results when one cannot smell due to damage of olfactory nerve or zinc deficiency
Eye & Vision
40% of cerebral cortex is dedicated to processing images captured by the eye and the eye is protected by a cushion of fat within the optical orbit
shade from sunlight & keep sweat away from the eyes
used for blinking & have glands producing eye grit. Tarsal glands release oil that forms a film & slows water evaporation
transparent mucous membrane covering inner surfaces of eyelids (white of the eye) and is known as pink eye when becomes inflammed due to bacteria or virus
consists of lacrimal gland & lacrimal duct secreting a fluid to keep eye moist with blinking eye spreading fluid on surface and lacrimal fluid killing the bacteria
extrinsic eye muscles
the six muscles moving the eye
Structures that protect the eye
extrinsic eye muscles
anatomy of eyeball
designed to protect photoreceptors, capture & process & image.
makes up sclera & cornea
transparent (avascular containing pain receptors) & allows light to enter eye...easily damaged, but has good regeneration ability
composed of choroids, ciliary body, and iris
dark in color containing melanin to absorb light; highly vascularized
encircles lens & helps to adjust it
colored part of eye with the color coming from amount of melanin in iris body
(note: iris has smooth muscles controlling size of pupil with the papillary light reflex protecting eye from light damage)
opening of iris
also called retina & contains melanocytes and a sheet of nervous tissue made up of photoreceptors (rods & cones)
Rods & Cones
Rods: dark & grays (do not regenerate themselves)
Cones: bright (do not regenerate themselves)
******Rods & cones contact a bipolar neuron synapsing with ganglion cells. Axon of the ganglion cells enter optic nerve & carry stimulus to occipital lobe
"yellow spot" at posterior pole
a pit at its center & is the area containing only cones providing visual acuity
(blind spot): where retina gathers to & from optic nerve and lies medial to fovea centralis
Internal chambers & fluids
fluids in these chambers nourish eye tissues & maintain appropriate pressure
The posterior chamber filled with vitreous humor
The anterior chamber filled with aqueous humor
filled with vitreous humor that regulates eye pressure, maintains retina against the eye wall, and allows the image to travel across the eye to the retina. This is formed as an embryo and lasts the entire life time.
filled with aqueous humor, it is more liquid than vitreous humor, periodically regenerated, and drains into scleral venous sinus.
a transparent disc that changes shape to adjust to focus light. The lens sends images that are upside down and reverse from left to right. The cerebral cortex reverses the image. With age the lens thickens and becomes less flexible reducing its ability to focus light.
eyes are designed to see best where...
pupil constricts when what?
when looking at closed up objects
Visual pathways of image
Image travels from retina to optic nerve to optic chiasma to optic tract (This tract travels to midbrain some tract branch out to control eye reflexes, other branch to the hypothalamus). From the hypothalamus to the thalamus to cerbral cortex (visual cortex in occipital lobe). Images are sent at different angles from both eyes, the brain process that information to create just one image