)
○ Prevertebral (preaortic) Ganglia = ganglia sits on aorta
 Celiac Ganglia
 Superior Mesenteric Ganglia
 Aorticorneal Ganglia
 Inferior mesenteric ganglia
○ PrG can also synapse at Adrenal Medulla with Chromaffin Cells which are modified PoG
neurons in adrenal gland => releases Epi/NE into blood
- Sympathetic Pathways
○ For the most part, the nerves that travel to effector organs are named after the arteries
they run with
Neuroanatomy Page 2
○ PrG leave ventral roots and go to either ganglia or adrenal medulla
 If entering paravertebral ganglion, PrG enter via WHITE RAMI COMMUNICANS (more
lateral)
□ NO WHITE RAMI ABOVE T1 or BELOW L2, ONLY GRAY RAMI -> neuronal cell
bodies are only at T1-L2 so axons have already entered Ganglia
 PrG can ascend or descend in Paravertebral ganglia before synapsing
○ PoG leave ganglion and synapse at effector organ
 If leaving paravertebral ganglion, PoG leave via GRAY RAMI COMMUNICANS (more
medial)
 PoG can project to:
□ Body Surface -> by following spinal nerve going to its target dermatome
Effectors include Sweat gland, blood vessels, arrector pilli
□
Head -> by following Carotid nerve above superior cervical
ganglion
 Effectors include Iris and face/head
□ Thoracic Viscera -> by following Cardiopulmonary splanchnic nerve
 Effectors include heart and respiratory tree
 These nerves are near CERVICAL region due to organ migration during
embryological development
 *POST-Ganglionic travels via Cardiopulmonary splanchnic nerve
□Abdominopelvic Viscera -> by following abdominal splanchnic nerve
 Effectors include GI Tract and other viscera
 *NOTE*: PRE-Ganglionic travels via abdominal splanchnic nerve
THEN synapses
- Sympathetic nuclei have Somatotropic distribution in terms of origination
○ Upper Limbs -> T1-T6
 Eye -> T1-T2
 Heart/Lungs/Esophagus -> T4-T6
○ Body Wall -> T7-T11
○ Lower Limbs -> T11-L2
Parasympathetic Division - PrG
neuron bodies are in:
Neuroanatomy Page 3
○ Brainstem Nuclei
 Axons travel via
□ CN 3 to Ciliary Ganglion => constricts iris
□ CN 7 to Pterogopalatine ganglion and submandibular ganglion => Lacrimal
glands and submandibular/sublingual glands respectively
□ CN 9 to Otic Ganglion => Parotid salivary glands
□ CN 10 to intrinsic ganglia of organs => Parasympathetic control of Thorax
(lungs/heart) and upper 2/3 of abdominal organs
 CRANIAL NERVES HAVE NO SYMPATHETIC FUNCTION ONLY PARASYMPATHETIC
○ Lateral horn of Sacral Spinal cord (S2-4)
 Axons of PrG leave via pelvic splanchnic nerve
 Exert Parasympathetic control over GU and distal digestive tract
Abdominal (Autonomic) Plexus
- Are networks of nerve fibers typically consisting of the Long axons of the ANS aka PrG
PARASYMPATHETIC axons and PoG SYMPATHETIC axons with some afferent axons (not part of
ANS)
-ANS is autonomic but still controlled by higher levels in CNS -> Hypothalamus
- Hypothalamus is main integration center of ANS
○ Signals for change in response to osmoreceptors, temperature changes, and feeding/satiety
centers
○ Sends signals to Vagal nucleus and PrG cell bodies in Spinal Cord
Dr. Ochs talks more about neurotransmitters of ANS but briefly
- Somatic is single axon system -> ACh
- All PrG of ANS -> ACh
- All PoG of Parasympathetic and sweat glands of sympathetic -> ACh
- Most PoG to organs for Sympathetic -> NE
- Chromaffin cells from Medulla -> Epi/NE
Neurotransmitter Pathway of the ANS
Neuroanatomy Page 4