Special Sense Organs Pt.1

What are the three layers/tunics of the eyeball from superficial to deep?

fibrous tunic

vascular tunic (uvea)

sensory tunic (retina)

What does the internal cavity consist of and what kind of liquid is in those segments in the eyeball.

Anterior segment which has aqueous humor

Posterior segment which has vitreous humor

The structure of the eyeball also includes a _____ which is behind the iris.

Lens

What is the fibrous tunic composed of?

sclera

cornea

How does light interact with the cornea and what does it look like?

clear

light passes through

refract (bend)

What does the sclera look like and why is it important?

whites of eyes

muscles attach

What is the innervation and actions of the superior rectus m.?

Elevation of eyeball

Oculomotor n. (CN III)

What is the innervation and actions of the inferior rectus m?

Depression of eyeball

oculomotor n (CN III)

What is the innervation and actions of the medial rectus m?

adduction of eyeball

oculomotor n (CN III)

What is the innervation and actions of the lateral rectus m?

abduction of eyeball

abducens n (CN VI)

What is the innervation and actions of the superior oblique m.?

depression and abduction of eyeball

trochlear n (CN IV)

What is the innervation and actions of the inferior oblique m?

elevation and abduction of eyeball

oculomotor n (CN III)

What is the vascular tunic composed of?

choroid

ciliary body

iris

What reaction does parasympathetic stimulation have on the pupil?

Constrict pupil

What reaction does sympathetic stimulation have on the pupil?

dilate pupil

How is the lens used by the eye?

Used to focus light on the retina by changing shape

What is the retina (sensory tunic) composed of?

photoreceptors

*optic n (CN II) is made up of axons of the retinal ganglion cells

What is the visual pathway order?

photoreceptors

ganglion cells (axons for the optic nerve)

optic chiasm (partial crossover)

Optic tract

thalamus

primary visual cortex

For visual pathway steps 1 and 2, what kind of signal is light converted into, what optic nerve do retinal ganglion cell axons leave the eye as, and what side does the right and left optic n carry info to?

Photoreceptors convert light into an electrical signal

retinal ganglion cell axons leave the eye as the optic nerve (CN II)

Right and left optic n carries info from both the right and left visual fields

For the visual pathway steps 3 and 4, where do fibers from the nasal aspect of each retina cross over, do these fibers continue, and what side does the right and left tract carry info to?

Fibers from the nasal aspect of each retina cross over at the optic chiasm (this is carrying peripheral vision)

These fibers continue via the optic tracts.

Right tract carries info for the left visual field

Left tract carries info for the right visual field

For the visual pathway for steps 5 and 6, where do most fibers synapse and what side does the right and left primary cortex integrate info from?

Most fibers in the optic tracts synapse with neurons in the thalamus

Fibers from the thalamus project to the primary visual cortex in the occipital lobes

Right primary cortex integrates info from left visual field

Left primary cortex integrates info from the right visual field