Lec 9 Cranial Nerves Flashcards
Where are cranial nerves I through IV found?
At the level of the midbrain
Where are cranial nerves V through VII found?
pons-level cranials
Where are cranial nerves IX through XII found?
In the medulla, connected to the spinal chord
I Olfactory Nerve
Sense of smell, pure sensory
Olfactory receptors in the nasal mucosa linked via olfactory filaments to olfactory tracts which pass to higher brain centres
Foramen: Olfactory filaments pass through cribiform plate of the ethmoid bone
Can be ruptured by head injury, causing loss of sense of smell (anosmia)
II Optic Nerve
- Special Somatic Afferent
- Vision
- Directly connected to the cerebrum
- Passes through the pupil to the retina
Vision, pure sensory
Retinal ganglion cell axons form the nerve
Foramen: optic canal at back of orbit
Nerve continues as optic tract, which ends mainly in the lateral geniculate nucleus (LGN) of the thalamus
LGN axons pass via the optic radiations to primary (V1) visual cortex in occipital lobe
Partial crossing/uncrossing of retinal axons occurs at the optic chiasm
III Oculomotor Nerve
- Made up of two components, the general somatic efferent and general visceral efferent (it is a motor nerve)
- The oculomotor nerve (cranial nerve III) supplies four of the six extraocular muscles, which are a group of muscles that control the movement of the eye
Eye movements are controlled by 6 extraocular muscles (EOMs) innervated by these nerves
Motor nuclei in midbrain (III,IV) & pons (VI)
Foramen: Superior Orbital Fissure, back of orbit
Oculomotor nerve supplies 4 EOMs: medial rectus, inferior & superior rectus & inferior oblique
Trochlear supplies superior oblique
Abducent supplies to lateral rectus
IV Trochlear Nerve
- The trochlear nerve (cranial nerve IV) supplies one of the extraocular muscles: the superior oblique muscle, which helps the eye move down and out.
- Arises from the mid brain
- General somatic efferent nerve (motor nerve)
V Trigeminal Nerve ***
V Trigeminal Nerve
The trigeminal nerve (cranial nerve V) is the main sensory nerve of the head, and carries information about touch, pain, temperature, and proprioception from the face and head. It also has motor functions, which include controlling the muscles of mastication (chewing)
- Devided into 3
- Ophthalmic - carries sensory information. Transmits general sensory information from the skin of the upper face, forehead scalp, cornea, iris, upper eyelid, conjunctiva, nasal cavity mucous membrane and lacrimal gland.
- Maxillary nerve - carries sensory information. It transmits info from the lower eyelid, skin on the sides of the nose, upper jaw, teeth, lip, mucosal lining of buccal and nasal cavities, maxillary sinuses and nasopharynx
- Mandibular branch - both general somatic afferent and special visceral efferent (both sensory and motor components)
Mixed, sensory & motor
Main somatic sensory (touch, pain, temperature)
nerve for face & head
Motor supplies muscles of mastication (chewing)
Extensive subnuclei throughout the brainstem
3 separate nerve divisions: ophthalmic, maxillary, mandibular
3 separate foramens: superior orbital fissure, foramen rotundum, foramen ovale
VI Abducens Nerve
- Abductor providing general somatic efferent.
- Motor nerve for the
VII Facial Nerve
VII Facial Nerve
Mixed sensory, motor & autonomic
Main function, from main motor nucleus to muscles of facial expression + stapedius muscle which braces the stapes bone inside the middle ear to dampen effects of loud noises
Sensory: from taste buds on anterior 2/3 of tongue (salt, sweet, sour) to nucleus solitarius
Parasympathetic: from superior salivatory nucleus, supplies the lacrimal gland (tear production) and the submandibular & sublingual salivary glands
Foramen: internal auditory/acoustic meatus
Lesion of nerve results in Bell’s Palsy
VIII Vestibulocochlear Nerve
VIII Vestibulocochlear Nerve
Pure sensory, originates from inner ear
Two different components
Cochlear nerve : carriers auditory information
Vestibular nerve: carries information regarding the position and movement of the head
Cochlear nerve ends in cochlear nuclei in medulla/pons junction
Vestibular nerve end in vestibular nuclei in medulla/pons junction
Foramen: internal auditory/acoustic meatus
Hearing Loss: conductive vs. sensory-neural causes
IX Glossopharyngeal Nerve
IX Glossopharyngeal Nerve
Mixed sensory, motor & autonomic
Main function, from nucleus ambiguous to stylopharyngeal muscles which elevate larynx for swallowing
Sensory: somatic sensation from pharynx & posterior 1/3 of tongue + taste buds (bitter) to nucleus solitarius
Parasympathetic: from inferior salivatory nucleus, supplies the parotid salivary gland
Foramen: jugular foramen
Test of motor function: ‘gag’ reflex
X Vagus Nerve
X Vagus Nerve
Mixed sensory, motor & autonomic
Main function, from nucleus ambiguous to muscles of pharynx, soft palate & larynx controlling swallowing & speech (recurrent laryngeal nerve to vocal cords)
Sensory: somatic from these same regions & from thoracic + abdominal organs to nucleus solitarius
Parasympathetic: from dorsal motor nucleus, widespread in the cardiovascular, respiratory & gastrointestinal systems (resting, digesting)
Foramen: jugular foramen
Test of motor functions: ‘gag’ reflex & speech production (e.g., lesions of recurrent laryngeal nerve results in hoarse speech)
XI Accessory Nerve
Pure motor, 2 Divisions
Largest, from cervical spinal cord, mainly supplies sternocleidomastoid (rotates head away) & trapezius (lifts shoulders) muscles
Foramen: foramen magnum & jugular foramen
Smaller, cranial part supplies these muscles too + some to internal laryngeal & soft palate for speech production
Foramen: jugular foramen
Lesion mainly causes difficulty in rotating the head towards the opposite side (sternocleidomastoid) & in elevating the shoulder on the affected side (trapezius)
XII Hypoglossal Nerve
XII Hypoglossal Nerve - Innervates the muscles of the tongue
Pure motor
Hypoglossal nucleus in medulla supplies intrinsic and extrinsic muscles of the tongue, movement for eating & speech production
Foramen: hypoglossal canal
Lesions are characterised by ‘fasciculation’ of the tongue (spasms, twitching) on the affected side & deviation towards the affected side on extension
