AVP, oxytocin, growth hormones and pituitary Flashcards
What is the pituitary gland?
Integrates signals and releases hormones that regulate the functions of other endocrine glands.
Vital roles in homeostasis
What is the two lobes the pituitary gland split into?
Anterior and posterior
What is the driving force of the pituitary gland?
The hypothalamus
Where is the pituitary gland located?
Base of the brain attached to the hypothalamus
Anterior lobe of the pituitary gland
Synthesizes and secretes hormones in response to hypothalamic regulation.
Posterior lobe of the pituitary gland
Stores and secrets hormones synthesized in the hypothalamus. (Does not produce any hormones)
Does the posterior pituitary produce hormones?
No
What two hormones are stored secreted by the posterior pituitary?
Antidiuretic hormones (ADH/vasopressin) Oxytocin
What does antidiuretic hormone regulate (ADH/vasopressin)?
Regulation of renal failure
What does oxytocin regulate?
Regulation of uterine contraction
What the 4 things that feed into the hypothalamus that stimulate the posterior pituitary gland?
- Hyperosmolarioty (main)
- Angiotensin II (main)
- Decreased atrial receptor firing
- Sympathritric stimulation
What two reports does ADH/vasopressin work on?
V1 and V2
What does activation of the V1 receptor do?
Acts on the blood vessels casing constriction, increased systemic vascular resistance.
What does activation of the V2 receptor do?
Kidneys, fluid reabsorption, increased blood volume
What is the overall affect of vasopressin/ADH after activation V1 and V2?
Increased arterial pressure (increased BP). V2 regulates water excretion by decreasing, so retaining water.
Effect of reduced ADH/vasopressin
Diabetes insipidus, copious hypotonic urine.
Treatment for reduced ADH/vasopressin
V2 agonist - desmopressin (mimics vasopressin)
Effect of excess ADH/vasopressin
Hyponatremia (diluted NA due to excess water)
Oedema
Treatment for excess ADH/vasopressin
Demeclocycline (blocks transduction of V2)
Tolvaptan (V2 antagonist) (expensive)
Restrict fluids
Cause of excess ADH/vasopressin
Tumor, head injury, TB
ADH/vasopressin mechanism (5)
- Hypothamalus stimulates posterior pituitary through hyperosmolarity and angiotensin, II
- Vapsoresisibe secreted and acts of V1 and V2 receptor.
- V1= blood vessel constriction = increased systemic vascular resistance
- V2= Kidney fluid reapportion = increased blood volume (water retention)
- Increased arterial pressure
Oxytocin mechanism (3)
- Stretch of uterus, uterine cervix and stimulation of breasts increases action potentials in axons of oxytocin-secreting neuron.
- Action potential go to hypothalamus and simulation secretion of oxytocin via posterior pituitary
- Oxytocin release increased uterine contraction and milk release from breasts.
Clinical use of oxytocin (3)
Labour induction (Slow IV)
Prevention/treatment of hemorrhage (Prophylactic IM)
Labour too quick (Antagonist: Atosiban)