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SENSATION

Peripheral Sensory Receptors. SENSATION: state of detection and communication of external or internal condition of body; may be unconscious.PERCEPTION: conscious registration or awareness of sensation.. 23 Nov. 2009. Sensation.ppt. 2. Sensation requires four components. Stimulus = energy change i

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SENSATION

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    1. SENSATION This is a sensational lecture! 23 Nov. 2009 Sensation.ppt 1

    2. Peripheral Sensory Receptors SENSATION: state of detection and communication of external or internal condition of body; may be unconscious. PERCEPTION: conscious registration or awareness of sensation. 23 Nov. 2009 Sensation.ppt 2

    3. Sensation requires four components Stimulus = energy change in environment initiates impulse in receptor/sensory neuron; Receptor = converts stimulus energy to impulse (action potential); Conduction = of impulse over sensory pathway to CNS; Translation = region of CNS receives impulse(s) & integrates information; may prepare response. 23 Nov. 2009 Sensation.ppt 3

    4. Sensation Conduction and translation considered in previous units. Primarily concerned here with Stimuli and Receptors 23 Nov. 2009 Sensation.ppt 4

    5. Stimulus Environmental energy, or energy change, that causes a receptor potential in a receptor cell sufficient to produce an action potential in a sensory neuron. 23 Nov. 2009 Sensation.ppt 5

    6. Stimuli and Receptor types Light : photoreceptor Heat : thermoreceptor Chemicals : chemoreceptor Pain : nociceptor Mechanical force : mechanoreceptor touch: light, deep pressure (including gravity) vibration stretch 23 Nov. 2009 Sensation.ppt 6

    7. Locations of Receptors Exteroceptors at or near body surface react to external stimuli Visceroceptors or interoceptors deep react to internal body condition Proprioceptors muscles, tendons, ligaments react to muscle tone, tension, stretch 23 Nov. 2009 Sensation.ppt 7

    8. Senses Sight, vision Hearing Taste Smell Touch = 5 according to Aristotle 23 Nov. 2009 Sensation.ppt 8

    9. Special Senses and Sensors Vision - photoreceptors (retina) Hearing - phonoreceptors (hair cells in cochlea) Balance, equilibrium - mechanoreceptors (hair cells in vestibules & semicircular ducts) Olfactory receptors - chemoreceptors (nasal mucosa) Gustatory receptors - chemoreceptors (taste buds) 23 Nov. 2009 Sensation.ppt 9

    10. General Senses and Sensors Light touch - Merkel discs, Meissner's corpuscles Deep pressure - Pacinian corpuscles, Ruffini's corpuscles Hair deflection - hair root plexuses Temperature change - free dendritic endings Muscle stretch - muscle spindles Tendon stretch - Golgi tendon organs Ligament & joint capsule stretch - “joint kinesthetic receptors” Pain - free dendritic endings Itch - free dendritic endings 23 Nov. 2009 Sensation.ppt 10

    11. How many senses? Five ?? 12-14 (above) 23 Nov. 2009 Sensation.ppt 11

    12. How receptors work Transduction 23 Nov. 2009 Sensation.ppt 12

    13. Receptors are Transducers Transducer (L. trans- = across, + ductare = to carry) Transducers convert energy from one form to another. 23 Nov. 2009 Sensation.ppt 13

    14. Receptors are Transducers Telephone contains transducers Converts sound (vibration in air) to varying electrical potential (over wire) then, varying potential to sound Ear Converts sound to vibration in cochlear fluid to receptor potential in hair cells to afferent impulses. 23 Nov. 2009 Sensation.ppt 14

    15. Somatosensory System Three levels of neural integration Processing at Receptor level Circuit level Perceptual level 23 Nov. 2009 Sensation.ppt 15

    16. Processing at Receptor Level Receptor potential Graded (variable) membrane potential in receptor cell Depolarization Hyperpolarization Strong receptor potential (depolarization) causes release of neurotransmitter, and Generator potential in sensory neuron Graded depolarization (EPSP) that may (or not) reach threshold. 23 Nov. 2009 Sensation.ppt 16

    17. Processing at Circuit Level Communication of action potentials to CNS Cranial nerves Peripheral nerves and ascending spinal tracts Synapses can spread action potentials to several areas of CNS = Diverging circuits Synapses can focus action potentials from several sensors on narrow area of CNS = Converging circuits 23 Nov. 2009 Sensation.ppt 17

    18. Processing at Perceptual Level How brain recognizes Type of sensation Location of sensation Intensity of sensation 23 Nov. 2009 Sensation.ppt 18

    19. Processing at Perceptual Level 1 & 2 “hardwired” Auditory sensation connected to primary auditory cortex Visual sensation connected to primary visual cortex Sensory nerve tracts carry impulses to appropriate part of brain If we could switch nerve tracts, … Phantom sensation Amputee “feels” missing part of body. 23 Nov. 2009 Sensation.ppt 19

    20. Processing at Perceptual Level 3. Intensity Stronger stimuli produce receptor potentials in more receptor cells More impulses in more sensory neurons Stronger stimuli produce stronger receptor potentials Increased frequency of impulses in each sensory neuron 23 Nov. 2009 Sensation.ppt 20

    21. General Senses 23 Nov. 2009 Sensation.ppt 21

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