The Pituitary Gland Flashcards
What are the prinicipal organisers of the endocrine system?
- Hypothalamus
- Pituitary gland
The hypothalamus is directly connected to the pituitry gland via a stalk called the
- Infundibulum
Hypothalamic communication with the pituitary gland is:
(A) Neural
(B) Endocrine
(C) Neuroendocrine
(C) Neuroendocrine
(endocrine with the anterior pituitary and neural with the posterior pituitary)
What is the integration centre for endocrine systems?
- Hypothalamus
The pituitary gland is located in the pocket of which bone?
- Sphenoid bone
State what is released by the hypothalamus and pituitary gland
- The HYPOTHALAMUS secretes neurohormones
- The POSTERIOR PITUITARY GLAND secretes neurohormones made in the hypothalamus
- The ANTERIOR PITUITARY GLAND secretes endocrine hormones
What is the difference between trophic and non-trophic hormones
Trophic hormone: Act on another endocrine gland (i.e neurohormones secreted into capillaries travelling to anterior pituitary)
Non-trophic hormone: Directly stimulates target cells to induce effects (i.e neurohormones produced in the hypothalamus and travel to posterior pituitary where they are released in the blood)
What do all hypothalamic trophic hormones do when they get to the anterior pituitary?
- Bind to receptors on the anterior pituitary and stimulate/inhibit release of anterior pituitary hormones
Hypothalamic trophic “releasing hormones” include:
–Thyrotropin Releasing Hormone (TRH)
–Corticotropin Releasing Hormone (CRH)
–Growth Hormone Releasing Hormone (GHRH)
–Gonadotropin Releasing Hormone (GnRH)
–Prolactin Releasing Hormone (PRH)
Hypothalamic trophic “inhibiting hormones” include:
–Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
–Dopamine aka Prolactin Inhibiting Hormone (PIH)
Which hypothalamic trophic hormone is NOT a peptide?
- Dopamine (Prolactin Inhibiting Hormone - PIH)
How to trophic hormones travel from the hypothalamus to the anterior pituitary?
- Via the hypothalamo-hypophyseal portal system
(Hormones are released from neurosecretory neurons at the median eminence)
Contrast the anterior and posterior pituitary gland in terms of:
(a) Type of tissue
(b) Tissue origin
(c) Connection to hypothalamus
(d) Other name?
(e) What proportion of the pituitary gland does it make up?
The production of anterior pituitary hormones is controlled by what?
- Hypothalamus
(becuase of trophic hormones coming from the hypothalamus to the anterior pituitary)
List the 6 hormones released from the anterior pituitary gland
Which anterior pituitary hormone is NOT a trophic hormone?
- Prolactin
Describe the hypothalamic-hypophyseal portal system
- Hypothalamic neurones produce either releasing or inhibiting neurohormones
- These neurohormones move through the portal system and bind to receptor on the surface of the anterior pituitary cell
- The anterior pituitary cell can then release hormones that diffuses into the capillary system and into circulation
The anterior pituitary feedback control is a complex, multi-tiered pathway involving up to what 3 integration centres?
- Hypothalamus
- Anterior pituitary
- Target endocrine cell
In anterior pituitary feedback control, how do hormones themselves act as a negative feedback signal?
- Each hormone feeds back to inhibit hormone secretion by integrating centres earlier in the reflex
(this prevents excess secretion of hormones my stopping secretion of the hormone when there is enough already)
The posterior pituitary releases what 2 peptide neurohormones?
- Vasopressin (aka ADH)
- Oxytocin
Where are vasopressin and oxytocin synthesised?
- Magnocellular neurones (by different subsets to make either vasopressin or oxytocin)
- These have their cell bodies in specific areas of the hypothalamus
Descibe magnocellular neurons
- Cell bodies in the hypothalamus
- Different subsets make EITHER vasopressin or oxytocin
- Axons project down the infundibulum to the posterior pituitary
- It does NOT synapse with other neurones, their terminals end directly on capillaries
- Release of either vasopressin or oxytocin directly inot the bloodstream at the posterior pituitary
Vasopressin notes:
Oxytocin notes:
