Hypothalamus and Pituitary Flashcards
What is the function of the hypothalamus?
Has regulatory control over many endocrine glands and their hormones.
What is the hypothalamus composed of?
Various nuclei and median eminence
What do the various nuclei do?
Synthesize hypothalamic releasing hormone (RHs) and posterior pituitary gland hormones (ADH and Oxytocin).
What is the median eminence?
Bottom portion of hypothalamus that contains RHs, which regulate anterior pituitary gland activity.
Where is the Pituitary located?
The base of the brain within bony socket (connected to brain by infundibulum).
What does the Pituitary contain?
Nerves that communicate with Posterior Pituitary and special veins that communicate with the Anterior Pituitary.
What are the 2 parts of the Pituitary?
Anterior Pituitary (Anterior lobe) and Posterior Pituitary (Posterior lobe)
Posterior Pituitary Hormone Secretion
- Cells within hypothalamus synthesizes hormones of Posterior Pituitary and stores them in secretory vesicles.
- Upon receiving neural impulses, cells release secretory vesicles into nerves which travel down nerve fibers via neuroplastic flow to enter Posterior Pituitary.
- Hormones are stores in Posterior Pituitary until action potential stimulates granules.
- Granules enter into capillary for hormones to be dispersed.
What are the neural extensions of hypothalamus?
- Nerve axons from mainly two nuclei in hypothalamus 2. Axons terminate near capillaries in Posterior Pituitary.
What are the 2 nuclei in the hypothalamus?
- Supraoptic nucleus (SON)
2. Paraventricular nucleus (PVN)
How are ADH and OT synthesized?
Synthesized as larger molecule first (pro-pressophysin and pro-oxyphysin) then split by specific proteases.
How are ADH and OT stored?
Stored in granules with remainder of molecule.
How are ADH and OT secreted?
Via AP reaching nerve terminals.
What happens when the stalk to the Posterior Pituitary is cut and foil is placed to prevent reattachment of nerves?
Secretory granules accumulate in hypothalamus above foil. Which results in increased plasma osmolarity, peeing, production of ADH, and thirst. After awhile, capillaries form to restore delivery of hormone from hypothalamus to Posterior Pituitary.
What condition is often seen in whiplash victims (especially pregnant women)?
Transient diabetes insipidus
What are the actions of ADH?
- Increase contractility of arterial smooth muscle, which causes increased BP.
- Increased water reabsorption (antidiuresis).
What are the actions of Oxytocin?
- Increased contractility of uterine smooth muscle.
2. Increased contractility of myoepithelial cells of mammary glands (leads to milk letdown/ejection).
What controls secretion of ADH?
- Decreased plasma volume
2. Increase osmolarity
Which ADH control is more sensitive?
Increased osmolarity. A plasma volume of 5% triggers increased ADH release versus an increased osmolarity by 1%.
What controls secretion of Oxytocin?
- Dilation of cervix
2. Suckling
