1. Nervous System III, part 2 Chapter 12

2. Special senses Sensory receptors within complex sensory organs Found in the head Smell in olfactory organs Taste in taste buds Hearing and equilibrium in ears Sight in eyes

3. Smell Chemoreception Olfactory bulb

4. Olfactory epithelium 3 cm 2

5. An individual neuron contains a single type of odorant receptor Combine signals for diversity Cilia Nerve fibers within the olfactory bulb Olfactory receptor cells Columnar epithelial cells

6. http://www.youtube.com/watch?v=H_WFlTtP ZmE

7. Olfactory stimulation Receptors undergo sensory adaptation rapidly Sense of smell drops by 50% within one second after stimulation

8. Taste (gustation) Chemoreceptors on taste buds Sweet, sour, salty, bitter, umami Each sensation triggered by the presence of different ions (e.g., H + sour, Na + salty)

9. Taste receptors One taste bud = 50-150 taste cells

10. Tasting Substance must be dissolved in saliva Molecules interact with receptor on epithelial taste cell Each cell is only responsive to one type taste sensation

11. Hearing Perception of energy carried by sound waves (pressure)

14. http://www.youtube.com/watch?v=0jyxhozq8 9g&list=PLBFFFFF039E4A8B05

15. Hearing loss Conductive- external, middle ear; reconstruction of bones in middle ear Central- rare, damage to neural pathway Sensorineural- inner ear, death of hair cells

16. Cochlear implants

17. Equilibrium Dynamic- movement through space Static- head position Inner ear Vestibular apparatus- endolymph

18. Equilibrium Semicircular canal system – Rotational acceleration – Movement of endolymph, hair cells transduce (a) Head in still position (b) Head rotating

19. Equilibrium Semicircular canal system – Linear acceleration – Movement of otoliths, hair cells transduce – Some otoliths horizontal, some vertical

21. Vision Light translated to a mental image Light enters eye, lens focuses light on retina Retina photoreceptors transduce light into electrical signal Electrical signals through neural pathways to brain

22. Optics of the eye Focal point must hit the back of the eye (retina)

23. Lens- bends light to focus on retina Pupil- changes amount of light that enters

24. 24 Focusing On Retina As light enters eye, it is refracted by: Convex surface of cornea Convex surface of lens Image focused on retina is upside down and reversed from left to right Light waves Object Cornea Image Retina Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

25. Light energy changes to electrical energy Occurs at retina Hits visual receptors behind retina

26. 26 Visual Receptors Rods Long, thin projections Contain light sensitive pigment called rhodopsin Hundreds of times more sensitive to light than cones Provide vision in dim light Produce colorless vision Produce outlines of objects Cones Short, blunt projections Contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe Provide vision in bright light Produce sharp images Produce color vision Fovea centralis contains just cones

27. Photoreceptors under layer of transparent neurons

28. Fovea- nothing to impede light

29. Stereoscopic Vision Provides perception of distance and depth Results from formation of two slightly different retinal images Light waves Right eyeLeft eye

30. In the brain Nerves cross in brain Binocular zone, constructs 3D representation