Lecture 10: Cranial Nerves Flashcards
What are the 12 cranial nerves, in order of location in allocortex/limbus, midbrain, pons, medulla and are they sensory, motor or both
Allocortex 1. Olfactory: s 2. Optic: s Midbrain 3. Occulomotor: m 4. Trochlear: m Pons 5. Trigeminal: b 6. Abducens: m 7. Facial: b 8. Vestibulocochlear/Auditory: s Medulla 9. Glossopharyngeal: b 10. Vagus: b 11. Accessory: m 12. Hypoglossal: m
What are the sensory modalities for skin, viscera, sight, sound, balance, taste and smell
Skin= general somatic sensory
Viscera= general visceral sensory
Sight, sound and balance= special somatic sensory
Taste, smell= special visceral sensory
What are the motor modalities for skeletal muscle, smooth muscles of gut and muscles of the pharyngeal arches
skeletal muscle: general somatic motor
SM of gut: general visceral motor
muscles of the pharyngeal arches: special visceral motor
Compare the position of the sensory nuclei and motor nuclei in the brainstem: V->D, L->M. And how the different modalities are organised.
Both have two nuclei on L&R side of brainstem.
Sensory nuclei is more dorsal than motor nuclei.
Sensory nuclei are lateral to the motor nuclei on both sides.
Both have nuclei separated vertically in tracts for different modalities.
Sensory has Special, somatic and visceral (L->M)
Motor has Visceral, Special (branchial), somatic (L->M)
What are the 3 foramen that the trigeminal (CNV) exits out of and which division exits in which one
V1: Opthalamic division: Superior orbital fissure
V2: Maxillary division; Foramen rotundum
V3: Mandibular division: Foramen ovale
What is the path and function of the olfactory nerve (CN1)
Path:
1) Olfactory epithelium-> olfactory nerve fibres.
2) Fibres form the Olfactor nerve which goes through the cribiform plate of the ethmoid.
3) termination of the olfactory nerve in the olfactory bulb of one nostril
4) extending from this is the olfactory tract towards the olfactory cortex of the cerebrum
Function: detect odours through the nose. The input of the olfactory bulb into the limbic system means that smells can elicit memories
What is the path of info going in the Optic nerve (CN2) and function
- Visual information from right visual field is sensed by the optic nerve in both eyes.
- Both optic nerves travel down until the optic chiasm where the optic nerve from the right eye crosses over and travels with the optic nerve from the left eye in the optic tract
- Then synapses at the lateral geniculate nucleus in thalamus
- Optic projection fibres then continue to the visual cortex in occipital lobe on the left side.
Function: Visual stimulus from one side of the body projects to the visual cortex on the opposite side of the brain
What are the eye movements that the occulomotor (CN3) nerve does
- Elevating eye = (via sup rectus)
- Depressing eye = (via inf rectus)
- Adduction of eye = (via med rectus)
- Rotating eye to outside (Extorsion) = (via inf oblique)
- Maintaining upper raised eyelid position= (via levator palpabrae superioris)
Also efferent to pupillary reflex via sphincter pupillae and cilliary muscle.
What are the eye movements that the trochlear (CN4) nerve does
- Rotating eye to the medial direction (Intorsion) via Sup oblique.
- Depression of the eye
What are the eye movements that the Abducens (CN6) nerve does
-Abduction of the eye (via Lat rectus). CN3 also helps this movement
For the cranial nerves of eye movement (3,4,6) are the cranial nucleus ipslilateral or contralateral.
Only trochlear (CN4) is contralateral control. For the others the left side controls left eye.
What happens when there is damage to cranial nerve of eye movement
The opposite muscle movement is unopposed so the eye is stuck in a position closer to the opposite muscle.
Eg. Adduction is gone, eye will be sitting at a more abducted position at rest
What is the function of 3 branches of the Trigeminal nerve (CNV)
V1 Opthalamic: Sensation from top of ant head to top of nose skin, cornea, iris, cilliary body (via cillary plexus)
V2 Maxillary: sensation from cheek, lower nose, top lip + upper teeth
V3 Mandibular: sensation from mouth, sideburns of face. Lingual branch give general sensation to ant 2/3 of tongue and bottom teeth.
Motor fibres travelling via V3 innervate muscles of mastication and tensor tympani in ear
What are the branches and functions of the Facial nerve (CN7)
- 6 motor branches to muscles of facial expression
- Parasympathetic branch for control salivation (submandibular ganglion) and tear film (pterygopalatine ganglion)
- Sensory: Chorda tympani nerve branch to receive taste from anterior 2/3 of tongue.
all branches exit the brainstem in the geniculate ganglion
What are the functions and branches of the Vestibulocochlear nerve (CN8)
- Sensory hearing via Cochlear nerve
- Sensing balance/ spatial orientation via Vestibular nerve which synapses within vestibular ganglion before going out to particular organs
Both go back to dorsal and ventral cochlear nuclei
