Hypothalamic-Pituitary Flashcards
Neurohypophysis
Functional relationship between hypothalamus & posterior pituitary gland
- PVN and SON of hypothalamus synthesize and send signal down to secrete **vasopressin & oxytocin **
- Magnocellular neurons send through infindiublar stalk to posterior pituitary
- Released into blood circulation; ultimately low concentration at target tissues, but high affinity
Stimulants of ADH (6)
- increase ECF osmolality
- Decrease in vol or pressure
- Pain, stress
- Increase in temp
- Beta adrenergic agonists
- Drugs: Nicotine, opiates, barbituates, sulfonylureas, antineoplastic agents
Inhibitors of ADH secretion (4)
- Decrease in temperature
- alpha adrenergic agonists
- ethanol
- ? Cortisol and thyroid hormone
What areas of the hypothalamus are associated with secretion of ADH and oxytocin?
Paraventricular nucleus (PVN)
&
Supraoptic nucleus (SO)
Functions of ADH & Oxytocin
- ADH: Regulates blood pressure by targeting kidney tubules to increase water reabsorption
- Targets smooth muscle (breast and uterus) for contractions
Adenohypophysis
Functional relationship between the hypothalamus and anterior pituitary gland
- Hypothalamus sends signals down median eminence through SHA
- Releasing factors act on cells; hypothalamic neurohormones
- Secretion of hormones from anterior pituitary to circulation –> target tissue
Releasing hormones of hypothalamus & anterior pituitary hormones
- GRH –> GH
- SS (Somatostatin) –x GH & TSH
- TRH —> TSH &PRL
- DA (Dopamine) –x PRL
- GnRH –> LH & FSH
- CRH —> ACTH, ß LPH, ß endor
Regulating hypothalamic releasing hormones (2)
Inhibiting hormones
Releasing hormones
Tissues affected by anterior pituitary hormones
- Growth hormone = bones
- Thyroid stimulating hormone = thyroid
- Prolactin = breats
- Leutenizing & follicle stimulating hormones = gonads
- ACTH = adrenal cortex –> glucocorticoids
Neuroendocrine system
- Rapid CNS of neurons and NT
- Long-lasting, amplified release of hormones
- Neurohormones: releasing factors from hypothalamus
Macroadenoma (5)
- Large pituitary tumors due to overproduction of hormones
*most common is Prolactin
- Due to presence of sphenoid bone, healthy tissue is pushed upwards
- Can impinge on optic chiasm & optic tracts= visual distrubances
- Can impinge on blood vessels in pituitary stalk = prevent flow to anterior pituitary =cell death
- Require surgical removal
Microadenoma (3)
- Often evade detection with imaging techniques
- Can measure hormone levels
- Treat with medical drug therapy
Long Loop Negative Feedback
RF (hypothalamus) –>
Stimulating hormone (anterior pituitary) –>
tropic hormone release –>
target organ –>
hormone release —>
Negative feedback on hypothalamus & anterior pituitary
Short loop negative feedback
Pituitary hormones —> hypothalamus
negative feedback
*occurs when hormone does not have a well-defined target gland
Ex: Growth hormone
Ex: prolactin b/c it stimulates an exocrine product; never enters circulatory system b/c milk is secreted (so it can’t do negative feedback)
Ultra short negative feedback
Releasing factor –> hypothalamus
- inhibitory recurrent collaterals back to cell body
- Inhibits firing of hypothalamus
