Autonomic Nervous System Flashcards
Enteric Nervous System
o ~100 million neurons (intrinsic neuronal network of GI tract – from esophagus to anus)
o Functions: reflexive functions of GI tract (gut secretions, absorption , & mixing/moving of food)
o Control:
SNS inhibits its function
PSNS excites/stimulates its function – vagus nerve
o Diverse neurotransmitters (ACh, NE, 5-HT)
o Arterial Supply: celiac trunk, SMA, IMA
o Venous Return: portal system to liver
o Meissner’s (submucus) Plexus - in the submucosa
o Auerbach’s (myenteric) Plexus – between the inner circular and outer longitudinal muscles
Sympathetic nervous System
– a.k.a. thoraco-lumbar outflow
o Two neuron hook-up system (SHORT preganglionic; LONG postganglionic neurons)
Myelinated preganglionic axons
Unmyelinated postganglionic axons
o Receives input via general visceral afferents that synapse in dorsal root ganglion
Dorsal root ganglion – pseudo-unipolar – where sensory neurons from viscera SYNAPSE; one axon has branches to both the peripheral and central nervous system
Preganglionic Sympathetic Neurons
– located in lateral horn (column) of spinal cord (T1-L2/3)
o Axons exit the spinal cord via ventral root and travel on spinal nerves to reach ganglion (sympathetic or parasympathetic)
Spinal nerve – forms after the dorsal and ventral root come together
• Dorsal primary rami – innervates deep muscles of back and medial/lateral cutaneous branches
o Main Function: send postganglionic fibers to skin to innervate smooth muscle of blood vessels, arrector pili muscles of hair cells in skin, sweat glands
• Vental primary rami – innervates superficial muscles of back and medial/lateral/anterior/posterior cutaneous branches
o White ramus communicantes – myelinated
o Gray ramus communicantes – unmyelinated
Postganglionic Sympathetic Neurons: synapse at different level
o Lateral horn ventral root spinal nerve white ramus communicantes up/down sympathetic trunk SYNAPSE at different level of vertebrae (cervical /lumbar/sacral ganglia) gray ramus communicantes
Above level of T1 there are inferior/middle/superior cervical ganglion that send out postganglionic fibers that form cardiac plexus to supply heart
Postganglionic Sympathetic Neurons: synapse at same level
o Lateral horn ventral root spinal nerve white ramus communicantes SYNAPSE sympathetic trunk gray ramus communicantes peripheral nerve
T1-T2 Intermedio-lateral Cell Column superior cervical ganglion pupillary dilator muscles, sweat glands, and vascular smooth muscle in head/neck
Ex: eye, mouth glands, parotid glands, heart, bronchi
Postganglionic Sympathetic Neurons: splanchnic nerves
o Lateral horn ventral root spinal nerve white ramus communicantes preganglionic splanchnic (greater, lesser, least) nerves SYNAPSE prevertebral (collateral) ganglion (celiac/superior mesenteric/inferior mesenteric) to viscera
Greater splanchnic – T5-T9 celiac ganglion (stomach, small intestine)
Lesser splanchnic – T10-T11 superior mesenteric ganglion (small intestine, beginning of large intestine via ENS)
Least splanchnic – T11 inferior mesenteric ganglion (end of large intestine via ENS, ductus deferens)
Postganglionic Sympathetic Neurons: adrenal
o Lateral horn ventral root spinal nerve white ramus communicantes sympathetic trunk gray ramus communicantes SYNAPSE adrenal medulla
NO postganglionic neurons; the preganglionic neuron themselves secrete catecholamines and are derived from neurocrest
Parasympathetic
– a.k.a. cranio-sacral outflow from brainstem nuclei travel on oculomotor (III), facial (VII), glossopharyngeal (IX), vagus (X) – hitchhike a ride on the cranial nerves
Parasympathetic involving oculomotor nerve
o Nucleus of Edinger-Westphal nucleus oculomotor (III) nerve ciliary ganglion pupillary constrictor and ciliary muscles
Parasympathetic involving facial nerve
o Lacrimal Nucleus facial (VII) nerve greater postnasal nerve pterygopalatine ganglion lacrimal and nasal glands
o Superior Salivatory Nucleus facial (VII) nerve chorda tympani nerve submandibular ganglion submandibular, salivary, sublingual glands and oral mucosa
Parasympathetic involving glossopharyngeal nerve
o Inferior Salivatory Nucleus glossopharyngeal (IX) nerve lesser petrosal nerve otic ganglion parotid gland
Parasympathetic involving vagus nerve
o Nucleus ambiguous vagus (X) nerve heart
o Dorsal Vagal Nucleus Vagus (X) nerve remaining thoracic and abdominal viscera UP TO left colic flexure
o Dorsal Vagal Nucleus pharyngeal (X) nerve superior laryngeal nerve enteric ganglion pharyngeal mucosal glands
o Dorsal Vagal Nucleus internal laryngeal (X) nerve recurrent laryngeal nerve enteric ganglion laryngeal mucosal glands
Parasympathetic Sacral Outflow
- from sacral spinal cord levels and travel on sacral nerves S2, S3, S4
o Supplies AFTER left colic flexure of large intestine, urinary bladder, & genital erectile tissue
o Travel as pelvic splanchnic nerve to parasympathetic ganglion
Autonomic Distribution of the Eye
o SNS: preganglionic fibers ascend from T1/T2 SYNAPSE superior cervical ganglion postganglion axons travel on internal carotid artery and form plexus pass through ciliary ganglion travel to eye via short ciliary nerve
o PSNS: preganglionic Edinger-Westphal nerves travel along oculomotor nerve SYNAPSE ciliary ganglion travel to eye via short ciliary nerve
o Afferent sensory fibers: send signal to brainstem (trigeminal ganglion)
Autonomic Distribution of Lacrimal Gland
o SNS: preganglionic fibers ascend from T1/T2 SYNAPSE superior cervical ganglion travel via internal carotid artery deep petrosal nerve joins with great petrosal nerve continues as nerve of pterygoid canal pterygopalatine ganglion
Deep petrosal nerve – ONLY purely sympathetic nerve in the body
o PSNS: superior salivatory nucleus along facial nerve to great petrosal nerve joins SNS fibers to join pterygoid canal pterygopalatine ganglion
Great petrosal nerve PURELY parasympathetic nerve
o Deep and great petrosal nerves come together to form nerve of pterygoid canal (mix of postganglionic SNS and preganglionic PSNS); fibers continue to pterygopalataine ganglion
SNS fibers go through nose via blood vessels for nasal mucosal & lacrimal gland supply
PSNS fibers synapse & go down to maxillary nerve then lacrimal nerve & lacrimal gland
Autonomic Distribution of Submandibular and Sublingual Glands
o SNS: fibers from T1/T2 ascend SYNAPSE superior cervical ganglion travel along maxillary artery branch of external carotid artery mucosa of nose, hard/soft palate, and into larynx/pharynx
o PSNS: superior salivatory nucleus along facial nerve to chorda tympani nerve joins with lingual nerve to reach and SYNAPSE submandibular ganglion sends fibers to submandibular and sublingual salivary glands and also to larynx/pharynx
Chorda tympani preganglionic parasympathetic nerve has two-way traffic carries taste fibers from anterior 2/3 of tongue back to brainstem
Chorda tympani and great petrosal nerves innervate ALL of the salivary glands
Autonomic Distribution of Parotid Gland
o SNS: fibers from T1/T2 ascend SYNAPSE superior cervical ganglion postganglionic fibers travel on branches of external carotid artery to parotid gland
o PSNS: inferior salivatory nucleus fibers along glossopharyngeal nerve tympanic nerve tympanic plexus lesser petrosal nerve SYNAPSE otic ganglion postganglion axons travel with auriculotemporal nerve to the parotid gland
Auriculotemporal nerve has a hole in the middle of it to allow the middle meningeal artery to pass through and supply the dura mater
Types of Synapses and Receptors used in Autonomic Nervous System
SNS
Preganglionic neurons – cholinergic synapses an d nicotinic receptors
Postganglionic neurons – adrenergic synapses and alpha/beta adrenergic receptors
PSNS
Preganglionic – cholinergic synapses and nicotinic receptors
Postganglionic – cholinergic synapses and muscarinic receptors
