Cranial Nerves and their Functions Flashcards
I - Olfactory
Sensory - Smell (sends information from nasal mucosa to olfactory bulb)
- Neural tract does not leave the bony cranium
- Some fibers align to dorsal midbrain and pons
- most will enter the cerebral cortex and hippocampus
II - Optic
Sensory - Vision (sends messages from retina to visual cortex and superior colliculus (visual reflexes))
•Nerve is contained in the bony cranium
III - Oculomotor
Motor - Eye movement; regulation of pupil; accomodation of lens for near vision; upper lid elevation
Controls eye muscular movement
- Up and down
- Inward and out
- Pupil construction
Deficits can include:
- Drooping of eyelid - ptosis
- Double vision - diplopia
- Dilated pupils
IV - Trochlear
Motor-based
- Aids in rotating eye slightly down and out
- Lesions can also cause double vision (diplopia)
- Innervates superior oblique muscle of eye
V - Trigeminal
Mixed sensory and motor nerve
- Innervates muscles of mastication, tongue, soft palate
- Relays sensations of eyes, nose, and face (mouth, lower jaw)
Three branches:
- Opthalamic= (S) branch supplies nasal cavity/sinuses, skin in upper facial region & anterior scalp
- Maxillary= (S) branch supplies part of dura, lower eyelid, skin/upper face, mucous of upper mouth(oral cavity and pharynx), sinus, gums and teeth
- Mandibular= (S & M) branch supplies sensation/motor of lower face (jaw/teeth), mastication muscles, anterior 2/3 of tongue (sensation, not movement)
VI Abducens
Motor
Supplies lateral eye muscles
VII - Facial
Motor - Facial expression; secretion of saliva and tears Sensory - Taste (anterior 2/3 of tongue)
Combination of two nerves:
- Upper facial Proper
- Nervous Intermedias
Upper Facial Proper: (M) muscles of voluntary facial expression and stapedius muscle
- Innervates forehead bilaterally & remaining face contralaterally
Nervous Intermedias: (S) stimulation of glands :
- lacrimal, sublingual & submaxillary for saliva
- nasal glands for mucous
Trauma to facial nerve may lead to Bell’s palsy: ipsilateral weakness/paralysis of face, sensitivity to low frequency sounds, decrease in tear/saliva production, closing eyelid (may be temporary, often resolves)
VIII - Vestibulocochlear
Sensory
AKA Vestibuloacoustic nerve or Acoustic nerve
2 branches:
- Vestibular- relays equilibrium and orientation info from hair cells in the semi-circular canals: Damage resultsin vertigo
- Acoustic: relays impulses for hearing form hair cells in the cochlea: Damage leads to deafness/partial hearing loss of ipsilateral ear; tinnitus, facial pain/numbness
IX - Glossopharyngeal
Mixed nerve (S & M)
Relays sensory information for posterior 1/3 of tongue: taste, touch, pain and temperature.
Innervates muscle movement for pharyngeal muscles: Stylopharyngeus and superior constrictor muscles (via pharyngeal plexus)
Stimulates parotid gland (for saliva)
X - Vagus
Mixed (S & N)
3 branches:
- Pharyngeal: both sensory and motor fibers that supply muscles and mucous membranes of pharynx and soft palate; Specifically motor to lower pharynx
- Superior Laryngeal: 2 divisions
Laryngeal : sensory info from the epiglottis and interior of larynx
External laryngeal : motor fibers that innervate cricothyroid and inferior pharyngeal constrictor muscles
- Recurrent Laryngeal:
Provides innervation to mucosa layer of vocal folds and intrinsic muscles of larynx, except for the cricoid muscle
Left recurrent loops under the aortic branch as it ascends between the trachea and esophagus
XI - Accessory
Motor-based nerve with two sections: cranial and spinal; Head and neck motor mvment and support
- Cranial: arise from the lateral side of medulla & innervate uvula and levator levi palatine ( muscle in the mouth)
- Spinal: arise from the anterior horn of the spinal cord to innervate spinal nerves.
Works with the Vagus nerve to innervate muscles of the larynx, pharynx, and soft palate.
XII - Hypoglossal
Motor-oriented nerve; arises from the hypoglossal nucleus in the medulla
- Supplies the innervation to the musculature of tongue (intrinsic & extrinsic)
- Does not innervate the palatoglossus muscle
- will mostly influence voluntary movement of the tongue
How is visual stimuli processed?
- Rods & cones in retina ( 1st order neurons in the eye)
- Synapse with Bipolar neurons (2nd order neurons)
- Synapse with Ganglion cells (3rd order neuron on the optic nerve)
- Optic nerves crosses at Optic Chiasm and half split to the other half of brain
- Optic tract to Lateral Genciculate Bodies in Thalamus (4th order)
- From the LGB to the Primary Visual Cortex
Which nerves control eye movement?
Occulomotor, trochlear, abducens
How do impulses move through the auditory pathway?
- Stimulation of ganglion in cochlea (1st order neruons)
- Ventral and dorsal cochlear nuclei in pons (2nd order neurons)
- Medulla
- Most fibers will cross to Superior Olivary Nucleus
- Then travel up to Lateral lemniscus (roughly in the pons)
- Then moves up to Inferior colliculus in Midbrain
- Travels to Medial Geniculate Body in Thalamus
- Fibers from the MGB (SLIM)
