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BIOL 2213 (22)
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Lecture 1

BIOL 2213 Lecture 1: Phys10:1

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Department
Biology
Course
BIOL 2213
Professor
Dr.Hill
Semester
Fall

Description
Slide 27: Retina has photoreceptors that can convert wavelengths to action potentials that exit the back of the eye through the optic nerve and travel to the optic cortex Outermost: Sclera provides structure, has lots of connective tissue Choroid: pigment epithelium (black) Innermost: Retina - posterior portion of the eye Optic disc makes the blind spot in the eye – won’t generate action potentials Two parts: optical and neural Optical – focusing light image onto the retina & regulating the amount of light that gets into the eye (Lens, Iris, Pupil) Neural – Modified neurons that are responsible for taking the light stimuli and turning it into action potentials (Retina, Optic Nerve) No photo receptors at the optic disc where the optic nerve enters (blind spot) Slide 28: When ciliary muscles contracts, the lens flattens out and changes the focal point – happens depending on the distance of where the object is relative to the eye Fovia Centralis – center of your field of vision, has a concentration of photoreceptors (rods and cones) of the eye Rods – don’t detect color (black and white) Cones – detect color Slide 30: Rods and Cones – cells that make up the retina (photoreceptive structure in the eye) Blue = cones, green = rods First cells in the pathway from taking the physical light and turning it into an action potential Rods & Cones are not capable of producing an action potential Rods and cones respond to the light & causes change in membrane potential (receptor potential) Rods & cones = bipolar cells, yellow = ganglion cells Photo pigments absorb light – colored because they absorb some wavelengths of light and now others Slide 31: ***1 OR 2 QUESTIONS THAT ARE ABOUT THE DETAILS OF THIS PROCESS*** Phototransduction – how we get light to turn into action potentials In the dark when the cone cell is not being stimulated by light it has a weird membrane potential (-35mv when there is no stimuli/light) When stimuli (light) hits them they hyperpolarize to -70mv, initiates release of neurotransmitter Pathway in blue = in the dark/ no stimuli – influx in sodium and calcium causes the cell to depolarize Big picture: in the dark, the cell is depolarized Opsin = photo pigment, what differs between Cones and Rods – protein that absorbs certain wavelengths of light Opsins in Rods: Rodopsin Vitamin A important for vision because you need the retinal (Low vitamin A won’t have enough Retinal) When light hits the cell, cGMP turns into something else and causes the channels to close (no more positive ions rushing in = hyperpolarization) Slide 32
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