CH14: Cranial nerves 2 Flashcards
Which reflexes involve the optic and oculomotor nerves?
- pupillary
- consensual
- accommodation
What is the pupillary reflex?
Pupil constricts when light is shined in the eye
What is the consensual reflex?
Pupil of eye constricts when light shined into opposite eye
What is the accommodation reflex?
- Lens adjusts to focus light on the retina
- Pupil constricts
- Pupils move medially
(when viewing object at close range)
What is the stimulus for the pupillary and consensual reflexes?
light shined in the eye
How are the eyes innervated by the ANS?
- parasympathetic (CN III, constricts pupil)
- sympathetic (dilates pupil)
3 branches of the trigeminal nerve
- ophthalmic (somatosensory)
- maxillary (somatosensory)
- mandibular (somatosensory/motor)
trigeminal nerve sensory nerve fibers transmit info from
- face
- TMJ
trigeminal nerve motor fibers transmit info to
muscles of mastication
Which reflexes are mediated by the trigeminal nerve?
- masseter
- corneal
What is the masseter reflex?
Masseter contracts when tapped with reflex hammer
masseter reflex
- afferents
- efferents
trigeminal (both)
What is the corneal reflex?
- “blink”
- Eyelids close when cornea is touched
corneal reflex
- afferents
- efferents
- trigeminal
- facial
Which muscles are innervated by the facial nerve?
- muscles of facial expression
- most glands in the head (salivary, nasal, lacrimal)
- eye closure
- lip movements
Aside from facial expression and glandular info, what other sensory info does the facial nerve convey?
- info from posterior ear canal
- taste from anterior tongue (to solitary nucleus)
- touch, pain, and pressure info from the tongue, pharynx, and skin near the ear canal to the trigeminal spinal nucleus
Where are signals to and from CN VII processed?
- pons
- medulla
- upper spinal cord
What are the branches of the vestibulocochlear nerve?
- vestibular branch
- cochlear branch
function of vestibular branch of CN VIII
Transmits information about head position and head movement
function of cochlear branch of CN VIII
transmits info related to hearing
Where are peripheral receptors for CN VIII functions?
in the inner ear (labyrinth)
labyrinth consists of
- vestibular apparatus
- cochlea
What does auditory information do in the CNS?
- orients head and eyes toward sounds
- increases activity level throughout the CNS
- provides conscious awareness and recognition of sounds
cochlea
Snail shell–shaped organ formed by a spiraling, fluid-filled tube.
What divides the cochlea into upper and lower chambers?
basilar membrane
What is the basilar membrane?
consists of fibers oriented across the width of the cochlea
Scala vestibuli is divided by a membrane that separates
- cochlear duct
- remainder of upper chamber
vestibulocochlear signals are first processed by this
cochlear nuclei
From the cochlear nuclei, signals are transmitted to these 3 structures
- reticular formation
- inferior colliculus
- medial geniculate body
connections to the reticular formation account for
activating effect on CNS (loud sound wakes you up)
What happens in the inferior colliculus?
directly and via the superior olive, auditory info is integrated from both ears to DETECT LOCATION OF SOUNDS
function of medial geniculate body
Serves as a thalamic relay station for auditory information to the primary auditory cortex
(where sounds reach conscious awareness)
What are the designated cortical areas for processing auditory information?
- primary auditory cortex
- auditory association cortex
- Wernicke’s area
primary auditory cortex
site of conscious awareness of the intensity of sounds
auditory association cortex
compares sounds with memories of other sounds, then categorizes the sounds as language, music, or noise
Wernicke’s area
where comprehension of spoken language occurs
sound waves » cochlea
- strike eardrum (tympanic membrane)
- ossicles move, causing vibration of membrane at opening of upper chamber
- fluid in upper chamber moves
- basilar membrane and attached hair cells vibrate
- hair cells bend and depolarize
- cochlear nerve endings activated
Why do hair cells bend?
embedded in immobile tectorial membrane
