1. Bellwork Use your next blank page to create a title page for “Chapter 8: Special Senses” Write the objectives below your title SWBAT describe the structure of the eye. SWBAT identify & explain their blind spot. SWBAT explain color blindness. SWBAT describe the structure of the eye. SWBAT identify & explain their blind spot. SWBAT explain color blindness. Chapter 8: Special Senses Example

2. The Eye and Vision

3. Anatomy of the Eye Protected by eyelids and eyelashes Conjunctiva is a delicate membrane lining eyelids and part of eyeball Secretes mucus to keep eye moist What is conjunctivitis? Inflammation of the conjunctiva Pink eye is conjunctivitis caused by a virus or bacteria

4. Anatomy of the Eye Lacrimal glands are above the lateral end of each eye Continually release a salt solution (tears) through several small ducts Tears wash medially across eye and then into lacrimal duct (which empties into nasal cavity) When irritated by foreign objects or chemicals and when we are upset lacrimal secretion increases

5. Practice 1. Draw an eye that includes the lacrimal gland and lacrimal duct. 2. Draw a circle around the area where the lacrimal secretion (tears) is formed 3. Draw an arrow to show the way it flows across the eye. 4. Draw a square around the area that collects the secretions to drain into the nasal cavity. 5. Write an explanation about how this explains why we get the “sniffles” when we cry.

6. Internal Anatomy of the Eye Tunics: 1. Sclera – outermost, thick, white connective tissue Clear “window” where light enters the eye Muscles attach to this layer to move eye Eyeball made of 3 coats (tunics) and filled with fluid (humor).

7. Internal Anatomy of the Eye Tunics: 2. Choroid – middle, contains blood vessels Anterior part is modified to form 2 structures: Ciliary body (attaches to lens) Iris (pigmented, has an opening called the pupil) Muscles to constrict or dilate pupil Eyeball made of 3 coats (tunics) and filled with fluid (humor).

8. Internal Anatomy of the Eye Tunics: 3. Retina – inner layer, Contains millions of photoreceptor cells that respond to light (rods & cones) Rods & cones cover entire retina EXCEPT optic disc (where the optic nerve leaves the eye Eyeball made of 3 coats (tunics) and filled with fluid (humor).

9. Blind Spot Experiment 1. Obtain blind spot test card. 2. Hold card ~18 inches from your eyes. (dot on the right side) 3. Close left eye, stare at “X” with right eye. 4. Slowly move card closer to face while staying focused on “X”. 5. When the dot focuses on your blind spot it will disappear

10. Blind Spot Experiment Why did the “dot” disappear as you moved the card closer to your face? “The dot disappeared when I moved the card closer to my face because….”

11. Photoreceptors Rods sensitive to: Light/dark changes Shape and movement Gray tones Cones sensitive to: Colors (red, blue, green) Work only in bright light Color blindness happens when someone lacks one type of cone (X linked, more common in males)

12. Color Blindness

13. Cool Video http://www.youtube.com/watch?v=W-yLfm5HsHc

14. Exit Ticket Explain this picture. Why the color blind person would see what they are seeing.