Cranial Nerves PDF

Module I UAB MorphoPHEN UNIT 35. CRANIAL NERVES J. Ruberte Acronym Definition...

Module I UAB MorphoPHEN UNIT 35. CRANIAL NERVES J. Ruberte Acronym Definition Function GSE General somatic efferent SOMATOMOTOR Innervation of somite-derived muscles GSA General somatic afferent SOMATOSENSORY Sensory innervation (skin, muscles and joints) GVE General visceral efferent VISCEROMOTOR Innervation smooth muscles GVA General visceral afferent VISCEROSENSORY Sensory from organs and glands SVE Special visceral efferent Innervation of brachial arch-derived muscles (masticatory and mimic muscles) SSA Special somatic afferent Vision, auditory perception, and vestibular sense SVA Special visceral afferent Taste and smell 1 Module I UAB MorphoPHEN 1. Olfactory (I) Name Qualities Function Other Olfactory* Special visceral afferent (SVA) Perception of Olfactory mucosa – cribriform plate (ethmoid) → Cribriform smell olfactory bulb – lateral olfactory tract → piriform I plate cortex. (ethmoid) Vomeronasal organ → accessory olfactory bulb. *Not a real nerve. Is part of the telencephalon. Part of the telencephalon. Origin: Comes from the olfactory mucosa in the labyrinth of the ethmoid, where the dendrites of the olfactory bulb are exposed. Dendrites pass through the cribriform plate. Pathway: From the olfactory bulb, the axon goes through the lateral olfactory tract and reaches the piriform cortex, where smell perception is conscious. There are also collateral tracts to other nuclei and regions. Notable Fact: It is the only sensation that does not go through the thalamus. Accessory Olfactory Bulb: Located in the middle (HE image) and receives afferences from the vomeronasal organ. This information is processed in the amygdala. 2 Module I UAB MorphoPHEN 2. Optic (II) Name Qualities Function Other Optic* Special somatic afferent (SSA) Perception of Retina – optic nerve (ipsilateral) – optic canal Optic canal visual stimuli (presphenoid) – x – chiasma opticum – optic tract II (presphenoid) (ipsi and contralateral) – lateral geniculate nucleus → primary visual cortex (visual area). *Not a real nerve. Is part of the diencephalon. Part of the diencephalon. Axons: Inside it contains the axons of the ganglion cells. The blind part of the retina is the optic disc. Pathway: The nerve enters the presphenoid bone through the optic canal of the preorbital fossa. Optic Chiasma (A): Ventral crossing point where nasal and temporal retina information separates. The left nasal retina crosses the chiasma and goes into the right optic tract. A Optic Tract (B): The optic tract ends at the LGN (Lateral Geniculate Nucleus) of the thalamus. B There are other collateral tracts that go to the superior colliculi. C Vision Consciousness (C): From the LGN, the tract goes to the primary visual cortex (in the occipital cortex) where vision becomes conscious. 3 Module I UAB MorphoPHEN 3. Oculomotor (III) Name Qualities Function Other Oculomotor General somatic efferent (GSE) Extraocular eye Oculomotor nucleus (mesencephalon) (somatomotor) muscles Dorsal, Ventral, Lateral (in human inn by VI) and Medial rectus muscles. Orbital fissure (basisphenoid) General visceral efferent (GVE) Intraocular eye Accessory nuclei oculomotor nerve III (visceromotor) muscles (parasympathetic) (mesencephalon) dorsal to the oculomotor nucleus near the level of the superior colliculus. Pupil: miosis. Ciliary body: lens accommodation. Function: Controls the contraction of extraocular muscles (up, down, in, and out) derived from the somites. Contraction of Intraocular Muscles: o Pupil: Controls miosis (close) and mydriasis (open). Active movement is only for miosis. Smooth muscle cells are involved, making it visceral. o Ciliary Body Muscles: These muscles pull the filaments in the ciliary body, changing the shape of the lens to enable accommodation. Note that this mechanism does not work in mice. Nuclei in Thalamus: GSE (General Somatic Efferent) and GVE (General Visceral Efferent) components go to their respective nuclei in the thalamus. These nuclei are closely related. Parasympathetic Accessory Nuclei: It is parasympathetic, as there is no sympathetic component in the brain (only in the spinal cord). The vagosympathetic trunk in the neck leads to a ganglion, the cervicotorachic ganglion, which is a sympathetic ganglion located behind the first rib. Therefore, sympathetic innervation doesn't reach the head. In the case of an accident in that region, miosis will be permanent as the miosis mechanism won't be inhibited. Belladonna is a parasympatholytic substance, leading to mydriasis. Pathway: The nerve passes through the optic fissure (ventral to the otic canal). 4 Module I UAB MorphoPHEN 4. Trochlear (IV) Name Qualities Function Other Trochlear General somatic efferent (GSE) Extraocular eye Trochlear nucleus (mesenchephalon): in the central /Pathetic (somatomotor) muscle grey matter of the midbrain, close to the midline, near the MLF and the decussating fibres of the IV Orbital fissure superior cerebellar peduncle. (basisphenoid) Dorsal oblique muscle: downward and inward – pathetic. Innervation: Innervates the extraocular eye muscle known as the dorsal oblique muscle, responsible for moving the eye down and inwards. Notable Fact: Also referred to as "pathetic" because the Virgin Mary (depicted in art) does not have the function of this muscle. This is why her eyes appear to be looking in the opposite direction of the muscle's function. Pathway: It exits through the orbital fissure located in the basisphenoid bone. 5 Module I UAB MorphoPHEN 5. Trigeminal (V) Name Qualities Function Other Trigeminal General somatic afferent (GSA) Facial skin, Trigeminal nerve: Ophthalmic + Maxillary nerves – Orbital fissure (somatosensory) meninges orbital fissure – Trigeminal ganglion → Spinal (basisphenoid) nucleus of the trigeminal nerve, longitudinally- shaped nucleus situated in the caudal pons and Foramen medulla. V ovale Sensitivity of the eye (ophthalmic) and sensitivity (basisphenoid) of the skin (maxillary), whiskers included. Special visceral efferent (SVE) Masticatory Trigeminal nerve: mandibular nerve – foramen (branchial arches) muscles ovale – Trigeminal ganglion (Gasser) – Motor trigeminal nucleus (caudal pons and medulla). Temporal, masseter and digastricus muscle. Origination: It originates in the pons. Three Branches: o Maxillary Branch: Responsible for sensitivity of the skin. Contains the Ganglion of Gasser. o Ophthalmic Nerve: Responsible for sensitivity of the eye. The ophthalmic and maxillary nerves exit through the orbital fissure. o Mandibular Branch: Originates in the oval foramen. 6 Module I UAB MorphoPHEN Whiskers: The whiskers are organized into different rows. The information within these rows is equally distributed in the thalamus and is consistent in the cortex. This is an example of neurotopic correlation. Mouseunculus: Represents the somatosensory area. The surface of the cortex dedicated to the analysis of information from the whiskers is extensive. 6. Abducens (VI) Name Qualities Function Other Abducens General somatic efferent (GSE) Extraocular eye Emerges from the brainstem at the junction of the Orbital fissure (somatomotor) muscle pons and the medulla, superior to the medullary VI (basisphenoid) pyramid, and medial to the facial nerve. Ventral oblique muscle (upwards and outwards) and lateral rectus muscle (doesn’t exist in humans) Innervates the ventral oblique muscle and the retractor bulbi muscle (protection muscle, does not exist in humans). Emerges from the brainstem at the junction of the pons and the medulla, superior to the medullary pyramid, and medial to the facial nerve, and crosses the orbital fissure. Innervates the retractor bulbi muscle and the ventral oblique muscle. In human there is not retractor bulbi muscle and the Lateral rectus muscle is innervated by the abducens nerve. 7 Module I UAB MorphoPHEN 7. Facial (VII) Name Qualities Function Other Facial General visceral efferent (GVE) Lacrimal glands, Superior salivatory nucleus (parasympathetic) (visceromotor) minor salivary glands (base of the tong) Special visceral efferent (SVE) Mimic muscles Dorsal buccal branch and ventral buccal branch VII (brachial arches) Facial nucleus originates in the pons (rostral to the pons-medulla transition) and exists laterally → stylomastoid foramen (pars petrosa of temporal) Special visceral afferent (SVA) Gustation Chorda tympani (2/3 anterior tongue) joins the VII (2/3 anterior) at the canaliculus for corda tympani – geniculate ganglion → solitary nucleus (vertical column of grey matter in the medulla). Function: o GVE (General Visceral Efferent): Innervates lacrimal glands and minor salivary glands. o SVE (Special Visceral Efferent): Controls mimic muscles, originating from the brachial arches. o SVA (Special Visceral Afferent): Involved in gustation (taste). Origins: It originates in the facial nuclei, specifically in the pons (rostrally to the pons-medulla transition). Exit Point: The facial nerve exits laterally through the stylomastoid foramen, which is part of the pars petrosa of the temporal bone. 8 Module I UAB MorphoPHEN 8. Vestibulocochlear (VIII) Name Qualities Function Other Vesibulocochlear Special somatic afferent Sense of Vestibular and cochlear nuclei (medulla and equilibrium pons) exit laterally (caudally to the facial nerve – internal acoustic meatus (petrous part of the Internal acoustic and VIII temporal) → semicircular canals and cochlea. meatus (temporal) perception of acoustic stimuli Function: perception of the acoustic stimuli and equilibrium. The nerve emerges from the brain at the cerebellopontine angle and exits the cranium via the internal acoustic meatus of the temporal bone. 9. Glossopharyngeal (IX) Name Qualities Function Other Glossopharyngeal General visceral efferent Major salivary glands Inferior salivary nucleus (GVE) (visceromotor) (parasympathetic) Parotid, mandibular and sublingual Posterior lacerate glands. foramen IX Special visceral efferent (SVE) Pharynx and larynx Ambigus nucleus (brachial arches) muscles Special visceral afferent Gustation Solitary nucleus (SVA) (1/3 posterior) Visceral innervation is always parasympathetic. VII, IX and X are related to gustation. They go to the solitary nucleus. 9 Module I UAB MorphoPHEN 10. Vagus (X) Name Qualities Function Other Vagus General visceral afferent Thoracic, abdominal (Spinal Vagosympathetic (GVA) (viscerosensory) and pelvic organs trigeminal trunk nucleus) (sympathetic + Posterior lacerate General visceral efferent Thoracic, abdominal Dorsal motor parasympatethic) foramen nucleus of vagus related to the (GVE) (motor) and pelvic organs X Visceral innervation is Special visceral efferent (SVE) Pharynx and larynx nerve trachea and vagus nerve always (brachial arches) muscles (parasympathetic) parasympathetic. Special visceral afferent (SVA) Gustation Solitary related to the nucleus. oesophagus Function: Innervates all the viscera in the body both afferently and efferently. Components: o GSE (General Somatic Efferent): Controls muscles in the thoracic, abdominal, and pelvic organs. o GVA (General Visceral Afferent): Monitors visceral sensations from these organs. o SVE (Special Visceral Efferent): Regulates muscles of the neck. o SVA (Special Visceral Afferent): Involved in gustation (taste). Exit Point: It exits through the posterior lacerated foramen. Pathway: The nerve descends through the esophagus. 10 Module I UAB MorphoPHEN 11. Accessory (XI) Name Qualities Function Other Accessory* General somatic efferent Trapezius and Some branches go through the lacerate foramen (GSE) (somatomotor) sternomastoid and other branches will go through the foramen Lacerate foramen magnum (following the spinal cord) muscles XI and foramen mangum Trapezius and sternomastoid muscles *Neurons of origin are located in the cervical spinal cord Neurons of origin are located in the cervical spinal cord. Function: GSE (General Somatic Efferent) nerve responsible for controlling the trapezius and sternomastoid muscles. Components: o One branch exits through the lacerate foramen. o The other part exits through the foramen magnum. 12. Hypoglossal (XII) Name Qualities Function Other Hypoglossal General somatic efferent Tongue Hypoglossal nucleus. (GSE) (somatomotor) muscles Exits lateral to the pyramids (more medial than the others) XII and exits through the hypoglossal canal (occipital) Extrinsic and intrinsic lingual muscles. Exit Point: Exits through the hypoglossal canal. Function: Innervates the muscles of the tongue, both intrinsic and extrinsic tongue muscles. 11 Module I UAB MorphoPHEN CRANIAL NERVES Name Qualities Function Other Olfactory* Special visceral afferent (SVA) Perception of smell Olfactory mucosa – cribriform plate (ethmoid) → olfactory bulb – lateral Cribriform plate olfactory tract → piriform cortex. I (ethmoid) Vomeronasal organ → accessory olfactory bulb. *Not a real nerve. Is part of the telencephalon. Optic* Special somatic afferent (SSA) Perception of visual stimuli Retina – optic nerve (ipsilateral) – optic canal (presphenoid) – x – chiasma Optic canal opticum – optic tract (ipsi and contralateral) – lateral geniculate nucleus → II (presphenoid) primary visual cortex (visual area). *Not a real nerve. Is part of the diencephalon. Oculomotor General somatic efferent (GSE) (somatomotor) Extraocular eye muscles Oculomotor nucleus (mesencephalon) Dorsal, Ventral, Lateral (in human inn by VI) and Medial rectus muscles. Orbital fissure III (basisphenoid) General visceral efferent (GVE) (visceromotor) Intraocular eye muscles Accessory nuclei oculomotor nerve (parasympathetic) (mesencephalon) dorsal to the oculomotor nucleus near the level of the superior colliculus. Pupil: miosis. Ciliary body: lens accommodation. Trochlear General somatic efferent (GSE) (somatomotor) Extraocular eye muscle Trochlear nucleus (mesenchephalon): in the central grey matter of the /Pathetic Orbital midbrain, close to the midline, near the MLF and the decussating fibres of the IV fissure superior cerebellar peduncle. Dorsal oblique muscle: downward and inward – pathetic. (basisphenoid) Trigeminal General somatic afferent (GSA) Facial skin, meninges Trigeminal nerve: Ophthalmic + Maxillary nerves – orbital fissure – (trigeminal Orbital fissure (somatosensory) ganglion → Spinal nucleus of the trigeminal nerve, longitudinally-shaped (basisphenoid) nucleus situated in the caudal pons and medulla. Sensitivity of the eye (ophthalmic) and sensitivity of the skin (maxillary), V Foramen ovale whiskers included. (basisphenoid) Special visceral efferent (SVE) (branchial Masticatory muscles Trigeminal nerve: mandibular nerve – foramen ovale – Trigeminal or ganglion arches) of Gasser – Motor trigeminal nucleus (caudal pons and medulla). Temporal, masseter and digastricus muscle. Abducens General somatic efferent (GSE) (somatomotor) Extraocular eye muscle Emerges from the brainstem at the junction of the pons and the medulla, Orbital fissure superior to the medullary pyramid, and medial to the facial nerve. VI (basisphenoid) Ventral oblique muscle (upwards and outwards) and lateral rectus muscle (doesn’t exist in humans) Facial General visceral efferent (GVE) (visceromotor) Lacrimal glands, minor Superior salivatory nucleus (parasympathetic) salivary glands (base of the tong) Special visceral efferent (SVE) (brachial arches) Mimic muscles Dorsal buccal branch and ventral buccal branch Stylomastoid VII foramen (temporal) Facial nucleus originates in the pons (rostral to the pons-medulla transition) and exists laterally → stylomastoid foramen (pars petrosa of temporal) Special visceral afferent (SVA) Gustation (2/3 anterior) Chorda tympani (2/3 anterior tongue) joins the VII at the canaliculus for corda tympani – geniculate ganglion → solitary nucleus (vertical column of grey matter in the medulla). 12 Module I UAB MorphoPHEN Name Qualities Function Other Vesibulocochlear Special somatic afferent Sense of equilibrium and perception of Vestibular and cochlear nuclei (medulla and pons) exit Internal acoustic acoustic stimuli laterally (caudally to the facial nerve – internal acoustic meatus VIII meatus (temporal) (petrous part of the temporal) → semicircular canals and cochlea. Glossopharyngeal General visceral efferent (GVE) (visceromotor) Major salivary glands Inferior salivary nucleus (parasympathetic) Parotid, mandibular and sublingual glands. Posterior lacerate foramen Special visceral efferent (SVE) (brachial arches) Pharynx and larynx muscles Ambigus nucleus IX Special visceral afferent (SVA) Gustation (1/3 posterior) Solitary nucleus Vagus General visceral afferent (GVA) (viscerosensory) Thoracic, abdominal and pelvic organs (Spinal trigeminal nucleus) Vagosympathetic trunk (sympathetic + parasympatethic) related to Posterior lacerate General visceral efferent (GVE) (motor) Thoracic, abdominal and pelvic organs Dorsal motor nucleus of the trachea and vagus nerve foramen vagus nerve (parasympathetic) related to the oesophagus Visceral innervation is X always Special visceral efferent (SVE) (brachial arches) Pharynx and larynx muscles parasympathetic. Special visceral afferent (SVA) Gustation Solitary nucleus. Accessory* General somatic efferent (GSE) (somatomotor) Trapezius and sternomastoid muscles Some branches go through the lacerate foramen and other branches will go through the foramen magnum (following the Lacerate foramen and spinal cord) XI foramen mangum Trapezius and sternomastoid muscles *Neurons of origin are located in the cervical spinal cord Hypoglossal General somatic efferent (GSE) (somatomotor) Tongue muscles Hypoglossal nucleus. Exits lateral to the pyramids (more medial than the others) and XII exits through the hypoglossal canal (occipital) Extrinsic and intrinsic lingual muscles. 13