Effects of Acetylcholine, Pilocarpine, and Other Drugs on Cholinergic Receptors

What is the refractive power of the cornea alone?

22 diopters

44 diopters (correct)

55 diopters

33 diopters

Which of the following contributes to the causes of corneal transparency?

High water content in the cornea

Presence of myelin sheath in the corneal nerve fibers

Irregular arrangement of corneal collagen bundles

Lack of vascularization in the cornea (correct)

What is the approximate diameter of the cornea?

13 mm

11 mm (correct)

12 mm

10 mm

Why is the refractive index the same in all corneal layers?

Regular arrangement of collagen bundles Signup and view all the answers

Which vitamin helps prevent keratinization of the cornea?

Vitamin A Signup and view all the answers

In maintaining corneal transparency, which pump is responsible for expelling fluid into the aqueous humor?

Metabolic pump Signup and view all the answers

What is the range of normal intraocular pressure (IOP) in humans?

15-20 mmHg Signup and view all the answers

Which structure separates the vitreous from the lens and allows slight bulging of the lens during accommodation?

Hyaloid canal Signup and view all the answers

What is the main function of the vitreous humor in the eye?

Maintains normal eye shape Signup and view all the answers

In the eye, what structure holds the lens in place behind the iris?

Suspensory ligament Signup and view all the answers

Which of the following is NOT a function of the vitreous humor?

Support vascularization of the eye Signup and view all the answers

What is the refractive index of the central part of the lens?

1.4 Signup and view all the answers

Which drug increases the excitability of the third cranial nerve nucleus?

Morphine Signup and view all the answers

What is the diagnostic sign of morphine poisoning related to the pupil?

Pinpoint pupil Signup and view all the answers

Which drug causes marked dilation and cycloplegia of the pupil for a long time?

Atropine Signup and view all the answers

What is the mechanism of action of prostigmine?

(Anticholine esterase →↑ Acetylcholine concentration) Signup and view all the answers

In which condition does mydriasis occur?

Pheochromocytoma Signup and view all the answers

What are the changes that occur during accommodation in the eye?

(Increase in the convexity of mainly the anterior surface of the lens) Signup and view all the answers

What is the physiological blind spot in the visual field caused by?

Overlap between the visual fields of both eyes Signup and view all the answers

What is the central part of the macula lutea called?

Fovea centralis Signup and view all the answers

What is found in the fovea centralis that contributes to its high visual acuity?

Densely packed thin cones Signup and view all the answers

Which ion is continuously pumped from the inner segment of rods and cones to flow inside again at the outer segment?

Na+ (Sodium) Signup and view all the answers

What term is used to describe the movements of Na+ from the inner segment to enter into the outer segment of rods?

Dark current Signup and view all the answers

What causes continuous release of an inhibitory chemical transmitter when the eye is not exposed to light?

Low resting membrane potential (r.m.p) Signup and view all the answers

What enzyme is responsible for transforming cGMP into 5'GMP in photoreceptors?

cGMP phosphodiesterase Signup and view all the answers

What is the result of hyperpolarization in photoreceptors?

Increased release of inhibitory chemical transmitter Signup and view all the answers

Which type of receptor potential is generated by photoreceptors in the retina?

Hyperpolarization Signup and view all the answers

What leads to the re-synthesis of cGMP and the subsequent opening of Na+ channels in photoreceptors?

Removal of light (Dark) Signup and view all the answers

Which cell type is mainly responsible for color vision in the retina?

Cones Signup and view all the answers

How does the sense of discrimination of various wavelengths that constitute the visible spectrum occur?

Function of cones Signup and view all the answers