Hypothalamus Structure Diagram and Meaning
Introduction:
- Hypothalamus is known as "master of the master gland"
- It is the nuclei of grey matter and neurosecretory cells producing neurohormones present at the diencephalon floor.
- There are two sets of hormones secreted by hypothalamus -
- One set consists of hormones that are directly stored in neurohypophysis and are released into the bloodstream,for eg. oxytocin and ADH
- Another set consists of hormones secreted by the nerve cells that are responsible for the stimulation or inhibition of the anterior pituitary. These are poured into the adenohypophysis (anterior and intermediate pituitary) through the hypophyseal portal system
- Nerve fibres transport hormones in the form of neurophysin-bound secretory granules.
Hormones poured into the adenohypophysis :
- These are peptides in nature and function as regulatory hormones, categorised in releasing or inhibiting hormones.
- Releasing hormones: Stimulates production of pituitary hormones, e.g., Gonadotropin-releasing hormone stimulates the pituitary gland to synthesise gonadotropins.
- Inhibiting hormones: Inhibit secretions of pituitary hormones, e.g., Somatostatin inhibits the secretion of growth hormone.
Regulatory hormones secreted by the hypothalamus:
i. Thyrotropin Releasing Hormone ( TRH) or TSH-RH (Thyroid Stimulating Hormone Releasing hormone): Stimulates the anterior pituitary to secrete thyrotropin or thyroid-stimulating hormone.
ii. Corticotropin Releasing Hormone ( CRH): Stimulates anterior pituitary to secrete adrenocorticotropic hormone.
iii. Gonadotropin-Releasing Hormone ( GnRH): Stimulates the secretion of gonadotropins by adenohypophysis which is of two types, FSH and LH.
iii. Somatotropin Releasing Hormone or Growth Hormone Releasing Hormone ( SRH or GHRH): Induces production of growth hormone by stimulating the anterior pituitary.
iv. Somatostatin or Growth Hormone Inhibiting Hormone (GHIH): It inhibits adenohypophysis to secrete growth hormone.
v. Prolactin Releasing Hormone (PRH): The anterior pituitary is stimulated to secrete prolactin.
vi. Prolactin Inhibiting Hormone (PIH): The hypothalamic hormone inhibits the synthesis of PRH by the anterior pituitary. The hormone prolactin is primarily controlled by the neurotransmitter dopamine produced by tuberoinfundibular neurons.
vii. Melanocyte Stimulating Hormone Releasing Hormone (MSH-RH): The releasing hormone induces the intermediate pituitary to secrete MSH.
viii. Melanocyte Stimulating Hormone Inhibiting Hormone (MSH-IH):The inhibiting hormone stops the synthesis of MSH.
Frequently Asked Questions (FAQs):
Q1. Hypothalamic hormones are released by which cells?
Ans : Hypothalamic hormones are released neurosecretory nuclei
Q2. Which hormones are released by hypothalamus ?
Ans : Hormones are released by hypothalamus is categorised into two sets -
- One set consists of hormones that are directly stored in neurohypophysis and are released into the bloodstream,for eg. oxytocin and ADH
- Another set consists of hormones secreted by the nerve cells that are responsible for the stimulation or inhibition of the anterior pituitary. These are poured into the adenohypophysis (anterior and intermediate pituitary) through the hypophyseal portal system
Q3. Why is hypothalamus known as the “master of master glands” ?
Ans :
- The hypothalamus is known as the “master of master glands” because it is the part of the brain that controls the endocrine system and regulates the endocrine glands with the help of the pituitary gland.
Q4. Where is the hypothalamus located ?
Ans :
- Hypothalamus forms the floor of diencephalon.
- It is present at the base of the 3rd ventricle.