The autonomic nervous system is regulated by the hypothalamus

## The sympathetic chain

First order neurone cell body: hypothalamus
Second order neurone cell body (preganglionic): ciliospinal centre of Budge

The first and second order neurones synapse in the centre of Budge, which is located in cell columns of the spinal cord, between C8 and T2.

Third order neurone cell body (postganglionic): superior cervical ganglion
Most preganglionic fibres exit the spinal cord in the T1 nerve root

Cell bodies originate in the lateral gray horns of the spinal cord
Myelinated axons leave the cord with the anterior nerve roots
These form the white rami communicantes to the paravertebral ganglia of the sympathetic trunk/chain

Cervical portion of the sympathetic chain extends from the base of the skull to the neck of the first rib near the lung apex

There are two sympathetic trunks which extend the length of the vertebral column from the skull base to the coccyx
There are three ganglia in the neck and all sit anterior to the transverse processes of the cervical vertebrae but behind the carotid sheath and covered by prevertebral fascia
The extension into the thorax is through the neck of the first rib and is covered by pleura within the thorax

The preganglionic fibres synapse with an excitor neuron in the superior cervical ganglion

The non-myelinated postganglionic fibres leave via the gray rami communicantes
They ‘hitch-hike’ along the internal and external carotid to their destinations in the head and neck.
Superior cervical ganglion branches

Internal carotid nerve forms the internal carotid plexus around the artery
Gray rami communicantes
Arterial branches to the common and external carotid arteries
Cranial nerve branches to the 9th, 10th, and 12th CNs
Pharyngeal branches
Superior cardiac branch

## Summary of parasympathetic supply

Midline nuclei in the brainstem give rise to myelinated preganglionic fibres
Edinger-westphal nucleus supplies fibres that ‘hitch-hike’ with the oculomotor nerve to the ciliary ganglion and onward to the sphincter pupillae and ciliary muscles
Super salivatory nucleus produces fibres which derive the nervus intermedius of the seventh cranial nerve, and which supply the lacrimal, submandibular, sublingual, nasal and palatal glands
Inferior salivatory nucleus is associated with the glossopharyngeal nerve supplying the parotid gland
Dorsal motor nucleus is the secretomotor nucleus of the vagus nerve
The cranial parasympathetic ganglia are:

Ciliary ganglion
Pterygopalatine ganglion
Submandibular ganglion
Otic ganglion
NB: all receive a sensory root from the trigeminal nerve

## Ciliary ganglion

This is the primary autonomic ganglion of the orbit

Sits near the orbital apex and lateral to the optic nerve
Sympathetic input comes from the internal carotid plexus (vasomotor)

This is the supply to the iris dilator and runs through the ciliary ganglion{' '} without synapsing and then into the long ciliary nerves which also supply sensory fibres to the cornea

Parasympathetic fibres come from the inferior division of the oculomotor nerve heading for the inferior oblique (and originating in the Edinger-westphal nucleus)

These fibres actually synapse in the ganglion giving rise to post-gangionic fibres which pass to the eyeball via the short ciliary nerves to innervate the ciliary muscle and sphincter pupillae

Short ciliary nerves contain parasympathetic, sympathetic and sensory fibres

## Pterygopalatine ganglion

Found in the pterygopalatine fossa and suspended from the lower edge of the maxillary nerve
Receives parasympathetic, sympathetic and sensory fibres
Parasympathetic supply originates from the nervus intermedius (itself from the superior salivatory aka lacrimatory nucleus of the facial nerve)

Travels in the greater petrosal nerve to the pterygoid canal to form the vidian nerve which reaches the pterygopalatine ganglion
Post-ganglionic fibres hitch-hike on the zygomaticotemporal branch of the maxillary nerve and on to the lacrimal nerve before entering the lacrimal gland

Sympathetic supply derives from the deep petrosal nerve (originally from the internal carotid plexus) and also joins the vidian nerve

Vidian nerve (aka nerve of the pterygoid canal): this is a confluence of the greater and deep petrosal nerves
Sensory fibres from the maxillary division of the trigeminal nerve pass through to innervate the palate, nasopharynx, lateral nose and parts of nasal septum