Visual sense


The interpretation of vision occurs in the visual cortex of the occipital lobes. The photoreceptors, which are rod and cone cells, perceive the stimulus of light and energy through the eyeball, and then transmit these visual impulses through the optic nerve and up the optic tract to reach the visual cortex.


Sensory components within the eyeballs are complete around the age of 20 weeks. The necessary accessory structures develop fully around the age of 32 weeks.

The visual organs, the eyes, refract and focus the incoming rays of light so that they can reach the photoreceptors at the back of each eyeball. The photoreceptors then send the information in the form of nerve impulses through the visual pathways of the brain until they reach the occipital lobes of the cerebrum. This is how vision is perceived.

Photoreceptor cells are really quite active, receiving and accepting stimulation of up to 1 billion variable forms of stimuli every second. These cells can perceive light variations and gradations and 7 million variations of color.


Visual sense
Image: Visual Sense

The eyeballs themselves are set at the exact appropriate distance apart to be able to achieve “vision in stereo,” or binocular vision. Positioned along the anterior portion of the skull, they achieve stereoscopic vision when focusing on an object. Depth is part of the visual picture for the human thanks to three dimensional perception. Visual experience is considered to be responsible for 80% of the information and knowledge which is gained.

The Accessory Structures of the Eye

The accessory structures of the eye refer to those structures which either protect the eyes or allow the eye to achieve its full range of motion. Structures such as the facial muscles, bony orbit, eyelids, eyebrows, eyelashes, conjunctiva, as well as the lacrimal structure responsible for the creation of tears, all help to protect the eye. The intrinsic eye muscles, which come from the orbit and then insert themselves along the puter layer of the eyeball, are responsible for the eye’s ability to move to its capacity.
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