HEENT physio test Flashcards
What does visual perception require?
Eye to focus visual image and neural pathways and brain to process the image.
There is a small range of visible light we can see on what spectrum?
Electromagnetic.
What is refraction?
Bending of light. Light passing obliquely through one medium and another.
Refraction to focus on the retina requires what?
The cornea and the lens. The lens to do fine tuning with the convex and concave
Why does the lens need to convex?
thicker at the center and converges light rays to accomodate for hyperopia
Images in the brain get turned how?
upside down, reversed, and inverted
Why does the lens need to concave?
thinner at the center and diverges light rays to prevent focusing to accomodate for myopia
What is the pathway of light entering the eye?
Cornea- aqueous humor- lens (entrance and leaving)- vitreous humor- entire neural layer of the retina- photoreceptors and pigmented layer of the retina.
The lens shape is a _______ disc.
Biconcave.
Refraction to focus on the retina via changes in lens shape is determined by what structures?
Zonular fibers/ciliary zonules attached to ciliary muscles.
The lens _______ for distant vision.
Flattens. Sympathetic input relaxes the ciliary muscle and this tightens the ciliary zonule and flattens the lens.
In distant vision the sight rays are nearly ___________.
parallel
In close vision the sight rays are _________.
divergent, but get accommodated for by the ciliary muscles.
The lens ________ for close vision.
Bulges. Parasympathetic input contracts the ciliary muscle. This loosens the ciliary zonule and allows the lens to bulge.
How do signals spread from photoreceptors to bipolar cells to ganglion cells?
Mediated by glutamate neurotransmitter.
Myopia vs. hyperopia
Myopia (nearsightedness) is difficulty seeing distant objects clearly, while hyperopia (farsightedness) is difficulty seeing close objects clearly.
Rods vs. Cones
Rods: noncolor vision (one visual pigment), high sensitivity, function in dim light, low acuity, many, peripheral retina.
Cones: color vision (three pigments), low sensitivity, function in bright light, high acuity, fewer, central retina.
What is rhodopsin?
Retinal (light absorbing molecule) + opsin.
Retinal is synthesized from what vitamin?
Vitamin A.
What are the 3 types of color blindness?
- Protanomaly: reduced sensitivity to red light.
- Deuteranomaly: reduced sensitivity to green light, which is the most common form of color blindness.
- Tritanomaly: reduced sensitivity to blue light, which is extremely rare and not X-linked, as it affects a different chromosome.
Medial vs. lateral nerve fibers
Medial nerve fibers= cross over at the optic chiasm and carry visual information from temporal/lateral visual field.
Lateral nerve fibers= DO NOT cross over at the optic chiasm and carry visual info from medial visual field.
Where do the medial and lateral nerve fiber travel to?
genticulate nuclei then the primary visual cortex in the brain to be made 3-D and turned right side up.
What are the two muscles of the iris?
Sphincter pupillae and dilator pupillae.
If there was an injury in the optic nerve before the chasm, what would happen?
total blindness in that one eye. (anopia)