B6A12Sensory - Sensors & Transducers SENSES Sensory...

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Heyer 1 SENSES SENSES Sensory Receptors (Sensors) Transducer : a structure that converts a stimulus into a graded depolarization. • Physiological transducers are derived from specialized dendrites, often associated with modified epithelia. 1. Exteroceptors : sense external stimuli a) passive — sense environmental stimuli b) active — sense self-generated stimuli ÿ bat sonar, flashlight fish, knife fish electric fields. 2. Interoceptors : sense internal body condition Types of Sensory Receptors: Mechanisms of Transduction 1. Chemoreceptors 2. Mechanoreceptors 3. Thermoreceptors 4. Photoreceptors 5. Other Electromagnetic Receptors Types of Sensory Receptors: Mechanisms of Transduction 1. Chemoreceptors : chemical stimulus binds to specific binding protein on cell surface open ion gates depolarization. Interoceptors Blood glucose, fatty acids, pH Nocioceptors — chemicals released by damaged cells (pain) Exteroceptors (special senses) Olfaction Taste Types of Sensory Receptors: Mechanisms of Transduction 1. 2. Mechanoreceptors : physical distortion of cell membrane open ion gates depolarization. Interoceptors Propioceptors — muscles, tendons, joints Visceral stretch receptors Blood pressure, osmotic pressure Exteroceptors (cutaneous senses) Exteroceptors (special senses) Auditory hair cells Equillibrium hair cells Types of Sensory Receptors: Mechanisms of Transduction 1. 2. 3. Thermoreceptors : temperature-induced change of membrane protein open ion gates depolarization. Interoceptors Body temperature [B T ] — hypothalamus Exteroceptors (cutaneous senses) (“Cold” is a perception, not a real physical entity.)
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Heyer 2 Types of Sensory Receptors: Mechanisms of Transduction 1. 2. 3. 4. Photoreceptors : light absorbed by pigment- protein close ion gates hyperpolarization. Exteroceptors (special senses) Types of Sensory Receptors: Mechanisms of Transduction 1. 2. 3. 4. 5. Other Electromagnetic Receptors: EM energy absorbed by special metallo-protein complexes transduction mechanism unclear Electromagnetic fields Infrared radiation Generator Potentials In response to stimulus, sensory nerve endings produce a local graded change in membrane potential. Potential changes are called receptor or generator potential. Must be cummulative to threshhold before decay n Phasic response: n Generator potential increases with increased stimulus, then as stimulus continues, generator potential size diminishes. n Tonic response: n Generator potential proportional to intensity of stimulus. Convergence Receptive fields Stimuli Sensors Sensory neurons Low convergence : few receptors converge on a single sensory neuron.
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This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.

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B6A12Sensory - Sensors & Transducers SENSES Sensory...

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