Lecture 4 - Sensory Mechanisms-Updated

Photoreceptors vision eyecup direc6on and intensity

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Unformatted text preview: le light energy •  Electroreceptors –  Respond to weak electrical signals emiied by all organisms –  Exist in some fish 32 Photoreceptors  ­ Vision •  Sensory receptor in the eyes •  Receptor ac6va6on closes Na+ channels hyperpolarizing the cell •  Inhibits the firing rate 33 Photoreceptors  ­ Vision •  Opsin protein detects light •  Rhodopsin is the opsin found in vertebrates –  When excited by light, cis to trans change in conforma6on closes the Na+ channel, hyperpolarizing the cell 34 Photoreceptors  ­ Vision •  Photoreceptors differ from other sensory receptor cells because their membrane poten6al is in a slightly depolarized state when the cell is at rest •  Hyperpolarizes rather than depolarizes in response to a s6mulus •  Depolariza6on in uns6mulated state results in con6nuous release of glutamate –  Interpreted as absence of light •  When exposed to light, cell hyperpolarizes –  Glutamate release stopped –  Interpreted as visual image 35 Photoreceptors  ­ Vision •  Cone cells contain color ­sensi6ve pigments •  Rod cells respond to light but not color –  Rod cells allow animals to see in low light 36 Photoreceptors  ­ Vision •  Cone/Rod react in response to light but do not fire...
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This document was uploaded on 03/05/2014.

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