Orbit Flashcards
Where do lower motor neurons of the ventral horn of the spinal cord terminate?
on muscles
-so even the cells terminating on the eye muscles are lower motor neurons
Retinal gangilion cells of the retina project to the ____, ____, ____ via the optic nerves and tracts
- SCN
- SC
- LGN
The LGN of the thalamus projects to the _________ via the optic radiations
- primary visual cortext (VI)
VI (Striate cortex) is found in the _____ lobe along the banks of ______
- VI striate cortex is found in the occipital lobe along the banks of the calcarine fissure
Light enters the eye and via the pupil and is focused on the retina via the _____
Lens
The initial processing of information occurs in the _____
Retina
What part of the eye contains the highest concentration of cones and is where the finest visual discrimination occurs
The fovea within the macula
Where do the axons of the ganglion cell exit the retina
Optic disc
What are the cells that give rise to the optic nerve?
retinal ganglion cells
The axons of the ganglion cells leave the retina at the _____
Optic disc
- no photoreceptors here, so this is a blind spot
Label these layers of this retina
Why is there pigemented epithelium in the retina?
- think of photons as particles
- you do not want these particles bouncing around so you want them to be absorbed by something incase they miss a photoreceptor cell
- you will have very blurry vision if you didnt have this
- albinos do not have pigemented epithelium
Where are the horizontal cells, bipolar cells and amcrine cells located?
in the INL
inner nuclear layer
Where are the cell bodies of rods and cones located?
ONL
Outer nuclear layer
Where are the cell bodies of ganglion cells?
GCL
Ganglion cell layer
Where is the outer segment located in the retina?
Where is the nucleus located?
Where is the synaptic body located?
Outer segment: PL photoreceptor layer
nucleus: ONL outer nuclear layer
Synaptic body: OPL outer plexiform layer
How many different types of rods and cones are there?
one type of rod
3 types of cones
each has a distinctive response to different wave lengths
If you have lesion of the optic nerve after the chiasm (in the optic tract) will you have loss of a visual field?
Yes the contralateral side
Which ganglion cell axons cross at the optic chiasm?
from the nasal or from the temporal?
- ganglion cell axons originating from the nasal retina cross at the optic chiasm to the contralateral side
- ganglion cell axons from the temporal retina do not cross at the optic chiasm and remain ipsilateral
The axons originating from the retinal ganglion cells which terminate in the superior colliculus form the ______
- the axons originating from the retinal ganglion cells which terminate in the superior colliculus form the brachium of the superior colliculus in close proximity to the superior colliculus
Where do the retinal ganglion cells project to?
- Suprachiasmatic nucleus of the hyothalamus (circadian pacemaker
- Pretectal nuclei (eye movements)
- Superior colliculus (visual reflex)
- Lateral geniculate nucleus of the thalamus
The superior colliculus (of the midbrain) receives direct retinal input via the ________
Brachium of the superior colliculus
The superior colliculus receives input from:
- brachium of the superior colliculus
- visual cerebral cortex
- pretectal nuclei
the superior colliculus is involved in:
visual reflexes
the superior colliculus projects to the spinal cord via the
tectospinal tract
The lateral geniculate nucleus (LGN) is located in the ____
Thalamus of the diencephalon
The LGN receives direct retinal input via the
Optic tract
The LGN projects to the _____ via the _____
Primary visual cortex (area 17) via the optic radiations
With these lesions what is your deficit?
A protective, thin, transparent mucous membrane that has two parts:
Conjuntvia:
- palpebral
- bulbar (ocular)
Which layer of the conjunctiva lines the innermost part of the eyelids?
- palpebral conjunctiva
Which layer of the conjunctiva lines the outermost part of the eyeball?
Bulbar (ocular) conjunctiva
Inflammation of the conjunctiva is commonly called
Pink eye
Explain the corneal reflex
- Afferent: nasociliary branch of the opthalmic branch of the trigeminal nerve (V1) sensing the stimulus on the cornea
- Efferent: facial nerve (zygomatic branch) initiating the motor response of the orbicularis oculi
Name this layer of the eye:
- dark reddish brown membrane between the sclera and the retina
- largest part of the vascular layer-all arteries feeding choroid are branches from opthalmic artery
- lines majority of the sclera
- “red eye” in pictures
Chorioid
- choriocapillaries nourish the outermost (cones and rods) layer of retina
What is the circumferential tissue inside the eye composed of the ciliary muscles and processes
- vascular layer
Ciliary body
What secretes aqueous humor which fills the anterior and posterior chambers of the eye
- nourishes lens and cornea because they are avascular
Ciliary processes
What is the space between cornea and the iris/pupil?
- anterior chamber
What is the space between the iris/pupil and the lens and ciliary body?
Posterior chamber
Explain the flow of aqueous humor:
- goes to posterior then anterior chamber
- then drains in vein of sclera
Blockage of schlemm’s canal (sclera venous sinus) can lead to increased pressure and ____?
Glaucoma
What is the adjustment in the len’s shape to focus at various distances
- under PARAsympathetic control
- contaction = release of tension = spherical lens = close vision
Accomodation
What is this vascular layer of the eye?
- colored circular muscle
- a central aperature-the pupil- for transmitting light
Iris vascular layer
What muscle:
- parasympathetic via ciliary ganglion
- closes the pupil
- “constriction”
Sphincter pupillae muscle
What muscle:
- sympathetic via superior cervical ganglion
- opens the pupil
DIlator pupillae muscle
Discuss eyeball movements
Discuss agonists, synergists, and antagonists
How is testing eye muscles individually with the H test different from their actions in a straight ahead gaze?
- muscles rarely act independently and almost always work together in syngergist and antagoist groups
- thus, clinical testing requires maneuvers to isolate muscle actions
- only the actions of the medial and lateral rectus are tested, starting from the primary postion
- the others must be tested either from an abducted or adducted postion
- When the eye is aBducted by the lateral rectus, only the rectus muscles can produce elevation and depression
- When the eye is aDducted by the medial rectus, only the oblique muscles can produce elevation and depression
Which nerve of the eye has parasympathetic fibers?
Oculomotor nerve (CN III)
Explain oculomotor nerve palsy
What muscle is innervated by trochlear nerve (CN IV)?
Superior Oblique
What muscle is innervated by abducent nerve (CN VI)?
Lateral Rectus m
Describe abducent nerve palsy
Lateral rectus is gone so medial rectus is pulling with no opposition
- but in B we were able to move it out of abduction
- Sherings Law
- we inhibit antagonist because brain is still trying to get the eye to move to abduction
- so the brain inhibits medial rectus for us and we can move the eye to the middle but still cant abduct
- Sherings Law
Describe the fibers running through the ciliary ganglion
Pass through ganglion without synapsing
Describe Horner’s sydrome
- Results from interruption of a cervical sympathetic trunk and is manifest by the absence of sympathetically stimulated functions of the ipsilateral side of the head
- Constriction of pupil (miosis)-because dialators are knocked out
- Drooping of superior eyelid (ptosis)-tone is gone
- Sunken in eye (enopthalmos)
- redness and increased temperature of skin (vasodialation)
- absense of sweating (anhydrosis)
What are the two arteries that supply extraocular muscles and what specifically do they supply?
Opthalmic artery:
- branch of internal carotid
- the opthalmic artery supplies most of the extraocular structures
Infraorbital artery:
- branch of external carotid artery
- the infraorbital artery supplies the lower portion (floor) of the orbit
Where do the presynaptic fibers of of sympathetic synapse?
- Superior cervical ganglion
- some fibers run with opthalmic all the way to the bulb via long ciliary
- other run through ciliary ganglion and pass to bulb via short ciliary nerves
Where do the presynaptic fibers of parasympathetic synapse with postsynaptic nucleus?
- Ciliary ganglion
What does contraction of the ciliary muscles do?
- Causes the circular ciliary body to decrease in diameter
- like a sphincter, the lens relaxes, rounding up or thickening (near vision)
- accommodation
- if you relax the ciliary body this increases its diameter
- thus the lens suspended in its center is stretched and become thinner (far vision)
What nerve does the corneal reflex?
- touching cornea with wisp of cotton envokes blink
Opthalmic nerve V1
