Esdin LS 2 Lec 4 Sensory

These rst light pigment epithethial cells ganglion

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Unformatted text preview: ntal –  Photoreceptors (rods and cones) responds to light go to optic nerve Retina strengthen the synapses Amacrine Horizontal bipolar cells do not respond to light Rod physically hits these first Light pigment epithethial cells Ganglion cells Bipolar cells sends info to NS Cones fewer ganglion cells then bipolar cells 16 4/21/13 Photoreceptor •  Rods dark or light black and white –  Sensitive to light –  Respond to low illumination •  Cones responds to wavelength –  Less sensitive to light –  Respond to high illumination •  Both types of photoreceptors contain pigments that absorb light Pigments colorblindness knock out one of the colored cones •  Rods –  Rhodopsin •  Cones s (blue), m (green), L (red) –  S, M, and L pigments –  Photopsin •  These proteins contain a pigment called retinal ________ 17 4/21/13 counterintuitive photoreceptors need to be hyperpolarized to see depolarization prevents us from seeing Rods in the Dark in the dark, retinal in the cis form; releasing glutamate no light exposure cGMP levels are high N a+ K+ Rods cyclic GMP dependent Na+ channels Na+ channels are open active due to high cGMP levels Na+ influx causes depolarization receptor potential Ca2+ channels open Ca2+ Ca2+ Influx occurs NT release causes graded potential in bipolar cells Bipolar cells VGCC - calcium influx, neurotransmitter release no signal is reaching the brain Rods Rhodopsin assoc w transducin Membrane pigment mlecule Retinal α βγ Phosphodiesterase α cGMP Breakdown enzyme that protein assoc. w Transducin pigment three part protein alpha subunit translocates changes and dissociates; travels along the conformation membrane and activates PPDE breaks down the cyclicGMP 18 4/21/13 glutamate inhibitory in the eye, not in the brain NT less important than the receptor, glutamate linked to a hyperpolarization channel Rods When Exposed to Light retinal becomes trans activates transducin, which removes GTP from the sodium channel, closes the channel, causes hyperpolarization When cGMP levels are low Na+ channels are closed Hyperpolarization occurs Rods less glutamate released No NT release No graded potential Bipolar cells very complex don't have Act. Pot. glutamate is excitatory Neural Pathway of Vision Left visual field Right visual field Binocular vision everything you see is called visual field binocular vision: depth perception highest density of photoreceptors sees best; visual acuity in middle of the eye Nasal retina Temporal retina peripheral vision isn't as good because it falls on an area with lower density of photoreceptors; seen with one eye only Optic nerve Optic chiasm intersection of optic nerves Optic tract Lateral geniculate nucleus in the thalamus Visual cortex if you lose an eye, you lose ipsi peripheral vision if optic chiasm severed, no eyesight 19 4/21/13 people are like wow; triple wow! Neural Pathway of Vision •  The two optic nerves meet to form the optic chiasm •  Some axons cross to the opposite side of the brain forming optic tracts •  Fibers pass to the thalamus •  Signals are sent from the thalamus to the visual cortex 20...
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