Ch 13 – PNS continued

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Transcript Ch 13 – PNS 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
Learning Objectives continued
The eyes have it!
Bionic Eye?
How Do We See?
The retina is a delicate
two-layered membrane. It
has a:
a) ___________ layer – the
outer layer that absorbs
light and prevents its
b) __________ layer, which
Photoreceptors that
transduce light energy
Bipolar cells and ganglion
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
– Lacks photoreceptors
(is known as the
Photoreceptors of the Retina
• Rods:
– Respond to ___ light
– Are used for ________ vision
• Cones:
– Respond to ______ light
– Have high-acuity ______ 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.
Putting It All Together: Physiology
of the Eye
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
– Smell – substances must be dissolved in fluids
of the nasal membranes
Organ of Smell
• A yellow-tinged patch of pseudostratified
epithelium called the _________
• Located in the _______ of the nasal cavity
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
A few taste buds are scattered on the soft palette, inner checks, & pharynx
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.