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Sensory Reception

Sensory Reception. Chapter 14. Sensory Systems. The means by which organisms receive signals from the external world and internal environment. Sensation and Perception. Sensation is conscious awareness of a stimulus Perception is understanding what a sensation means

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Sensory Reception

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  1. Sensory Reception Chapter 14

  2. Sensory Systems • The means by which organisms receive signals from the external world and internal environment

  3. Sensation and Perception • Sensation is conscious awareness of a stimulus • Perception is understanding what a sensation means • A perception of wetness arises from numerous sensations

  4. Types of Receptors Mechanoreceptors Thermoreceptors Pain receptors Chemoreceptors Osmoreceptors Photoreceptors

  5. Assessing a Stimulus • Action potentials don’t vary in amplitude • Brain tells nature of stimulus by: • Particular pathway that carries the signal • Frequency of action potentials along an axon • Number of axons recruited

  6. Recordings of Action Potentials

  7. Sensory Adaptation A decrease in response to a stimulus being maintained at constant strength

  8. Somatic Sensations • Touch • Pressure • Temperature • Pain • Motion • Position

  9. Somatosensory Cortex

  10. Receptors in Skin • Free nerve ending • Ruffini ending • Pacinian corpuscle • Bulb of Krause • Meissner’s corpuscle

  11. Referred Pain • Sensations of pain from internal organs may be wrongly projected to part of the skin surface • Heart attack can be felt as pain in skin above the heart and along the left shoulder and arm

  12. Properties of Sound • Ear detects pressure waves • Amplitude of waves corresponds to perceived loudness • Frequency of waves (number per second) corresponds to perceived pitch

  13. Taste • A special sense • Chemoreceptors • Five primary sensations: • sweet, sour, salty, bitter, and umami

  14. Smell • A special sense • Olfactory receptors • Receptor axons lead to olfactory lobe olfactory bulb receptor cell

  15. Anatomy of Human Ear stirrup anvil auditory nerve hammer auditory canal eardrum cochlea

  16. Sound Reception • Sound waves make the eardrum vibrate • Vibrations are transmitted to the bones of the middle ear • The stirrup transmits force to the oval window of the fluid-filled cochlea

  17. Sound Reception • Movement of oval window causes waves in the fluid inside cochlear ducts

  18. Sound Reception • Organ of Corti senses fluid movement • Hair cells are bent against overlying tectorial membrane, and they fire

  19. Balance and Equilibrium • In humans, organs of equilibrium are located in the inner ear • Vestibular apparatus

  20. Dynamic Equilibrium • Rotating head movements cause pressure waves that bend a gelatinous cupula and stimulate hair cells inside it cupula

  21. Acceleration-Deceleration • Moving in response to gravity, otoliths bend projections of hair cells and stimulate the endings of sensory neurons HEAD LEVEL hair cell otolith HEAD TILTED

  22. Vision • Sensitivity to light does not equal vision • Vision requires two components • Eyes • Capacity for image formation in the brain

  23. Human Eye sclera retina choroid iris fovea optic disk lens pupil cornea part of optic nerve aqueous humor ciliary muscle vitreous body

  24. Pattern of Stimulation • Light rays pass through lens and converge on retina at back of eye • The image that forms on the retina is upside down and reversed right to left compared with the stimulus • Brain accounts for this during processing

  25. Pattern of Stimulation

  26. Visual Accommodation • Adjustments of the lens • Ciliary muscle encircles lens • When this muscle relaxes, lens flattens, moves focal point farther back • When it contracts, lens bulges, moves focal point toward front of eye

  27. The Photoreceptors • Rods • Contain the pigment rhodopsin • Detect very dim light, changes in light intensity • Cones • Three kinds; detect red, blue, or green • Provide color sense and daytime vision

  28. Organization of Retina • Photoreceptors lie at the back of the retina, in front of a pigmented epithelium • For light to reach the photoreceptors, it must pass layers of neurons involved in visual processing

  29. To the Visual Cortex (1) • Signals from photoreceptors are passed to bipolar sensory neurons, then to ganglion cells bipolar cell rod ganglion cell cone

  30. To the Visual Cortex (2) Visual cortex

  31. Disorders of the Eye (1) • Color blindness • Focusing problems • Nearsightedness and farsightedness • Eye diseases • Trachoma • Histoplasmosis • Herpes simplex infection

  32. Disorders of the Eye (2) • Age-related problems • Cataracts • Macular degeneration • Glaucoma • Injuries • Retinal detachment

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