1. Definition
The cranial nerve nuclei are clusters of perikaryons (of neural cells) that are located in the brainstem.
2. Function
The cranial nuclei act as relay stations for nerve signals in the brain. They connect the brain to different parts of the body (mostly head and neck) through the cranial nerves, processing and transmitting motor commands (e.g.: eye or facial movements) and sensory information (e.g.: touch, taste, balance, and pain). There are different categories of information which are being processed.
- Somatomotor or general somatic efferent (GSE): Controls voluntary muscles → skeletal muscle! (e.g.: muscles of the tongue)
- Special visceromotor or special visceral efferent (SVE): Controls muscles derived from the pharyngeal arches → skeletal muscle! (e.g.: masticatory muscles, muscles of facial expression)
- General visceromotor or general visceral efferent (GVE): Regulates involuntary muscles and glands → smooth muscle! (e.g.: ciliar muscle, parotid gland, heart rate)
- General viscerosensory or general visceral afferent (GVA): general sensory fibers of the visceral organs, receptors of the viscera and vessels (e.g.: blood pressure)
- Special viscerosensory or special visceral afferent (SVA): the gustatory nucleus ( → taste buds)
- Special somatosensory or special somatic afferent (SSA): receive auditory and vestibular informations
- General somatosensory or general somatic afferent (GSA): receptors of the skin and the muscles (3 different kinds of sensation: proprioception, epicritic, protopathic)
3. List of the cranial nerve nuclei
3.1 Somatomotor nuclei
- Oculomotor nucl. (CN III)
- Trochlear nucl. (CN IV)
- Abducens nucl. (CN VI)
- Hypoglossal nucl. (CN XII)
3.2 Special visceromotor nuclei
- Motor nucleus of trigeminal nerve (CN V)
- Facial nucl. (CN VII)
- Ambiguus nucl. (CN IX, X, XI)
3.3 General visceromotor nuclei
- Accessory oclumotor nucl. also called Edinger-Westphal nucl. (CN III)
- Superior salivatory nucl. (CN VII)
- Inferior salivatory nucl. (CN IX)
- Dorsal motor nucl. (CN X)
3.4 General viscerosensory and special viscerosensory nuclei
- Solitary tract nucleus (CN VII, IX, X)
3.5 Special somatosensory nuclei
- Cochlear nuclei + vestibular nuclei (CN VIII)
3.6 General somatosensory nuclei
- Mesencephalic nucl. of trigeminal nerve (CN V)
- Main sensory nucl. of trigeminal nerve (CN V)
- Spinal nucl. of trigeminal nerve (CN V)
Additional explanation
Note, that in general the direction in which the information is being forwarded is different for the motor and sensory nuclei:
- a motor command would for example form in your cerebral cortex (e.g.: “Smile!”) → and the information goes (through different systems) to one of the somatomotor nuclei where the information is being processed and forwarded to your muscle.
- sensory information goes the other way: a skin receptor senses something (e.g.: touch) and forwards it to one of the somatosensory nuclei. There it will be forwarded to the Thalamus and finally to your cerebral cortex.