1. Learning Objectives continued
Read 454 – 468. Review structure and functions of the eye. Explain how we see color. Explain vision. If you’d like to read ahead, we’re heading to the ear, hearing , and balance pgs 469 – 480 next.
Ch 13 – PNS continued
Learning Objectives continued
The eyes have it!

2. Bionic Eye?

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: The optic disc:
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

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.