Friday 28 December 2012

Usmle Step 1 MCQ’s # 37

Title: Usmle Step 1 MCQ’s # 37
Subject: Behavioral Science

Q NO 37: A 19-year-old mother brings her first child, a 10-day-old infant, to the pediatrician. In a fearful tone of voice she states: “Every time I drop something or the dog barks, he jumps and jerks his little arms to his chest like he’s afraid. Is something wrong with him?” The pediatrician explains that the behavior is normal and will most likely be naturally extinguished at what age?

A. 1 month
B. 5 months
C. 8 months
D. 12 months
E. Never

Explanation:
The correct answer is B. The Moro reflex can be elicited in the infant by any startling event; it consists of extension and abduction of the arms followed by flexion and adduction of the arms. This is a normal reflex that appears between the ages of 25 and 36 weeks of gestation, and will normally disappear between 3-6 months.
The palmar grasp reflex, characterized by the infant’s hand closing over an object placed in the palm of the hand, normally disappears after 1-2 months of age (choice A)
The tonic neck reflex consists of extension of the ipsilateral leg and flexion of the contralateral arm and leg when the head is turned. This reflex normally disappears between 7 and 8 months of life (choice C)
The Babinski reflex is elicited when the lateral surface of the sole of the foot is stroked, resulting in the great toe going up and the other toes fanning. It normally disappears at 1 year of age (choice D).
Deep tendon reflexes can be elicited by tapping a tendon with a reflex hammer, stretching the tendon and producing contraction in the corresponding muscle. These reflexes are present throughout life (choice E)

Source: http://www.usmleworldwide.com/blog/?p=745

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