The Autonomic Nervous System

4 fates of sympathetic trunk motor fibers

1. The nerve synapses at the first ganglion that it encounters in the sympathetic trunk. The postganglionic fibers rejoin the spinal nerve via grey communicating rami. 2. The nerve passes through the first ganglion and synapses at ganglia up or down from the first one. There are grey communicating rami at all levels. 3. The nerve passes through the sympathetic trunk and out into the body where it synapses down a thoracic, lumbar, or sacral splanchnic nerve channels to the pre vertebral (collateral) ganglia. 4. The nerve passes through everything and synapse with chromaffin cells of the adrenal medulla.

Autonomic Nervous system innervation

2 neuron system. Recall that this is motor. The first neuron has its cell body in the CNS and the axons extend out. The second neuron has a cell body outside the CNS.

Where do the vagus, facial, oculomotor, and glossophayngeal nerves stem from?

3/4 stem from the medulla. One stems from the midbrain.

Sympathetic

A subdivision of the autonomic nervous system that activates nerves, glands and visceral muscles in times of stress or threat (prepares the body for action). Uses epinephrine almost always. Effects are long lasting and body-wide. Sweating (a sympathetic response), is engendered by acetylcholine, not epinephrine. This is unusual.

Parasympathetic

A subdivision of the autonomic nervous system that calms the body after action and also retains the body functioning at is normal state (homeostasis). Uses achetylcholine almost always. Effects are short lasting and localized.

Physical changes brought about by the sympathetic branch of the autonomic nervous system....

Blood vessel contraction, goosebumps, secretion of sweat glands.

Thoracolumbar outflow

Describes the motor innervation from the sympathetic trunk.

Stellate ganglion

Fusion (occurs sometimes) of the inferior cervical ganglion with the first thoracic ganglion. This makes this sympathetic ganglion rather large.

Chromaffin cells

Modified SNS post ganglionic fibers in the adrenal medulla that respond to Ach with the release of epi and norepi into circulation (with epi>norepi)

Sympathetic trunk

Myelinated preganglionic axons exit the ventral ramus as a bundle of white communicating ramus and enter the sympathetic trunk, which extends from the level of C1 to the coccyx, punctuated with thick "beads" of ganglia. The two trunks extend bilaterally and meet at the coccyx, where they merge.

White communicating ramus. Which specific locations are they found?

Myelinated preganglionic sympathetic fibers (preganglionic fibers) from the ventral ramus enter the sympathetic chain via this; only found at T1-L2/3

Vagus nerve

One of four major preganglionic nerves of the autonomic parasympathetic nervous system. Serves 75% of the bodies' preganglionic parasympathetic fibers. Emerge as rootlets from the lateral medulla->exit skull via jugular foramen->traverses down neck in carotid sheath->enters superior mediastinum and gives rise to recurrent laryngeal nerves->then reforms as vagal trunks into the abdomen. Continues to enervate up to the colon midgut.

Where are parasympathetic postganglionic neurons situated?

Parasympathetic postganglionic nerves are part of the autonomic nervous (visceral-> motor-effector) system. They are situated around or in the organs that they are acting upon.

Pterygopalatine ganglion

Part of one of four major preganglionic nerves of the autonomic parasympathetic nervous system. Branch from Maxillary (facial) Nerve. Located behind the nose.

Submandibular ganglion

Part of one of four major preganglionic nerves of the autonomic parasympathetic nervous system. Ganglion for facial neurons that controls submandibular and sublingual salivary glands. Fed by facial nerve.

Otic ganglion

Part of one of four major preganglionic nerves of the autonomic parasympathetic nervous system. Located medial to the pyerygopalatine ganglion. Fed by the Glossopharyngeal nerve.

Cilliary ganglion

Part of one of four major preganglionic nerves of the autonomic parasympathetic nervous system. Resides in the optic cavity. Fed by the oculomotor nerve.

How are superior cell ganglia involved in a sympathetic neural pathway?

Postganglionic sympathetic fibers that affect the head have cell bodies in a collection of superior cervical ganglion. They are a bundle of nerves that follow the carotid artery branches.

Pelvic splanchnic nerves

Short nerves that span from the ventral rami of S2, S3 and S4 to structures below where the vagus nerve system left off. Nerve components: para/pre, viscerosensory pain & reflex. ONLY SPLANCHNIC NERVE IN THE PARASYMPATHETIC DIVISION.

Preganglionic neurons

These are coming from the CNS of the ANS. They are myelinated (white). These always emit acetylcholine.

Where are the cell bodies of parasympathetic preganglionic neurons located.

These are located in the spinal cord, just like sympathetic ones. But these arise from the brain stem and S2-S4.

What are the fates of nerves affecting the renal medulla? (sympathetic response)

These nerves pass through sympathetic trunk, prevertebral ganglia, and synapse with chromaffin cells on the renal medulla to cause the emission of epinephrine and norepinephrine in the blood stream.

What is the fate of sympathetic nerves that will innervate viscera within the abdominal-pelvic cavity?

These nerves pass through the sympathetic trunk and synapse at the prevertebral ganglia via the thoracic, lumbar, or sacral splanchnic nerves.

How do parasympathetic fibers affect the clitoris and penis?

They allow increased blood flow to the vessels and facilitate erection.

Postganglionic neurons

They are connected with the preganglionic neurons and extending outside the CNS. They are unmyelinated (grey). These emit either acetylcholine or norephinephrine, depending on whether parasympathetic or sympathetic.

Preganglionic sympathetic fibers that provide autonomic enervation to head, neck, body wall, limbs, and thoracic cavity have ___ fates?

They synapse either at the first ganglion of the sympathetic trunk, or above or below on the trunk.

Where do parasympathetic postganglionic neurons act?

This division of the nervous system reaches just about everywhere, but it does not enervate the limbs or body wall, with the sole exception of erectile tissues of the clitoris and penis.

Crainosacral flow

This refers to the brain stem and S2-S4, which are there preganglionic neurons of the parasympathetic division of the autonomic nervous system arise.

Ganglion Impar

point anterior to the coccyx where the 2 sacral sympathetic trunks form 1 ganglion