Vision Lecture 2

Question 1

What is the electrical gradient?

Answer 1

Cell at rest is polarized (balanced) has + on the outside & - on the inside

Question 2

What is the chemical gradient?

Answer 2

Cell at rest:

Has NA on the outside & K on the inside

Question 3

What happens in your eyes when you are in the dark (chemically wise)?

Answer 3

Opsin & Retinal combine to make rhodopsin

Question 4

Describe the process of what happens in your eyes chemically when you are in the dark.

Answer 4

1. cGMP (Ligand, cyclic guanosine mono phosphate) binds to & opens Ligand gated cation channels that open to allow influx of cations
2. When opened, Na+ diffuses into cell w/ + charges
3. Rod/Cone Becomes depolarized (Ligand Gated Channel steps 1-3)
4. a Influx of Ca++ Ions start coming in due to the depolarization (keeps voltage calcium channels open)
5. b Causes neurotransmitter vesicles to migrate to the membrane
6. c Causes neurotransmitter vesicles (sacs that hold neurotransmitter that were inside the cell) to migrate towards the cell membrane to release the neurotransmitter (or hatch the egg)
7. d When the neurotransmitter fuses with the membrane, it hatches (spills its contents thru exocytosis) and releases glutamate
   3e. Leads to inhibiting bipolar cells so they will not activate ganglion cells (axons that make up the optic nerve)

Question 5

Light-Dark Adaptation

Answer 5

Eyes become more sensitive to light in the dark & less sensitive to light in the light

Question 6

Light Adaptation

Answer 6

25,000x Less Sensitive to light in 40 min. (Where you’re exposed to light for 40 min, your eyes become less sensitive)

• Rhodopsin is broken down in light & the eyes become less sensitive
  (ig: Movie Theatre you were 25,000 MORE sensitive to light, so the eyes are blinded once the lights turn back on)

Question 7

Dark Adaptation

Answer 7

When you’re in the dark, the eyes become more sensitive to light
- Rhodopsin produced during the dark makes the eyes more sensitive to light (so you can see better in the dark)

Question 8

What are the visual pathways to the brain?

Answer 8

1. Axons from the ganglion cells that make up the optic nerve
2. Optic chasm-Some fibers cross to opposite side of brain, but most stay ipsilateral
3. Optic Tract
4. Lateral Geniculate Body of the thalamus to the
   a. Primary visual center in occipital lobe of cerebral cortex (why when you get knocked in the back of your head, you can lose visual sight)
   b. Superior colliculi (2 superior & 2 inferior, the 2 superior are coordinated to vision) to extrinsic m’s of eye
   c. pretectal nuclei-Pupillary reflexes (pupils constrict/dilate)
   d. Suprachiasmatic nucleus-w/pineal gland regulate biological clock

Question 9

Conjunctivitis

Answer 9

Pink eye (bacterial infection) -Inflammation of the conjunctiva
(when your eyes look like road maps, blood vessels are apparent)
-allergies, toxins, pollin, etc.

Question 10

Hyperopia

Answer 10

Far sightedness-unable to focus close in-eyeball too short or lens system too weak

Question 11

Myopia

Answer 11

Nearsightedness-unable to focus on distant objects

Question 12

Astigmatism

Answer 12

Reflective error (refraction in how light is bent)

Question 13

Astigmatism

Answer 13

Refractive error (refraction in how light is bent; cornea problem)

Question 14

Night blindness

Answer 14

w/ Vitamin A deficiency

- Causes a reduction in Retinal which causes a reduction in rhodopsin

Question 15

Diplopia

Answer 15

Double vision (usually due to having the eyes crossed)

Question 16

Strabismus

Answer 16

Cross-eyed; caused by muscular weakness in extrinsic muscles of the eye (like that girl from SK8House who couldn’t uncross her eyes); can be corrected with surgery by tightening eye muscle

Question 17

Nystagmus

Answer 17

Involuntary Jerky Movement of the eye

especially when they go thru anesthesia, or when you wake up in the morning or during the day due to inner ear fluids

Question 18

Glaucoma

Answer 18

Inability of scleral venous sinus to drain aqueous humor

- Compression of the Reina & optic nerve if drainage of aqueous humor is blocked

Question 19

Detached Retina

Answer 19

Detachment of the neural portion of the retina (can lead to you seeing spider webbing, or you can’t see like a black veil)

Question 20

Presbyopia

Answer 20

The inability to focus close up due to the lens becoming less elastic (the lens cannot relax & become round again) which is why you may need reading glasses

Question 21

Cataracts

Answer 21

Lens becomes opaque/yellow (therefore light is unable to pass thru) (before, lens was transparent)

Question 22

Describe the process of what happens to your eyes physiologically when exposed to light.

Answer 22

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