1. Memory and Senses Nervous Part D H. Biology II Adapted 2014-2015

2. Vision- Light Our eyes respond to visible light, a small portion of the electromagnetic spectrum Light: packets of energy called photons (quanta) that travel in a wavelike fashion Rods and cones respond to different wavelengths of the visible spectrum

3. Figure 15.10 Wavelength (nm) Visible light (b) (a) Blue cones (420 nm) Rods (500 nm) Green cones (530 nm) Red cones (560 nm) X raysUVInfrared Micro- waves Radio waves Gamma rays Light absorption (pervent of maximum)

4. Functional Anatomy of Photoreceptors Rods and cones – Outer segment of each contains visual pigments (photopigments)—molecules that change shape as they absorb light – Inner segment of each joins the cell body

5. Rods Functional characteristics – Very sensitive to dim light – Best suited for night vision and peripheral vision – Perceived input is in gray tones only – Pathways converge, resulting in fuzzy and indistinct images

6. Cones Functional characteristics – Need bright light for activation (have low sensitivity) – Have one of three pigments that furnish a vividly colored view – Nonconverging pathways result in detailed, high- resolution vision

7. Chemistry of Visual Pigments Retinal – Light-absorbing molecule that combines with one of four proteins (opsin) to form visual pigments – Synthesized from vitamin A – Two isomers: 11-cis-retinal (bent form) and all-trans- retinal (straight form) Conversion of 11-cis-retinal to all-trans-retinal initiates a chain of reactions leading to transmission of electrical impulses in the optic nerve Color blindness is due to a congenital lack of one or more of the cone types

8. Light Adaptation Occurs when moving from darkness into bright light – Large amounts of pigments are broken down instantaneously, producing glare – Pupils constrict – Dramatic changes in retinal sensitivity: rod function ceases – Cones and neurons rapidly adapt – Visual acuity improves over 5–10 minutes

9. Dark Adaptation Occurs when moving from bright light into darkness – The reverse of light adaptation – Cones stop functioning in low-intensity light – Pupils dilate – Rhodopsin accumulates in the dark and retinal sensitivity increases within 20–30 minutes

10. Refraction and Lenses Refraction – Bending of a light ray due to change in speed when light passes from one transparent medium to another – Occurs when light meets the surface of a different medium at an oblique angle

11. Refraction and Lenses Light passing through a convex lens (as in the eye) is bent so that the rays converge at a focal point The image formed at the focal point is upside- down and reversed right to left

12. Figure 15.12 Point sources (a) Focusing of two points of light. (b) The image is inverted—upside down and reversed. Focal points

13. Focusing Light on the Retina Pathway of light entering the eye: cornea, aqueous humor, lens, vitreous humor, neural layer of retina, photoreceptors Light is refracted – At the cornea – Entering the lens – Leaving the lens Change in lens curvature allows for fine focusing of an image

14. Focusing for Distant Vision Light rays from distant objects are nearly parallel at the eye and need little refraction beyond what occurs in the at-rest eye Far point of vision: the distance beyond which no change in lens shape is needed for focusing; 20 feet for emmetropic (normal) eye Ciliary muscles are relaxed Lens is stretched flat by tension in the ciliary zonule

15. Figure 15.13a Lens Inverted image Ciliary zonule Ciliary muscle Nearly parallel rays from distant object (a) Lens is flattened for distant vision. Sympathetic input relaxes the ciliary muscle, tightening the ciliary zonule, and flattening the lens. Sympathetic activation

16. Focusing for Close Vision Close vision requires – Accommodation—changing the lens shape by ciliary muscles to increase refractory power Near point of vision is determined by the maximum bulge the lens can achieve Presbyopia—loss of accommodation over age 50 – Constriction—the accommodation pupillary reflex constricts the pupils to prevent the most divergent light rays from entering the eye – Convergence—medial rotation of the eyeballs toward the object being viewed

17. Problems of Refraction Myopia (nearsightedness)—focal point is in front of the retina, e.g. in a longer than normal eyeball – Corrected with a concave lens Hyperopia (farsightedness)—focal point is behind the retina, e.g. in a shorter than normal eyeball – Corrected with a convex lens Astigmatism—caused by unequal curvatures in different parts of the cornea or lens – Corrected with cylindrically ground lenses, corneal implants, or laser procedures

18. Figure 15.14 (2 of 3) Concave lens moves focal point further back. Eyeball too long Uncorrected Focal point is in front of retina. Corrected Myopic eye (nearsighted)

19. Figure 15.14 (3 of 3) Eyeball too short Uncorrected Focal point is behind retina. Corrected Convex lens moves focal point forward. Hyperopic eye (farsighted)

20. Taste/Smell

21. Chemical Senses Taste and smell (olfaction) Their chemoreceptors respond to chemicals in aqueous solution

22. Sense of Smell The organ of smell—olfactory epithelium in the roof of the nasal cavity Olfactory receptor cells—bipolar neurons with radiating olfactory cilia Bundles of axons of olfactory receptor cells form the filaments of the olfactory nerve (cranial nerve I) Supporting cells surround and cushion olfactory receptor cells Basal cells lie at the base of the epithelium

23. Sense of Smell The organ of smell—olfactory epithelium in the roof of the nasal cavity Olfactory receptor cells—bipolar neurons with radiating olfactory cilia Bundles of axons of olfactory receptor cells form the filaments of the olfactory nerve (cranial nerve I) Supporting cells surround and cushion olfactory receptor cells Basal cells lie at the base of the epithelium

24. Figure 15.21a Olfactory tract Olfactory bulb (a) Nasal conchae Route of inhaled air Olfactory epithelium

25. Sense of Taste Receptor organs are taste buds – Found on the tongue On the tops of fungiform papillae On the side walls of foliate papillae and circumvallate (vallate) papillae

26. Taste Sensations There are five basic taste sensations 1.Sweet—sugars, saccharin, alcohol, and some amino acids 2.Sour—hydrogen ions 3.Salt—metal ions 4.Bitter—alkaloids such as quinine and nicotine 5.Umami—amino acids glutamate and aspartate – Cranial nerves VII and IX carry impulses from taste buds to the solitary nucleus of the medulla

27. Figure 15.23a (a) Taste buds are associated with fungiform, foliate, and circumvallate (vallate) papillae. Fungiform papillae Epiglottis Palatine tonsil Foliate papillae Lingual tonsil

28. Figure 15.23b (b) Enlarged section of a circumvallate papilla. Taste bud Circumvallate papilla

29. Figure 15.23c Taste fibers of cranial nerve Connective tissue Gustatory (taste) cells Taste pore Gustatory hair Stratified squamous epithelium of tongue (c) Enlarged view of a taste bud. Basal cells

30. Hearing

31. The Ear: Hearing and Balance Three parts of the ear 1.External (outer) ear 2.Middle ear (tympanic cavity) 3.Internal (inner) ear

32. The Ear: Hearing and Balance External ear and middle ear are involved with hearing Internal ear (labyrinth) functions in both hearing and equilibrium Receptors for hearing and balance – Respond to separate stimuli – Are activated independently

33. Figure 15.25a External acoustic meatus Auricle (pinna) (a) The three regions of the ear Helix Lobule Pharyngotympanic (auditory) tube Tympanic membrane External ear Middle ear Internal ear (labyrinth)

34. External Ear The auricle (pinna) is composed of: – Helix (rim) – Lobule (earlobe) External acoustic meatus (auditory canal) – Short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous glands

35. External Ear Tympanic membrane (eardrum) – Boundary between external and middle ears – Connective tissue membrane that vibrates in response to sound – Transfers sound energy to the bones of the middle ear

36. Middle Ear A small, air-filled, mucosa-lined cavity in the temporal bone – Flanked laterally by the eardrum – Flanked medially by bony wall containing the oval (vestibular) and round (cochlear) windows

37. Middle Ear Epitympanic recess—superior portion of the middle ear Pharyngotympanic (auditory) tube—connects the middle ear to the nasopharynx – Equalizes pressure in the middle ear cavity with the external air pressure

38. Figure 15.25b Pharyngotympanic (auditory) tube Auditory ossicles Entrance to mastoid antrum in the epitympanic recess Tympanic membrane Semicircular canals Cochlea Cochlear nerve Vestibular nerve Oval window (deep to stapes) Round window Incu (anvil) Malleus (hammer) Stapes (stirrup) (b) Middle and internal ear Vestibule

39. Ear Ossicles Three small bones in tympanic cavity: the malleus, incus, and stapes – Suspended by ligaments and joined by synovial joints – Transmit vibratory motion of the eardrum to the oval window – Tensor tympani and stapedius muscles contract reflexively in response to loud sounds to prevent damage to the hearing receptors

40. Figure 15.26 Pharyngotym- panic tube Tensor tympani muscle Tympanic membrane (medial view) Stapes Malleus View Superior Anterior Lateral Incus Epitympanic recess Stapedius muscle

41. Internal Ear Bony labyrinth – Tortuous channels in the temporal bone – Three parts: vestibule, semicircular canals, and cochlea Filled with perilymph – Series of membranous sacs within the bony labyrinth – Filled with a potassium-rich endolymph

42. Figure 15.27 Anterior Semicircular ducts in semicircular canals Posterior Lateral Cristae ampullares in the membranous ampullae Utricle in vestibule Saccule in vestibule Stapes in oval window Temporal bone Facial nerve Vestibular nerve Superior vestibular ganglion Inferior vestibular ganglion Cochlear nerve Maculae Spiral organ (of Corti) Cochlear duct in cochlea Round window

43. Vestibule Central egg-shaped cavity of the bony labyrinth Contains two membranous sacs 1.Saccule is continuous with the cochlear duct 2.Utricle is continuous with the semicircular canals These sacs – House equilibrium receptor regions (maculae) – Respond to gravity and changes in the position of the head

44. Semicircular Canals Three canals (anterior, lateral, and posterior) that each define two-thirds of a circle Membranous semicircular ducts line each canal and communicate with the utricle Ampulla of each canal houses equilibrium receptor region called the crista ampullaris Receptors respond to angular (rotational) movements of the head

45. Figure 15.27 Anterior Semicircular ducts in semicircular canals Posterior Lateral Cristae ampullares in the membranous ampullae Utricle in vestibule Saccule in vestibule Stapes in oval window Temporal bone Facial nerve Vestibular nerve Superior vestibular ganglion Inferior vestibular ganglion Cochlear nerve Maculae Spiral organ (of Corti) Cochlear duct in cochlea Round window

46. The Cochlea A spiral, conical, bony chamber – Extends from the vestibule – Coils around a bony pillar (modiolus) – Contains the cochlear duct, which houses the spiral organ (of Corti) and ends at the cochlear apex

47. The Cochlea The cavity of the cochlea is divided into three chambers – Scala vestibuli—abuts the oval window, contains perilymph – Scala media (cochlear duct)—contains endolymph – Scala tympani—terminates at the round window; contains perilymph The scalae tympani and vestibuli are continuous with each other at the helicotrema (apex)

48. The Cochlea The “roof” of the cochlear duct is the vestibular membrane The “floor” of the cochlear duct is composed of: – The bony spiral lamina – The basilar membrane, which supports the organ of Corti The cochlear branch of nerve VIII runs from the organ of Corti to the brain

49. Figure 15.28a (a) Helicotrema Modiolus Cochlear nerve, division of the vestibulocochlear nerve (VIII) Cochlear duct (scala media) Spiral ganglion Osseous spiral lamina Vestibular membrane

50. Figure 15.28b (b) Cochlear duct ( scala media ; contains endolymph) Tectorial membrane Vestibular membrane Scala vestibuli (contains perilymph) Scala tympani (contains perilymph) Basilar membrane Spiral organ (of Corti) Stria vascularis Spiral ganglion Osseous spiral lamina

51. Figure 15.28c (c) Tectorial membrane Inner hair cell Outer hair cells Hairs (stereocilia) Afferent nerve fibers Basilar membrane Fibers of cochlear nerve Supporting cells

52. Figure 15.28d Inner hair cell Outer hair cell (d)