Question
Diurnal variation of ACTH depends on ‑
| A. |
Suprachiasmatic nucleus
|
| B. |
Supraoptic nucleus
|
| C. |
Ventrolateral nucleus
|
| D. |
Thalamus
|
Show Answer
|
Correct Answer � A
Explanation
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|
Ans. A. Suprachiasmatic nucleus
The biologic clock responsible for the diurnal ACTH rhythm is located in the suprachiasmatic nuclei of the hypothalamus.
Regulation of circadian rhythms:
- “Biological clock” – Suprachiasmatic nucleus in the hypothalamus.
- Regulates circadian rhythms according to light-dark cycles.
Pathways involved:
- Afferents from “Retinohypothalamic fibers & lateral geniculate nuclei”.
- Information about light & darkness conveyed through tracts to the suprachiasmatic nucleus.
Clinical significance:
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- Information deprival of the suprachiasmatic nucleus results in a disturbance in circadian cycle precision.
- Yet, 24 hours of rhythm maintained approximately.
- Hence, the Suprachiasmatic nucleus also referred to as the “Endogenous biological clock”.
