Eye Flashcards
What is the cornea?
What other tissue does it blend with?
A transparent, non-adjustable lens of the eye.
The cornea blends into the peripheral sclera (white of the eye)
What controls the lens?
What joins the lens and its controls?
The “lens” proper, is controlled by muscles of the ciliary body. Joinin these to structures is the Zonula Fibers which act as Guy-Wires.
Where is the iris? What does it do? What does the retina house? What do radial muscles and circular muscles do?
Anterior to the lens proper is the iris diaphragm, which surrounds the pupil. Action of the muscle of the iris changes the pupil diameter. This controls the amount of light passing to the depths of the eye.
Contraction of the Radial Muscles causes dilation.
Contraction of the Circular (Sphincter) Muscles causes constriction.
The retina is the location of the Rods and Cones.
What does this mean–RetinaGeniculoStriate pathway
What is it?
Where does it travel?
The principle visual pathway.
Goes from the retina to the lateral geniculate body of the thalamus to the striate cortex of the occipital lobe (aka V1 primary visual cortex.
What is the Tectal Pathway. Type of pathway? Function? What is the route of its projection? Further processing is carried out where?
(see a deer move in the forest.)
Primary Reflex pathway.
Visual attention and movement detection.
Projects from the retina to the superior colliculus in the midbrain.
Further processing is carried out by projections to the thalamus and on to the inferotemporal cortex (in the inferior temporal gyrus)
Retinohypothalamic tract is associated with what type of rhythms?
What are the 4 cycles?
What gland is it functional connected with?
Functionally it is associated with circadian rhythms such as:
Sleep-wake cycles
Day-night cycles
Reproductive cycles,
Other periodic events.
Functionally connected with the pineal gland. (They work together to give us the cycles. Nighttime vehicle accidents are often due to these.)
What are the halves of the retinal region?
Lateral half is the Temporal Hemiretina. (close to the temple. Visual field from the left goes to the hemiretina on the right.)
The medial half is called the Nasal Hemiretina. or medial hemiretina. (closer to the nose)
Eah hemiretina is divided by a horizontal line through the macula into quadrants.
The Retina is subdivided into what 3 concentric rings?
- This small innermost macular area. (highest density of rods and cones to give detail.
- The pericentral area or Paramacular area.
- The peripheral area or Monocular area. (Can only see with one eye.)
What happens to images in the retinal regions?
To what are they directed?
Images are inverted by the lens and reversed as they projected onto the retina.
The temporal visual field is projected onto the nasal hemiretina.
The lower visual field is projected onto the upper hemiretina.
Define Binocular field and Monocular field
Binocular–Most of the visual field is received by both eyes.
The remainder is received by only one eye .(Monocular field.)
What are the 5 types of Retinal Cells?
1 receptor cells-rods and cones
- bipolar cells
- horizontal cells
- amacrine cells
- ganglion cells–its projection axons are in the optic nerve and optic tracts.
What is the path of the nasal hemiretina and temporal hemiretina?
Nasal hemiretina projects its ganglionic axons across the optic chiasm to the contralateral geniculate body.
Temporal hemiretina projects its ganglionic axons ipsilateral to the lateral geniculate body of the thalamus.
Where does the optic nerve end and optic tract begin?
Optic Chiasm
How is the Lateral geniculate nucleus arranged?
It is a six-layered, dome-shaped nucleus. A given point in the visual field is represented by a column of cells extending through the six layers. They are stacked in a double eye grouping… ie. 1 &2, 3&4 etc. 1&2 see the same point and so on.
Describe Optic Radiation
The inverted retinal field is projected caudally from the Lateral Geniculate Nucleus (Body) in spatially corrected orientation so that the upper visual field is projected above the calcarine sulcus.
