Which of the following hormones is secreted by the pineal gland and plays a key role in regulating the circadian rhythm (sleep-wake cycle)? MCQ with Answer and Explanation
Which of the following hormones is secreted by the pineal gland and plays a key role in regulating the circadian rhythm (sleep-wake cycle)?
A. Oxytocin
B. Thymosin
C. Melatonin
D. Calcitonin
Answer: Option C
Solution (By JKSSB Mock Tests)
Melatonin is a hormone secreted by the pineal gland, a small endocrine gland located in the brain. Its secretion is highly sensitive to light and dark cycles, being produced in higher amounts at night. Melatonin is crucial for regulating the circadian rhythm (sleep-wake cycle), maintaining biological clocks, and influencing seasonal reproductive functions in some animals. Thymosin is from the thymus, oxytocin from the posterior pituitary.
Explanation:
Malaria, caused by Plasmodium parasites, is transmitted by the female Anopheles mosquito. Dengue and chikungunya are transmitted by Aedes mosquito, filariasis by Culex mosquito. Malaria remains a major global health concern.
Explanation:
Body Mass Index (BMI) is a simple index used to classify underweight, overweight, and obesity. It is calculated as a person's weight in kilograms divided by the square of their height in meters (kg/m2). While it is a useful population-level screening tool, it does not directly measure body fat and may not be accurate for athletes or the elderly.
Explanation:
The sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium ions, which trigger muscle contraction. Mitochondria produce ATP, Golgi processes proteins, nucleus controls gene expression.
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