1. Sensory Reception Chapter 35

2. Sensory Systems The means by which organisms receive signals from the external world and internal environment Many animals can sense stimuli that humans cannot

3. Sensory Receptors Convert the energy of a stimulus into action potentials Mechanoreceptors Thermoreceptors Pain receptors Chemoreceptors Osmoreceptors Photoreceptors

4. Assessing a Stimulus Action potentials don’t vary in amplitude Brain tells nature of stimulus by: –Particular pathway that carries the signal –Frequency of action potentials along an axon –Number of axons recruited

5. Recordings of Action Potentials Figure 35.3 Page 609

6. Sensory Adaptation A decrease in response to a stimulus being maintained at constant strength

7. Somatic Sensations Touch Pressure Temperature Pain Motion Position

8. Somatosensory Cortex Figure 35.4 Page 610

9. Receptors in Skin Free nerve ending Ruffini ending Pacinian corpuscle Bulb of Krause Meissner’s corpuscle Figure 35.5 Page 611

10. Referred Pain Sensations of pain from internal organs may be wrongly projected to part of the skin surface Heart attack can be felt as pain in skin above the heart and along the left shoulder and arm

11. Taste A special sense Chemoreceptors Five primary sensations: –sweet, sour, salty, bitter, and umami Figure 35.8 Page 612

12. Smell A special sense Olfactory receptors Receptor axons lead to olfactory lobe olfactory bulb receptor cell Figure 35.7 Page 612

13. Balance and Equilibrium In humans, organs of equilibrium are located in the inner ear Vestibular apparatus vestibular apparatus saccule utricle semicircular canals Figure 35.9b Page 613

14. Moving in response to gravity, otoliths bend projections of hair cells and stimulate the endings of sensory neurons Acceleration-Deceleration hair cellotolithsmembrane vestibular nerve Figure 35.9b Page 613

15. Dynamic Equilibrium Rotating head movements cause pressure waves that bend a gelatinous cupula and stimulate hair cells inside it cupula Figure 35.9c Page 613

16. Properties of Sound Ear detects pressure waves Amplitude of waves corresponds to perceived loudness Frequency of waves (number per second) corresponds to perceived pitch

17. Anatomy of Human Ear cochlea auditory nerve eardrum auditory canal hammer anvil stirrup Fig. 35.11a Page 614

18. Sound Reception Sound waves make the eardrum vibrate Vibrations are transmitted to the bones of the middle ear The stirrup transmits force to the oval window of the fluid-filled cochlea

19. Sound Reception Movement of oval window causes waves in the fluid inside cochlear ducts Figure 35.11b Page 615 eardrumround window oval window (behind stirrup) scala vestibuli scala tympani

20. Sound Reception hair cells in organ of Corti tectorial membrane lumen of cochlear duct basilar membrane lumen of scala tympani to auditory nerve Figure 35.11c Page 615

21. Vision Sensitivity to light does not equal vision Vision requires two components –Eyes –Capacity for image formation in the brain

22. Invertebrate Eyes Limpet ocellus sensory neuron epidermis cuticle lens Land snail eye Compound eye of a deerfly ommatidium Figures 35.13 & 35.14 Pages 616 & 617

23. Human Eye sclera choroid iris lens pupil cornea aqueous humor ciliary muscle vitreous body retina fovea optic disk part of optic nerve Figure 35.17 Page 618

24. Pattern of Stimulation Light rays pass through lens and converge on retina at back of eye The image that forms on the retina is upside down and reversed right to left compared with the stimulus Brain accounts for this during processing

25. Pattern of Stimulation Figure 35.18 Page 619

26. Visual Accommodation Adjustments of the lens Ciliary muscle encircles lens When this muscle relaxes, lens flattens, moves focal point farther back When it contracts, lens bulges, moves focal point toward front of eye

27. Organization of Retina Photoreceptors lie at the back of the retina, in front of a pigmented epithelium For light to reach the photoreceptors, it must pass layers of neurons involved in visual processing

28. Organization of Retina Signals from photoreceptors are passed to bipolar sensory neurons, then to ganglion cells Figure 35.21a Page 620

29. The Photoreceptors Rods –Contain the pigment rhodopsin –Detect very dim light, changes in light intensity Cones –Three kinds; detect red, blue, or green –Provide color sense and daytime vision

30. Receptive Fields Restricted areas that influence the activity of individual sensory neurons Response of neuron to orientation of bar signals to oscilloscope time (sec) Figure 35.22 Page 621

31. Retina to Brain retina optic nerve lateral geniculate nucleus visual cortex Figure 35.31 Page 621

32. Disorders of the Eye (1) Color blindness Focusing problems –Nearsightedness and farsightedness Eye diseases –Trachoma –Histoplasmosis –Herpes simplex infection

33. Disorders of the Eye (2) Age-related problems –Cataracts –Macular degeneration –Glaucoma Injuries –Retinal detachment