Mammalian Pineal Body Structure and Also Functions

Pineal gland

1. PRESENTATION OF
ZOOLOGY
TOPIC :Structure of mammalian pineal body,
Functional significance of pineal hormones
SUBJECT : COMPARATIVE ENDOCRINOLOGY
(MZOO - 402)
SUBMITTED BY:
Name - Yogesh
Class - M.Sc. Zoology 4th Semester
Class Roll No. - 2256001
University Roll No. - 81221680020
SUBMITTED TO:
Assistant Professor
Dr. Asha Garg

2. INTRODUCTION
• It is an important endocrine
gland in higher vertebrates.
• Its name is derived from its
pinecone like structure.
• It is also known as 'third eye' as
this gland receives its stimuli
through vision.
• It was first discovered by
Herophilus about 2000 years ago.
• Embryologically derived from
neuroectoderm of diencephalic
roof.

3. • This gland produces melatonin which regulates sleep -
wake cycle and circadian rhythm.

4. Mammalian Pineal Body

5. • The pineal gland is a small reddish - grey gland.
• It is approximately 8mm long & 5-7mm wide.
• It is located in the epithalamus, a region of the brain
that connects to thalamus and the midbrain.
• Pineal gland is surrounded by a capsule of connective
tissue and contains many pinealocyoes which are
specialized cells that produce and secrete melatonin.
• Pineal gland is a circumventricular organ ( which are
specialized structures located in walls of 3rd & 4th
ventricle which lacks a blood - brain barrier) .

7. • These pinealocytes produce and secretes melatonin.

8. PHYSIOLOGY OF PINEAL BODY
• The pineal gland is controlled by the suprachiasmatic
nucleus which is located in the hypothalamus
• The suprachiasmatic nucleus is responsible for regulating
the circardian rhythm which is the internal biological clock
that regulate the sleep - wake cycle.
• Pineal gland produce and secretes melatonin in a
response to change in light exposure.
• When light levels are low such as night , pineal gland
produces more melatonin.
• When light levels are high such as during the day the
pineal gland produces less melatonin.

12. • Melatonin production is regulated by the hormone
norepinephrine which is the released from sympathhetic
nerve fibres that innervates Pineal gland.
• Norepinephrine stimulates the production of cyclic
adenosine monophosphate which in turn activates the
production of melatonin.
• Melatonin is N - acetylated product of serotonin.
• Synthesis of melatonin is initiated by the conversion of
tryptophan to serotonin which is then converted to
melatonin by the action of enzyme Arylalkylamine
N-acetyltransferase.

14. FUNCTIONAL SIGNIFICANCE OF PINEAL HORMONES
• Melatonin is the only known hormone synthesized by the pineal gland
and is released in response to darkness hence the name, “hormone of
darkness.
1) Regulation of Circadian Rhythms
• Sleep-Wake Cycle: Melatonin helps regulate the sleep-wake cycle by
promoting sleep during the night and wakefulness during the day.
• Synchronization with Light-Dark Cycle: Melatonin levels are influenced
by light exposure, helping align biological rhythms with environmental
light-dark cycles.
2) Seasonal Reproduction
• Photoperiodism: Melatonin regulates reproductive cycles in response to
changes in day length. It triggers breeding behaviors in long-day and
short-day breeders, ensuring that offspring are born in optimal conditions.
3) Antioxidant Protection
• Scavenging Free Radicals: Melatonin acts as a powerful antioxidant,

15. neutralizing free radicals and reducing oxidative stress.
•Enhancing Antioxidant Enzymes: It boosts the activity of enzymes that
protect cells from oxidative damage.
4) Immune Modulation
• Immune Cell Activity: Melatonin enhances the activity of various immune
cells, including T lymphocytes, natural killer cells, and macrophages.
• Cytokine Production: It influences the production of cytokines, which are
crucial for immune response regulation.
5) Neuroprotection
• Protection Against Neurodegeneration: Melatonin protects neurons from
damage caused by excitotoxicity, apoptosis, and neuroinflammation.
• Aging and Brain Health: Declining melatonin levels with age are linked to
neurodegenerative diseases, and supplementation may help mitigate
age-related neural decline
6) Metabolism and Weight Regulation

16. • Energy Balance: Melatonin affects lipid metabolism and adipogenesis,
helping regulate body weight and energy balance.
• Insulin Sensitivity and Glucose Homeostasis: It improves insulin
sensitivity and helps maintain stable blood glucose levels.
7) Regulation of Seasonal Behaviors
• Adaptation to Seasonal Changes: Melatonin influences behaviors such
as migration, hibernation, and changes in fur thickness or fat storage,
helping animals adapt to seasonal variations.
8) Clinical Applications
• Treatment for Sleep Disorders: Melatonin supplements are used to treat
insomnia, jet lag, and other sleep disorders.
• Potential Therapeutic Uses: Research suggests potential benefits for
conditions like seasonal affective disorder (SAD), certain cancers, and
cardiovascular diseases.

17. THANK YOU

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