Lec16 Senses - Chapter 14 The Senses Sensory Receptors May...

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Chapter 14 The Senses
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Sensory Receptors May be relatively simple: pressure, temperature, touch, pain, stretch, chemical stimuli Or take the form of more complex organs: Eye, ear, tongue, nasal cavity
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Simple Receptors Some receptors are constructed from the dendrites of sensory neurons Some receptors (pain, blood pressure) are simply unspecialized dendrites Other receptors have dendrites that have various structural modifications Many are specialized epithelial cells that synapse with sensory neurons
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How does sensation occur? Sensory receptors respond to environmental stimuli Nerve impulses travel to the cerebral cortex Sensation (conscious perception) of stimuli occurs Sensory adaptation, decrease in stimulus response, can occur with repetitive stimuli (i.e. odor)
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Continuous Stimulation of Many Receptors Causes Adaptation i.e. after a while receptors cease to respond Pressure receptors in skin show adaptation Pain receptors do not Complex senses like vision have more complex patterns of adaptation
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Sensory receptors Sensory receptors – dendrites specialized to detect certain types of stimuli Exteroceptors : detect stimuli from outside the body (e.g. taste, hearing, vision) Interoceptors : receive stimuli from inside the body (e.g. change in blood pressure)
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Types of sensory receptors Chemoreceptors – respond to nearby chemicals Pain receptors – a type of chemoreceptors that respond to chemicals released by damaged tissue Respond to excessive pressure, chemicals, extremes in temperature Impulses from these neurons are interpreted as pain in the CNS Pain originating from trauma in internal organs sometimes appears to come from the skin or from skeletal muscles remote from the organ
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Types of sensory receptors Photoreceptors – respond to light energy Mechanoreceptors – respond to mechanical forces such as pressure Thermoreceptors – stimulated by temperature changes
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Senses and the receptors involved
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Stretch Receptors (Propioreceptors) Muscles have contain specialized "spindle fibers" which are modified muscle cells wrapped with the dendrites of sensory neurons Stretching causes stimulation of these neurons which transmit impulses to the CNS The CNS in turn, initiates muscle contractions which allow us to walk and maintain posture Tendons and joints have similar structures which prevent over- stretching
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Cutaneous receptors Receptors in the dermis that make the skin sensitive to touch, pressure, pain and temperature
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Taste Taste receptors are located in structures called taste buds Located within numerous small projections called papillae that cover the surface of the tongue Taste buds mainly around front back and sides of tongue, relatively few in middle ~ 3,000 taste buds mostly on the tongue 80-90% of what we perceive as taste is actually due to the sense of smell
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Papillae
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Taste Receptors Taste receptors have microvilli called taste
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This note was uploaded on 04/07/2009 for the course BIOL 115 taught by Professor Irving during the Spring '08 term at Illinois Tech.

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Lec16 Senses - Chapter 14 The Senses Sensory Receptors May...

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