Lecture 9 - Autonomic

What is the autonomic nervous system (ANS)?

A division of the peripheral nervous system responsible for automatic motor control.

What structures does the ANS primarily target?

Smooth muscle and glands.

What is the main role of the ANS?

Maintaining homeostasis.

How many neurons are in the typical autonomic motor pathway?

Two: a preganglionic neuron and a postganglionic neuron.

Where is the preganglionic neuron cell body located?

In the central nervous system (CNS).

Where is the postganglionic neuron cell body located?

In an autonomic ganglion outside the CNS.

What is an autonomic ganglion?

A collection of neuron cell bodies outside the CNS where autonomic neurons synapse.

What preganglionic-to-postganglionic neuron ratio is given in the lecture?

Approximately 1:32.

What does the 1:32 ratio suggest functionally?

One preganglionic neuron can influence many postganglionic neurons, allowing widespread distribution of autonomic signals.

Where does the sympathetic division originate?

Preganglionic cell bodies in 12 thoracic and 3–4 lumbar spinal cord segments.

What is another name for sympathetic outflow?

Thoracolumbar outflow.

Where is the sympathetic chain located?

It is bilateral, with a chain of sympathetic ganglia on each side of the vertebral column.

What are white communicating rami?

Pathways containing myelinated preganglionic sympathetic fibers.

What type of fibers are found in white communicating rami?

Myelinated preganglionic sympathetic fibers.

What type of fibers are generally found in gray communicating rami?

Mostly unmyelinated postganglionic sympathetic fibers.

What do gray communicating rami connect?

The sympathetic chain back to spinal nerves.

What three functions are supplied through gray communicating rami?

Vasomotor control, pilomotor activity, and sweat gland innervation.

What does vasomotor mean?

Regulation of blood vessel diameter.

What does pilomotor mean?

Control of the muscles that raise hairs.

Which ganglion provides sympathetic fibers to the head?

The superior cervical sympathetic ganglion.

Where do branches from the superior cervical ganglion form sympathetic plexuses?

Along the internal and external carotid arteries.

What is the function of superior cardiac nerves?

They carry sympathetic accelerator fibers to the cardiac plexus and myocardium.

Where is the cardiac plexus located?

At the base of the heart, near the tracheal bifurcation and roots of the great vessels.

Which sympathetic ganglia contribute branches to the thoracic aorta and posterior pulmonary plexus?

Five thoracic ganglia, according to the lecture.

What is the sympathetic effect on the bronchi?

Bronchodilation, or widening of the bronchi.

Where do the lower seven thoracic ganglia send splanchnic nerves?

To the celiac and superior mesenteric ganglia.

What do thoracic splanchnic nerves help supply?

Abdominal viscera through connections involving the celiac and superior mesenteric ganglia and plexuses.

Where do lumbar splanchnic nerves originate?

From sympathetic trunk ganglia in the lumbar region.

Where do lumbar splanchnic nerves send sympathetic fibers?

To the inferior mesenteric ganglion and hypogastric plexus.

What regions receive fibers distributed through the hypogastric plexus?

Lower abdominal and pelvic viscera.

Where does the parasympathetic division originate?

In the brainstem and middle three segments of the sacral spinal cord, according to the lecture.

What is another name for parasympathetic outflow?

Craniosacral outflow.

Which cranial nerves carry parasympathetic fibers to the head?

CN III, CN VII, and CN IX.

Which cranial nerve carries parasympathetic fibers to many thoracic and abdominal viscera?

The vagus nerve (CN X).

Where do parasympathetic preganglionic neurons typically synapse?

In terminal ganglia near or within the walls of their target organs.

What are the Meissner and Auerbach plexuses?

Enteric nerve plexuses containing ganglion cells associated with the digestive tract.

Where does the parasympathetic branch of CN III synapse?

In the ciliary ganglion.

Where do parasympathetic branches of CN VII synapse?

In the pterygopalatine and submandibular ganglia.

Where does the parasympathetic branch of CN IX synapse?

In the otic ganglion.

What are the three cranial nerves distributing parasympathetic fibers to the head?

CN III (oculomotor), CN VII (facial), and CN IX (glossopharyngeal).

What viscera receive parasympathetic fibers through the vagus nerve?

Thoracic and abdominal viscera.

What structures receive parasympathetic fibers through the pelvic nerves?

Most of the large intestine, pelvic viscera, and genitalia.

Which plexus helps distribute pelvic parasympathetic fibers?

The hypogastric plexus.

What is the general structural difference between sympathetic and parasympathetic pathways?

Parasympathetic preganglionic fibers travel close to the target organ before synapsing;

sympathetic pathways use the sympathetic chain and other ganglia.

What is a nerve plexus?

A network of nerves that redistributes nerve fibers to different structures.

What does mixed input mean for autonomic plexuses?

They receive fibers from both sympathetic and parasympathetic pathways.

Where is the cardiac plexus located?

Near the bifurcation of the trachea and the roots of the great vessels at the base of the heart.

Which nerves form the cardiac plexus?

Cardiac sympathetic nerves and cardiac branches of the vagus nerve.

What organ does the cardiac plexus supply?

The heart.

Where are the pulmonary plexuses located?

At the roots of the lungs, around the primary bronchi and pulmonary arteries.

Which nerves form the pulmonary plexuses?

The vagus nerve and upper thoracic sympathetic fibers.

What structures do the pulmonary plexuses supply?

The lungs and associated airway structures.

Where is the celiac plexus located?

In the epigastric region over the abdominal aorta near the superior mesenteric artery.

Which fibers contribute to the celiac plexus?

Vagal fibers from the esophageal plexus and sympathetic fibers associated with the celiac ganglia.

What is the main distribution of the celiac plexus?

Most abdominal viscera.

Name major subplexuses associated with the celiac plexus.

Phrenic, hepatic, splenic, superior gastric, suprarenal, renal, spermatic/ovarian, superior and inferior mesenteric, and abdominal aortic plexuses.

Where is the hypogastric plexus located?

In front of the fifth lumbar vertebra and the sacral promontory.

Which sympathetic pathways contribute fibers to the hypogastric plexus?

Fibers from the aortic plexus and lumbar sympathetic trunk ganglia.

Which parasympathetic pathway contributes fibers to the hypogastric plexus?

The pelvic nerve.

What structures does the hypogastric plexus supply?

Pelvic viscera and genitalia.

Name subplexuses associated with the hypogastric plexus.

Middle hemorrhoidal, vesical, prostatic, and uterine plexuses.

Which plexus is associated with the heart?

The cardiac plexus.

Which plexuses are associated with the roots of the lungs?

The right and left pulmonary plexuses.

Which plexus distributes fibers to most abdominal viscera?

The celiac plexus.

Which plexus distributes fibers to pelvic viscera and genitalia?

The hypogastric plexus.

Which ganglion provides sympathetic innervation to the skin of the face and scalp?

The superior cervical sympathetic ganglion.

Which head structures receive dual autonomic innervation according to the lecture?

The intrinsic muscles of the eye, salivary glands, and mucous membranes of the nose and pharynx.

How many pairs of autonomic ganglia are emphasized in the lecture's overview of head innervation?

Four pairs.

What three roots are associated with each of the four head ganglia?

Sympathetic, parasympathetic, and sensory roots.

Which fibers synapse in the autonomic ganglia of the head?

Parasympathetic fibers.

What happens to sympathetic and sensory fibers passing through these head ganglia?

They pass through without synapsing in the ganglia.

What are the four major autonomic ganglia of the head?

Ciliary, pterygopalatine (sphenopalatine), otic, and submandibular (submaxillary) ganglia.

Where is the ciliary ganglion located?

In the posterior orbit, between the optic nerve and lateral rectus muscle.

Where does the parasympathetic root of the ciliary ganglion originate?

From the Edinger–Westphal nucleus and upper medial oculomotor nucleus, as described in the lecture.

Which ganglion receives parasympathetic fibers from CN III?

The ciliary ganglion.

Where does the sympathetic root of the ciliary ganglion originate?

The superior cervical sympathetic ganglion.

Which nerve provides the sensory root of the ciliary ganglion?

The ophthalmic nerve.

How are fibers distributed from the ciliary ganglion to the eye?

Through approximately 12–15 short ciliary nerves.

Which eye structures receive autonomic fibers through the ciliary nerves?

The ciliary muscle of the lens and muscles of the iris.

Where is the pterygopalatine ganglion located?

Deep in the pterygopalatine fossa, associated with the maxillary nerve.

Which cranial nerve is associated with the parasympathetic pathway to the pterygopalatine ganglion?

CN VII (facial nerve).

Which structures receive fibers distributed through the pterygopalatine ganglion?

Mucous membranes of the roof of the pharynx, nasal cavity, uvula, palatine tonsil, hard and soft palates, periosteum of the orbit, and lacrimal glands.

Where is the otic ganglion located?

Medial to the mandibular nerve, just below the foramen ovale in the infratemporal fossa.

Which cranial nerve carries the parasympathetic pathway to the otic ganglion?

CN IX (glossopharyngeal nerve).

Where does the parasympathetic root of the otic ganglion originate?

The salivatory nucleus of the medulla, according to the lecture.

Where does the sympathetic root of the otic ganglion originate?

The superior cervical sympathetic ganglion.

Which sensory roots are listed for the otic ganglion in the lecture?

Roots associated with CN IX and CN VII.

Which major salivary gland receives autonomic fibers through the otic ganglion?

The parotid gland.

Which somatic motor functions are also mentioned near the otic ganglion?

Supply to the tensor tympani and tensor veli palatini muscles through the trigeminal nerve.

Where is the submandibular ganglion located?

Between the lingual nerve and the submandibular duct.

Where does the parasympathetic root of the submandibular ganglion originate?

The superior salivatory nucleus.

Where does the sympathetic root of the submandibular ganglion originate?

The plexus of the external maxillary artery, as named in the lecture.

What sensory pathway is described for the submandibular ganglion?

From the geniculate ganglion through pathways involving the glossopalatine, chorda tympani, and lingual nerves.

Which salivary glands receive fibers through the submandibular ganglion?

The submandibular and sublingual glands.

Which ganglion is associated with the ciliary muscle and iris?

The ciliary ganglion.

Which ganglion is associated with the lacrimal glands and nasal mucous membranes?

The pterygopalatine ganglion.

Which ganglion supplies the parotid gland?

The otic ganglion.

Which ganglion supplies the submandibular and sublingual glands?

The submandibular ganglion.

Which head ganglion is associated with the maxillary nerve?

The pterygopalatine ganglion.

Which head ganglion is located below the foramen ovale?

The otic ganglion.