Lec 7 - Mam Phys
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93 Terms
What is the function of the eye?
To detect light and convert it into electrical signals interpreted by the brain.
What is phototransduction?
The conversion of light into electrical signals by photoreceptors.
Which part of the eye bends the most light?
The cornea.
Approximately what percentage of light refraction occurs at the cornea?
About 70%.
What is the primary function of the lens?
To fine-tune focus onto the retina.
Which structure changes shape during accommodation?
The lens.
What is accommodation?
The process of changing lens shape to focus on objects at different distances.
What muscle controls accommodation?
The ciliary muscle.
What happens to the ciliary muscle when viewing a nearby object?
It contracts.
What happens to the suspensory ligaments when the ciliary muscle contracts?
They relax.
What happens to the lens when the suspensory ligaments relax?
It becomes rounder.
Why does a rounder lens improve near vision?
It increases refractive power.
What happens to the ciliary muscle when viewing distant objects?
It relaxes.
What happens to the suspensory ligaments when viewing distant objects?
They become taut.
What happens to the lens during distant vision?
It flattens.
What structure regulates the amount of light entering the eye?
The iris.
What is the opening in the center of the iris?
The pupil.
Which muscles constrict the pupil?
Circular (sphincter) muscles.
Which autonomic division constricts the pupil?
Parasympathetic.
Which muscles dilate the pupil?
Radial muscles.
Which autonomic division dilates the pupil?
Sympathetic.
What is miosis?
Pupil constriction.
What is mydriasis?
Pupil dilation.
What is the retina?
The light-sensitive neural layer lining the back of the eye.
What are the two major photoreceptors?
Rods and cones.
Which photoreceptors function best in dim light?
Rods.
Which photoreceptors function best in bright light?
Cones.
Which photoreceptors detect color?
Cones.
Which photoreceptors provide the greatest visual acuity?
Cones.
Which photoreceptors are more numerous?
Rods.
Approximately how many rods are in the human retina?
About 120 million.
Approximately how many cones are in the human retina?
About 6 million.
Where are cones most concentrated?
The fovea centralis.
Where are rods absent?
The fovea centralis.
What is the fovea centralis?
The region of highest visual acuity.
Why does the fovea produce the sharpest vision?
It contains densely packed cones with minimal light scattering.
What is the macula?
The central region of the retina responsible for detailed vision.
What is the optic disc?
The location where the optic nerve exits the eye.
Why is the optic disc called the blind spot?
It contains no photoreceptors.
What pigment is found in rods?
Rhodopsin.
What pigment is found in cones?
Photopsins.
What molecule changes shape when light strikes rhodopsin?
Retinal.
What vitamin is required to produce retinal?
Vitamin A.
What happens if vitamin A is deficient?
Night blindness may occur.
What is dark adaptation?
Increased visual sensitivity after moving into darkness.
What is light adaptation?
Reduced visual sensitivity after moving into bright light.
Which photoreceptors dominate during dark adaptation?
Rods.
Which photoreceptors dominate during daylight?
Cones.
What neurotransmitter do photoreceptors continuously release in darkness?
Glutamate.
What happens to photoreceptors when light strikes them?
They hyperpolarize.
Do photoreceptors depolarize or hyperpolarize in response to light?
Hyperpolarize.
What happens to glutamate release in light?
It decreases.
Which retinal neurons receive input directly from photoreceptors?
Bipolar cells.
Which retinal neurons generate action potentials?
Ganglion cells.
Which retinal neurons form the optic nerve?
Ganglion cells.
What is the optic nerve?
The bundle of ganglion cell axons leaving the eye.
Where do optic nerves partially cross?
The optic chiasm.
What is the optic chiasm?
The location where nasal retinal fibers decussate.
Which retinal fibers cross at the optic chiasm?
Nasal retinal fibers.
Which retinal fibers remain on the same side?
Temporal retinal fibers.
Where do optic tracts project first?
The lateral geniculate nucleus (LGN) of the thalamus.
Which cortical lobe contains the primary visual cortex?
The occipital lobe.
What is the primary visual cortex?
The first cortical region that processes visual information.
Which visual field projects onto the left cerebral hemisphere?
The right visual field.
Which visual field projects onto the right cerebral hemisphere?
The left visual field.
Why does each hemisphere receive information from both eyes?
Because fibers partially cross at the optic chiasm.
What is binocular vision?
The overlapping visual field seen by both eyes.
Why is binocular vision important?
It provides depth perception.
What is depth perception?
The ability to judge distance using input from both eyes.
What is visual acuity?
The sharpness of vision.
Which retinal region has the highest visual acuity?
The fovea centralis.
What is emmetropia?
Normal vision.
What is myopia?
Nearsightedness.
Where is the focal point in myopia?
In front of the retina.
How is myopia corrected?
With a concave (diverging) lens.
What is hyperopia?
Farsightedness.
Where is the focal point in hyperopia?
Behind the retina.
How is hyperopia corrected?
With a convex (converging) lens.
What is astigmatism?
Blurred vision caused by an irregularly shaped cornea or lens.
What causes cataracts?
Clouding of the lens.
How do cataracts affect vision?
They reduce the amount of light reaching the retina and blur vision.
What is glaucoma?
Damage to the optic nerve often caused by elevated intraocular pressure.
Why is glaucoma dangerous?
It can cause irreversible vision loss.
What is age-related macular degeneration (AMD)?
Degeneration of the macula leading to loss of central vision.
Which retinal region is damaged in AMD?
The macula.
What color receptors do humans possess?
Red, green, and blue cones.
What causes most inherited color blindness?
Defective or absent red or green cone photopigments.
Which color blindness is most common?
Red-green color blindness.
What reflex constricts the pupils in bright light?
The pupillary light reflex.
Which cranial nerve detects light for the pupillary reflex?
CN II (Optic).
Which cranial nerve constricts the pupil during the light reflex?
CN III (Oculomotor).
Which cranial nerve carries visual information to the brain?
CN II (Optic nerve).
What is the sequence of visual processing?
Light → Photoreceptors → Bipolar cells → Ganglion cells → Optic nerve → Optic chiasm → Optic tract → LGN → Visual cortex.