Sensory Systems.pptx - Chapter 44 Sensory Systems Sensory receptors All stimuli represent forms of energy Sensation involves converting energy into a

Sensory Systems.pptx - Chapter 44 Sensory Systems Sensory...

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Chapter 44: Sensory Systems
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Sensory receptors All stimuli represent forms of energy. Sensation involves converting energy into a change in the membrane potential of sensory receptors . Sensations are action potentials that reach the brain via sensory neurons. The brain interprets sensations, giving the perception of stimuli.
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Sensory Pathways Functions of sensory pathways: sensory reception, transduction, transmission, and interpretation. 1. sensory reception , detection of stimuli by sensory receptors. 2. Sensory transduction is the conversion of stimulus energy into graded action potentials 3. transmission – conduction of action potentials to the CNS along an afferent pathway. 4. Interpretation – the brain creates a sensory perception
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Amplification and Adaptation Amplification is the strengthening of stimulus energy by cells in sensory pathways. Sensory adaptation is a decrease in responsiveness to continued stimulation.
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Types of Sensory Receptors Receptors fall into 3 categories: Mechano receptors Chemo receptors Electromagnetic receptors Also can be either Exteroceptors – receptors that sense stimuli that arise in the External environment Interoceptors – sense stimuli from within the body
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Sensory Transduction and Gated Ion Channels Stimulus-gated ion channels Ion channels that open or close depending on the sensory system involved Usually cause a depolarization Receptor potential: a depolarization that occurs in a sensory receptor upon stimulation. (the next step after the initial receptor) The greater the sensory stimulus, the greater the depolarization of the receptor potential and the higher the frequency of action potentials.
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The relationship between stimulus intensity and action potential is (usually) logarithmic This way the CNS has a simple method of interpreting the strength of the stimulus based on the frequency of incoming signals.
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Chemoreceptors General chemoreceptors respond to chemicals/ chemical changes. When a stimulus molecule binds to a chemoreceptor, the chemoreceptor becomes more or less permeable to ions.
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Mechanoreceptors Mechanoreceptors sense physical deformation caused by stimuli such as pressure , pain, heat, cold, stretch, motion , and touch . Cutaneous receptors found in skin Technically are classified as interoceptors
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Cutaneous Receptors Merkle cells – near the surface, sensitive to touch pressure and duration Meissner Corpuscle – in hairless skin, sensitive to fine touch Ruffini Corpuscle – near the skin surface that are sensitive to pressure and duration Pacinian Corpuscle – located deep within the subcutaneous tissue and is sensitive to pressure
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Phasic vs Tonic Phasic – intermittently activated So for instance the phasic sensors could send a signal when the stimulus is applied and when it stops.
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