1. Chapter 12 Somatic and Special Senses
Sensory Receptors
12-2

2. Receptor Types Chemoreceptors Pain receptors Thermoreceptors
Mechanoreceptors
Photoreceptors
12-3

3. Sensory Impulses stimulation of receptor causes change in its membrane
if receptor is part of a neuron, the membrane potential may generate an action potential
peripheral nerves transmit impulses to CNS
Sensation
12-4

4. Sensory Adaptation stronger stimulus required to activate receptors
smell receptors undergo sensory adaptation
12-1

5. Somatic Senses
senses associated with skin, muscles, joints, and viscera
three groups
exteroceptive senses –
proprioceptive senses – senses associated with changes in muscles and tendons
visceroceptive senses –
12-6

6. Touch and Pressure Senses
Free nerve endings
common in epithelial tissues
detect touch and pressure
Meissner’s corpuscles
abundant in hairless portions of skin
detect light touch
Pacinian corpuscles
common in deeper subcutaneous tissues, tendons, and ligaments
detect heavy pressure
12-7

7. Touch and Pressure Senses
12-8

8. Temperature Senses Warm receptors sensitive to temperatures above
unresponsive to temperature above
Cold receptors
sensitive to temperature between and
Pain receptors
respond to temperatures below oC
respond to temperatures above oC
12-9

9. Sense of Pain free nerve endings widely distributed
nervous tissue of brain lacks pain receptors
Visceral Pain
not well localized
12-10

10. Referred Pain
12-11

11. Pain Nerve Fibers Chronic pain fibers Acute pain fibers
conduct impulses more slowly
Acute pain fibers
conduct impulses rapidly
12-12

12. Regulation of Pain Impulses
Thalamus
allows person to be aware of pain
Pain Inhibiting Substances
enkephalins
serotonin
endorphins
Cerebral Cortex
judges intensity of pain
locates source or pain
produces motor response to pain
produces emotions to pain
12-13

13. Stretch Receptors proprioceptors
send information to CNS concerning lengths and tensions of muscles
2 main kinds of stretch receptors
muscle spindles –
Golgi tendon organs –
12-14

14. Special Senses
sensory receptors are within large, complex sensory organs in the head
smell in
taste in
hearing and equilibrium in
sight in
12-16

15. Smell Olfactory Receptors chemoreceptors Olfactory Organs
contain olfactory receptors and supporting epithelial cells
12-17

16. Olfactory Receptors
Sense of Smell.mov
12-18

17. Taste Taste Buds organs of taste Taste Receptors chemoreceptors
taste cells –
taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells
12-20

18. Taste Receptors
Sense of Taiste.mov
12-21

19. Taste Sensations Four Primary Taste Sensations sweet – sour – salty –
bitter –
Spicy foods activate pain receptors
12-22

20. Hearing
Ear – organ of hearing
3 Sections
12-24

21. External Ear auricle external auditory meatus tympanic membrane
lined with ceruminous glands
terminates with tympanic membrane
tympanic membrane
12-25

22. Middle Ear tympanic cavity air-filled space in temporal bone
auditory ossicles
malleus, incus, and stapes
oval window
opening in wall of tympanic cavity
12-26

23. Auditory Tube eustachian tube
usually closed by valve-like flaps in throat
Sense of Hearing.mov
12-27

24. Inner Ear complex system of labyrinths osseous labyrinth
bony canal in temporal bone
12-28

25. Inner Ear 3 Parts of Labyrinths cochlea semicircular canals vestibule
12-29

26. Equilibrium Dynamic Equilibrium Static Equilibrium semicircular canals
vestibule
12-36

27. Macula responds to changes in head position
bending of hairs results in generation of nerve impulse
Sense of Equilibrium.mov
Sense of Rotation.mov
12-38

28. Sight Visual Accessory Organs eyelids lacrimal apparatus
extrinsic eye muscles
12-41

29. Lacrimal Apparatus lacrimal gland lateral to eye canaliculi
lacrimal sac
collects from canaliculi
nasolacrimal duct
collects from lacrimal sac
12-43

30. Extrinsic Eye Muscles Superior rectus rotates eye up and medially
Inferior rectus
rotates eye down and medially
Medial rectus
rotates eye medially
12-44

31. Extrinsic Eye Muscles Lateral rectus rotates eye laterally
Superior oblique
rotates eye down and laterally
Inferior oblique
rotates eye up and laterally
12-45

32. Structure of the Eye hollow spherical wall has 3 layers
outer fibrous tunic
middle vascular tunic
inner nervous tunic
12-46

33. Outer Tunic Cornea anterior portion transparent light transmission
light refraction
Sclera
posterior portion
opaque
protection
12-47

34. Middle Tunic Iris anterior portion pigmented controls light intensity
Ciliary body
anterior portion
pigmented
holds lens
moves lens for focusing
Choroid coat
provides blood supply
pigments absorb extra light
12-48

35. Anterior Portion of Eye
filled with aqueous humor
12-49

36. Lens transparent biconvex lies behind iris
largely composed of lens fibers
elastic
held in place by suspensory ligaments of ciliary body
12-50

37. Ciliary Body forms internal ring around front of eye
ciliary processes – radiating folds
ciliary muscles – contract and relax to move lens
12-51

38. Iris composed of connective tissue and smooth muscle
dim light stimulates radial muscles and pupil dilates
12-53

39. Aqueous Humor fluid in anterior cavity of eye
secreted by epithelium on inner surface of the ciliary body
provides nutrients
maintains shape of anterior portion of eye
leaves cavity through canal of Schlemm
12-54

40. Inner Tunic retina contains visual receptors
continuous with optic nerve
ends just behind margin of the ciliary body
composed of several layers
macula lutea – yellowish spot in retina
fovea centralis – center of macula lutea; produces sharpest vision
optic disc – blind spot; contains no visual receptors
vitreous humor – thick gel that holds retina flat against choroid coat
12-55

41. Light Refraction Refraction bending of light
occurs when light waves pass at an oblique angle into mediums of different densities
12-57

42. Types of Lenses
Convex
Concave
12-58

43. 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
12-59

44. Visual Receptors Rods contain light sensitive pigment called rhodopsin
produce colorless vision
produce outlines of objects
Cones
short, blunt projections
contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe
12-60

45. Stereoscopic Vision
results from formation of two slightly different retinal images
12-63

46. Visual Pathway
Sense of Sight.mov
12-64

47. Life-Span Changes Age related hearing loss due to
damage of hair cells in organ of Corti
degeneration of nerve pathways to the brain
tinnitus
Age-related visual problems include
dry eyes
floaters (crystals in vitreous humor)
loss of elasticity of lens
glaucoma
cataracts
macular degeneration
12-65

48. Clinical Application Refraction Disorders
concave lens corrects nearsightedness
convex lens corrects farsightedness
12-66