Nerve ganglia

Dorsal root ganglia

Dorsal root ganglia are the most common type of sensory ganglia. As their name suggests, they are found in the posterior (dorsal) root of spinal nerves, following the emergence of the dorsal root that emerges from the intervertebral neural foramina.

Dorsal root ganglia contain clusters of sensory neuron cell bodies which transmit messages relating to pain, touch, and temperature from the PNS, towards the CNS. Satellite glial cells separate and inhibit interaction between cell bodies in the ganglion. Most of the body’s sensory neurons are contained here.

Sensory ganglia of the cranial nerves

Another type of sensory ganglia, are the ones that are found in the cranial nerves. Those are ganglia with special sensory functions and they are similar to the dorsal root ganglia except for they are associated with the cranial nerves and not the spinal nerves.

1. Trigeminal (Gasser’s) ganglion

This is a semilunar ganglion (also known as Gasser’s ganglio) that contains the cell bodies of the sensory fibers that provide sensory innervation to the larger part of the head. The ganglion is found on the anterior surface of the petrous part of the temporal bone, in a dural pouch known as Meckel’s cave. The trigeminal ganglion is the largest of the cranial nerve ganglia.

2. Geniculate ganglion

The geniculate ganglion is the sensory ganglion of the facial nerve (CN VII) found at the anterior third of the facial nerve genu. It contains cell bodies of sensory fibers that transmit the sensation of taste from the anterior two-thirds of the tongue. In addition it contains the cell bodies for fibers that gather sensory information from the nasal cavity, part of the soft palate, and the sinus cavities, the auricle and the external auditory meatus (outer ear).

3. Spiral ganglion

The spiral ganglion is the sensory ganglion of the cochlear branch of the vestibulocochlear nerve (CN VIII). It is found in the modiolus of the cochlea and contains the bodies of the first-order neurons of the acoustic pathway. The dendrites (peripheral extensions) of these neurons receive the stimuli from the receptors in the organ of Corti, whereas their axons (central extensions) form the cochlear part of the vestibulocochlear nerve.

4. Vestibular ganglion

The vestibular ganglion (also known as Scarpa’s ganglion) is the sensory ganglion of the vestibular branch of the vestibulocochlear nerve (CN VIII). It is found within the fundus of the internal auditory meatus and contains primary bipolar sensory neurons of the vestibular pathway.

5. Superior and inferior ganglia of the vagus nerve

The vagus nerve displays two ganglia inferior to the jugular foramen: the jugular (or superior) ganglion, and the nodose (or inferior) ganglion. Inside the superior ganglion lie the cell bodies of pseudounipolar first-order sensory neurons. Those neurons receive afferent information from the dura of the posterior cranial fossa, the auditory meatus, and the auricle of the ear

Inside the inferior (or the nodose) ganglion there are cell bodies of neurons that transmit general sensory information from the mucosa of the larynx, pharynx, and soft palate.

6. Glossopharyngeal ganglia

As with the vagus nerve, the glossopharyngeal nerve (CN IX) contains two ganglia. The superior ganglion contains cell bodies of neurons which innervate the middle ear and internal surface of the tympanic membrane.

The inferior ganglion houses cell bodies of neurons that supply the mucosa of the posterior one-third of the tongue, adjacent pharyngeal wall, auditory tube, and tympanic cavity.

Test your knowledge on the peripheral nervous system with this quiz.

Sympathetic chain ganglia (paravertebral ganglia)

Sympathetic chain ganglia, also known as paravertebral ganglia, are the autonomic ganglia of the SNS. They consist of a paired chain of ganglia found ventral and lateral to the spinal cord. The ganglia extend from the upper neck to the coccyx, where the two chains fuse to form the unpaired ganglion impar.

23 pairs of ganglia can be found: 3 in the cervical region (which fuse to create the superior, middle and inferior cervical ganglions), 12 in the thoracic region, 4 in the lumbar region, four in the sacral region, and a single, and the unpaired ganglion impar mentioned above.

Sympathetic chain ganglia receive their input from the lateral horn of the thoracic and upper lumbar spinal cord and are involved in the relay of information relating to stress and danger.

Prevertebral (collateral) ganglia

Prevertebral ganglia (also known as preaortic ganglia or collateral ganglia) lie between the sympathetic chain ganglia and the target organs.

They have also sympathetic functions but they are not part of the sympathetic chain, rather are close to the splachnic nerves that follow the main aortic branches to innervate all organs found in the abdominal and pelvic cavities (with the exception of the adrenal gland).

Parasympathetic ganglia

The parasympathetic ganglia are the autonomic ganglia of the parasympathetic nervous system.

Those ganglia can be found both in head and neck (and they are part of the cranial nerves) and in the trunk, close to the thoracic and abdominal/pelvic organs.

Their preganglionic neurons are located in the cranial nuclei of the brainstem, and in the lateral horn of the sacral spinal cord. The parasympathetic nervous system is thus referred to as the craniosacral outflow. We’ll look at each segment in turn.

Parasympathetic ganglia related to head and neck

In the head and neck there are four parasympathetic ganglia: ciliary, pterygopalatine, otic and submandibular. A good mnemonic to remember the parasympathetic ganglia is: "Cats Prefer Sexy Owners". Those ganglia are related to the following nerves:

1. Oculomotor nerve (CN III)
The neurons from the Edwinger-Westphal nucleus synapse in the ciliary ganglion in the orbit and then the fibers go on to innervate the sphincter pupillae muscle and muscles of the ciliary body, which respectively act to constrict the pupils and accommodate the lens of the eye when focusing on nearby objects.

2. Facial nerve (CN VII)
The neurons from the lacrimal and superior salivatory nuclei of the brainstem send fibers in the pterygopalatine ganglion and submandibular ganglion. The postganglionic fibers go on to innervate the lacrimal gland and glands in the nasal mucosa. This gives rise to tear and mucus production respectively.

3. Glossopharyngeal nerve (CN IX)
Neurons from the inferior salivatory nucleus of the brainstem synapse in the otic ganglion. Postganglionic fibers go on to innervate the parotid gland and minor salivary glands, eliciting the production of saliva.

Parasympathetic ganglia related to the rest of the body

In this category we have two distinct groups:

• The ganglia surrounding the bronchial passages (eliciting bronchoconstriction), pancreas (stimulating the release of pancreatic enzymes and buffer), and in Meissner’s submucosal and Auerbach’s myenteric plexus along the gastrointestinal tract (stimulating digestion and releasing sphincter muscles). Those ganglia receive innervation from the vagus nerve.
• The ganglia that provide parasympathetic innervation to the pelvic viscera (the prostate, urinary bladder, penis, seminal vesicles, uterus, vagina, and clitoris). Due to their position close to or within the organs they innervate, those parasympathetic ganglia are known as terminal or intramural ganglia.

Vagus nerve (CN X)

Preganglionic parasympathetic neurons originate in the nucleus ambiguus and the dorsal motor nucleus of the brainstem. Fibers from the nucleus ambiguus synapse in the cardiac ganglia, going on to innervate the sinuatrial node, and thus decreasing heart rate.

Fibers traveling from the dorsal motor nucleus synapse in ganglia surrounding the bronchial passages (eliciting bronchoconstriction), pancreas (stimulating the release of pancreatic enzymes and buffer), and in Meissner’s submucosal and Auerbach’s myenteric plexus along the gastrointestinal tract (stimulating digestion and releasing sphincter muscles).