Non ACTH mediated hormones - Na+/ homeostasis - Aldosterone/ADH

9 important questions on Non ACTH mediated hormones - Na+/ homeostasis - Aldosterone/ADH

What does aldosterone do after it is produced?

It binds to mineralocorticoid receptors in distal tubules and collecting ducts, then produces epithelial sodium channels (ENaC) and ATPases

How is aldosterone stimulated to be produced?

1. High K+: depolarization of cells of zona glomerulosa
2. Low Na+: renin-angiotensin system

What is ADH (vasopressin)?

They are peptide hormones produced by the supraoptic nucleus of the hypothalamus, used for modulating water permeability in the collecting ducts for water reabsorption
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What is the mechanism of ADH?

1. ADH binds to Gs-protein coupled receptors (cAMP) on collecting duct membrane
2. CAMP promotes vesicles with aquaporin channels to travel from Golgi and fuse with plasma membrane of collecting duct

What happens to the collecting duct membrane when ADH is no longer present?

Aquaporin channels are removed by endocytosis

How does ADH change the blood volume?

- More ADH = higher blood volume
- Less ADH = lower blood volume (activates aldosterone)

What can lead to ADH levels being decreased?

Drinking water

How do Aldosterone and ADH collaborate?

- ADH responds to osmolality changes, which will alter blood volume
- Aldosterone responds to blood volume changes from ADH

How is ADH secretion regulated?

Increased venous return leads to more stretch in left atrium, leading to the vagus nerve sending this information to the posterior pituitary to inhibit further secretion of ADH

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