Autonomic Nervous System Flashcards
What does autonomic nervous system regulate
Involuntary functions (blood pressure, heart rate, resp., body temp., glandular secretion, digestion, reproduction
3 divisions of autonomic nervous system
Sympathetic, parasympathetic, enteric nervous system
Location of sympathetic preganglionic neurons
Intermediallateral cell column (IML) of T1-L2 segments of spinal cord
Spinal sympathetic preganglionic neurons ( rostral to caudal)
Most rostral: innervate eyes
More caudal: heart and lungs
Most caudal: G.I tract, bladder, genitals
Location of sympathetic postganglionic neurons
Paraventricular ganglia located on each side of sympathetic chain of vertebral column
Myelination of axons in ANS
Preganglionic axons are myelinated
Postganglionic axons are NOT myelinated
Axons route of preganglionic neurons
Exit spinal cord through ventral roots travel through corresponding spinal nerve and enter sympathetic chain via white rami. Some synapse with post.gang. Neurons in PARAvertebral ganglia others pass through paravertebral ganglia without synapsing and synapse at PREvertebral ganglia
Axon route of postganglionic neurons
Some that are in PARAvertebral ganglia exit sympathetic chain via visceral branches and innervate different organs
Postganglionic fibers from superior cervical ganglion
Exit sympathetic chain and innervate head and neck
Post sympathetic fibers of middle and inferior cervical ganglia
Innervate organs in chest cavity (heart, lungs, bronchi)
Postganglionic fibers that exit through gray rami
Re-enter corresponding spinal nerve, course within or along spinal nerve, innervate blood vessels, sweat glands, erectile muscles of hair follicles
What levels are grey rami present at
All levels of sympathetic chain
What levels are white rami present at
Only In thoracic lumbar region (T1-L2)
Which sympathetic postganglionic Neurons are located in PREvertebral ganglia
The ones that innervate abdominal viscera
Where is prevertebral ganglia located
Anterior to sympathetic chain on the abdominal aorta and closer to organs they innervate
Axons of sympathetic preganglionic neurons located in IML segments T5-T9 course
Exit through ventral roots, travel short distance in spinal nerve, enter sympathetic chain via white rami, exit chain without synapsing, and form GREATER SPLANCHNIC NERVE
Axons of sympathetic preganglionic neurons located in IML segments T10-T12 course
Similar course and form lesser and least splanchnic nerve
Where do Axons of greater, lesser, and least splanchnic nerve synapse
On postganglionic neurons located in the celiac, superior mesenteric, and inferior mesenteric ganglia but MAJORITY of lesser and least synapse in superior and inferior mesenteric ganglia
What do postganglionic fibers emerging from celiac ganglion innervate
Smooth muscle, glands in stomach, small intestine, liver, spleen, pancreas, and kidney
Sympathetic preganglionic fibers in greater, lesser, and least that pass through celiac ganglion
Don’t synapse there but synapse on cells in adrenal medulla that secrete epinephrine and norepinephrine
Postganglionic neurons located in mesenteric ganglion innervate
distal portions of small and large intestine including ascending and transverse colons
Sympathetic preganglionic fibers from L1-L2 spinal segment route
Pass through sympathetic chain without synapsing travel in the lumbar splenic nerves, synapse on postganglionic neurons in INFERIOR mesenteric ganglion
Postganglionic fibers from inferior mesenteric ganglion innervate
Pass through hypogastric (pelvic plexus) and innervate transverse and distal colon, rectum, urinary bladder, and male and female sex organs
Preganglionic L1-L2 fibers that pass PARAvertebral ganglia synapse with postganglionic fibers that innervate
Urinary bladder, male and female sex organs
Preganglionic fibers from L1-L2 that descend in sympathetic chain and synapse on postganglionic neurons in PARAvertebral ganglia
Re-enter spinal nerves via grey rami and innervate blood vessels, sweat glands, and erectile muscles of some hair follicles in lower limb and lower trunk
Functions of sympathetic nervous system
Activated in stressful situations:
- increased blood flow in skeletal muscle
- increased heart rate, blood pressure, blood sugar level
- pupillary dilation
Involved in fight or flight response
Parasympathetic preganglionic neurons location
Brainstem, midbrain, and sacral region of spinal cord (S2-S4)
Edinger-Westphal nucleus
Contains brainstem parasympathetic preganglionic neurons
Oculomotor nerve (CN III),
located in midbrain
Innervates: constrictor muscles of iris and circumferential muscles of ciliary body
Superior salivatory nucleus of facial nerve (CN. VII)
Brainstem parasympathetic preganglionic neurons
Located: Lower pons
Innervates: lacrimal, sublingual, submandibular glands
Inferior salivatory nucleus of glossopharyngeal nerve (CN. IX)
Brainstem parasympathetic preganglionic neurons
Located: caudal to superior salivatory nucleus in upper medulla
Innervates: parotid salivary gland
Nucleus ambiguus
Location: caudal aspect of ventral medulla
Innervation:
compact region: muscles of larynx and pharynx
Region surrounding compact region: heart and mediate decrease in heart rate
Dorsal motor nucleus of vagus (CN X)
Location: caudal aspect of dorsal medulla
Innervate: lungs, pancreas, portions of GIT and control secretion of glands in these organs
Actions activate peristalsis in aforementioned portions of GIT
Cardiac inhibitory action but less then nucleus ambiguus
Spinal parasympathetic preganglionic neuron route
Exit through ventral root, travel through pelvic splanchnic nerves, synapse on postganglionic neurons close to or within organs being innervated (meaning they are shorter than sympathetic postganglionic fibers)
Functions of parasympathetic nervous system
Conservation and restoration of body energy
- decrease heart rate
Effects are localized and last a short time
Enteric nervous system
Neurons in the wall of the gut that regulate GI motility and secretion
Has two layers: myeteric (Auerbach’s) and Submucosal (meissner’s) plexuses
What do neurons of myenteric plexus control
Motility
What do neurons of submucosal plexus control
Water and ion movement across intestinal epithelium
Type of neurons in enteric plexuses
Excitatory and inhibitory neurons
neurotransmitter at parasympathetic preganglionic nerve terminals, intrinsic excitatory inter neurons, and nerves innervating the muscle
Ach
Neurotransmitter at postganglionic sympathetic nerves
Norepinephrine
Other substances in enteric nervous system
Serotonin: excitatory interneurons
ATP: enteric inhibitory nerves supplying external layers of smooth muscle of GIT
VIP: enteric inhibitory nerves and enteric vasodilator nerves
Somatostatin: interneurons of descending pathway in myenteric plexus
Enkephalins: inhibitor of Ach release
Sympathetic innervation of enteric system derives from
Branches of thoracic, lumbar, and sacral sympathetic chains
Most of extrinsic innervation are postganglionic
Parasympathetic innervation of enteric system derives from
Vagus and pelvic nerves
Most of the extrinsic innervation are preganglionic
Nonadrenergic Noncholinergic (NANC) Neurotransmission
Response to autonomic nervous system that are not mediated by Ach or norepinephrine.
Ex: ATP, GABA, serotonin, dopamine, NO, variety of peptides
The parasympathetic and sympathetic divisions have antagonist effects EXCEPT in
Salivary glands (both produce increase salivation)
Levator palpebrae superior muscle
Action: raises upper eyelid
Innervated by: caudal-central nucleus of oculomotor nucleus complex
Superior tarsal muscle (portion of this muscle): innervated by sympathetic postganglionic fibers arising from superior cervical ganglion
Interruption of tarsal muscle: pseudoptosis (partial drooping of upper eyelid)
Orbital muscle of Muller
Action: maintains eyeball in forward position in the orbit
Innervated by: sympathetic postganglionic fibers from superior cervical ganglion
Interruption: enopthalmos (sinking of the eyeball in the orbit)
