54. In dim light, parasyn athtic nerve brs stimudate the smooth muscles of the i

Question

54. In dim light, parasyn athtic nerve brs stimudate the smooth muscles of the iris to contract, and this diates the pupits size 55. The retina is the only place in the body where blood vessels can be viewed directly and examined for pathological changes 56. To ensure that the seon image upon the retina remains sharp and clear, melanin in the choroid and the pigment epithelium absorb stray light that enters the eyebai. 57. The retina's neural portion is an outgrowth of the brain. 58. Because the fovea allows sharp vision, both rods and cones are present in it 58. Rod number decreases from the fovea toward the retinas periphery. 60. The neuron order that light travols is frorm the photoreceptors to the ganglion cells, and finally to the bipolar cells 61. The optic disc is void of rods and cones. 62. Crystallins function as enzymes that convert glucose into ATP to provide energy for metaboism in the lens. 63. The leading cause of blindness in the U.S. is diabetes, with the second leading cause being cataracts 64. Aqueous humor eventually drains into the blood. 65. The pressure in the eye is produced mainly by the vitreous humor

Explanation / Answer

Answer 54. True statement. Parasympathetic nerve causes the dilation of the pupil by stimulation of the smooth muscles of the iris to contract and increase the size of the pupil. This is called as mydriasis. Sympathetic nerve causes decrease in the pupil size this is called as miosis.

Answer 55. True statement. Retina is the only place in the body where blood vessels can be viewed directly and examined pathological changes. The central retinal artery and vein can be viewed directly to examine the pathological changes of that blood vessels.

Answer 56. True statement. For the clear and sharp image formation on the retina the light must be focussed on the retina. The lens focusses the light on retina and choroid and pigment epithelium absorbs the scattered light.

Answer 57. True statement. During the development of the fetus the retina develops as the outgrowth of the brain. The neural layer of the retina consists of photoreceptor cells which generates action potential that transmits to the brain via optic nerve. Optic nerve is the continuation of the ganglion cell layer of the retina.

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