Vision Flashcards
What are the four stages of vision and where do they occur?
- Light conduction - eye.
- Transduction - photoreceptors.
- Neural Procesing - retina.
- Neural Processing - visual cortex.
What is the major refractive element in the eye?
Cornea
What causes Glaucoma?
A blockage in the reabsorption of the reabsorption of aqueous humor at the canal of schlemm and trabecular meshwork.
What happens to the lens during far vision accommodation?
Lens is flattened as the cilliary muscle relaxes.
What happens to the lens during near vision accommodation?
The lens is rounded as the cilliary muscle contracts.
What is the protein that causes opacity in cataracts?
Crystallins
What is tapetum?
Reflective material on the retina of animals who have good night vision. Gives photoreceptors 2 chances to absorb light.
What is the condition when you lose pigmented epithelial cells called?
Macular Degeneration
What do photoreceptors do in response to light? Do they generate an action potential?
They hyperpolarize. Do NOT generate AP.
Describe retinal recycling.
Retinal binding protein transports trans retinal pigment to epithelial cells where it is conveted to retinal (Vit. A).
Describe Calcium Feedback.
Normally Ca is coming into the cell as part of the dark current. When cGMP channels close Na/Ca transporter depletes Ca, decreasing inhibition of Rhodopsin kinase, which activates rhodopsin.
What determines the optimal wavelength for a photorecpetor?
The Opsin it contains.
The Dark Current
Elevated cGMP concentration, more cGMP gated channels open, which causes the release of glutamate.
Large receptive field, involved in motion detection.
M type retinal ganglion cell.
Small receptive field, involved in colour vison.
P type retinal ganglion cell.
