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Physiology

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Central Nervous System

Question
9 out of 18
 

Circadian rhythm is controlled by (AIIMS NOV 2008)



A Supraoptic nucleus
B Suprachiasmatic nucleus

C Paraventricular nucleus
D Median eminence

Ans. B Suprachiasmaticnucleus
  1. In mammals, including humans, most of the cells in the body have circadian rhythms.
  2. In the liver, these are influenced by the pattern of food intake, but in almost all other cells, the rhythms are entrained by the paired suprachiasmatic nuclei, (SCN) one on each side, above the optic chiasm. (Entrainment means synchronization of the circadian rhythm to the day-night light cycle in the environment).
  3. These nuclei receive information about the light-dark cycle via a special neural pathway called the retino hypothalamic fibres that pass from the optic chiasm to the SCN.
  4. Efferents from the SCN initiate neural and humoral signals that entrain a wide variety of well-known circadian rhythms.
  5. These include the rhythms in the secretion of ACTH and other pituitary hormones, the sleep-wake cycle, activity patterns, and the secretion of the pineal hormone melatonin.

Central Nervous System Flashcard List

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