Hypothalamus and Posterior Pituitary Flashcards
(25 cards)
What is the true gland of the pituitary gland?
Anterior pituitary (adenohypophysis)
What is not a true gland of the pituitary gland?
Posterior pituitary (neurohypophysis) - just a down growth of neurons from base of hypothalamus
What are functions of hypothalamus?
- Central relay for collecting and integrating diverse signals and sending them to pituitary
- Regulate characteristic pulsatility of secretion
Where do inputs to hypothalamus come from above? From below?
Above - Higher brain centers, diurnal rhythms, adjacent functional nuclei, autonomic nervous system
Below - Feedback
How does hypothalamus relay information to pituitary?
Portal blood to anterior pituitary
Neurons to posterior pituitary
Trace blood flow from hypothalamus to anterior pituitary.
Superior hypophyseal branch –> capillaries –> long portal vessels (veins) pick up hypothalamic factors (releasing factors) from neurons of hypothalamus –> vein empties into ant. pituitary
Trace flow of releasing factors from hypothalamus to posterior pituitary.
Releasing factors go to Herring bodies –> Products are stored in axonal terminals –> Nerve is stimulated –> Product released into systemic venous system
How would you damage both anterior and posterior pituitary?
Cut connecting stalk
What part of pituitary do most pituitary tumors destroy
Anterior pituitary
Generally trace hormone release starting with hypothalamus.
Hypothalamus - secretes releasing hormone, travels down portal circulation to anterior pituitary
Anterior pituitary - secretes trophic hormone, which travels to target gland and activates it
End-organ/target gland - secretes hormone that can negatively feedback
What are two different mechanisms of feedback?
Stimulating an inhibiting hormone OR inhibiting a releasing hormone
Name the anterior pituitary target hormones of the following hypothalamic hormones:
TRH, GnRH, CRH, GHRH, Somatostatin, Prolactin inhibiting factor
Which is an inhibitor of GHRH?
TRH - TSH GnRH - LH, FSH (reproductive) CRH - ACTH GHRH - Growth hormone Somatostatin - TSH, prevents growth hormone Prolactin inhibiting factor - Dopamine
Somatostatin inhibits GHRH
What are two key posterior pituitary hormones?
ADH (vasopressin) and oxytocin
What is the origin of ADH and oxytocin?
Supraoptic and paraventricular nuclei in hypothalamus - “magnocellular neurons”
What supplemental protein protects prohormone as it travels down stalk?
Neurophysin
Explain osmoreceptor regulation of ADH.
Osmoreceptors sense osmotic pressure in blood - if plasma becomes concentrated, it can be sensed by osmoreceptor b/c water leaves osmoreceptor cell for plasma - shrinkage is the stimulus for osmoreceptor firing.
This activates neurons that make ADH and end up in the posterior pituitary where they are stored.
What osmolality is the thirst threshold?
290 mOsm
At what plama osmolality will you stop making ADH?
280 mOsm
What percent of blood volume depletion is needed before there is increased ADH release?
10-15% (more of a pathological state)
What does oxytocin do?
Milk ejection from breast contraction of uterus, labor induction, behavior effects like nurturing, neuroendocrine reflex
What other hormones regulate milk secretion into ducts?
Prolactin, estrogens
What is an example of positive feedback?
Secretion of oxytocin at parturition - labor induction/contraction of uterus
What causes hypovolemic thirst?
Angiotensin II acting on hypothalamus to stimulate ADH
What causes hypervolemic water excretion (as a result of Na excretion)
ANF - acting on renal tubules and suppressing thirst
