30 Questions
What is the refractive power of the cornea alone?
44 diopters
Which of the following contributes to the causes of corneal transparency?
Lack of vascularization in the cornea
What is the approximate diameter of the cornea?
11 mm
Why is the refractive index the same in all corneal layers?
Regular arrangement of collagen bundles
Which vitamin helps prevent keratinization of the cornea?
Vitamin A
In maintaining corneal transparency, which pump is responsible for expelling fluid into the aqueous humor?
Metabolic pump
What is the range of normal intraocular pressure (IOP) in humans?
15-20 mmHg
Which structure separates the vitreous from the lens and allows slight bulging of the lens during accommodation?
Hyaloid canal
What is the main function of the vitreous humor in the eye?
Maintains normal eye shape
In the eye, what structure holds the lens in place behind the iris?
Suspensory ligament
Which of the following is NOT a function of the vitreous humor?
Support vascularization of the eye
What is the refractive index of the central part of the lens?
1.4
Which drug increases the excitability of the third cranial nerve nucleus?
Morphine
What is the diagnostic sign of morphine poisoning related to the pupil?
Pinpoint pupil
Which drug causes marked dilation and cycloplegia of the pupil for a long time?
Atropine
What is the mechanism of action of prostigmine?
(Anticholine esterase →↑ Acetylcholine concentration)
In which condition does mydriasis occur?
Pheochromocytoma
What are the changes that occur during accommodation in the eye?
(Increase in the convexity of mainly the anterior surface of the lens)
What is the physiological blind spot in the visual field caused by?
Overlap between the visual fields of both eyes
What is the central part of the macula lutea called?
Fovea centralis
What is found in the fovea centralis that contributes to its high visual acuity?
Densely packed thin cones
Which ion is continuously pumped from the inner segment of rods and cones to flow inside again at the outer segment?
Na+ (Sodium)
What term is used to describe the movements of Na+ from the inner segment to enter into the outer segment of rods?
Dark current
What causes continuous release of an inhibitory chemical transmitter when the eye is not exposed to light?
Low resting membrane potential (r.m.p)
What enzyme is responsible for transforming cGMP into 5'GMP in photoreceptors?
cGMP phosphodiesterase
What is the result of hyperpolarization in photoreceptors?
Increased release of inhibitory chemical transmitter
Which type of receptor potential is generated by photoreceptors in the retina?
Hyperpolarization
What leads to the re-synthesis of cGMP and the subsequent opening of Na+ channels in photoreceptors?
Removal of light (Dark)
Which cell type is mainly responsible for color vision in the retina?
Cones
How does the sense of discrimination of various wavelengths that constitute the visible spectrum occur?
Function of cones
This quiz covers the effects of acetylcholine, pilocarpine, eserine, prostigmine, and b-morphine on cholinergic receptors. It also includes topics such as mydriasis and the impact on the third cranial nerve nucleus. Test your knowledge on these pharmacological agents and their actions.
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