1A. What you will draw
Vision starts with light bending through the cornea and lens, and ends with action potentials traveling up the optic nerve. Today you'll draw the eye in sagittal section and the retinal layers in close-up.
BIO 304 . WEEK 5 . THURSDAY . LAB WORKBOOK
Vision
The eye, the retina, and how light becomes a neural signal.
Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.
Part 1 of 2
Anatomy Lab
Box A. Eye in sagittal section
Directions
- Draw an eye in cross-section as viewed from the side. The front of the eye is on the LEFT, the back is on the RIGHT.
- Draw the cornea (transparent dome at the front).
- Draw the iris (colored ring) and the pupil (opening in the center). Label both.
- Draw the lens behind the iris. Show the ciliary body and suspensory ligaments holding the lens.
- Label the anterior chamber (between cornea and iris, contains aqueous humor) and the posterior chamber.
- Fill the rest of the eye (the large back portion) with vitreous humor. Label.
- Line the back of the eye with the retina. Label.
- Mark the fovea centralis (small pit in the central retina, point of sharpest vision).
- Show the optic nerve leaving the back of the eye. Label the optic disc (blind spot) where the nerve exits.
- Wrap the eye with sclera (white outer layer) and choroid (vascular middle layer).
Draw here. Sketch by hand.
Box B. Retinal layers (light path)
Directions
- Draw a horizontal section of retina. The light arrives from the BOTTOM (yes, paradoxically) and the photoreceptors face the TOP (away from the light).
- Layer 1 (bottom): retinal ganglion cells. Their axons form the optic nerve. Label.
- Layer 2: bipolar cells.
- Layer 3 (top): photoreceptors. Draw both rods (long, dim light, peripheral vision) and cones (shorter, bright light, color vision, concentrated at the fovea).
- Above the photoreceptors, draw the retinal pigment epithelium (RPE, a dark layer that absorbs stray light).
- Add arrows showing the path of light entering at the bottom and the path of the neural signal going DOWN from photoreceptors to bipolars to ganglion cells.
Draw here. Sketch by hand.
1C. Structures to label (20)
After you finish each drawing, label every structure below directly on your sketch.
- Cornea
- Iris
- Pupil
- Lens
- Ciliary body
- Suspensory ligaments
- Aqueous humor
- Vitreous humor
- Retina
- Fovea centralis
- Optic disc
- Optic nerve
- Sclera
- Choroid
- Photoreceptor
- Rod
- Cone
- Bipolar cell
- Retinal ganglion cell
- Retinal pigment epithelium
Part 2 of 2
Physiology Lab
2A. Trace: from photon to action potential
List the 7 steps that occur from a photon entering the eye to an action potential traveling up the optic nerve. Be precise about which structures the light passes through and where signal transduction happens.
2B. Synthesis questions
Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.
1. A patient with myopia (nearsightedness) has trouble seeing distant objects. Explain the optical defect (eyeball shape or lens shape) and how a corrective lens fixes it.
2. A patient is diagnosed with macular degeneration (loss of cone-rich foveal retina). Predict which type of vision is lost FIRST (peripheral, central, color, night) and which is preserved longest, with a one-sentence reason.
3. Why is the optic disc called the blind spot? Predict what happens when an image falls on the optic disc, and explain why we don't normally notice this gap in our visual field.
3. What to submit
Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.