1. Chapter 10 – Somatic Senses

2. Types of Receptors Chemoreceptors Pain receptors Thermoreceptors
Chemical concentrations
Pain receptors
Detect tissue damage
Thermoreceptors
Changes in temperature
Mechanoreceptors
Changes in pressure or movement
Photoreceptors
Light energy

3. Sensations
Feeling that occurs when the brain interprets sensory impulses
Depends on area of brain that receives the impulse
Projection
brain sends the sensation back to its apparent source
Sensory adaptations
Sensory impulses sent at decreasing rates until receptors fail to send impulses unless there is a change in strength of the stimulus

4. Touch and Pressure Receptors
Sensory nerve fibers
Found in epithelial tissues
Sense touch and pressure
Meissner’s corpuscles
Are flattened connective tissue sheaths found in hairless portions of skin (Ex. Lips)
Respond to the light motion of objects that barely touch the skin

6. Touch and Pressure Receptors
Pacinian corpuscles
Made of connective tissue
Found in deeper subcutaneous layers, muscle tendons, joint ligaments
Respond to heavy pressure and deep pressure

8. Temperature Senses Heat receptors Cold receptors
Triggered at degrees Fahrenheit
Cold receptors
Triggered at degrees Fahrenheit

9. Sense of Pain Free nerve endings
Stimulated due to tissue damage
Visceral Pain Receptors (referred pain)
Only receptors in viscera to produce sensations
Referred pain - felt in at location other than where the painful stimulus is originating
Occurs due to common nerve pathway leading from skin to internal organs

11. Pain Nerve Fibers Acute pain fibers Chronic pain fibers
sensation of sharp pain
seldom continues once stimulus is removed
Chronic pain fibers
dull, aching pain
may continue after stimulus ceases
Pain impulses sent to thalamus, hypothalamus, and cerebral cortex

12. Regulation of Pain Impulses
Enkephalins
Suppress acute and chronic pain impulses
Serotonin
Stimulates other neurons to release enkaphalins
Endorphins
Pain-suppressing, morphine-like actions
Natural pain control sent by brain

13. Olfactory Organs Contain olfactory receptor cells (chemoreceptors)
Smell receptors
Cilia
Sensitive part of the receptors
Chemical detected once dissolved in watery- fluid surrounding cilia

14. Sense of Taste Taste buds Taste sensations Found in papillae of tongue
Modified epithelial cells that serve as receptors
Chemical must be dissolved in saliva to be tasted
Taste sensations
Sweet – near tip of tongue
Sour – along lateral edges of tongue
Salty – tip and upper portion of tongue
Bitter – back of tongue
Umami – MSG taste

15. Sense of Taste

16. Flavor = taste + smell

17. Aging and Taste After age 50, ability to smell and taste decrease
Membranes lining nose become thinner & drier  olfactory nerve deteriorate
# taste buds decrease with age  more difficult to detect sweet/salty  foods taste more bitter
As people age, their food tastes more bland  eat less  possible malnutrition

18. Sense of Hearing - Parts of the Ear
External Section
Consists of:
Auricle – collects sound-waves
External auditory meatus – passageway for sound
Middle Section
Tympanic Membrane (ear drum)
Auditory ossicles – malleus, incus, and stapes
Transmit and amplify sound
Inner Section
Cochlea – hearing organ
Semi-circular canals function in equilibrium
Organ of Corti – houses receptors (hair cells)

19. Parts of the Ear

20. Ear Disorders Otitis Media Tinnitus Ear infection
May require Eustachian tubes
Tinnitus
Ringing of the ear
Sometimes accompanied with Meniere’s disease
Spontaneous episodes of vertigo

21. The Structures of the Eye

22. Eyelid Skin covers lids outer surface Muscles
orbicularis oculi & levator palpebrae superioris
Conjunctiva - mucous membrane that lines the inner eye
Conjunctivitis – inflammation of conjunctiva (pink eye)

23. Conjunctivitis

24. Visual Accessory Organs
Lacrimal gland
Secretes tears
Secretes tears continuously over the eye and into the nasal cavity
Lysozyme- enzyme that is an antibacterial agent against eye infections
Extrinsic muscles
Attached to the sclera and move eye in various directions

25. Strabismus – misalignment of eyes

26. Structures of the Eye Cornea Sclera Optic nerve Window of the eye
Helps focus entering light rays
Sclera
White portion of the eye
Protects eye & attaches extrinsic muscles
Optic nerve
Found in the back of the eye
Transmits stimuli to the optic lobe

27. Structures of the Eye Ciliary body Choroid Coat Lens Iris
Forms internal ring around the eye
Choroid Coat
Nourishes tissues of eye and keeps inside dark
Lens
Behind iris and pupil
Focuses light
Affected during cataract formation
Iris
Smooth-muscle diaphragm that adjusts amount of light entering
Colored portion of eye

28. Cataracts

29. Structures of the Eye Aqueous humor Pupil
Watery fluid between cornea and lens
Nourishes and maintains shape of eye
Glaucoma – causes damage to optic nerve due to built up pressure
Pupil
Circular opening in the center of the iris

30. Glaucoma

31. Structures of the Eye Retina Vitreous humor
Contains photoreceptor cells
Fovea centralis – sharpest point of vision in retina
Optic disk – where nerve fibers leave eye to join optic nerve
Blind spot
Vitreous humor
Fluid of the inner eye
Supports internal parts and maintains the shape

34. Visual Receptors of Retina
Rods
Provide colorless vision in dim light and general outlines of objects
Cones
Detect color and provide sharp images in bright light
Move eyes so image falls on the fovea centralis
Contains the highest concentration of cones

35. Visual Pigments Rods Contain Rhodopsin (visual purple)
Breaks down opsin (protein) and retinal (form of Vitamin A) in presence of light
Cones
Contain Iodopsins
Three sets of cones, each containing a different visual pigment
Wavelength of light determines the color perceived from it
Each of the three pigments is sensitive to different wavelengths of light
Color perceived depends upon which sets of cones the light stimulates
If all three sets are stimulated, the color is white
If none are stimulated, the color is black

36. Eye Disorders Myopia Hyperopia Astigmatism Diabetic retinopathy
Color blindness

37. Myopia - “Nearsighted”

38. Hyperopia - “Farsighted”

39. Astigmatism

40. Diabetic Retinopathy

41. Color Blindness – caused because of faulty cone formation

42. Visual Acuity Clearness or sharpness of visual perception First number
distance between person and chart
Second number
represents the # of feet a person with normal acuity would have to stand to see the same object clearly
legally blind

43. Vision Tests

44. Are the squares inside the blue and yellow squares all the same color?

45. Bezold effect
The smaller squares inside the blue and yellow squares are all the same color.
They seem different (magenta and orange) because a color is perceived differently depending on its relation to adjacent colors (here blue or yellow depending on the outer square).

46. Are the horizontal lines straight or crooked?

47. Café Wall Illusion
The horizontal lines are straight, even though they do not seem straight.  In this illusion, the vertical zigzag patterns disrupt our horizontal perception.

48. Does Lincoln’s face look normal?

49. Some neurons in the brain seem specialized in processing faces
Some neurons in the brain seem specialized in processing faces. Faces are usually seen upright. When presented upside down, the brain no longer recognizes a picture of a face as a face but rather as an object. Neurons processing objects are different from those processing faces and not as specialized. As a consequence these neurons do not respond to face distortions as well. This explains why we miss the weird eyes when the face is inverted.

50. Can you see a baby?

51. Illusory Contour
The baby’s head is on the left, the baby’s feet are against the trunk of the tree on the right. Illusory Contour: a form of visual illusion where contours are perceived without a luminance or color change across the contour

52. How quickly can you say the color of the words below?

54. Genetics of Taste

55. PTC = phenylthiocarbamide
Discovered in 1931 by when a DuPont chemist named Arthur Fox accidentally released a cloud of fine crystalline PTC in the lab.
A nearby colleague complained of the bitter taste, while Dr. Fox tasted nothing.
Fox continued to test the taste buds of family and friends, setting the groundwork for future genetic studies.

56. Genetics of PTC Tasting
Gene for tasting PTC (Tas2r38) is located on Chromosome 7.
PAV = taster (T), AVI = non-taster (t), AAV = another allele
PAV-PAV = TT = very bitter
PAV-AVI = Tt = somewhat bitter
AVI-AVI = tt = non-taster
General Population: 70% Tasters, 30% Non-tasters
TAS2R38

57. Bitter tastes = Result of selection pressures?
Thiocynate Compounds (bitter taste) found in broccoli, cauliflower, mustard family
Tasters: avoid these foods in diet
Nontasters: more varied diet, include green leafy veggies
Thiocynates might inhibit thyroid function  tasters may have protection against thyroid diseases

58. Bitter tastes = Result of selection pressures?
Poisons = bitter taste
Tasters: part of hunter-gatherer societies?
Genetic Drift
Europeans: all 3 alleles (PAV, AVI, AAV)
Asians: AAV allele rare
Native Americans: 98% have PAV allele only

59. Denver Museum of Nature and Science
Expedition Health: Genetics of Taste Study
Purpose of Study:
Is ability to taste bitter compounds related to what foods you eat, your % body fat, and BMI?
Is your ability to taste bitter compounds related to your genetic ancestry?

60. Substances related to PTC
Thiourea (thiocarbamide) – very bitter!!!
Sodium benzoate – sweet, salty, bitter, no taste
Food preservative

61. Family Pedigree Tasters: Supertasters (TT) Tasters (Tt)
Non-tasters (tt)