Lecture 2 - Hypothalamo-hypophysial axis: Adenohypophysis Flashcards
Draw a diagram of Hypotalamo-hypophysial axis
Remember: 3rd ventricle Optic chiasma Hypothalamus Mamillary body Adenohypophysis Neurohypophysis
Anterior pituitary (AP) key features:
Median eminence Pars tuberalis Pars distalis (Adenohypophysis) Superior hypophysial artery - to medial eminence and causes hypothalamic neurosecretion when activated Primary capillary plexus - neurosecretion collects here Long portal veins - neurosecretion circulates & acts on cells Secondary capillary plexus - neurosecretion circulates & acts on cells Cavernous sinus (out via jugular veins) - release of adenohypophysial hormones
Where is the pituitary gland located?
Sella Turcica
What does the median eminence do?
It’s a separator of the hypothalamus and pituitary gland
Innervation of pituitary gland
Hypothalamic nuclei can send their axons into the posterior PG or their axons stop before the median eminence
What is the name of the adenohypophysis?
Pars distalis
List the adenohypophysial cells and their secretions
Somatotrophs - somatotrophin Lactotrophs - Prolactin Thyrotrophs - Thyrotrophin (Thyroid stimulating hormone) Gonadotrophs - Gonadotrophin (LH and FSH) Corticotrophs - Corticotrophin (ACTH) Other cells - non defined
What are the general features of adenohypophysial hormones?
All made from Prohormones Enzyme cleavage leads to bioactive hormone AH hormones stored in secretory granules Released by exocytosis
What are some specific adenohypophysial hormones?
Proteins: Somatotrophin (191 a.a.), Prolactin (199 a.a.) Glycoproteins (all have same alpha subunit of 92 a.a.): TSH (beta 110), LH & FSH (115 beta) Polypeptide: ACTH (39 a.a.)
What are the hyothalamoadenohypophysial hormones and what do they cause?
What are the main target cells for adenohypophysial hormones?
Somatotrophin - body tissues and MAINLY liver
Prolactin - Breasts
Thyrotrophin - thyroid
Gonadotrophin - Tests and Ovaries
Corticotrophin - Adrenal cortex
What is the mode of action of somatotrophin?
Adenohypophysis > Somatotrophin released > Liver and Body tissues > Somatomedins (IGF I, IGF II) > Body tissues - metabolic actions –> GROWTH AND DEVELOPMENT
What metabolic actions are caused by somatotrophin via IGF I (direct and indirect effect)?
Stimulation of a.a. into cells Stimulation of protein synthesis Increased cartilaginous growth Stimulation of lipid metabolism > increased FA production Decreased glucose utilisation and increased gluconeogenesis > INCREASED blood glucose conc
How is somatotrophin regulated?
What are the effects of prolactin?
BREAST LACTOGENESIS Effects on IS (stimulating T cells) Increases LH receptors Pituitary - Decreases LH releases Hypothalamus - Decreases sexual behaviour Renal Na+/Water reabsorption Steroidogenesis
How is the release of prolactin stimulated (regulation)?
What is the neuroendocrine reflex arc for prolactin?
