Ch 13

1
Ch 13 PNS continued
Read 454 468. Review structure and functions of
the eye. Explain how we see color. Explain
vision. If youd like to read ahead, were
heading to the ear, hearing , and balance pgs 469
480 next.

• Learning Objectives continued

The eyes have it! http//video.google.com/videopla
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2
Bionic Eye?

• http//video.google.com/videoplay?docid2713236639
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3
How Do We See?

• The retina is a delicate two-layered membrane.
  It has a
• ___________ layer the outer layer that absorbs
  light and prevents its scattering.
• __________ layer, which contains
• Photoreceptors that transduce light energy
• Bipolar cells and ganglion cells

4
Retina continued

• Ganglion cell axons
• Run along the inner surface of the retina
• Leave the eye as the
• _____________
• The optic disc
• Is the site where the optic nerve leaves the eye
• Lacks photoreceptors (is known as the
• ___________)

5
Photoreceptors of the Retina

• Rods
• Respond to ___ light
• Are used for ________ vision
• Cones
• Respond to ______ light
• Have high-acuity ______ vision

6
Vision
When light passes from one transparent medium to
another its speed changes and it refracts or
______. Light passing through a convex lens (as
in the eye) is bent so that the rays converge to
a focal point. When a convex lens forms an
image, the image is _______ down and ________
right to left.
7
Putting It All Together Physiology of the Eye

• http//video.google.com/videoplay?docid-539089006
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8
How Do We Taste?

• Taste is ____ smell
• Chemical senses gustation (____) and olfaction
  (_____)
• Chemoreceptors respond to chemicals in aqueous
  solution
• Taste substances must be dissolved in saliva
• Smell substances must be dissolved in fluids of
  the nasal membranes

9
Organ of Smell

• A yellow-tinged patch of pseudostratified
  epithelium called the _________ epithelium.
• Located in the _______ of the nasal cavity

10
Most of the 10,000 or so taste buds are found on
the tongue1
Taste buds are found in the fungiform and
circumvallate papillae of the tongue mucosa
1 A few taste buds are scattered on the soft
palette, inner checks, pharynx
11
Taste Sensations

• There are ______ basic taste sensations
• Sweet sugars, saccharin, alcohol, and some
  amino acids
• Salt metal ions
• Sour hydrogen ions
• Bitter alkaloids such as quinine and nicotine
• Umami elicited by the amino acid glutamate

In order to be tasted, a chemical - Must be
dissolved in saliva - Must contact gustatory hairs
What are gustatory hairs? Gustatory cells? Look
it up on page 467. Write your conclusion next to
this slide in your notes.