BIOL 2P93 Lecture Notes - Aquaporin, Antidiuretic, Osmoreceptor

12 views1 pages
Control of ECF Volume I—Guggino
I. Conserving and balancing body H2O
a. Humans can excrete large or small quantities of water independently of solutes
b. Kidneys regulate water excretion over large range!
c. Sensing changes in Osmolality
i. Osmoreceptors—located in circumventricular organs in brain; contain non-selective
Ca channels
1. regulate thirst & secretion of ADH
2. only respond to changes in effective osmolality (ie if a freely permeable solute
is responsible for the change in osmolality, osmoreceptors won’t notice)
ii. Thirst
1. also very sensitive to changes in plasma osmolality, but can also be stimulated
by changes in bl. volume/pressure
2. Factors controlling thirst: osmolality, blood volume, blood pressure,
angiotensin II, gastric distention, dryness of mouth
II. ADH (Antidiuretic Hormone)
a. Synthesized in paraventricular & supraoptic nuclei of hypothalamus
b. Stored in and released from the posterior pituitary
c. ADH secretion is very sensitive to small changes (↑) in osmolality but
d. Mechanism of ADH action
i. Triggers cascade that => aquaporins insertion in to apical cell membranes of distal
tubules & collecting ducts
ii. Increases water permeability of distal tubules & collecting ducts => ↑ reabsorption
e. KEY for concentrating urine (absent/decreased fxn in diabetes insipidus)
(Raymond has removed images summarizing the ADH and thirst response to an increase or decrease in ECF
osmolality.)
Unlock document

This preview shows half of the first page of the document.
Unlock all 1 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.