Test: Introduction to Endocrine Glands, Hormones & Hypothalamus - NEET MCQ

Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

The pituitary gland is a tiny organ, the size of a pea, found at the base of the brain. As the “master gland” of the body, it produces many hormones that travel throughout the body, directing certain processes or stimulating other glands to produce other hormones.

Line in NCERT: "The hypothalamus contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones."

ANF (atrial natriuretic factor) is secreted by the atrial walls of the heart. It is responsible for a decrease in blood pressure. When the blood pressure is increased, ANF which is secreted dilates the blood vessels causing a decrease in blood pressure.

- Statement i is correct because the hypothalamus indeed produces both releasing hormones (e.g., GnRH) and inhibiting hormones (e.g., somatostatin) to regulate the secretion of pituitary hormones.

- Statement ii is incorrect as the hormones from the hypothalamus are released into a portal circulatory system, which then carries them to the anterior pituitary, not directly into the bloodstream.

- Statement iii is correct because GnRH stimulates the anterior pituitary to secrete gonadotrophins.

- Statement iv is incorrect since somatostatin actually inhibits the release of growth hormone, rather than enhancing it.

Thus, the correct answer is Option A, which includes statements i and iii only.

• Assertion (A) is correct because hormones indeed function as intercellular messengers and are secreted in very small amounts by the endocrine glands.
• Reason (R) is also correct; the term "ductless glands" accurately describes endocrine glands as they release hormones directly into the bloodstream rather than through ducts.

• The reason states a fact about the structure of endocrine glands (being ductless), which facilitates the direct release of hormones into the bloodstream. While this is an important characteristic of endocrine glands, it does not directly explain why hormones specifically act as intercellular messengers or why they are produced in trace amounts. The lack of ducts explains the method of hormone release rather than the role and quantity of hormone production.

  Therefore, the correct answer is: B: If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.