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SPECIAL SENSES

SPECIAL SENSES. Making Sense of The World. Sensation. relationship between physical energies in the environment & psychological experience of those energies to perceive & detect physical energies & encode them into neural signals. Basic Senses. Sight Hearing Touch Smell Taste also

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SPECIAL SENSES

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  1. SPECIAL SENSES Making Sense of The World

  2. Sensation • relationship between physical energies in the environment & psychological experience of those energies • to perceive & detect physical energies & encode them into neural signals

  3. Basic Senses • Sight • Hearing • Touch • Smell • Taste • also • Pain • Pressure • Temperature • Joint position • Muscle sense • Movement

  4. SENSES • systems that translate outside information into activity in nervous system • gather information by detecting energies • environment contains many different forms of energies

  5. Receptors • detect only the energies have receptor for • restricted awareness • receptor cells transduce or change physical energy into a signal brain can understand

  6. Transduction • conversion of physical energies into language of brain • receptor cells convert physical energies into neural impulses which travel to cerebral cortex to be decoded • all sense signals except smell go to relay station-thalamus • from there to primary sensory areas in cerebrum-different for each sense • here they are modified and sent on to higher regions of brain

  7. Olfaction • sense of smell • chemical sense • air borne chemicals detected • oldest sense • all organisms have some type of chemical sense • major senses in most animals • help locate food, recognize trails & territories identify kin & find receptive mates • social insects send & receive intricate chemical signals which tell themwhere to go and how to behave • social behavior of most animals is controlled by chemical signals • olfactory receptor area in German Shepherd-72X bigger than in humans

  8. Olfactory System • humans are able to distinguish 10,000 smells • detected in paired olfactory organs in nasal cavity by specialized receptor cells found in olfactory epithelium-olfactory receptor neurons

  9. Olfactory System • olfactory organs posses 2 layers • olfactory epithelium • lamina propria • olfactory epithelium covers inferior cribifrom plate, superior perpendicular plate & superior nasal conchae of ethmoid bone • covered by mucus which contains olfactory receptors • lamina propria-comprised of areolar tissue, blood vessels, nerves & olfactory or Bowman’s glands • produce secretions that bathe surface of olfactory receptors

  10. Olfactory System • 10 – 100 million olfactory receptors • modified bipolar neurons • have terminal enlargements or knobs whichproject above epithelial surface • from each 8-20 olfactory cilia extend into mucus • contain smell receptors • cilia project from knob & lie parallel to epithelia surface • exposes considerable surface area to dissolved compounds • at other end of receptor cell, axons project to olfactory bulb • 10-100 axons form into bundles, penetrate cribriform plate terminate in olfactory bulb • stem cells allow neurons to regenerate

  11. Olfaction • refers to breathing in chemicals • Inhaletake in chemicals or odorants • chemicals that stimulate olfactory receptors • must be smallenough to be volatile to vaporize, reach the nose & dissolve in mucus to stimulate olfactory receptors • at olfactory organswater & lipid soluble materials diffuse into mucus

  12. OLFACTION • dissolved chemicals interact with receptors- odorant binding proteins • 4 odorant molecules will activate an olfactory receptoractivates adenylate cyclaseconverts ATPcAMPopens Na channels in membrane local depolarizationdepolarization large enough action potential in axon conveyed to CNS

  13. Olfactory Pathways • axons of receptors extend through olfactory foramina in cribiform plate to form right & left olfactory nerves • terminate in brain in the olfactory bulbsaxons of bulbs extend posteriorlyform olfactory tract projects to primary olfactory cortex located at inferior & medial surface of the temporal lobe • projects to hypothalamus & amygdala • parts of limbic system • amygdale associate experiences with smellsproducing emotion • projections are sent to thalamus and to frontal cortex-recognition

  14. Olfactory Discrimination • can recognize 2000-4000 chemical stimuli • several primary smells for which thousands of receptors are needed • 1) ethereal2) camphoraceous3) musky4) floral5) minty6) pungent7) putrid • 1% of genes are needed to make receptor proteins to recognize smells • no distinct receptor for each detectable odor

  15. Gustation • chemical sense • chemicals are taken into the body & dissolved in oral cavity • drives appetite • protects from poisons • bitter & sour tastes produce aversive, avoidance reactions • most poisons are bitter • off food goes sour or has an acidic taste

  16. Taste Discrimination • 5 primary sensations • Sweet • Salty • Sour • Bitter • Umami • MSG • taste of beef, chicken broth & parmesan cheese • taste combined with smell gives flavor • when nose is blocked foods seem bland or tasteless

  17. Anatomy of Gustation • receptor-taste bud • 10,000 • tongue, soft palate, pharynx & epiglottis • survives about 10 days • Consists of: • taste receptors or gustatory cells • basal or stem cells • supporting cells

  18. Anatomy of Gustation • Supporting cells • surrounds about 50 gustatory receptors cells in each taste bud • one single long micovillus (gustatory hair) projects from each gustatory receptor cell to surface through taste pore • Basal cells • stem cells • found in periphery of taste buds

  19. Anatomy of Gustation • gustatory receptors • embedded in specializations of surrounding epithelium called papillae • three types contain taste buds • vallate • fungiform papillae • folliate

  20. PapillaeTypes • Vallate or circumvallate papillae • have100 taste buds • back of tongue • Fungiform papillae • possess5 tastebuds • over entire tongue • Folliate • lateral margins • taste buds degenerate in early childhoog • Filiform papillae • no taste buds • Tactile receptors • provide friction sensations

  21. Gustatory Transduction • dissolved chemicals contact taste hairs • bind to receptor proteins on gustatory cell • causes series of chemical reactions producingaction potential

  22. Gustatory Transduction • different tastes involve different receptor mechanisms • salt receptorsdepolarize after Na channels open • sweet receptors depolarize after K channels open

  23. Gustatory Transduction

  24. Gustatory Pathways • Taste is monitored by cranial nerves VII-facial • picks up sensation from anterior 2/3rds of tongue • IX-glossopharyngeal • covers posterior 1/3rd of tongue • X-vagus • receives information from epiglottis • axons from these nerves synapse on nucleus solitarius in medulla oblongata • axons of postsynaptic neurons enter medial lemniscus & synapse in thalamus • then project to gustatory cortex conscious perception • here information is correlated with other sensory data such as texture, peppery, hot

  25. Vision • primary sense in humans • sensory organs-eyes

  26. Accessory Eye Structures • Eyelids or palpebrae • continuations of skin • blink continually to keep surfaces lubricated & things out of eyes • Palpebral fissure • gap separating free margins of upper & lower eyelids • Medial & Lateral canthus • where eyelids are connected • Eyelashes • keep foreign materials out Medial Canthus Lateral Canthus

  27. Accessory Eye Structures • Tarsal glands • sebaceous glands associated with eyelashes at inner margin • secrete lipids to keep eyelids from sticking together • Lacrimal Caruncle • medial canthus • makes a thick, gritty secretion often found in eyes after sleeping

  28. ACCESSORY STRUCTURES • Palpebral conjunctiva • epithelium covers inner surface of eye • Ocular conjunctiva • covers anterior surface • extends to edges of cornea • transparent part of outer fibrous layer

  29. ACCESSORY STRUCTURES-Lacrimal Apparatus • produces, distributes & removes tears • tears reduce friction, remove debris, prevent bacterial infections & provide nutrients and O2 to eye • consists of • lacrimal gland • lacrimal canaliculi • lacrimal sac • nasolacrimal duct • lacrimal gland produces key ingredients and most of volume • tears accumulate at medial canthus or lacrimal lake • lacrimal puncta drains lakeempties into lacrimal caniliculilacrimal sacnasolacrimal duct nasolacrimal canalnasal cavity

  30. THE EYE • irregular spheroid • three layers or tunics • outer fibroustunic • intermediate vascular tunic • inner neuraltunic • two hollow cavities • posterior, vitreouschamber • contains gelatinous vitreousbody • helps stabilize shape of eye • anterior chamber • filled with aqueous humor • functions to retain shape of eyeball

  31. Fibrous Tunic • sclera & cornea • Functions: • mechanical support • physical protection • attachment site-extrinsic eye muscles • housing of focusing structures • Sclera • white of eye • site for insertion of 6 extrinsic eye muscles • contains blood vessels & nerves • Cornea-continuous with sclera • cornea & lens comprise-refractive system • focuseslight on retina • where photosensitive pigments are found

  32. Vascular Tunic-Uvea • site of attachment for intrinsic eye muscles • provides route for blood & lymph • regulates amount of light entering eye • secretes & reabsorbs aqueous humor • controls shape of lens • Parts: • iris • cilliary body • choroid

  33. THE IRIS • consists of pigment cells & 2 layers of smooth muscle • contraction of muscle produces change in diameter of pupil • central opening in iris • controlled by ANS • bright light causes constriction via consensuallight reflex • parasympathic pathway • dim light causes dilatation via pupillary reflex • sympathetic pathway

  34. Cilliary Body • thicken area at periphery of eye • iris is attached to it • composed of cilliary muscles

  35. CHOROID • separates fibrous & neural tunics

  36. Neural Tunic-Retina • light sensitive • thin, pigmented outer layer • sheet of melanin containing cells • thick, inner layer-contains light receptors • begins visual pathway • consists of three layers

  37. Retina Layers • Photoreceptor layer • Bipolar cell layer • Ganglion cell layer

  38. The Retina • Third layer • lightenergy converted into neural activity • contains specialized photoreceptor cells-rods & cone • transduce light wavelengths into information the brain understands • Second layer • bipolar cells • magnifies image • First layer • ganglion cells • further adjust image • axons form optic nerve

  39. Retina • if eyes simply transferred stimuli from retina to brainimages would be blurry • images are sharpened by sending information from photoreceptor cells backthrough first 2 layers ofretina • Bipolar cells connect photoreceptors to retinal ganglion cells • axons from ganglion cells form optic nerve

  40. Third Layer • lightenergy is converted into neural activity • contains specialized photoreceptor cells-rods & cones • rods cannot see color • more sensitive than cones • sensitive enough to respond to a single photon of light • basic unit of light • create coarse, gray image • adequate for seeing in poor or dim light • can make out shapes fairly well • colors are completely absent • no color vision in dim light

  41. RODS & CONES • 18X more rods than cones • approximately 125 million rods • 6 million cones • arranged to produce best possible combination of night & day vision

  42. Cones • color vision • operate in bright light • Three types • Blue • Red • Green • experience of color is due to combination of these three cones

  43. Cones • concentrated in macula leutea • center is fovea centralis • site of highest visual acuity or resolution

  44. THE LENS • transparent structure located behind pupil in cavity of eyeball • consists of concentric layers of cells, filled with crystallins • transparent proteins responsible for clarity of lens & for focusing

  45. Focusing • requires the cornea & lens • light is refracted or bent as it passes from one medium to another with different density • greatest amount of refraction occurs as light passes from air to cornea • more refraction occurs as light passes from aqueous humor to lens • lens provides extrarefraction needed to focus light from object to focal point • specific point of interaction in retina • distance between center of lens & focal point is focal length or distance

  46. PhotoPathway • Horizontal cells extend across outer part of retina at level of synapses between photoreceptor & bipolar cells • Amacrine cellsfound where ganglion cells synapse with bipolar cells • Light energy must pass through both ganglion & bipolar cells to get to photoreceptor cells where light energy is converted into neural signals which activates bipolar cells • One cone converges on one bipolar cell • preserves precise information, provides high acuity and fine detail • 1000 or more rods funnel information onto one bipolar cell • increases originalillumination & activates ganglion cells

  47. OPTIC NERVE • Axons from 1 X 106 ganglion cells converge on optic disc • circular region medial to fovea • origin of optic nerve • penetrates wall of eye at area known as blind spot • no photoreceptors • forms optic nerve which partially crosses at optic chiasm • continues on to thalamus • from there to other areas of cortex all at the same time

  48. Refraction • light rays reflected by object enter eye through cornea • light proceeds through pupil • size controlled by iris • behind pupillens focuses light rays into an invertedimage onto retina at back of eye

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