Biology · Chemical Coordination and Integration · NEET
Both are made by the hypothalamus, but they act in opposite ways. A releasing hormone stimulates (turns ON) the pituitary to secrete a hormone — for example, GnRH (Gonadotrophin releasing hormone) makes the anterior pituitary release LH and FSH. An inhibiting hormone stops (turns OFF) a pituitary secretion — for example, the hormone that inhibits the release of prolactin. Remember: releasing = GO, inhibiting = STOP.
It is both. Structurally the hypothalamus is the basal part of the diencephalon in the forebrain, so it is brain tissue. But it also contains neurosecretory cells (nuclei) that make hormones, so it acts as an endocrine control centre too. This is why it is called a neuroendocrine link — it connects the nervous system and the endocrine system.
Neurosecretory cells are nerve cells that, instead of only sending electrical signals, also make and release hormones into the blood. In the hypothalamus these cells are grouped into clusters called nuclei. These nuclei produce the releasing and inhibiting hormones that control the pituitary. Do not confuse this 'nuclei' with the nucleus inside a single cell.
The releasing and inhibiting hormones from the hypothalamus reach the anterior pituitary through a special set of blood vessels called the hypophyseal portal system. This is a short blood link between the hypothalamus and the anterior pituitary, so the hormones do not have to travel through the whole body first. NCERT tests that GnRH reaches the anterior pituitary through this portal circulation.
Oxytocin and vasopressin (ADH) are RELEASED from the posterior pituitary but are actually SYNTHESISED by the hypothalamus. They are made in hypothalamic neurosecretory cells and transported down the axons to the posterior pituitary, where they are stored and released. This is a favourite NEET trap — the posterior pituitary only stores them, it does not make them.
The hypothalamus controls the pituitary. It sits above the pituitary and its releasing and inhibiting hormones decide how much of each hormone the anterior pituitary secretes. So the chain of command is: hypothalamus → pituitary → target gland (like thyroid, adrenal, gonads). The target gland hormones then feed back to the hypothalamus and pituitary.
GnRH, a hypothalamic hormone, needed in reproduction, acts on
Which of the following hormones released from the pituitary is actually synthesized in the hypothalamus?
Changes in GnRH pulse frequency in females is controlled by circulating levels of:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
It is the basal (lower) part of the diencephalon in the forebrain, sitting just above the pituitary gland. It is connected to the pituitary by a stalk.
A releasing hormone example is GnRH (Gonadotrophin releasing hormone), which stimulates LH and FSH secretion. An inhibiting hormone example is the one that inhibits prolactin release. NCERT names the two categories and gives GnRH as the key example to remember.
GnRH stands for Gonadotrophin Releasing Hormone. It is made by the hypothalamus and stimulates the anterior pituitary to synthesise and release the gonadotrophins LH and FSH, which then act on the gonads in reproduction.
Because it is brain tissue (nervous system) that also contains neurosecretory cells producing hormones (endocrine system). It receives nerve signals and responds by releasing hormones that control the pituitary, joining the two control systems.
No, it controls them indirectly. The hypothalamus controls the pituitary, and the pituitary's tropic hormones then act on target glands like the thyroid, adrenal cortex and gonads. This three-step chain is the hypothalamo-hypophyseal axis.
