Structure of the Autonomic Nervous System

thoracic part of sympathetic trunk

10-12 pairs of ganglia interconnected by interganglionic fibers and to the corresponding spinal nerves by the communicating rami (white and gray) -1st of this is fused with inferior cervical ganglion to form stellate ganglion -thoracic splanchnic nerves: preganglionic fibers that traverse thoracic ganglia without synapsing and extend into abdomen where they synapse on postganglionic neurons

1. myenteric (Auerbach's) plexus: controls GI movement 2. submucosal (Meissner's) plexus: controls GI secretion, local blood flow, and local movement of the mucosa

2 plexuses of neurons embedded in the wall of the digestive tract from esophagus to anus

superior, middle, and inferior cervical ganglion interconnected by interganglionic fibers

3 ganglia of cervical part of sympathetic trunk

1. sympathetic nervous system 2. parasympathetic nervous system 3. enteric nervous system

3 subdivisions of ANS

sacral part of the sympathetic trunk

3-4 pairs of ganglia and single ganglion impar -NO white communicating rami -connected to inferior hypogastric plexus by sacral splanchnic nerves

ciliac, aorticorenal, superior mesenteric, and inferior mesenteric ganglia

4 ganglia of prevertebral ganglia

lumbar part of sympathetic trunk

4 pairs of ganglia- connected to each other and thoracic and sacral sympathetic trunks by interganglionic fibers -lumbar splanchnic nerves: preganglionic fibers that pass through lumbar ganglia and end in prevertebral ganglia

1. ciliary ganglion (CN III) 2. pterygopalatine (sphenopalatine) ganglion (CN VII) 3. otic ganglion (CN IX) 4. submandibular ganglion (CN VII)

4 parasympathetic ganglia in the head region

parasympathetic -sympathetic is opposite: short preganglionic neurons and long postganglionic neurons -preganglionic are myelinated, postganglionic are not

Which division of the ANS have long preganglionic neurons and short postganglionic neurons? Which are myelinated?

-sympathetic: acetylcholine by preganglionic neurons and acetylcholine or norepinephrine by postganglionic neurons -parasympathetic: acetylcholine by both neurons

Which neurotransmitters are released by the sympathetic and parasympathetic nervous systems?

sympathetic trunk (chain) -divided into cervical, thoracic, lumbar, and sacral parts

a chain of paravertebral ganglia on each side of the vertebral column

gray communicating rami

after the synapse of preganglionic neurons, the unmyelinated axons of the postganglionic neurons form the ____ _____ _____

ganglion impar (of Walther)

caudally, the R and L trunks/chains converge and end on a single ganglion ventral to the coccyx or at the level of the sacrococcygeal joint

modified postganglionic sympathetic cells (sympathicoblasts or chromaffin cells)

cells in the adrenal medulla

1. constricted pupil (miosis) 2. partial drooping of the upper eyelid (partial ptosis) 3. absence of sweating (anhidrosis) on the face of the affected side

classical triad of symptoms for Horner syndrome

-heart rate: increases -bp: increases (constricts arterioles) -bronchioles: dilates -blood vessels in skin: constricts; in skeletal and heart muscles: dilates -GI motility: inhibits -bladder contractility: inhibits

how does the sympathetic nervous system act on: heart rate, blood pressure, bronchiole tone, blood vessels in skin and skeletal and heart muscles, GI motility, and bladder contractility

-autonomic: preganglionic and postganglionic neurons (connect CNS to organ)-> 2 neuron pathway -somatic: one neuron connects CNS to organ

how many neurons make up the autonomic and somatic nervous systems?

1. brain stem 2. spinal cord 3. hypothalamus 4. cerebral cortex

integrating and processing centers in the CNS connected to ANS

enteric nervous system

local nervous system of the digestive system

preganglionic neurons arise from pelvic splanchnic nerve (Nervi erigentes), enter hypogastric plexus of their respective side, and innervate the lower portion of GI and genitourinary tract- Regulate bladder and rectum emptying and genital erection

parasympathetic ganglia from sacral part

interganglionic fibers

paravertebral ganglia are paired (R and L) and those on the same side are interconnected by what?

cervical part of sympathetic trunk

part of sympathetic trunk cranial to the 1st rib involved in sympathetic innervation of the organs of the head, neck, upper limb, heart and lungs -NO white communicating rami

white communicating rami

preganglionic neurons exit spinal cord through ventral root and separate from rest of ventral root fibers to enter paravertebral ganglia as ____ _______ ______

enteric glial cells

regulate and preserve intestinal epithelial barrier function, promote epithelial cell transcription, synaptic transmission, and neuronal maintenance

expenditure (catabolic)

responses of the sympathetic nervous system are associated with ____ of energy

splanchnic (visceral) nerves

some preganglionic fibers traverse the ganglia without synapses and descend as thoracic, lumbar, and sacral ___ _____ to synapse with postganglionic neurons in the prevertebral ganglia of the abdominopelvic cavity or in the adrenal medulla

done by injecting local anesthetics into stellate ganglion to relieve regional pain syndromes and pain caused by vascular spasm or occlusion in the head, neck, and upper limbs (migraine, Raynaud syndrome)

stellate ganglion block

preganglionic neurons

the axons of which type of neurons are myelinated?

in nuclei of cranial nerves in brain stem and in the cell column of the sacral portion of the spinal cord -aka craniosacral division of the ANS with craniosacral outflow

the cell bodies of the preganglionic neurons of the parasympathetic system are located where?

cervicothoracic or stellate ganglion

the inferior cervical ganglion fused with the 1st thoracic ganglion found ventral to the neck of the 1st rib at the level of the transverse process of the C7 vertebra dorsal to the origin of the vertebral artery -clinically relevant because all sympathetic nerves of head, neck, upper limbs, and heart and lungs pass through it

-with: complementary for some functions -against: antagonistic in most body functions (one speeds up while the other slows it down)

the sympathetic and parasympathetic divisions provide dual innervation to organs and work ____ and _____ each other

1. Neurons (sensory neurons, motor neurons, and interneurons) to integrate info from sensory and provide it to enteric motor neurons (programming) 2. enteric glial cells

types of cells in the enteric nervous system

somatic: skeletal muscle (voluntary) autonomic: smooth muscle, cardiac muscle, and glands (involuntary)

what do the somatic and autonomic nervous systems innervate?