USMLE Step 1 Renal Physiology Review 59 11 Antidiuretic Hormone

USMLE Step 1 Renal Physiology Review 59 11 Antidiuretic Hormone

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Play USMLE Audio MP3  59 11 Antidiuretic Hormone Below

Begin  59 11 Antidiuretic Hormone Transcription

Now let’s talk about antidiuretic hormone. What kind of hormone is ADH? The answer starts with PHH.

  • ADH is a polypeptide hypothalamic hormone.

What two hypothalamic nuclei synthesize it? They start with S and P.

  • ADH is synthesized in the hypothalamus by the supraoptic and paraventricular nuclei.

What gland takes care of the storage and release of ADH? It starts with a P.

  • The pituitary.

Specifically, where in the pituitary is ADH stored and released from?

  • In the secretory granules located in the posterior lobe.

What are the two main things that stimulate the release of antidiuretic hormone. Both start with H.

  • Hyperosmolality and hypovolemia.

Normally, what is the number one regulator for the secretion of ADH? It starts with PO.

  • Normally, plasma osmolality is the number one regulator of ADH secretion.

As plasma osmolality increases, does secretion of antidiuretic hormone increase or decrease?

  • ADH secretion increases as plasma osmolality increases.

Stimulation of what receptors triggers the release of ADH? They start with HO.

  • Hypothalamic osmoreceptors.

As plasma osmolality increases what happens to the osmoreceptor cells?

  • They shrink.

Does urea stimulate these receptors?

  • No. Urea doesn’t stimulate the hypothalamic osmoreceptors.

Why not?

  • Urea is a small non-electrolyte that easily penetrates the cell memebrane.

What solute has the strongest effect on the osmoreceptors?

  • Sodium.

Why does sodium have a greater osmotic effect on the osmoreceptor cells?

  • Sodium is confined to the extracellular space because the osmoreceptor cells are relatively impermeable to it.

What disease when uncontrolled will cause glucose to effectively stimulate the osmoreceptors? It starts with DM.

  • Diabetes mellitus.

Where are there osmoreceptors that regulate thirst?

  • Osmoreceptors that regulate thirst are located in the hypothalamic thirst center.

How does hyperosmolality affect the thirst center osmoreceptors?

  • It stimulates them.

What hormone stimulates the thirst mechanism? It starts with an A.

  • Angiotensin II.

Student doctor, please pause the tape and summarize what we’ve discussed about the production, storage, and release of ADH, as well as how plasma osmolality affects ADH secretion and the thirst mechanism.

Antidiuretic hormone is a polypeptide hypothalamic hormone synthesized in the supraoptic and paraventricular nuclei of the hypothalamus. Secretory granules in the posterior lobe of the pituitary gland take care of its storage and release. The two main things that stimulate the release of ADH are hyperosmolality and hypovolemia. ADH secretion increases as plasma osmolality increases which is normally the number one regulator for ADH release. Stimulation of the hypothalamic osmoreceptors triggers antidiuretic hormone secretion. As plasma osmolality increases, the osmoreceptor cells shrink. Urea doesn’t stimulate the osmorecptors because it is a small non-electrolyte that easily penetrates the cell membrance. Sodium has the strongest effect on the osmoreceptors because the cells are relatively impermeable to it which confines it to the extracellular space. Uncontrolled diabetes mellitus will cause glucose to effectively stimulate the osmoreceptors.

 

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