The pineal gland is a small endocrine gland that helps connect environmental light conditions with the body's daily rhythms. Its hormone, melatonin, is closely associated with sleepiness and wakefulness.
The pineal gland is a tiny endocrine gland located inferior and somewhat posterior to the thalamus in the brain. The hypothalamus lies inferior and somewhat anterior to the thalamus, providing a useful landmark for distinguishing the two structures.
All flashcards
Where is the pineal gland located?
It is a tiny endocrine gland located inferior and somewhat posterior to the thalamus.
What are pinealocytes, and what do they secrete?
Pinealocytes are the cells that make up the pineal gland; they produce and secrete the hormone melatonin.
How does light affect melatonin secretion?
Light stimulates the retinas and starts a pathway involving the hypothalamic SCN, spinal cord, and pineal gland. The resulting signals inhibit melatonin production, so blood levels fall and wakefulness is promoted.
What is the relationship between darkness and melatonin?
As environmental light declines, inhibition of melatonin production eases. Melatonin levels rise, which promotes drowsiness.
Why does jet lag occur, and how does melatonin relate to it?
Travel across time zones shifts a person's light-dark schedule. Melatonin synthesis may take several days to adjust to the new pattern, so sleepiness and wakefulness can temporarily occur at inconvenient times.
Quiz questions
Which cells of the pineal gland produce and secrete melatonin?Answer: Pinealocytes
From which substance is melatonin derived?Answer: Serotonin
What happens to melatonin production when light stimulates the retinas?Answer: Signals involving the SCN ultimately inhibit melatonin production at the pineal gland.
Why can a person feel sleepy during the day after traveling across several time zones?Answer: The body's biological timing and melatonin synthesis have not yet adjusted to the new light-dark cycle.
What is a possible effect of bright light exposure during a normal sleep period?Answer: It can suppress melatonin secretion and increase alertness.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.