1. BIO 265 Human Anatomy and Physiology II
Introduction
BIO 265
Human Anatomy and Physiology II

2. The Prophet’s View of Education
“You are all in school. Do not waste your time. This is a time of great opportunity that you will never have again as long as you live. Make the most of it right now….
“…you can’t afford to waste your time. There is so much to learn. Give it the very best that you have.” – Gordon B. Hinckley

3. Syllabus Syllabus What does it take to succeed in Bro. Wray’s class?
First Reading Assignment – Due Wednesday in Class

4. Chapter 15 – The Special Senses
BIO Human A&P II
Chapter 15 – The Special Senses

5. Introduction What are the special senses?
The special senses vs. the general senses
Location
Receptors
Chemoreceptors – taste and smell
Mechanoreceptors – hearing and equilibrium
Photoreceptors - vision

6. Taste The senses of taste and smell are similar
chemoreceptors are stimulated by chemicals that bind to them and generate action potentials
There are about 10,000 taste buds on the tongue
Each taste bud has about 50 gustatory cells that are responsible for taste
The gustatory cells have several microvilli called gustatory hairs
Figure 15.1

7. Taste Buds
Figure 15.1

8. Taste The sensation of taste:
molecules become dissolved in the saliva
The molecules can then bind to chemoreceptors
This causes depolarization of the cell
This results in an action potential that is conducted to the cerebral cortex
Figure 15.2

9. Taste Buds
Figure 15.1

10. Gustatory Pathway
Figure 15.2

11. Taste
The sensation of taste is derived from a small number of primary tastes
Sour, salty, bitter, sweet, and umami
Hot or spicy foods actually stimulate pain receptors

12. Taste
CD animation
The wide variety of tastes also come from the sense of smell
Smell actually accounts for about 80% of our sensation of taste

13. Olfaction
Olfaction or smell occurs by stimulation of receptors located in the nasal cavity
in the olfactory recess
Figure 15.3

14. Sense of Smell
Figure 15.3

15. Olfaction
There are 10 million olfactory neurons within the olfactory epithelium
These connect with the left or right olfactory bulbs
Figure 15.3 and from other text

16. Sense of Smell
Figure 15.3

17. 7

18. Olfaction
The olfactory neurons have a tuft of cilia that lie at the end of the dendrite
(olfactory hairs)
surrounded by a layer of mucus
When chemicals become dissolved in the mucus they can bind to chemoreceptors on the cilia
This depolarizes the cilia and leads to an action potential in the olfactory neuron

19. Olfaction
The action potential is conducted into the cerebrum where the smell is perceived
Figures from other text

20. 7

21. 6

22. Olfaction CD animation
It is believed that the 4000 (or more) different smells perceived by humans actually come from a combination of 7 to 50 primary odors
Olfactory adaptation occurs in response to continual exposure to a certain odor
Barn yard, paper mill, cookies, etc.
Actual receptor function – Figure 15.4

24. Visual System
The visual system includes the eyes, accessory structures, and the optic nerves.
What are some of the accessory structures?
Eye brows
Eye lids
blink every 3-7 seconds
blinking reflex from eyelashes
Figure 15.5 and from other text

27. Visual System Conjunctiva Pink eye or conjunctivitis
Figure from other text

29. Visual System Lacrimal apparatus
Watery eyes and one of the mysteries of life
Figure 15.6

31. Visual System
Extrinsic eye muscles – Figure 15.7

33. Visual System Anatomy of the eye
The eye contains three layers or tunics
Fibrous tunic
Sclera – whites of the eye, made of dense connective tissue with elastic fibers
Cornea – transparent structure covering the anterior surface of the eye
Very sensitive to touch
Figure 15.8

35. Visual System
Vascular tunic – contains most of the blood vessels of the eye
Choroid – dark brown, thin membrane associated with the sclera
Ciliary body – contains ciliary muscles that attach to the lens by suspensory ligaments
These muscles change the shape of the lens for focusing
Iris – the colored portion of the eye, contains smooth muscle to control the size of the pupil
Eye color details
Figures 15.8 and 15.9 and from other text

39. Visual System Nervous tunic – also called the retina Pigmented retina
Sensory retina – contains photoreceptor cells called rods and cones
Figures 15.8 and 15.10

42. Visual System
Optic disk and the blind spot
Figure 15.10b

44. Visual System
There are about 250,000,000 rods and cones in the retina!!!
Rods are very sensitive to light, but cannot detect colors
Cones require more light, but they are sensitive to color and allow us to distinguish fine detail
Retina organization and the fovea centralis

45. Visual System
Viewing the retina – Figure 15.11

47. Visual System Compartments of the eye:
Anterior segment – filled with aqueous humor that provides nutrients for the cornea
Glaucoma and blindness
Posterior segment – filled with vitreous humor
Figure 15.12

49. Visual System Lens – transparent, flexible structure
Allows focusing of light on the retina
Figures and 15.17

52. Visual Systems Focusing problems Myopia – nearsightedness
Hyperopia – farsightedness
Figure 15.18

54. Visual Systems
So, how do we see things?

55. Visual Systems

56. Visual Systems
CD Demo – preview of sight

57. Visual Systems Function of the Retina
There are about 120 million rods and 6-7 million cones in each retina
Rods are bipolar photoreceptor cells involved in non- color vision
They are especially important in low light conditions
Rods contain a special light-sensitive molecule called rhodopsin composed of:
Opsin – protein portion (membrane protein)
Retinal – light absorbing pigment (derived from Vit. A)
Figure 15.19

59. Visual Systems
When light strikes the rhodopsin, the retinal changes shape
This activates a messenger system that leads to hyperpolarization of the cell
Figure 15.21

61. Visual Systems This hyperpolarization is strange
A photoreceptor cell not exposed to light has open Na+ ion channels
The movement of Na+ into the cell causes depolarization
This depolarization causes the cell to release an inhibitory neurotransmitter (glutamate)
Glutamate blocks action potential generation in the neighboring association neurons
Figure 15.22

63. Visual Systems
When photoreceptor cells are exposed to light, the Na+ channels are closed
This causes hyperpolarization of the cell
Hyperpolarization blocks the release of glutamate
Therefore the association neuron generates an action potential which is conducted to the brain
Figure from other text

64. Visual Systems

65. Visual Systems CD-animation Light and dark adaptation?
involves rhodopsin as well as pupil size
Bright light lowers the amount of rhodopsin in the rods
Figure 15.21

67. Visual Systems Cones function in color vision and visual acuity
Differences between rods and cones (sensitivity and color)
Cool Marker Example
Cones function much like rods, but they contain iodopsin instead of rhodopsin
Iodopsin is a combination of retinal and a color-specific opsin protein

68. Visual Systems
The opsin in cones can respond to either blue, green, or red light
Color blindness comes from not having one type of cone
The color of an object results from the combination of blue, green, and red cones that respond
Orange color – 99% of red cones, 42% of green cones, 0% of blue cones
Yellow would lead to more green cones, etc.
Figure from other text

70. Visual Systems Distribution of rods and cones
~35,000 cones in the fovea centralis, no rods
Neuronal pathways for vision
Figure and from other text

72. Visual Systems

73. Visual Systems
Summary of Vision

74. Hearing Hearing involves three parts of the ear: Figure 15.25
The external ear – the auricle (or pinna) and external auditory meatus (this ends at the tympanic membrane)
The middle ear – air-filled space containing the ossicles (the malleus, incus, and stapes)
The inner ear – fluid-filled cavities containing the sensory organs of hearing and balance
Figure 15.25

76. Hearing Steps involved in hearing:
Sound waves are collected by the auricle
The waves move through the external auditory meatus to the tympanic membrane
This causes vibration of the membrane
The vibration of the tympanic membrane is conducted to the inner ear by the ossicles
Figure 15.25

78. Hearing
The stapes is connected to a flexible membrane covering the oval window on the cochlea
As the stapes vibrates, the sound waves are conducted into the inner ear
This causes waves in the fluid of the cochlea
Figure from other text

80. Hearing
As the waves pass through the inner ear, microvilli on hair cells are bent
The bending of the microvilli results in action potentials
The action potentials are then conducted through the vestibulocochlear nerve to the brain
Figures 15.28

82. Hearing
CD Demo of Hearing

83. Balance The organs of balance:
Vestibule – gives position of the head relative to gravity
Semi-circular canals – evaluates movements of the head

84. Balance
Head position – there are 2 patches of sensory cells in the vestibule
These are covered by a gelatinous fluid containing otoliths
The gelatinous mass moves in response to gravity and bends microvilli on the sensory cells
The brain interprets the pattern of action potentials as head position
Figures and 15.36

87. Balance Detection of Motion – semicircular canals
The base of each semicircular canal is enlarged to form the ampulla
Within the ampulla is the cupula
Figure from other text

89. Balance
When the fluid moves past the cupula it bends and generates action potentials
This is perceived as motion of the head
Figure and from other text

93. Balance
CD animations