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Sensory systems

Sensory systems. Chapter 50. Five senses. Touch Taste Smell Sound Vision. Sensory systems. Sensory info is received Nerve impulse or action potential All or nothing response Response depends on part of brain that receives the info. Sensory information. Sensory info to CNS

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Sensory systems

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  1. Sensory systems Chapter 50

  2. Five senses • Touch • Taste • Smell • Sound • Vision

  3. Sensory systems • Sensory info is received • Nerve impulse or action potential • All or nothing response • Response depends on part of brain that receives the info

  4. Sensory information • Sensory info to CNS • 1. Sensory reception • 2. Transduction • Graded potential • Ion channels open or close • Receptor potential • Change in membrane potential • Depolarization

  5. Sensory information • 3. Transmission • Goes to CNS via afferent pathway • 4. Interpretation • Perception by the brain

  6. Sensory receptors • Nerve endings • Specialized neurons or epithelial cells • Associated with sensory organs -eyes • All stimuli is a form of energy

  7. Sensory receptors • Stimuli-outside body • Heat, light, pressure & chemicals • Stimuli-inside body • BP, body position, body temperature

  8. Types of sensory receptors • Mechanoreceptors • Pressure, stretch, touch • Chemoreceptors • chemicals • Electromagnetic receptors (photoreceptors) • Nociceptors (pain) • Thermoreceptors

  9. Receptors • Cutaneous receptors: • Skin • Heat, cold, pressure, pain & touch • Thermoreceptors • Heat/Cold • Hypothalamus • Regulates temp of blood (core temp)

  10. Receptors • Mechanoreceptors • Touch • Close to surface of skin • Hair follicle receptors • Pressure • Deeper

  11. Hair Cold Gentletouch Pain Heat Epidermis skin Dermis Hypodermis Hairmovement Connectivetissue Strongpressure Nerve

  12. Receptors • Nociceptors: • Pain • Severe temperature change • Tissue damage • Free nerve endings (naked dendrites) • Located in the epidermis

  13. PAIN

  14. Receptors • Proprioceptors • Give info on animal’s body parts • Position • Movement • Stretch receptors on muscle • Prevent over stretch

  15. Receptors • Baroreceptors: • Detect tension or stretch in blood vessel walls • Internal carotids • Aortic arch • Drop in BP • Stimulation to increase HR & vasoconstriction

  16. Receptors • Chemoreceptor • Aorta & carotid • Medulla oblongata • pH (blood & CSF) • Slow breathing • Increased CO2 • Lowers pH • Causes an increased respiration rate

  17. Taste • Taste buds • Collections of receptor cells • Epithelial cells • Papillae • Raised areas on tongue • Taste buds located

  18. Taste • Taste buds contain 50-100 taste cells • Food dissolves in saliva • Contact taste cells • Taste salty, sweet, sour, bitter

  19. Taste • Chemoreceptors • Salt: Na+1 • Sour: H+1 • Directly through ion-channel • Sweet: receptor proteins for sugar • Bitter: K+channels are closed by receptor proteins

  20. TONGUE

  21. Sugar molecule G protein Sweetreceptor Tongue Phospholipase C SENSORYRECEPTORCELL Sweet Sugarmolecule Taste pore PIP2 Sensoryreceptorcells Tastebud IP3(secondmessenger) Sodiumchannel Sensoryneuron IP3-gatedcalciumchannel Nucleus ER Ca2+(secondmessenger) Na+

  22. Smell • Olfactory receptors • Chemoreceptors • Located upper portions of nasal passages • Dendrites are in cilia • Axon goes directly to cerebral cortex • Odorant or odorous substance binds proteins • Second messenger response in receptor cell

  23. Smell • Opens membrane to Ca & Na • Causes impulse (action potential) • Distinguish thousands of odors • Very accurate • Single odorant molecule

  24. NOSE

  25. Brain Action potentials Olfactorybulb Nose Odorants Nasal cavity Bone Epithelialcell Odorantreceptors Chemo-receptor Plasmamembrane Cilia Odorants Mucus

  26. Hearing • Outer ear: • Pinna, canal • Middle ear: • Tympanic membrane (ear drum) • Eustachian tube • Small bones (malleus, incus, stapes) • Inner ear: • Cochlea, auditory nerve

  27. EAR

  28. Ear

  29. Hearing • Vibrations move in canal • Cause eardrum to move • Vibrations pass through the bones • Stapes pass vibration to inner ear • Causes pressure waves in fluid in cochlea • Basilar membrane of the cochlea vibrates

  30. Hearing • Hair cells on membrane vibrate • Leads to change in membrane potentials in sensory neurons • Sound interpreted • Humans hear 20-20,000 hertz • Age decreases higher frequencies • Dogs hear sounds at 40,000 hertz

  31. Ears • Inner ear • Body position & balance • Two chambers near the cochlea • Utricle & saccule • Filled with fluid • Hair cells in chambers respond to changes in head positions

  32. Ears • Utricle: horizontal motion • Saccule: vertical motion • Different movement causes different sensory neurons to be stimulate • Labyrinth system • Spin around become dizzy

  33. Semicircular canals Flow of fluid Equilibrium Vestibular nerve Cupula Hairs Haircells Axons Vestibule Utricle Body movement Saccule

  34. Eye • Sclera: • White outer layer of connective tissue • Conjunctiva: • Epithelial layer • Covers outer surface of sclera • Under surface of the eyelid • Cornea: • Clear part of sclera, light passes through

  35. Eye • Choroid • Pigmented layer under the sclera • Iris • Color part of eye formed by the choroid • Pupil • Opening at the center of the iris • Controlled by iris • Lens • Behind the pupil, held in place by ligaments

  36. Eye • Retina • Back of eye where image is focused • Optic nerve • Sensory neurons • Vitreous humor • Jellylike substance behind the lens • Aqueous humor • Thinner fluid • Fills smaller chamber in front of the lens

  37. EYE

  38. Eye • Light enters eye through cornea • Passes through pupil to lens • Lens focuses images on retina • Photoreceptor cells of retina transduce light energy • Action potentials pass via sensory neurons in the optic nerve

  39. Eye • Rods & cones • Photoreceptors of eyes • Rods: black and white vision in dim light • Cones: high visual acuity & color vision • Located in center of retina

  40. EYE

  41. Retina Choroid Photoreceptors Neurons Retina Cone Rod Rods/cones Light Tobrain Optic nerve Light Ganglioncell Amacrinecell Horizontalcell Opticnerveaxons Bipolarcell Pigmentedepithelium

  42. Eyes • Binocular vision • Axons of ganglion cells form optic nerves • Optic nerves meet at the optic chiasm (base of the cerebral cortex) • Visions from the right visual field go to the left side of the brain and vise versa • Thalamus • Cortex

  43. Rightvisualfield Opticchiasm Righteye Vision Lefteye Leftvisualfield Optic nerve Primaryvisual cortex Lateralgeniculatenucleus

  44. Eyes • Nearsightedness: longer eyeball • Farsightedness: shorter eyeball • Asitgmatism: problems with lens or cornea • Light rays converge unevenly • Colorblindness: inherited lack of one or more types of cones

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