Zoology - Chemical Coordination and Integration Question with Solution | TestHub

Circadian rhythm is a 24-hour sleep-wake cycle. It is controlled by hormone melatonin. Melatonin is secreted by pineal gland. This gland is attached via a stalk with the epithalamus and hence it is also known as epiphysis. It is also known as the third eye as this gland is present at the axis traced from the third eye. Melatonin secretion depends on light. It increases due to darkness and decreases due to light.