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Sensory Physiology equilibrium & vision

Sensory Physiology equilibrium & vision. Equilibrium: Mechanoreceptor. Body balance Body position Body movement Propioceptors Vision Vestibular apparatus. Organs of Equilibrium. Receptor cells are in two structures Vestibule Semicircular canals. Figure 8.16a, b. Organs of Equilibrium.

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Sensory Physiology equilibrium & vision

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  1. Sensory Physiology equilibrium & vision

  2. Equilibrium: Mechanoreceptor • Body balance • Body position • Body movement • Propioceptors • Vision • Vestibular apparatus

  3. Organs of Equilibrium • Receptor cells are in two structures • Vestibule • Semicircular canals Figure 8.16a, b

  4. Organs of Equilibrium • Equilibrium has two functional parts • Static equilibrium – sense of gravity at rest • Dynamic equilibrium – angular and rotary head movements Figure 8.16a, b

  5. Static Equilibrium - Rest • Maculae – receptors in the vestibule • Report on the position of the head • Send information via the vestibular nerve • Anatomy of the maculae • Hair cells are embedded in the otolithic membrane • Otoliths (tiny stones) float in a gel around the hair cells • Movements cause otoliths to bend the hair cells

  6. Function of Maculae Figure 8.15

  7. Dynamic Equilibrium - Movement • receptors in the semicircular canals • Tuft of hair cells • Cupula (gelatinous cap) covers the hair cells Figure 8.16c

  8. Dynamic Equilibrium • Action of angular head movements • The cupula stimulates the hair cells • An impulse is sent via the vestibular nerve to the cerebellum Figure 8.16c

  9. Equilibrium: Mechanoreceptor • Integration • Medulla • Cerebellum • Thalamus • Cortex Figure 10-26: Central nervous system pathways for equilibrium

  10. Equilibrium: Vestibular Apparatus • Otolith organs • Gravity • Calcite crystals • Hair cells • Semicircular canals • Fluid moves • Cristae • Cupula • Hair cells

  11. Equilibrium: Vestibular Apparatus Figure 10-23a, b: ANATOMY SUMMARY: Vestibular Apparatus

  12. Equilibrium: Vestibular Apparatus Figure 10-23c, d: ANATOMY SUMMARY: Vestibular Apparatus

  13. The Eye and Vision • 70 percent of all sensory receptors are in the eyes, only see 1/6th of eye • Each eye has over a million nerve fibers • Protection for the eye • Most of the eye is enclosed in a bony orbit • A cushion of fat surrounds most of the eye

  14. Accessory Structures of the Eye • Eyelids • Eyelashes Figure 8.1b

  15. Accessory Structures of the Eye • Eyelashes =have modified sebacious glands produce an oily secretion to lubricate the eye Figure 8.1b

  16. Accessory Structures of the Eye • Conjunctiva • Membrane that lines the eyelids • Connects to the surface of the eye • Secretes mucus to lubricate the eye

  17. Accessory Structures of the Eye • Lacrimal gland • Tears: antibodies, lysozymes, stress? Figure 8.1a

  18. Extrinsic Eye Muscles • Muscles attach to the outer surface of the eye • Produce eye movements Figure 8.2

  19. Structure of the Eye • The wall is composed of three layers • Sclera&Cornea fibrous outside layer • Choroid – middle layer • Sensory (retina) inside layer Figure 8.3a

  20. The Fibrous layer • Sclera • White connective tissue layer • Seen anteriorly as the “white of the eye” • Cornea • Transparent, central anterior portion • Allows for light to pass through • Repairs itself easily • The only human tissue that can be transplanted without fear of rejection

  21. Choroid Layer • Blood-rich nutritive layer • Pigment prevents light from scattering • Modified interiorly into two structures • Cilliary body – smooth muscle • Iris • Pigmented layer that gives eye color • Pupil – rounded opening in the iris

  22. Sensory layer (Retina) • Contains receptor cells (photoreceptors) • Rods • Cones • Signals pass from photoreceptors and leave the retina toward the brain through the optic nerve

  23. Neurons of the Retina Slide 8.11

  24. Neurons of the Retina and Vision • Rods • Most are found towards the edges of the retina • Allow dim light vision and peripheral vision • Perception is all in gray tones

  25. Neurons of the Retina and Vision • Cones – 3 types detect different colors • Most dense at the center of the retina • Fovea centralis – area of the retina with only cones • Lack of one type = color blindness • No photoreceptor cells are at the optic disk, or blind spot

  26. Lens • Biconvex crystal-like structure • Held in place by a suspensory ligament attached to the ciliary body Figure 8.3a

  27. Internal Eye Chamber Fluids • Aqueous humor in Anterior Segment • Watery fluid found in chamber between the lens and cornea • Similar to blood plasma • Helps maintain intraocular pressure • Provides nutrients for the lens and cornea • Reabsorbed into venous blood • Blocked drainage = glaucoma

  28. Internal Eye Chamber Fluids • Vitreous humor in Posterior Segment • Gel-like substance behind the lens • Keeps the eye from collapsing • Lasts a lifetime and is not replaced

  29. Lens Accommodation • Light must be focused to a point on the retina for optimal vision • The eye is set for distance vision (over 20 ft away) • The lens must change shape to focus for closer objects Figure 8.9

  30. Correcting the Eye • Nearsightedness = myopia • Focus of light in front of retina • Eyeball too long or lens too thick • Distant objects are blurry • Farsightedness = hyperopia • Focus of light beyond the retina • Short eyeball or lens too thin • Near objects are blurry.

  31. Correct focus

  32. Hyperopia

  33. Astigmatism • Unequal curvatures in cornea & lens

  34. Vision: Photoreceptors • Reflected light translated into mental image • Pupil limits light, lens focuses light • Retinal rods and cones are photoreceptors Figure 10-36: Photoreceptors in the fovea

  35. Photoreception and Local Integration • Rods – night vision • Cones – color & details • Bipolar & ganglion cells converge, integrate APs

  36. Photoreception and Local Integration Figure 10-35: ANATOMY SUMMARY: The Retina

  37. Retina: More Detail • Rod cells: monochromatic • Cone cells: red, green, & blue • Discs: visual pigments • Pigmented epithelium • Melanin granules • Prevents reflection

  38. Retina: More Detail Figure 10-38: Photoreceptors: rods and cones

  39. Phototransduction • Photons "bleach" opsin, retinal released, cascade, Na+ channel closes, K+ opens , hyperpolarization • Reduces NT release

  40. Phototransduction Figure 10-40: Phototransduction in rods

  41. Vision: Integration of Signals to Perception • Bipolar • Ganglion • Movement • Color • Optic nerve • Optic chiasm • Optic tract • Thalamus • Visual cortex Figure 10-29b, c: Neural pathways for vision and the papillary reflex

  42. Summary • Sensory pathway: receptor, sensory neuron(s) & CNS • Somatic senses: touch, temperature, pain & proprioception communicate body information to CNS • Special senses: taste, smell, hearing, equilibrium, & vision • Outside conditions for CNS integration into perception • Receptors transduce mechanical, chemical or photon energy into GPs then to APs

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