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! http://video.google.com/videoplay?docid=528627177432537232

Bionic Eye? http://video.google.com/videoplay?docid=2713236639365268873&q=how+eye+works&total=3516&start=0&num=10&so=0&type=search&plindex=1

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

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 ___________)

Photoreceptors of the Retina Rods: Respond to ___ light Are used for ________ vision Cones: Respond to ______ light Have high-acuity ______ vision

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 http://video.google.com/videoplay?docid=-5390890065360196056&q=rods+and+cones+of+eye&total=10&start=0&num=10&so=0&type=search&plindex=6

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

Organ of Smell A yellow-tinged patch of pseudostratified epithelium called the _________ epithelium. 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 1 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.