trigeminal ganglion

Examples of trigeminal ganglion in the following topics:

• Trigeminal (V) Nerve

  • Its name, trigeminal, means three twins.
  • The three branches converge on the trigeminal ganglion that is located within the trigeminal cave in the brain; it contains the cell bodies of incoming sensory nerve fibers.
  • The trigeminal ganglion is analogous to the dorsal root ganglia of the spinal cord, which contain the cell bodies of incoming sensory fibers from the rest of the body.
  • From the trigeminal ganglion, a single large sensory root enters the brainstem at the level of the pons.
  • Motor fibers pass through the trigeminal ganglion on their way to peripheral muscles, but their cell bodies are located in the nucleus of the trigeminal nerve, deep within the pons.

• General Organization of the Somatosensory System

  • The cell body of the primary neuron is housed in the dorsal root ganglion of a spinal nerve or, if sensation is in the head or neck, the ganglia of the trigeminal or cranial nerves.

• Postganglionic Neurons

  • In the autonomic nervous system, fibers from the ganglion to the effector organ are called postganglionic fibers.
  • Chromaffin cells of the adrenal medulla are analogous to post-ganglionic neurons; the adrenal medulla develops in tandem with the sympathetic nervous system and acts as a modified sympathetic ganglion.
  • In all cases, the axon enters the paravertebral ganglion at the level of its originating spinal nerve.
  • After this, it can then either synapse in this ganglion, ascend to a more superior ganglion, or descend to a more inferior paravertebral ganglion and synapse there, or it can descend to a prevertebral ganglion and synapse there with the postsynaptic cell.
  • From these four ganglia the postsynaptic fibers complete their journey to target tissues via Cranial nerve V (trigeminal) (ophthalmic, maxillary, mandibular branches ).

• Facial (VII) Nerve

  • The facial nerve forms the geniculate ganglion prior to entering the facial canal.
  • In regards to the corneal reflex, the afferent arc is mediated by the general sensory afferents of the trigeminal nerve.

• Oculomotor (III) Nerve

  • The Edinger-Westphal nucleus supplies parasympathetic fibers to the eye via the ciliary ganglion, and controls the pupillae muscle (affecting pupil constriction) and the ciliary muscle (affecting accommodation).
  • It then runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic nervous system, and a communicating branch from the ophthalmic division of the trigeminal nerve.

• Parasympathetic (Craniosacral) Division

  • Example nerves supplying parasympathetic fibers to the parasympathetic ganglia of the head include the oculomotor nerve (ciliary ganglion); the facial nerve (pterygopalatine ganglion, submandibular ganglion); the glossopharyngeal nerve (otic ganglion); the vagus nerve (no named ganglion); and the pelvic splanchnic nerves (no named ganglion).
  • These paired ganglia supply all parasympathetic innervation to the head and neck: ciliary ganglion (spincter pupillae, ciliary muscle), pterygopalatine ganglion (lacrimal gland, glands of nasal cavity), submandibular ganglion (submandibular and sublingual glands), and otic ganglion (parotid gland).
  • The sensory root carries general sensory fibers (general somatic afferent fibers) that also do not synapse in the ganglion.
  • Nerves supplying parasympathetic fibers to the parasympathetic ganglia of the head include the oculomotor nerve (ciliary ganglion), the facial nerve (pterygopalatine ganglion, submandibular ganglion), the glossopharyngeal nerve (otic ganglion), the vagus nerve, and the pelvic splanchnic nerves.
  • Pre- and post-ganglionic fibers and targets are depicted.

• Autonomic Ganglia

  • An example of parasympathetic ganglion is the ciliary ganglion, involved in pupil constriction and accommodation , .
  • A dorsal root ganglion (or spinal ganglion) is a nodule on a dorsal root of the spine that contains cell bodies of nerve cells (neurons) that carry signals from sensory organs towards the appropriate integration center.
  • The axons of dorsal root ganglion neurons are known as afferents.
  • The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
  • Postganglionic fibers (labeled) travel from the ganglion to the effector organ.

• Sympathetic Nervous System

  • This response is also known as the sympathetico-adrenal response because the pre-ganglionic sympathetic fibers that end in the adrenal medulla (but also all other sympathetic fibers) secrete acetylcholine, which activates the secretion of adrenaline (epinephrine) and to a lesser extent noradrenaline (norepinephrine) from it.
  • An example of a sympathetic ganglion in a thoracic nerve is shown in .
  • The chain extends from the upper neck down to the coccyx, forming the unpaired coccygeal ganglion.
  • There are usually 21 or 23 pairs of these ganglia: 3 in the cervical region, 12 in the thoracic region, 4 in the lumbar region, 4 in the sacral region and a single, unpaired ganglion lying in front of the coccyx called the 'Ganglion impar'.
  • This intercostal nerve shows the sympathetic ganglion at the top left.

• Pons

  • The alar plate produces sensory neuroblasts, which will give rise to the solitary nucleus and its special visceral afferent column, the cochlear and vestibular nuclei (which form the special somatic afferent fibers of the vestibulocochlear nerve), the spinal and principal trigeminal nerve nuclei (which form the general somatic afferent column of the trigeminal nerve), and the pontine nuclei, which is involved in motor activity.
  • Basal plate neuroblasts give rise to the abducens nucleus (forms the general somatic efferent fibers), the facial and motor trigeminal nuclei (form the special visceral efferent column), and the superior salivatory nucleus, which forms the general visceral efferent fibers of the facial nerve.
  • The chief or pontine nucleus of the trigeminal nerve sensory nucleus (V)- mid-pons

• Preganglionic Neurons

  • In the autonomic nervous system (ANS), fibers from the central nervous system to the ganglion are known as preganglionic fibers.
  • Prevertebral ganglia celiac ganglion, aorticorenal ganglion, superior mesenteric ganglion, inferior mesenteric ganglion
  • Pre- and post-ganglionic fibers and targets are depicted.