Endocrine Glands & Hormones
The body's **"Chemical Messengers"**. Explore Glands, Hormones, and Target Organs.
Head & Neck
Growth Hormone (GH)
Stimulates growth of bones and muscles. Also known as the 'Master Gland' because it controls other endocrine glands.
TSH (Thyroid Stimulating Hormone)
Signals the thyroid gland to produce thyroxine.
Thyroxine
Controls the rate of metabolism (how fast cells use energy), growth, and development.
Melatonin
Regulates sleep-wake cycles (circadian rhythm). Secretion increases in darkness.
Chest & Abdomen
Adrenaline
Prepares body for 'Fight or Flight' during stress. Increases heart rate, blood pressure, and blood sugar.
Insulin
Signals cells to absorb glucose from the blood, reducing blood sugar levels.
Glucagon
Signals the liver to release stored glucose into the blood when sugar levels are low.
Reproductive
Testosterone
Controls development of male reproductive organs and secondary sexual characteristics (deep voice, facial hair).
Estrogen
Controls development of female reproductive organs and secondary sexual characteristics (breast development, menstrual cycle).
Progesterone
Prepares and maintains the uterus for pregnancy. Regulates menstrual cycle.
Chemical Coordination in Humans
Unlike the nervous system (electrical wires), the endocrine system acts like a chemical postal service. It sends packages (hormones) through the blood to specific addresses (target organs) to deliver instructions.
Gland Types: What's the difference?
Endocrine Glands
Release hormones directly into the bloodstream. They travel far to reach target organs.
Exocrine Glands
Release secretions through ducts (tubes) to a specific surface or organ.
Use Case: Blood Sugar Regulation
Pancreas
Releases INSULIN
Pancreas
Releases GLUCAGON
Example of a Negative Feedback Loop: The body always tries to return to the set point.
The Master Gland
Pituitary Gland
Small (pea-sized) but mighty. Located at the base of the brain, it receives orders from the Hypothalamus and sends out hormones to control the Thyroid, Adrenals, and Reproductive organs.
Frequently Asked Questions
What is the "Master Gland" and why?
The Pituitary Gland is called the Master Gland because it produces hormones that control the activity of other endocrine glands (like the Thyroid and Adrenals).
Difference between Endocrine and Exocrine glands?
Endocrine glands are ductless and release hormones directly into the blood. Exocrine glands (like sweat or salivary glands) have ducts to release secretions to specific surfaces.
How does Insulin regulate blood sugar?
Insulin acts like a key, allowing cells to absorb glucose from the blood for energy. This lowers blood sugar levels. Without insulin, sugar stays in the blood (Diabetes).
What is the "Fight or Flight" hormone?
Adrenaline (Epinephrine), secreted by the Adrenal glands, prepares the body for emergency action by increasing heart rate, breathing, and blood flow to muscles.
Why is Iodine important for the Thyroid?
The Thyroid gland needs Iodine to produce the hormone Thyroxine, which regulates metabolism. Lack of iodine can cause Goitre (swelling of the neck).
What hormone regulates sleep?
Melatonin, produced by the Pineal Gland, regulates the sleep-wake cycle (circadian rhythm). Its production increases in darkness.
What are the male and female sex hormones?
Testosterone is the primary male sex hormone (Testes). Estrogen and Progesterone are the primary female sex hormones (Ovaries).
What happens when blood sugar is too low?
The Pancreas releases Glucagon, which signals the Liver to convert stored glycogen back into glucose and release it into the blood, raising sugar levels.
Which gland regulates Calcium levels?
The Parathyroid Glands (located behind the Thyroid) produce Parathormone to regulate Calcium levels in the blood and bones.
What is a Feedback Mechanism?
It is a regulatory system where the output of a process controls the process itself. For example, high blood sugar triggers Insulin (Negative Feedback) to lower it back to normal.