Pituitary Physiology
Terms
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- What is the glandular portion of the pituitary called?
- Anterior Pituitary
- What is the neural portion of the pituitary called?
- Posterior Pituitary
- What are the three parts of the Adenohypophysis?
-
AKA Anterior Pituitary:
Distalis
Intermedia
Tuberalis - What are the three parts of the Neurohypophysis?
-
AKA Posterior Pituitary:
Nervosa
Infundibular (stem/stalk)
Median eminence - When is a Pituitary Gland larger?
-
In Women (in general)
or during pregnancy - What is the Anterior Pituitary derived from?
- Upgrowth of Oral Ectoderm from the roof of the mouth.
- What is the Posterior Pituitary derived from?
- Downgrowth of Diencephalon from the brain.
- Magnocellular Neurons
- Large diameter neurons of the hypothalamus.
- What do Magnocellular Neurons synthesize?
- ADH and Oxytocin
- Where do magnocellular neurons terminate?
- Fenestrated capillaries in the Posterior Pituitary
- What are the principal stimuli for ADH secretion?
-
Increased Plasma Osmolarity
Decreased Blood Volume
Stress - What aare the principal stimuli for Oxytocin secretion?
-
Suckling
Vaginal Distention - What are the three categories of hormones of the Anterior Pituitary?
-
Corticolipotropins
Glycoprotein
Somatomammotropins - What are all corticolipotropins derived from?
-
pro-opiomelanocortin which is cleaved into:
N-terminal fragment
ACTH and Beta-LPH - What is the principle action of ADH?
-
open water channels in connecting tubule
Constriction of arterioles = Higher BP - What is the principle action of Oxytocin?
-
Milk production
Uterine Contraction - What hormones are considered corticolipotropins?
-
ACTH
Beta-Lipoprotein
Beta-Endorphin - What is the principle action of ACTH?
- Stimulates Adrenal gland to synthesize glucocorticoids
- What hormones are considered Glycoprotein?
-
LH
FSH
TSH - What is unique about the structure of Glycoprotein hormones?
- Consist of 2 noncovalently linked alpha & beta subunits. All alpha units are the same.
- What is another name for TSH (besides Thyroid Stimulating Hormone)?
- Thyrotropin
- What hormones are considered Somatomammotropins?
-
GH
Prolactin - What is the princple functions of PRL?
-
Stimulate breast development during pregnancy
Stimulate postpartum lactation - Acidophilic-staining cells of the Pars Distalis may secrete what hormones?
-
GH
PRL
note: same color as WBCs - Basophilic-staining cells of the Pars Distalis may secrete what hormones?
-
ACTH (most basophilic)
LH
FSH
TSH - What does Oxytocin antagonists do in males?
- Block erections
- What are the five types of cells in the Pars Distalis
-
Somatotroph (GH)
Lactotroph (PRL)
Corticolipotroph (ACTH)
Gonadotroph (LH/FSH)
Thyrotroph (TSH) - What are the most common types of cells in the Pars Distalis?
- Somatotrophs (50%)
- What are the second most common types of cells in the Pars Distalis?
- Lactotrophs (10-25%)
- Which cell types are frequently found disbursed laterally in the Pars Distalis?
- Somatotrophs
- Which cells are most frequently found in the anteromedial part of the Pars Distalis?
-
Thyrotrophs
Corticotrophs - Which cells are most frequently found randomly dispersed througout the Pars Distalis?
-
Lactotrophs
Gonadotrophs - What stimulates Somatotroph Cells?
- GRH
- What inhibits Somatotroph Cells?
- Somatostatin
- What Inhibits Lactotroph Cells?
- Dopamine
- What Stimulates Thyrotroph Cells?
- TRH
- What stimulates Corticotroph Cells?
- CRH
- What stimulates Gonadotrophs?
- GnRH
- What other peptides does GRH show homology with?
-
Gastrin
VIP - Why feature of TRH makes it possible to have so few Thyrotrophic Cells in the Pars Distalis?
- The prohormone of TRH contains six copies of TRH.
- What are the names of the nuclei observed in the pars nervosa?
- special glial cells called pituicytes
- Increased production of ACTH in the Pituitary gland can lead to what secondary physiological change?
- Increased skin pigmentation due to MSH contained in the intermediate proteins from which ACTH is derived.
- What factors stimulate GH secretion?
-
hypoglycemia
decreased free fatty acids
arginine
fasting/starvation
puberty (estrogen/testosterone)
exercise
stress
sleep - What factors inhibit GH secretion?
-
Hyperglycemia
Increased free fatty acid conc.
obesity
senescence
somatostatin
somatomedin
GH
Pregnancy