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Chapter 10c

Chapter 10c. Sensory Physiology. The Ear: Equilibrium . Vestibular apparatus Semicircular canals Otolith organs Equilibrium pathways. The Vestibular Apparatus . Vestibular apparatus A series of interconnected fluid-filled chambers Provides information about movement and position in space.

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Chapter 10c

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  1. Chapter 10c Sensory Physiology

  2. The Ear: Equilibrium • Vestibular apparatus • Semicircular canals • Otolith organs • Equilibrium pathways

  3. The Vestibular Apparatus • Vestibular apparatus • A series of interconnected fluid-filled chambers • Provides information about movement and position in space

  4. Anatomy Summary: The Vestibular Apparatus SEMICIRCULAR CANALS (a) Superior Horizontal Posterior Cochlea Cristae withinampulla Utricle Saccule Maculae Figure 10-25a

  5. Anatomy Summary: The Vestibular Apparatus Vestibularapparatus Superior canal(nod for “yes”) Posterior canal(head tilt) Left right Horizontal canal(shake headfor “no”) (b) Figure 10-25b

  6. Anatomy Summary: The Vestibular Apparatus Cupula Endolymph Haircells Supportingcells Nerve (c) Figure 10-25c

  7. Anatomy Summary: The Vestibular Apparatus Hair cells Gelatinousotolithmembrane Otoliths are crystalsthat move in responseto gravitational forces. Nerve fibers (d) Macula Figure 10-25d

  8. Transduction of Rotational Forces in the Cristae • The semicircular canals sense rotational acceleration Cupula Bone Brush movesright Endolymph Stationaryboard Bristlesbend left Hair cells Bone Direction of rotation of the head When the head turns right, endolymph pushes the cupula to the left. Figure 10-26

  9. Otoliths Move in Response to Gravity or Acceleration Figure 10-27a

  10. Otoliths Move in Response to Gravity or Acceleration Figure 10-27b

  11. Dynamic Equilibrium and the crista ampullaris

  12. Meniere's disease Vincent van Gogh, whose artistic brilliance and supposed madness have made him a focus of popular fascination, suffered not from epilepsy or insanity but from Meniere's disease,

  13. Central Nervous System Pathways for Equilibrium Cerebralcortex Thalamus Reticularformation Vestibular branch ofvestibulocochlearnerve (VIII) Cerebellum Somaticmotor neuronscontrolling eyemovements Vestibularnuclei ofmedulla Vestibular apparatus Figure 10-28

  14. The Eye and Vision • Light enters the eye • Focused on retina by the lens • Photoreceptors transduce light energy • Electrical signal • Electrical signal • Processed through neural pathways

  15. External Anatomy of the Eye Muscles attached toexternal surface of eyecontrol eye movement. Lacrimal glandsecretes tears. Uppereyelid Sclera Pupil Iris Lowereyelid The orbit is a bonycavity that protectsthe eye. Nasolacrimal ductdrains tears intonasal cavity. Figure 10-29

  16. Anatomy Summary: The Eye Lens Zonules Optic disk(blind spot) Canal ofSchlemm Central retinalartery and vein Aqueoushumor Cornea Optic nerve Pupil Fovea Iris Macula Vitreous chamber (b) Retina Ciliary muscle Sclera is connective tissue. (a) Sagittal section of the eye Figure 10-30

  17. Anatomy Summary: The Eye Lens Zonules Optic disk(blind spot) Canal ofSchlemm Central retinalartery and vein Aqueoushumor Cornea Optic nerve Pupil Fovea Iris Vitreous chamber Retina Ciliary muscle Sclera is connective tissue. (a) Sagittal section of the eye Figure 10-30a

  18. Anatomy Summary: The Eye Optic disk(blind spot) Central retinalartery and vein Fovea Macula (b) Figure 10-30b

  19. Neural Pathways for Vision and the Pupillary Reflex (a) Dorsal view Optic tract Eye Optic chiasm Optic nerve Figure 10-31a

  20. Neural Pathways for Vision and the Pupillary Reflex (b) Neural pathway forvision, lateral view Eye Optictract Lateral geniculatebody (thalamus) Opticchiasm Visual cortex(occipital lobe) Opticnerve Figure 10-31b

  21. Neural Pathways for Vision and the Pupillary Reflex (c) Collateral pathwaysleave the thalamusand go to themidbrain. Optictract Lateral geniculatebody (thalamus) Opticchiasm Visual cortex(occipital lobe) Opticnerve Eye Light Midbrain Cranial nerve III controlspupillary constriction. Figure 10-31c

  22. The Pupil • Light enters the eye through the pupil • Size of the pupil modulates light • Photoreceptors • Shape of lens focuses the light • Pupillary reflex • Standard part of neurological examination

  23. Refraction of Light Figure 10-32a

  24. Refraction of Light Figure 10-32b

  25. Optics Figure 10-33a

  26. Optics Figure 10-33b

  27. Optics Figure 10-33c

  28. Ciliary muscle Lens Cornea Ligaments Iris (a) The lens is attached to the ciliarymuscle by inelastic ligaments (zonules). Accommodation • Accommodation is the process by which the eye adjusts the shape of the lens to keep objects in focus Figure 10-34a

  29. Accommodation Ciliary musclerelaxed Lens flattened Cornea Ligamentspulled tight (b) When ciliary muscle is relaxed, theligaments pull on and flatten the lens. Figure 10-34b

  30. Accommodation Ciliary musclecontracted Lens rounded Ligamentsslacken (c) When ciliary muscle contracts, itreleases tension on the ligamentsand the lens becomes more rounded. Figure 10-34c

  31. Common Visual Defects Figure 10-35a

  32. Common Visual Defects Figure 10-35b

  33. The Electromagnetic Spectrum Figure 10-36

  34. Anatomy Summary: The Retina Horizontalcell Amacrinecell Light Ganglioncell Cone (color vision) Neurons where signalsfrom rods and conesare integrated Bipolarcell Rod (monochromatic vision) (d) Retinal photoreceptors are organized into layers. Figure 10-37d

  35. Phototransduction Figure 10-38

  36. Photoreceptors: Rods and Cones PIGMENTEPITHELIUM Old disks at tip arephagocytized bypigment epithelial cells. Melanin granules OUTER SEGMENT Disks Visual pigments inmembrane disks Disks Connectingstalks INNER SEGMENT Mitochondria Location of majororganelles and metabolicoperations such asphotopigment synthesisand ATP production Rhodopsinmolecule Cone Rods Retinal Opsin SYNAPTIC TERMINAL Synapses withbipolar cells Bipolar cell LIGHT Figure 10-39

  37. Photoreceptors: Rods and Cones PIGMENTEPITHELIUM Old disks at tip arephagocytized bypigment epithelial cells. Melanin granules OUTER SEGMENT Disks Visual pigments inmembrane disks Disks Connectingstalks Figure 10-39 (1 of 2)

  38. Photoreceptors: Rods and Cones INNER SEGMENT Mitochondria Location of majororganelles and metabolicoperations such asphotopigment synthesisand ATP production Rhodopsinmolecule Rods Cone Retinal Opsin SYNAPTIC TERMINAL Synapses withbipolar cells Bipolar cell LIGHT Figure 10-39 (2 of 2)

  39. Light Absorption of Visual Pigments Figure 10-40

  40. Phototransduction in Rods (a) In darkness, rhodopsin isinactive, cGMP is high, andCNG and K+ channels are open. Pigment epithelium cell Disk Transducin(G protein) Inactiverhodopsin(opsin and retinal) cGMPlevels high Ca2+ CNG channelopen Na+ K+ Membrane potentialin dark = –40mV Rod Tonic release ofneurotransmitteronto bipolar neurons Figure 10-41a

  41. Phototransduction in Rods (b) Light bleaches rhodopsin. Opsindecreases cGMP, closes CNGchannels, and hyperpolarizes the cell. Opsin (bleachedpigment) Activatestransducin Activatedretinal Cascade DecreasedcGMP Ca2+ Na+ CNG channelcloses K+ Membranehyperpolarizesto –70 mV Light Neurotransmitter releasedecreases in proportionto amount of light. Figure 10-41b

  42. Phototransduction in Rods (c) In the recovery phase, retinalrecombines with opsin. • When light activates rhodopsin, a second-messenger cascade is initiated through transducin Retinal converted toinactive form Retinal recombineswith opsin toform rhodopsin. Figure 10-41c

  43. Ganglion Cell Receptive Fields Figure 10-42

  44. Visual Fields and Binocular Vision Visual field Binocular zone Left visual field Right visual field Optic chiasm Optic nerve Optic tract Lateral geniculate body (thalamus) Visual cortex Figure 10-43

  45. Summary • General properties • Four types of sensory receptors • Adequate stimulus, threshold, receptive field, and perceptual threshold • Modality, localization, intensity, and duration • Somatic senses • Four modalities, second sensory neurons, and somatosensory cortex • Nociceptors, spinal reflexes, and pain

  46. Summary • Chemoreception • Olfaction and taste • The ear: hearing and equilibrium • The eye and vision • Retina, pupil, ciliary muscle, and photoreceptors

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