Lecture 7- Brainstem and Cranial Nerves 2 Flashcards
What is bitemporal hemianopia? What is it caused by?
- Visual field defect: bitemporal hemianopia is when lose outer vision in both eyes this occurs from a cut at the optic chiasm
- Tumors in the pituitary or the hypothalamus can damage vision.
What is the optic nerve?
Axons of the retinal ganglion cells
What is the optic chiasm?
fibers originated from nasal retina cross over to the opposite side
What is the optic tract?
contains crossed axons from nasal retina & uncrossed axons from
temporal retina
What is the optic tract?
contains crossed axons from nasal retina & uncrossed axons from
temporal retina
What is the Lateral geniculate nucleus of the thalamus/ it’s role in vision?
Processes & relays visual information to visual cortex
What is the Superior colliculus and it’s role in vision?
visual reflex centres controlling the extrinsic eye muscles
Where is the primary visual cortex and what is its role in vision?
- In the occipital lobe
- processes basic visual information (contrast information & object orientation)
- conscious perception of visual images
Where is the visual association areas and what is their role in vision?
- Also in occipital lobe
- Processes visual information concerned with shape, colour & movement
How do different lobes of the brain contribute to complex visual processing?
Ventral parts of the temporal lobe - identify objects in the visual field (what)
Parietal cortex - assess the spatial location of objects (where)
Frontal cortex - uses visual information to guide movement
What is the third cranial nerve? Where does it sit/ extend to?
- Oculomotor nerves
- Axons extend from ventral midbrain & pass through the superior orbital fissure to the eye
Are the oculomotor nerves considered motor sensory of mixed?
Mixed or chiefly motor
What do the different parts of the oculomotor nerves do?
Somatic motor axons
- to four of the six extrinsic eye muscles (inferior oblique muscle and superior, inferior and medial rectus muscles)= move eyeball
- to levator palpebrae superior muscle= raising upper eyelid
Parasympathetic (autonomic) motor axons
- to constrictor muscles of iris= causing pupil to constrict
- to ciliary muscle= controlling shape of lens for visual
focusing
• Sensory (proprioceptor) afferents - from eye muscles to midbrain
What is the primary purpose of the oculomotor nerves? What therefore is the result of damage?
Provide most of the movement of each eye Also - opening of eyelid - constriction of pupil - focusing
Damage causes drooping upper eyelid, dilated pupil, double vision, difficulty focusing & inability to move eye in certain directions
What is cranial nerve number four? Where does it emerge from and run to?
-Trochlear Nerves
-Axons emerge from dorsal midbrain, course ventrally
around midbrain, pass through the superior orbital
fissure to the eye
**Only cranial nerve emerging from dorsal brainstem
Are the trochlear nerves motor, sensory or mixed?
Motor
What are the functions of the trochlear nerves and therefore what does damage cause?
- Supply somatic motor axons to (& carry proprioceptor axons from) the superior oblique muscle (which rotates the eye downward & laterally) [SO4]
- This muscle has a tendon that hooks around a pulley called a trochlea
- Provide eye movement
- Damage causes double vision & inability to rotate eye inferolaterally (out and down)
What is cranial nerve number 5? Where does it sit/ run to?
- Trigeminal nerves
- Axons extend from face to pons (S) & pons to muscles (M)
- Cell bodies of sensory neurons are located in large trigeminal ganglion
Why are the trigeminal nerves called trigeminal?
Because they are three fold. The divisions are:
- Ophthalmic division (V1)
- Maxillary division (V2)
- Mandibular division (V3)
What does the Ophthalmic division (V1) of the trigeminal nerve do?
-Axons run from face to pons via superior orbital fissure
-Convey sensory impulses from skin of anterior scalp,
upper eyelid & nose, & from nasal cavity mucosa,
cornea & lacrimal (tear) gland
What does the Maxillary division (V2) of the trigeminal nerve do?
•Axons run from face to pons via foramen rotundum
• Convey sensory impulses from nasal cavity mucosa,
palate, upper teeth, skin of cheek and upper lip
What does the Mandibular division (V3) of the trigeminal nerve do?
- Axons pass through skull via foramen ovale
- Convey sensory impulses from anterior tongue (except taste buds), lower teeth, skin of chin, & temporal region of scalp
Which division of the trigeminal nerves also has a motor output and what does this do?
- Mandibular division (V3)
- Supply motor axons to (carry proprioceptor axons from) muscles of mastication
Overall are the trigeminal nerves motor, sensory or mixed?
Mixed nerves (mainly sensory)
- Largest cranial nerves
- Main sensory nerve from face (transmitting afferent impulses from touch, temperature & pain receptors)
- Supply motor axons to muscles of mastication (motor)
What does damage to the trigeminal nerves cause?
-Loss of sensation & impaired chewing
Tic Douloureux (Trigeminal Neuralgia)
• excruciating pain
• provoked by a sensory stimulus in area of supply
• inflammation of trigeminal nerve (pressure on nerve root)
• analgesics - partially effective
• Nerve cut in severe case to relieve pain (but causing sensation loss)
What nerves are anaesthetised during dental procedures?
Trigeminal nerves
What is cranial nerve number 6 and what is it’s function?
-Abducens nerve
- Axons leave inferior pons & pass through superior orbital fissure to eye (lateral rectus muscle)
- Provide eye movement (abducts the eyeball)
- Damage results in inability to rotate eye laterally & at rest eye rotates medially
What is cranial nerve number 7 and where does it sit/ run through?
-Facial nerves
-Axons emerge from pons, enter temporal bone via
internal auditory meatus and run within bone (through
inner ear cavity) before emerging through stylomastoid
foramen; course to lateral aspect of face
What 5 branches are there of the facial nerves?
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
(think a hand with each finger labelled)
Are the facial nerves sensory, motor or mixed? + functions related to these labels….
Mixed nerves
- Major motor axons of the face
- Supply motor axons to (convey proprioceptor impulses from) skeletal muscles of face (muscles of facial expression), except for chewing muscles served by cranial nerve V
- Transmit parasympathetic (autonomic) motor impulses to lacrimal (tear) glands, nasal & salivary glands
- Convey sensory impulses from taste buds of anterior 2/3 of tongue
What happens if you damage the facial nerves? Causes? Treatment?
-Damage produces sagging facial muscles (mask like face) & disturbed sense of taste (missing sweet, salty & umami)
-A specific condition is bell’s Palsy:
• characterized by paralysis of facial muscles (affected side) & partial loss of taste sensation.
• viral infection causing inflammation of facial nerve
• symptoms: lower eyelid droops, corner of mouth sags,
tears drip continuously, eye cannot be completely closed,
paralysed face is ‘pulled’.
• Treatment: steroids, rest
What is cranial nerve number 8? Where does it sit/ run?
- Vestibulocochlear Nerve
- Axons arising from hearing & equilibrium apparatus within inner ear of temporal bone, passing through internal acoustic meatus to enter brainstem at the pons medulla border
Are the vestibulocochlear nerves motor, sensory or mixed? How does this relate to function?
- Purely sensory
- Provide hearing (cochlea nerves) and sense of balance (vestibular nerves)
- Damage produces deafness, dizziness, nausea, loss of balance and nystagmus (rapid involuntary eye movements)
Label the diagram on OneNote showing the auditory pathway…
Answers there
What is the cranial nerve number 9 called? Where do they sit?
Glossopharyngeal Nerves
Axons emerge from medulla & leave skull through
jugular foramen
Are the glossopharyngeal nerves motor, sensory or mixed? What is their function related to this?
Mixed nerves
-Supply motor axons to (carry proprioceptor fibers from) a pharyngeal muscle= stylopharyngeus
-Provide parasympathetic motor axons to parotid salivary gland
-Sensory axons conduct taste & general sensory impulses
from pharynx & posterior 1/3 of tongue
-Conducting sensory impulses from chemoreceptors in
the carotid body & pressure receptors of carotid
sinus
-Provide control over swallowing, salivation, gagging,
sensations from posterior 1/3 of tongue, control of
blood pressure & respiration
What does damage to the glossopharyngeal nerves cause?
Damage results in loss of bitter & sour taste, and impaired swallowing
What is cranial nerve number 10? Where does it sit/ pass through?
Vagus Nerve
-Axons emerge from medulla, pass through skull via
jugular foramen, descend through neck region into
thorax & abdomen
Are the vagus nerves sensory, motor or mixed?
-Mixed nerves
-Supply motor axons to (carry proprioceptor fibers from)
skeletal muscles of pharynx & larynx
- Parasympathetic motor fibers supply heart, lungs
& abdominal viscera
Sensory axons:
-conducting sensory impulses from thoracic &
abdominal viscera
-transmitting sensory impulses from chemoreceptors
in the carotid & aortic bodies, & pressure
receptors of carotid sinus
- conducting sensory impulses from taste buds of
posterior tongue & pharynx
How is the vagus nerve special in terms of its location?
The only cranial nerve extending beyond the head &
neck to the thorax & abdomen
Complete the major of motor axons in the vagus nerve are…
Parasympathetic
What is the general function of the vagus nerve and therefore the result if they are damaged?
- Provide swallowing & speech; regulate activities of major viscera
- Damage causes hoarseness or loss of voice, impaired swallowing & digestive system mobility. If both are cut it’s fatal as critical to keeping heart and lungs going.
What is cranial nerve number 11?
-Accessory nerve
Are the accessory nerves primarily motor, sensory or mixed? What is there function and result of damage?
-Mixed nerves (primarily motor)
-Cranial root joins with axons of vagus nerve (X) to supply motor axons to larynx, pharynx & soft palate. Damage causes hoarseness or loss
of voice & impaired swallowing.
-Spinal root supplies motor axons to (conveys proprioceptor
impulses from) trapezius & sternocleidomastoid muscles, therefore
provides head, neck & shoulder movement. Damage causes impaired head, neck & shoulder movement. eg. unable to shrug on one side if unilateral injury
What is cranial nerve number 12? Where does it sit?
-Hypoglossal nerves
-Axons arise by a series of roots from medulla, exit from
skull via hypoglossal canal to tongue. Axons emerge between the pyramid & olive
Are the hypoglossal nerves motor, sensory or mixed? What is the function and result of damage?
- Primarily motor
-Supply somatic motor axons to (convey proprioceptor
impulses from) intrinsic & extrinsic muscles of
tongue
-Damage causes difficulties in speech & swallowing
Both sides - inability to protrude tongue
One side - tongue deviates (leans) towards injured side & results in ipsilateral atrophy eventually
