PHGY 210 Lecture Notes - Lecture 2: Posterior Pituitary, Anterior Pituitary, Pituitary Gland

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Published on 28 Nov 2015
Department
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Phgy 210
January 7, 2015
Endocrinology Lecture 2
Feedback Control of Hormone Secretion
Hormone secretion is precisely regulated by feedback mechanisms
An excess of hormone, or excess hormonal activity, leads to a
diminution of hormone secretion
Conversely, a deficiency of hormone leads to an increase in hormone
secretion
Ca++ acts in a negative feedback loop to regulate plasma calcium
levels
Hormonal Feedback Mechanisms
CRH: corticotropin releasing hormone
ACTH: adrenocorticotropic hormone
Cortisol (glucocorticoid)
Endocrine Glands and their Secretions
1) Anatomic location
2) Hormones secreted
3) Chemical nature of hormones
4) Effects
5) Mechanism of action
6) Control of release
7) Problems
8) Treatment
Pituitary Gland
Two distinctly different tissues
o Adenohypophysis (aka anterior pituitary, or pars
distalis)
o Neurohypophysis (aka posterior pituitary, or pars
nervosa)
Histologically, the anterior pituitary is endocrine tissue
The posterior pituitary is neural tissue
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Phgy 210
January 7, 2015
Signalling between the hypothalamus and the
pituitary
FSH: follicle stimulating hormone
LH: luteinizing hormone
IGF-1: insulin-like growth factor 1
TSH: thyroid-stimulating hormone
Dopamine is a prolactin release inhibiting
hormone
These are all produced by the anterior
pituitary
Most hormones are encoded by a gene,
except for dopamine
Posterior Pituitary Gland (Neurohypophysis)
Outgrowth of hypothalamus connected by the pituitary stalk
Secretes oxytocin and vasopressin (aka antidiuretic hormone
ADH)
Oxytocin and vasopressin synthesized in two hypothalamic
nuclei (supraoptic nucleus and paraventricular nucleus),
whose axons run down the pituitary stalk and terminate in
the posterior pituitary close to capillary blood vessels
Prohormones processed in secretory granules during axonal
transport
Mature hormones liberated from the carrier molecules,
neurophysins
Circulating half lives: 1-3 minutes
Oxytocin
Females
o Parturition
Uterus extremely sensitive to oxytocin at end of
pregnancy
Dilation of uterine cervix by fetal head causes release of oxytocin uterine contraction,
which assists the expulsion of fetus and then placenta
o Milk ejection
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