Moderate

The 24 hour (diurnal) rhythm of our body such as the sleep­wake cycle is regulated by which hormone?

Correct answer: D. Melatonin

  • A. Calcitonin
  • B. Prolactin
  • C. Adrenaline
  • D. Melatonin

Explanation

Melatonin is a hormone secreted by the pineal gland and retinas of vertebrates. Melatonin secretion by the pineal gland is linked to the darklight cycle of the organism's environment, being greatest at night and lowest by day. The hormone is involved in regulating certain diurnal and seasonal changes in the body, such as the reproductive cycle in seasonally breeding animals. It is used as a drug to treat sleep disorders and symptoms of jet lag.

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About Coordination and Control

Coordination depends on receptors, neurons, synapses and nerve impulses, with reflex actions traced through the reflex arc and the roles of major brain regions. Chemical coordination covers endocrine glands and hormones, including how hormones regulate growth, metabolism, reproduction and internal balance, unlike rapid nervous control.

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