CH14: Cranial nerves 1 Flashcards
Cranial nerves exchange info between
PNS CNS
types of functions of cranial nerves
sensory
motor
autonomic
How do cranial nerves differ from spinal nerves?
specialization
- motor only
- sensory only
- both
4 functions of cranial nerves
- supply motor to muscles of face, eyes, tongue, jaw, and 2 neck muscles
- transmit somatosensory info from skin, muscles of face, and from TMJ
- transmit special sensory info
- parasympathetic regulation
What special sensory info is transmitted by cranial nerves?
info related to sensations
- visual
- auditory
- vestibular
- gustatory
- olfactory
- visceral
What parasympathetic regulation is provided by cranial nerves?
- pupil size
- curvature of lens
- HR
- BP
- breathing
- digestion
Which two cranial nerves area actually considered part of the CNS? What are their functions?
- olfactory: smell
- optic: vision
Much of info attributed to taste is from here.
olfactory
Why is olfactory nerve such a big contributor to taste?
because the information from taste buds is limited to chemoreceptors for
- salty
- sweet
- sour
- umami (i.e., “savory”)
- bitter
retina
inner layer of posterior eye
What happens to light striking the retina (overall)?
converted into neural signals by photosensitive cells
Visual signals sent to the midbrain are involved in
- reflexive responses of the pupil
- awareness of light and dark
- orienting the head and eyes
Where are visual signals sent from the retina?
- lateral genticulate body (thalamus)
- nuclei in midbrain
Axons in the retina send neural signals through this path
- down optic nerve
- through optic chiasm
- into the optic tract
*synapse in the lateral geniculate body
Which CNs are lumped together?
III, IV, VI
Why are CNs III, IV, and VI lumped together?
All contain motor neuron axons innervating the six extraocular muscles that move the eye and control reflexive constriction of the pupil
rectus muscles attach to
anterior half of eyeball
oblique muscles attach to
posterior half of eyeball
How many rectus muscles?
4
How many oblique muscles?
2
CN III controls these eye muscles
- levator palpebrae superioris
- superior rectus
- medial rectus
- inferior rectus
- inferior oblique
- pupillary sphincter
- ciliary
CN IV controls these eye muscles
superior oblique
CN VI controls these eye muscles
lateral rectus
function of levator palpebrae superioris
lifts eyelid
function of superior rectus
pupil up
function of medial rectus
pupil medial
function of inferior rectus
pupil down
function of inferior oblique (if eye is adducted)
pupil up
function of inferior oblique (if eye abducted)
rotates eye
function of pupillary sphincter
constricts pupil
function of ciliary
increases lens curvature
function of superior oblique (if eye adducted)
pupil down and in
function of superior oblique (if eye abducted)
rotates eye
function of lateral rectus
pupil lateral
Head and eye movements are coordinated by signals in
the medial longitudinal fasciculus
When does the ciliary muscle contract? Why?
- when viewing objects closer than 20 cm
- increase curvature of lens
What is the action of the ciliary muscle called?
accommodation
What is accommodation?
increases refraction of light rays to ensure that the focal point will be maintained on the retina
