Afferent 8- Retina


– OKAY SO THIS IS A SLICE
OF RETINA. AND IF THAT LAST LECTURE PIECE
DIDN’T BLOW YOUR MIND, THEN SURELY THIS ONE WILL. THIS IS A SLICE OF RETINA
THAT IS NOT THE FOVEA. SO WE HAVE SEVERAL
DIFFERENT LAYERS IN THE RETINA AND WE’RE GOING TO TALK ABOUT
EACH AND EVERY SINGLE LAYER. THE FIRST LAYER OF THE RETINA,
OKAY, NO, STOP, I CAN’T REALLY
REACH IT DOWN HERE, BUT YOU HAVE TO KNOW THAT LIGHT
IS GOING TO COME INTO THIS SCENE IN THIS DIRECTION
WHICH MAKES SENSE BECAUSE HERE ARE MY PHOTO
RECEPTORS MY RODS AND CONES. AND WE’LL GET THERE IN A SECOND
BUT LOOK AT ALL THIS STUFF THAT IS BETWEEN THE LIGHT
ENTRY POINT AND OUR PHOTO RECEPTORS. OKAY, NOW LET’S LABEL PARTS. YOU HAVE A LAYER
THAT IS THE FARTHEST AWAY FROM THE STIMULUS AND IT’S
CALLED THE PIGMENTED LAYER. AND THE PIGMENTED
LAYER OF THE RETINA, ITS ESSENTIAL
FUNCTION IS TO PREVENT, IT’S DARK, IT’S FULL OF MELANIN AND IT PREVENTS LIGHT
FROM BOUNCING AROUND AND REFLECTING
AROUND THE EYEBALL. SO LIGHT WAVES
THAT GET PAST THE CONES AND RODS DON’T BOUNCE AROUND
AND STIMULATE OTHER THINGS IN OTHER PLACES
AND MESS UP YOUR SIGHT, MAKE YOUR SIGHT BLURRY. SO YOU GOT YOUR PIGMENTED LAYER
FARTHEST AWAY FROM THE LIGHT. THEN YOU’VE GOT YOUR RODS
AND YOUR CONES, AND YOU CAN SEE HERE
THAT MY RODS ARE THE BLUE GUYS AND MY CONES ARE ORANGE. DO YOU AGREE THAT THE RODS AND THE CONES ARE ACTUALLY
FOUND IN THE SAME LAYER? AND THESE ARE
MY PHOTO RECEPTORS. AND WE’VE ALREADY TALKED
ABOUT HOW THEY FUNCTION. SO WE NEED LIGHT
TO REACH RECEPTORS. WE NEED THE LIGHT
TO REACH THESE GUYS IN ORDER, WE NEED THE LIGHT
TO REACH THESE GUYS FIRST. NOW IT’S ABOUT TO GET FUNKY. ARE YOU READY FOR THIS? BECAUSE WE’VE GOT THESE THINGS
CALLED HORIZONTAL CELLS, SERIOUSLY, HORIZONTAL CELLS. AND HORIZONTAL CELLS LOOK
AT HOW THEY’RE SET UP. THEY’RE ACTUALLY MAKING CONTACT
WITH MY RODS AND MY CONES. AND THEY REACH OUT AND
CONTACT RODS AND CONES IN A LINE AND THEY PREVENT,
REALLY THIS IS WEIRD, THAT THEY PREVENT CROSS TALK
BETWEEN THE RODS AND CONES. THEY PREVENT A STIMULUS FROM,
THEY KEEP IT MORE FOCUSED. THEY PREVENT THE INFORMATION, THEY’LL INHIBIT THAT ROD OR CONE OVER THERE THAT’S THINKING THAT
IT WANTS TO FIRE A NON MESSAGE, IT WILL INHIBIT IT
BECAUSE THE LIGHT, IT PERCEIVES THE LIGHT AS BEING
MORE FOCUSED RIGHT HERE. OKAY, DID YOU FOLLOW THAT? HORIZONTAL CELLS LIKE PREVENT, HOW DID I WRITE IT IN MY NOTES? LATERAL SPREAD. AND YOU GOT TO REMEMBER
THESE GUYS ARE ALL SITTING IN THE SAME
EXTRA CELLULAR FLUID. SO ANY CHANGES IN IONS,
ANY CHANGES IN, IN, DETAILS OF THE EXTRA
CELLULAR FLUID ARE GOING TO AFFECT OTHER CELLS
IN THE VICINITY. SO WE’VE GOT THIS WHOLE
LAYER THAT’S BASICALLY LIKE A BUNCH OF POLICEMEN
THAT ARE SAYING NO, THAT STIMULUS
DIDN’T COME TO YOU, SO EVEN THOUGH YOU’RE
FEELING THE FUNK IN THE EXTRA CELLULAR FLUID,
WE DON’T WANT YOU FIRING. THIS WASN’T YOURS. CRAZY TALK, OKAY,
YOU THOUGHT THAT WAS CRAZY, HOW ABOUT THESE BIPOLAR CELLS. BIPOLAR CELLS ARE
JUST CHILLING HERE. THEY’RE THE ONES
THAT INFORMATION GETS DUMPED ON THEM FIRST
FROM THE RODS AND CONES, SO BASICALLY
THEY’RE A MESSENGER, MESSENGER FROM RODS AND CONES. SO THEY’RE GOING
TO TAKE THE MESSAGE. HORIZONTAL CELLS ARE SAYING HEY, YOU, ROD OVER THERE,
DON’T YOU BE FIRING AND HEY YOU, GUY OVER THERE, DON’T
YOU BE DOING ANYTHING. BUT THE BIPOLAR CELLS RECEIVE
THE INFORMATION DIRECTLY FROM THE RODS AND CONES AND SEND IT ON AND SOMETIMES
THEY DON’T SEND IT ON. THEN YOU’VE GOT A SET
OF AMACRINE CELLS, AND IT LOOKS LIKE I’M GOING FOR,
YOU KNOW, KIND OF A GRAY COLOR
FOR THESE AMACRINE CELLS, AMACRINE CELLS. AND I LOVE THIS, I WAS JUST THINKING IN MY BRAIN
WHAT DO AMACRINE CELLS DO? THEY HAVE A HUGE VARIETY OF
CELL FUNCTIONS THAT ESSENTIALLY HELP INTERPRET VISUAL DATA
BEFORE IT LEAVES THE EYE. YOU GO AHEAD. I MEAN I FEEL LIKE OKAY, WE COULD PROBABLY
HAVE SIX LECTURES ON AMACRINE CELL FUNCTION
AND HOW THOSE THINGS WORK. BUT IT’S ANOTHER LAYER,
LOOK WHO’S CONNECTED. MY LITTLE BIPOLAR CELLS ARE
CONNECTED TO AMACRINE CELLS AND THEY’RE ALSO CONNECTED
TO THESE YELLOW GUYS, WHICH I’M HOPING
ARE MY GANGLION CELLS. ARE THEY, NO. I DON’T KNOW
WHO THE YELLOW GUYS ARE. THEY START WITH,
I DON’T KNOW WHO THEY ARE. BUT THAT’S OKAY ‘CAUSE WE
DON’T HAVE TO KNOW THEM, WE HAVE TO KNOW
THE GANGLION CELLS. BECAUSE GUESS WHAT,
THE GANGLION CELLS ULTIMATELY, THROUGH ALL THESE LAYERS
OF DON’T TALK TO THAT GUY AND GO AHEAD
AND SEND YOUR MESSAGE AND DON’T SEND THAT MESSAGE, AND THAT MESSAGE
CLEARLY IS IRRELEVANT, ALL OF THEM PUTTING IN
THEIR LITTLE TWO CENTS IF THE MESSAGE GETS
THROUGH TO THE GANGLION CELLS, THESE GUYS ARE WHO BASICALLY
BECOME THE OPTIC NERVE. SO IF YOU LOOK, YOU CAN’T REALLY SEE IT DOWN
HERE AT THE BOTTOM, BUT I’M, I JUST CIRCLED THE OPTIC NERVE. THEY GET INFORMATION, COME ON, EVERYBODY, TELL ME
WHAT THE–AND THEN THEY TAKE THAT INFORMATION THEIR
AXONS BECOME THE OPTIC NERVE. ALL THE AXONS FROM ALL
THE GANGLION CELLS IN THE RETINA CONVERGE
ON THE OPTIC DISC AND BECOME THE OPTIC NERVE
AND EXIT THE EYEBALL AND THAT’S HOW THE INFORMATION
GETS TO THE BRAIN. IF THIS IS LIKE, LIKE WIDE EYES, LIKE IF YOU LOOK LIKE THIS,
OH, MY GOSH, THEN YOU DID UNDERSTAND WHAT WE
JUST DID BECAUSE IT’S, IT, WOW, WE NEED AN EYEBALL CLASS,
NOT ONLY THAT, DUDE ONCE THIS INFORMATION GETS
TO THE BRAIN, THERE IS A RANGE OF THINGS
THAT HAPPEN TO IT IN THERE. YOU ARE SO AMAZING,
PAT YOUR EYEBALLS AND YOUR EARS AND YOUR NOSE AND YOUR TONGUE.
OH. THAT’S IT THAT WAS THE AFFERENT
NERVOUS SYSTEM AND NOW WE’RE GOING TO DO

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