Crainal Nerves π§ Flashcards
Name and describe the course of CNI
The Olfactory Nerve
Stemming from the left and right olfactory bulbs, exits the Skull through the cribriform plate and terminating in the roof of the nasal cavity, this nerve governs the olfactory nerve fibers which register smell.
Name and describe the course of CN II
The Optic Nerve Stemming on the left and right side from the optic chiasm, exiting the skull through the optic canal and terminating in the eye, this nerve governs the ocular and sensory functions.
Name and course of CNIII
The Oculomotor Nerve
Stemming from the mesial superior margin of the left and right side of the pons, exiting the skull through the superior orbital fissure and terminating in the muscles of the eye: ciliary, sphincter pupillae and all the external eye muscles except: superior oblique and lateral rectus.
This nerve motorically innervates the previously mentioned eye muscles and allows the eye to move within the orbit
Name and course of CN IV
The Trochlear Nerve
Stems from the lateral superior margin of the left and right side of the pons, exiting the skull through the superior orbital fissure and terminating in the superior oblique eye muscle
Motorically governs the abduction, depression and internal rotation of the eye.
Name and course of CN V
The Trigeminal Nerve
Stems from the lateral superior margin of the left and right side of the pons, this nerve branches into three: V/I ophthalmic, V/II maxillary and V/III mandibular nerves. These branches exit the skull through the superior orbital fissure (V/I), the foramen rotundum (V/II) and the foramen ovale (V/III).
This nerve governs the sensory innervation of the face, sinuses and teeth.
Name and course of CN VI
The Abducent Nerve
Stems from the medial inferior margin of the left and right side of the pons and the left and right pyramids, this nerve exits the skull via the superior orbital fissure and innervates the lateral rectus muscle of the eye, which retracts the eye within the orbit.
How many cranial nerves are there? State whether they are part of the CNS of PNS.
12 Pairs
PNS
Name and course of CN VII
The Facial Nerve
Stems from the lateral inferior margin of the left and right side of the pons and the left and right olives, this nerve exits the skull through the Internal acoustic meatus.
It supplies the muscles of the face with motoric fibers and taste sensation to the anterior two thirds of the tongue.
Name and course of CN VIII
The Vestibulocochlear Nerve
Stemming from the lateral inferior margin of the left and right side of the pons and the cerebellum, exiting the skull via the internal acoustic meatus, this single nerve contains both vestibular and cochlear fibers. The cochlear fibers terminate in the cochlea and the vestibular fibers terminate in the ampullae of the vestibulum.
They supply sensory innervation to the inner ear.
Name and course of CN IX
The Glossopharyngeal Nerve
Stemming from between the olives and the cerebellum, this nerve exits the skull via the jugular foramen.
Name and course of CN X
The Vagus Nerve
Stemming from between the olives and the cerebellum, this nerve exits the skull via the jugular foramen.
It motorically innervates the heart, lungs, palate, pharynx, larynx, trachea, bronchi and gastrointestinal tract. It provides sensation to the heart, lungs, trachea, bronchi, larynx, pharynx, gastrointestinal tract and the external ear.
Name and course of CN XI
The Accessory Nerve
Stemming from between the cuneate fasciculus and lateral funiculus and exiting the skull via the jugular foramen, this nerve motorically innervates the Sternocleidomastoid muscles and Trapezius muscles.
Name and course of CN XII
The Hypoglossal Nerve
Stemming from between the gracile and cuneate fasciculus, this nerve exits the skull via the hypoglossal canal. It motorically innervates the muscles of the tongue, except the palatoglossus, which is innervated by the vagus nerve (CN X). It also gives C1-3 fibers to the strap muscles (infrahyoid muscles).
How is the optic nerve different from the other cranial nerves?
The optic nerve is surrounded by cranial meninges (not by epi-, peri- and endoneurium like most other nerves).
Describe the contents of the left and right optic tracts.
Left optic tract β contains fibres from the left temporal (lateral) retina, and the right nasal (medial) retina.
Right optic tract β contains fibres from the right temporal retina, and the left nasal retina.
Describe the effect of a pituitary tumour pressing on the optic chiasm
This produces visual defect affecting the peripheral vision in both eyes, known as a bitemporal hemianopia
Describe the cell types found within the olfactory mucosa
Basal cells: Form the new stem cells from which the new olfactory cells can develop.
Sustentacular cells: Tall cells for structural support. These are analogous to the glial cells located in the CNS.
Olfactory receptor cells: bipolar neurons which have two processes, a dendritic process and a central process. The dendritic process projects to the surface of the epithelium, where they project a number of short cilia, the olfactory hairs, into the mucous membrane. These cilia react to odors in the air and stimulate the olfactory cells. The central process (also known as the axon) projects in the opposite direction through the basement membrane.
In addition to the epithelium, there are Bowmanβs glands present in the mucosa, which secrete mucus.
Where does the olfactory bulb lie?
Olfactory groove
What does the superior branch of the occulomotor nerve innervate and what are its actions?
Superior rectus β Elevates the eyeball
Levator palpabrae superioris β Raises the upper eyelid.
What does the inferior branch of the occulomotor nerve innervate?
Inferior rectus β Depresses the eyeball
Medial rectus β Adducts the eyeball
Inferior oblique β Elevates, abducts and laterally rotates the eyeball