Chapter 5 - Regulation of body fluid osmolality - regulation of water balance

Question 1

What is AVP? What is another name for AVP?

Answer 1

AVP is a small peptide that is nine amino acids in length. It is made in neuroendocrine cells located within the supraoptic and paraventricular nuclei of the hypothalamus. The synthesized hormone is packaged in granules that are transported down the axon of the cell and stored in the nerve terminals located in the neurohypophysis (posterior pituitary).

Question 2

What are the two primary physiologic regulators of AVP secretion?

Answer 2

The two primary physiologic regulators of AVP secretion are the osmolality of the body fluids (osmotic) and volume and pressure of the vascular system (hemodynamic).

Question 3

What other factors can alter AVP secretion?

Answer 3

Other factors that can alter AVP secretion include nausea (stimulates), atrial natriuretic peptide (inhibits), and angiotensin II (stimulates). A number of drugs, prescription and nonprescription, also affect AVP secretion.

Question 4

Although the neurons in the supraoptic and paraventricular nuclei respond to changes in body fluid osmolality by altering their secretion of AVP, it is clear that separate cells exist in the anterior hypothalamus that sense changes in body fluid osmolality and regulate the activity of the AVP-secreting neurons. What area these cells?

Answer 4

These cells, termed osmoreceptors, appear to sense changes in body fluid osmolality by either shrinking or swelling. The osmoreceptors respond only to solutes in plasma that are effective osmoles.

Question 5

Both groups of receptors are sensitive to stretch of the wall of the structure in which they are located (e.g., the cardiac atrial wall and the wall of the aortic arch) and are termed _____

Answer 5

Baroreceptors

Question 6

A decrease in blood volume or pressure also stimulates AVP secretion. The receptors responsible for this response are located in both the low-pressure (_____ and _______) and the high-pressure (______ and _______) sides of the circulatory system.

Answer 6

Low-pressure (left atrium and large pulmonary vessels) and High-pressure (aortic arch and carotid sinus) sides of the circulatory system.