Eye – Second Timers – V8

RODS AND CONES:  In the back of the eye is the retina.  It has different cells in it, two of with are the light detecting rod cells and the cone cells.The rod cells see black and white and the cones see color. When you focus on something,  you are only using your cone cells.

RODS AND CONES:  Unlike the cone cells, rod cells cannot detect color. However, they are ten thousand times more sensitive to light than the cones cells! This extra sensitivity is fantastic for night vision!

RODS AND CONES:  Rod cells look like skyscrapers, with floors stacked on top of each other. These floors are called discs. There are over one thousand discs in a single rod cell!

RODS AND CONES:  Woven Into each of these tiny discs in the rods there are incredibly small protein molecules called rhodopsin. When light enters the eye, it strikes the rhodopsin proteins. This causes a change in the rhodopsin. This causes a chemical change to begin to take place. When enough rhodopsin proteins are activated,  a signal is sent from the rod cell to a cell that lies right above it called a bipolar cell.

RODS AND CONES:  The bipolar cells sit on top of the rod cells. Each of the bipolar cells has about ten rod cells attached to it. If the majority of them send a message to a bipolar cell, the bipolar cell will then fire a message to the cell on top of it called the ganglion cell. The ganglion cells send messages to the brain.

RODS AND CONES:  Ganglion cells have long wire-like axons growing side-by-side that form the optic nerve for each eye. These two optic nerves cross over each other at a place called the optic cheddar.  They then continue on to the opposite side of the brain’s eyesight center, the visual cortex. Your two optic nerves are very skinny,  only the width of a pencil lead, and yet together they send over 60 million complex messages a second to give you the fantastic gift of sight!

MESSAGES PER SECOND:  Your eyes are sending messages to the brain at the rate of 30-60 times a second.

MESSAGES PER SECOND:  Many birds and some insects send messages at 200 times per second!

MESSAGES PER SECOND: Birds’ auditory cortex operates at a faster level than ours does.  We can’t even see what birds are doing sometimes because our eyes don’t transmit messages fast enough.

MESSAGES PER SECOND:  Seeing quickly all has to do with the speed of molecular reactions.  The cone cells’  first step in sending a message to the brain is having the light-detecting opsin proteins in them go through a molecular change when light photons hit them. This happens in several femtoseconds.  That’s a thousand times faster than a trillionth of a second.