Hypothalamic Control of Pituitary
Posterior Pituitary
-called NEUROHYPOPHYSIS because hormones are released directly from axonal endings into circulation
-uses large MAGNOCELLULAR neurons
-hormones are synthesized exclusively in HYPOTHALAMUS but stored in neurohypo.
-made in PARAVENTRICULAR and SUPRAOPTIC nuclei
-releases neurophysin 1 (oxytocin) and neurophysin 2(ADH) co-peptides
-**NEURAL input with HORMONAL output
Oxytocin
-no diurnal rhythm
-controls MILK-LET DOWN reflex upon tactile stimulation by infant
-travels in spino-hypothalamic tract (nipple to paraventriuclar/suprapoptic)
-causes CONTRACTIONS of uterine myometrium during birthin’
-reproductive tract contraction during sperm transport
-NO KNOWN DISEASES
Vasopressin/Antidiretic Hormone
-acts on V2 receptors on contraluminal collecting duct to increase WATER and ELECTROLYTE transport
-has a diurnal peak at night and early morning
-sensors for plasma osmolarity in PV/SO nuclei evoke secretion
-afferent inputs from organum vasculosum and subfornical organ evoke secretion
-renin/angiotensin system evokes secretion
-Diseases: DIABETES INSIPIDUS-dilute urine, dehydration, thirst
Syndrome of Inappropriate AVP Secretion-caused by hypervasopressin secretion-edema, hypovolemia, hyponatremia
Anterior Pituitary
-all hormones are SYNTEHSIZED and STORED in the adenohypophysis (anterior pit.)
-hormones are NOT released directly into blood stream
-Hyptholamic control is via RELEASING FACTORS
-uses PARVOCELLULAR neurons
Releasing factors synthesized in Arc/PVN/SO nuclei… Tuberoinfindibular tract… superior hypophyseal artery… hypothalamic portal circulation
Hormones: Remember F.L.A.T. P.I.G.
Follicle Stimulating Hormone-controls gonads in men and women (Arcuate)
Leutinizing Hormone- as above (Arcuate)
Adrenocorticotropic Hormone-pulses with early morning peak controlling gluco/minero corticoidoids (PVN/SO)
Thyroid Stimulating Hormone- controls metabolism (PVN)
Prolactin-synthesis of milk in breasts (Arcuate/PVN)
Growth Hormone-linear growth (Arcuate)
Feedback Loops (Adenohypophysis)
Ultrashort: used for autocrine regulation of hypothalamic secretions between nuclei (Periventricular nuc.inhibits Arcuate secretion of GH-releasing factor)
Short: inhibits releasing factor secretion by hormone itself from pituitary to hypothalamus (GH inhibits GH-Relseaing factor secretion)
Direct Long: peripheral hormone secretion inhibits hormone secretion from pituitary (Ex: T3 inhibits TSH secretion)
Indirect Long: Peripheral Hormone inhibits secretions of Hypothalamus
Diseases of Anterior Pituitary
Acromegaly/Gigantism hypersecrtion of GH, multiple system failure
Dwarfism hyposecretion of GH
Hyperprolactinemia associated with pituitary adenomas
Hypogonadism hyposecretion of LHRH
Cushing’s Disease increase adipose, muscle weakness, hypertension caused by microadenomas of pituitary due to increased ACTH production
Immune Responses to Pituitary Gland
All hormones act on lymphocytes affecting immunity. Steroid hormones
immunosupressively to prevent excessive clonal expansion from inappropriate
lymphocyte cell lines.
Pituitary hormones serve to reallocate energy sources to appropriate systems by
suppressing certain systems.
Interleukin 1B is chief mediator of acute phase immune response. Induces formation of
Prostaglandins through COX2 enzymes which cross blood/brain barrier to induce fever response from paraventricular A2 nuclei.
Interleukin 6 is mediator of prolonged acute phase response.
Eustress- (good stress) acts as a endocrine regulator of immune response. Deploys leukocytes and INCREASES resistance to infection.
Distress – (bad stress)- disrupts homeostasis and increases incidence of infection.
Tags: adenohypophysis, Cushing's Disease, dwarfism, gigantism, homeostasis, Hyperprolactinemia, hypogonadism, hypothalamus, immune responses, magnocellular, neurohypophysis, pituitary gland
