ch 42 - Lecture 6 Sense Organs (Chapter 42) I. Sensory...

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Lecture 6 – Sense Organs (Chapter 42) I. Sensory Systems A. Sensory Reception 1. Sensory receptors a. neuron endings or specialized receptor cells in close contact with neurons b. detect info about changes in internal or external environment 2. Sense organs b. eyes, ears, nose, etc. 1. Sensory receptors a. energy transduction (e.g. beam of light, chemical compound) i. transduction couples a stimulus with opening & closing of ion channels in plasma membrane of sensory receptors ii. alters permeability of plasma membrane to ions iii. produce receptor potentials (membrane depolarizations or hyperpolarizations) b. Receptor potentials are graded responses i. like EPSP – summation; excitatory, inhibitory C. Sensory Systems 1. Receptor potential generates action potential that transmit info to CNS a. Receptor potentials stimulate release of neurotransmitter(s) which flow across b. Action potential in afferent neuron travels along axon to CNS c. Depth of stimulation depends on: number of neurons firing, specific receptor, D. Sensory Adaptation 1. Sensory receptors send coded signals to CNS through sensory neurons 2. Sensory adaptation a. during a sustained response i. firstly, receptor sensitivity decreases reducing frequency of action potential in a sensory neuron ii. release of transmitter from presynaptic terminal may decrease in response to series of AP - slowly adapt (continue firing) e.g. allows sensation of continued pain - fast adaptation (e.g. nasty smells; ability to get used to pungent odor that then no longer worries us) E. Perception 1. brain interprets sensations by converting them to perceptions of stimuli 2. Sensory perception F. Sensory Receptors Classified by Location of Stimuli 1. Exteroceptors
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a. receive stimuli from outside environment b. how to determine type of food source, friendly associations, hot or cold, etc. 2. Interoceptors a. detect changes within body b. changes in pH, osmotic pressure, body temperature, chemical composition of blood c. unaware of messages sent to CNS until signal internal conditions; e.g. thirst in diabetes insipidus G. Sensory Receptors Classified by Type of Energy a. receptors in antennae locate prey, or ticks identifying an endothermic prey b. mammals i. external: skin, tongue, ear, eye ii. changes in temp. via receptors/nerve endings on body surface signal thermoreceptors in hypothalamus - homeostatic mechanisms ensure constant internal body temperature 2. Electroreceptors a. used by predatory fish to detect prey i. respond to electrical potential - electric fields from muscle activity
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This note was uploaded on 02/27/2009 for the course BIO 102 taught by Professor Brey during the Spring '08 term at Rutgers.

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ch 42 - Lecture 6 Sense Organs (Chapter 42) I. Sensory...

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