1. Senses Sense: ability to perceive stimuli Sensation:
conscious awareness of stimuli received by sensory neurons
Sensory receptors:
sensory nerve endings that respond to stimuli by developing action potentials

2. Types of Senses General senses: - receptors over large part of body
- somatic provide info. about body and env’t
- visceral provide info. about internal organs,
pain, pressure
- touch, pressure, pain, temp., and itch
Special senses:
smell, taste, sight, hearing, and balance

3. Types of Receptors Mechanoreceptors: - detect movement
- Ex. touch, pressure, vibration
Chemoreceptors:
- detect chemicals
- Ex. Odors
Photoreceptors:
detect light

4. Thermoreceptors:
detect temp. changes
Nociceptors:
detect pain

5. Types of Touch Receptors
Merkel’s disk:
detect light touch and pressure
Hair follicle receptors:
detect light touch
Meissner corpuscle:
- deep in epidermis
- localizing tactile sensations

6. Ruffini corpuscle:
- deep tactile receptors
- detects continuous pressure in skin
Pacinian corpuscle:
- deepest receptors
- associated with tendons and joints
- detect deep pressure, vibration, position

7. Figure 9.1

8. Pain
What is it?
unpleasant perceptual and emotional
experience

9. Types of Pain Localized: - sharp, pricking, cutting pain
- rapid action potential
Diffuse:
- burning, aching pain
- slower action potentials

10. Pain Control Local anesthesia:
- action potentials suppressed from pain
receptors in local areas
- chemicals are injected near sensory nerve
General anesthesia:
- loss of consciousness
- chemicals affect reticular formation

11. Referred Pain What is it?
- originates in a region that is not source of pain
stimulus
- felt when internal organs are damaged or
inflamed
- sensory neurons from superficial area and
neurons of source pain converge onto same
ascending neurons of spinal cord

13. Olfaction What is it? - sense of smell - occurs in response to
odorants
- receptors are located
in nasal cavity and
hard palate
- we can detected
10,000 different smells

14. How does olfaction work?
Nasal cavity contains a thin film of mucous where odors become dissolved.
Olfactory neurons are located in mucous. Dendrites of olfactory neurons are enlarged and contain cilia.
3. Dendrites pick up odor, depolarize, and carry odor
to axons in olfactory bulb (cranial nerve I).
4. Frontal and temporal lobes process odor.

15. Figure 9.3b

16. Taste Taste buds: - sensory structures that detect taste
- located on papillae on tongue, hard palate,
throat
Inside each taste bud are 40 taste cells
Each taste cell has taste hairs that extend into taste pores

17. Figure 9.4

18. How does taste work?
Taste buds pick up taste and send it to taste cells.
Taste cells send taste to taste hairs.
Taste hairs contain receptors that initiate an action potential which is carried to parietal lobe.
Brain processes taste.

19. Types of Tastes Sweet Sour Salty Bitter Umami
Certain taste buds are more sensitive to certain
tastes.
Taste is also linked to smell.

20. Vision Accessory Structures Eyebrow: - protects from sweat
- shade from sun
Eyelid/Eyelashes:
- protects from foreign objects
- lubricates by blinking

22. Conjunctiva:
thin membrane that covers inner surface of
eyelid
Lacrimal apparatus:
produces tears
Extrinsic eye muscles:
help move eyeball

24. Figure 9.8

26. Anatomy of Eye Hollow, fluid filled sphere
Composed of 3 layers (tunics)
Divided into chambers

27. Fibrous Tunic Outermost layer Sclera: - firm, white outer part Cornea:
- helps maintain eye shape, provides attachment
sites, protects internal structures
Cornea:
- transparent structure that covers iris and pupil
- allows light to enter and focuses light

28. Vascular Tunic Middle layer Contains blood supply Choroid:
- black part (melanin)
- delivers O2 and nutrients to retina
Ciliary body:
helps hold lens in place
Suspensory ligaments:
help hold lens in place

29. Lens:
- flexible disk
- focuses light onto retina
Iris:
- colored part
- surrounds and regulates pupil
Pupil:
- regulates amount of light entering
- lots of light = constricted
- little light = dilated

31. Figure 9.10

32. Nervous Tunic Innermost tunic Retina: - covers posterior 5/6 of eye
- contains 2 layers
Pigmented retina:
- outer layer
- keeps light from reflecting back in eye

33. Sensory retina:
- contains photoreceptors (rods and cones)
- contains interneurons
Rods:
- photoreceptor sensitive to light
- 20 times more rods than cones
- can function in dim light
Cones:
- photoreceptor provide color vision
- 3 types blue, green, red

34. Figure 9.12b

35. Figure 9.12c

36. Rhodopsin:
photosensitive pigment in rod cells
Opsin:
colorless protein in rhodopsin
Retinal:
- yellow pigment in rhodopsin
- requires vitamin A

37. Effects of Light on Rhodopsin
Light strikes rod cell
Retinal changes shape
Opsin changes shape
Retinal dissociates from opsin
Change rhodopsin shape stimulates response in rod cell which results in vision
Retinal detaches from opsin
ATP required to reattach retinal to opsin and return rhodopsin to original shape

38. Figure 9.13

39. Retina Structures Continued
Rods and cones synapse with bipolar cells of sensory retina
Horizontal cells of retina modify output of rods and cones
Bipolar and horizontal cells synapse with ganglion cells
Ganglion cells axons’ converge to form optic nerve

40. Nervous Tunic (Retina)
Innermost layer
2 parts of retina: sensory and pigmented
Keeps light from reflecting back into eye
Rods:
photoreceptors that detect amount light
Cones:
- photoreceptors that detect colors
- 3 types: red, blue, green

41. Macula:
small spot near center of retina
Fovea centralis:
- center of macula
- where light is focused when looking directly
at an object
- only cones
- ability to discriminate fine images

42. Optic disk:
- white spot medial to macula
- blood vessels enter eye and spread over retina
- axons exit as optic nerve
- no photoreceptors
- called blindspot

44. Chambers of Eye Anterior chamber: - located between cornea and lens
- filled with aqueous humor (watery)
- aqueous humor helps maintain pressure, refracts
light, and provide nutrients to inner surface of
eye
Posterior chamber:
- located behind anterior chamber
- contains aqueous humor

45. Vitreous chamber:
- located in retina region
- filled with vitreous humor: jelly-like substance
- vitreous humor helps maintain pressure, holds
lens and retina in place, refracts light

46. Functions of Eye Light Refraction Bending of light Focal point:
- point where light rays converge
- occurs anterior to retina
- object is inverted

47. Focusing Images on Retina
Accommodation:
- lens becomes less rounded and image can be
focused on retina
- enables eye to focus on images closer than
20 feet

49. Neuronal Pathway for Vision
Optic nerve:
leaves eye and exits orbit through optic foramen to enter cranial cavity
Optic chiasm:
where 2 optic nerves connect
Optic tracts:
route of ganglion axons

50. Figure 9.16b

51. Eye Defects Myopia: - nearsightedness - image is in front of retina
Hyperopia:
- farsightedness
- image is behind retina
Presbyopia:
- lens becomes less elastic
- reading glasses required

52. Clinical Focus 9A

53. Astigmatism:
- irregular curvature of lens
- glasses or contacts required to correct
Colorblindness:
- absence or deficient cones
- primarily in males
Glaucoma:
- decreased pressure in eye
- can lead to blindness

54. Clinical Focus 9B

55. Hearing and Balance External (Outer) Ear
Extends from outside of head to eardrum
Auricle:
fleshy part on outside
External auditory meatus:
canal that leads to eardrum
Tympanic membrane:
- eardrum
- thin membrane that separates external and
middle ear

56. Middle Ear
Air filled chamber
Malleus (hammer):
bone attached to tympanic membrane
Incus (anvil):
bone that connects malleus to stapes
Stapes (stirrup):
bone located at base of oval window

57. Oval window:
separates middle and inner ear
Eustachian or auditory tube:
- opens into pharynx
- equalizes air pressure between outside air
and middle ear

59. Inner Ear
Set of fluid filled chambers
Bony labyrinth:
- tunnels filled with fluid
- 3 regions: cochlea, vestibule, semicircular
canals
Membranous labyrinth:
- inside bony labyrinth
- filled with endolymph

60. Endolymph:
clear fluid in membranous labyrinth
Perilymph:
fluid between membranous and bony labyrinth
Cochlea:
- snail-shell shaped structure
- where hearing takes place

61. Scala vestibuli:
- in cochlea
- filled with perilymph
Scala tympani:
Cochlea duct:
- filled with endolymph

62. Spiral organ:
- in cochlear duct
- contains hair cells
Tectorial membrane:
- in cochlea
- vibrates against hair cells
Hair cells:
attached to sensory neurons that when bent produce an action potential

63. Vestibular membrane:
wall of membranous labyrinth that lines scala vestibuli
Basilar membrane:
wall of membranous labyrinth that lines scala tympani

65. How do we hear?
Sound travels in waves through air and is funneled into ear by auricle.
Auricle through external auditory meatus to tympanic membrane.
Tympanic membrane vibrates and sound is amplified by malleus, incus, stapes which transmit sound to oval window.
Oval window produces waves in perilymph of cochlea.

66. 5. Vibrations of perilymph cause vestibular membrane and endolymph to vibrate.
6. Endolymph cause displacement of basilar membrane.
7. Movement of basilar membrane is detected by hair hairs in spiral organ.
8. Hair cells become bent and cause action potential is created.

68. Balance (Equilibrium)
Static equilibrium:
- associated with vestibule
- evaluates position of head relative to gravity
Dynamic equilibrium:
- associated with semicircular canals
- evaluates changes in direction and rate of head
movement

69. Vestibule:
- inner ear
- contains utricle and saccule
Maculae:
- specialized patches of epithelium in utricle
and saccule surround by endolymph
- contain hair cells
Otoliths:
- gelatinous substance that moves in response
to gravity
- attached to hair cell microvilli which initiate action
potentials

72. Semicircular canals:
- dynamic equil.
- sense movement if any direction
Ampulla:
base of semicircular canal
Crista ampullaris:
in ampulla
Cupula:
- gelatinous mass
- contains microvilli
- float that is displaced by endolymph movement