BIOL 2P93 Lecture Notes - Aromatase, Breastfeeding, Adrenocorticotropic Hormone

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Published on 4 Feb 2013
The Hypothlamo-pituitary Unit
I. Introduction
a. Pituitary (“mucus”) = hypophysis (“small/under growth”)
b. Brain acts as an endocrine gland thru hypothalamus via the pituitary gland
c. Pituitary has a portal system—(vessels w/ capillary network on either side); blood
flows from neurohypophysis to adenohypophysis via the vessels & then out to
II. Neurohypophysis—(posterior pituitary) releases ADH & oxytosin; hormones
synthesized in hypothalamus & stored/released from pituitary
a. ADH (arginine-vasopressin)
i. Neurophysin II—transport protein carrying ADH from hypothalamus to
ii. circulates as free peptide; ½ life = 2 min
iii. Fxn—increases H2O absorption from renal tubuli
iv. Stimuli
1. changes in blood volume—volume receptors in carotid sinus, L
atrium, & aortic arch; exponential relationship (quadratic) between
ADH release & blood volume loss
2. changes in serum osmolality—↑ osmolality => ↑ ADH secretion;
linear relationship+
3. fear & pain
b. Oxytocin
i. Neurophysin I—transport protein carrying oxytocin from hypothalamus
to neurohypophysis
ii. circulates as free peptide; ½ life = 2 min
iii. Fxn—stimulates contraction of uterine mm. & letdown of milk
iv. Stimuli—parturition, suckling, coitus
III. Adenohypophysis—(anterior pituitary)
a. Cytology of adenohypophysis
i. Somatotropes (GH-secreting) ~50%
ii. Lactotropes (PRL-secreting) ~15-25%
iii. Corticotropes (ACTH secreting) 15-20%
iv. Gonadotropes (LH & FSH secreting) 10-15%
v. Thyrotropes (TSH secreting) 3-5%
b. PIT-1 Gene
i. transcription factor that regulates (characterizes) pituitary stem cells
ii. gives rise to GH, PRL & TSH hormones => determines differentiation of
somatotropes, thyrotropes, & lactotropes
IV. Hypothalamic Hypophysiotropic Hormones
a. Growth Hormone releasing hormone (GRH)
i. Fxn—Induces production of GH from pituitary; sleep induction
ii. Two forms, both are equally active; ½ life = 5 min
iii. Binds to a GPCR
iv. Part of H-P-growth hormone axis
b. Somatostatin
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