Question
Snow blindness in Antarctic region is due to [NEET (Sep.) 2020]
(a) inflammation ot cornea due to high dose of UV-B radiation
(b) high reflection of light from snow
(c) damage to retina caused by intrared rays:
(d) freezing of fluids in the eye by low temperature
Answer/Explanation
Ans. (a)
Snow blindness in Antarctic region is due to intlammation ot comea due to high dose of UV-B radiation. It is a painful, temporary loss of vision due to averexposure to the sun’s UV rays. It also called ‘photo keratitis[photo = light, keratitis= inflammation of the comes).
Question
In a man, abducens nerve is injured. Which one of the following functions will be affected? [CBSE AIPMT 2005]
(a) Movement of the eye ball
(b) Swallowing
(c) Movement of the tongue
(d) Movement of the neck
Answer/Explanation
Ans. (a)
Abducens (abducent) nerve is a cranial nerve which originates trom the ventral surface of medulla oblongata. It innervates the lateral rectus muscle of eyeball. It is a motor nerve and controls the movements of the eyeball. Hence, if abducens nerve is injured in a man, movement of eyeball will be affected.
Question
Parkinson’s disease (characterised by tremors and progressive rigidity of limbs) is caused by degeneration of brain neurons that are involved in movement control and make use of neurotransmitter [CBSE AIPMT 2005]
(a) acetylcholine
(b) norepinephrine
(c) dopamine
(d) GABA
Answer/Explanation
Ans. (c)
Abnormal release of neurotransmitter dopamine leads to Parkinson’s disease in humans. It is caused by degeneration of brain neuron that are involved in control movement.
Question
Injury to vagus nerve in human is not likely to affect [CBSE AIPMT 2004]
(a) tongue movements
(b) gastrointestinal movements
(c) pancreatic secretion
(d) cardiac movements
Answer/Explanation
Ans. (a)
Yagus nerve is a mixed cranial nerve which is, cantrolling much of the gut, ventilatory system and heart. it does not affect tangue movements. Tangue movement is controlled by glossopharyngeal nerve.
Question
A person suffering from the deficiency of the visual pigment rhodopsin is advised to take more [CBSE AIPMT 2000]
(a) radish and potato
(b) apple and grapes
(c) carrot and ripe papaya
(d) guava and ripe banana
Answer/Explanation
Ans. (c)
Carrat and ripe papaya contain carotene trom which vitamin- $A$ is synthesised. Vitamin-A is necessary for the formation of rhodopsin.
The visual pigments in vertebrate eyes are located in the tips of specialised sensory cells called rod cell and cone cells. Rod cells contain fhodopsin and are responsible tor black and white vision.