Cranial nerves Flashcards
where does the efferent system go from and to?
CNS to muscles / glands
where does the afferent nervous system go from and to
sensory nerve endings to CNS
what type are each of the cranial nerves?
III - oculomotor
IV - trochlear
V - trigeminal
VI - abducens
VII - facial
what are the muscles that are around the eyeball?
(check screenshots and be able to label the diagram)
what does cranial nerve IV do?
causes abduction to the lateral rectus muscle
what is the annulus of zinn
a tendonous ring that surrounds the optic foramen
what extraocular muscle is cranial nerve IV and what is it for
the superior oblique muscle of the contralateral orbit
-depression
-abduction
-intorsion
where is the origin of CN IV? what muscle is it’s final innervation?
the midbrain, superior oblique muscle
what are the two components to CN IIIs mechanism
somatic motor and visceral motor
what is the somatic motor component of CN III
supplies the SR MR IR and IO extraocular muscles of the eye and the levator palpebrae superiosis muscle of the upper eyelid
what is the visceral motor component of CN III
parasympathetic innervation of the constrictor pupillae and ciliary muscles part of the pupillary light reflex and accommodation reflex
what is different about the superior rectus muscle with cranial nerve III
its nucleus is on the contralateral side of the brain while the 3 other muscles that are innervated are ipsilateral
what four muscles does CN III innervate and what side of the brain?
ipsilateral inferior rectus muscle
ipsilateral inferior oblique muscle
ipsilateral medial rectus muscle
contralateral superior rectus muscle
how does CN III innervate the iris and cillary muscles parasympathetically
-innervates the constrictor pupillae to trigger pupillary light reflex
-innervates ciliary muscles to trigger accomodation reflexes
give the parasympathetic pathway to the iris sphincter
- preganglionic cells in the nucleus of edinger westphal
- axons exit through CN III
- synapse in ciliary ganglion
- iris constrictor via short ciliary nerves
what happens when the eye is exposed to light?
- CN III triggers pupillary light reflex
- light entering eye causes signals sent to pretectal nuclei in the midbrain via the optic nerve of CN II
- the pretectal nucleus of the midbrain in turn projects bilaterally to the edinger-westphal nucleus’
- preganglionic parasympathetic fibres from each half of the edinger westphal nucleus project to the ciliary ganglion of the ipsilateral orbit
- post ganglionic parasympathetic fibres exit the ciliary ganglion to innervate the constrictor pupillae muscle of the ipsilateral eye
why can people who are completely blind retain a pupillary light reflex?
as in humans, ipRGCs account for only ~0.2% of all RGCs
give the sympathetic pathway to the iris dilator
hypothalamus
preganglionic cells in spinal cord
superior cervical ganglion
iris dilator
what three muscles make up the accommodation reflex and what happens to them?
-ciliary muscle increases in curvature of the lens and hence increases the refractive power of the lens
-iris sphincter causes pupil to constrict to help sharpen the image on the retina
-medial rectus causes the eyes to converge so they can fixate on the target object
what eye movement do each of the following cause:
-adduction
-abduction
-depression
-elevation
-intorsion
-extorsion
-dextrocycloduction
-levocycloduction
-nasal rotation
-temporal rotation
-downward rotation
-upward rotation
-upper corneal pole rotates inwards
-upper corneal pole rotates outwards
-upper corneal pole rotates rightward
-upper corneal pole rotates leftward
name each of the eye muscles, their origins and their insertions
-medial rectus: common ring tendon: anterior globe
-lateral rectus: common ring tendon and greater wing of sphenoid: anterior globe
-superior rectus: common ring tendon and optic nerve sheath: superior anterior globe
-inferior rectus: common ring tendon: inferior anterior glove
-superior oblique anatomic: lesser wing of sphenoid: superior posterior lateral globe
-inferior oblique: medial maxillary bone: posterior lateral globe
where in the brain is the origin of CN VI?
pons
whats the final innervation of CN VI
the lateral rectus muscle
where is the origin of the cranial nerve III
the midbrain
for the medial rectus
what’s its primary (2ndary and tertiary if they have it) action and what CN is it’s innervation?
adduction and inferior III
for the lateral rectus,
what’s its primary (2ndary and tertiary if they have it) action and what CN is it’s innervation?
abduction and VI