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. skin Connective tissue Heat Strong pressure Hair movement Nerve Dermis Epidermis Hypodermis Gentle touch Pain Cold Hair

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 CO 2 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. Papillae Papilla Taste buds Tongue (a) The tongue Taste bud Sensory neuron Sensory receptor cells Sweet Salty Sour Bitter Umami (b) A taste bud Taste pore Food molecules

21. Sweet G protein Sugar molecule Phospholipase C Tongue Sodium channel PIP 2 Na + IP 3 (second messenger) Sweet receptor ER Nucleus Taste pore SENSORY RECEPTOR CELL Ca 2+ (second messenger) IP 3 -gated calcium channel Sensory receptor cells Taste bud Sugar molecule Sensory neuron

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. Nose Olfactory bulb Odorants Bone Epithelial cell Plasma membrane Odorant receptors Odorants Nasal cavity Brain Chemo- receptor Cilia Mucus Action potentials

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. Figure 50.10a Outer ear Middle ear Inner ear Skull bone Malleus Incus Stapes Auditory canal Tympanic membrane Oval window Round window Cochlea Eustachian tube Semicircular canals Auditory nerve to brain Pinna

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

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. Sclera Choroid Retina Fovea Optic nerve Central artery and vein of the retina Optic disk Vitreous humor Lens Aqueous humor Pupil Iris Cornea Suspensory ligament

40. 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

41. 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

42. EYE

43. Rods/cones Retina Photoreceptors Light Optic nerve Light To brain Choroid Neurons ConeRod Ganglion cell Optic nerve axons Amacrine cell Horizontal cell Bipolar cell Pigmented epithelium

44. Figure 50.17ba Rod Cone Synaptic terminal Cell body Outer segment Disks

45. 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

46. Vision Right visual field Right eye Left visual field Left eye Optic chiasm Primary visual cortex Lateral geniculate nucleus Optic nerve

47. Near and Distance Vision

48. 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