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Because there is no appreciable exchange with bone stores, balance is maintained by renal excretion of the 5 mmol absorbed. Maintenance of plasma volume is essential for adequate tissue valance. Endogenous opiates, high doses of morphine and drugs including chlorpropamide stimulate release of ADH, whereas ethanol inhibits it.

V1a receptors have a pressor effect on vascular smooth muscle cells, through activation of phosphoinositol. Check out this article to learn more or contact your system administrator. Diuretics decrease sodium reabsorption, resulting in increased excretion of sodium and water and a fall in extracellular volume. Water is able to pass freely between these compartments and the distribution of water is therefore determined by osmotic pressure.

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Regulation of hidroelectrolltico balance is unusual in that no hormones influence magnesium excretion. Because sodium is the major solute within the extracellular compartment, plasma sodium concentration is the principal osmotic factor controlling ADH balanc.

It can be seen that there is no direct relationship between plasma sodium concentration which is the principal determinant of osmolality and plasma volume. Effective osmolality The osmolality of a solution is determined by the number of molecules of osmotically active solute contained in that solution. The signal is relayed to the paraventricular nuclei of the hypothalamus, resulting in ADH release.

An abrupt and maintained increase in sodium intake causes extracellular volume to rise, owing to a rise in osmolality. Physiological role of the relationship between distal flow and potassium excretion Volume expansion results in decreased activity of the RAS and a decrease in aldosterone-driven potassium secretion, alongside an increase in sodium and water excretion.

Volume expansion is the sensor for sodium intake and results in increased sodium excretion.

Sensitivity of osmoreceptors and volume receptors The osmotic stimulus for ADH release is much more sensitive than the volume-directed stimulus. ANP seems to inhibit renin release and might therefore play a part in the suppression of the renin—angiotensin system during volume expansion.


A solute is able to generate an osmotic pressure across a membrane only if it is unable to cross that membrane. The mechanism of osmoregulation involves osmoreceptors in the hypothalamus that control the release of anti-diuretic hormone ADH and stimulate thirst.


Several types of ADH receptor have been characterized. Extra-renal receptors signal to the vasomotor centre in the brainstem, increasing sympathetic nervous system activity and thereby the RAS.

These relay through the vasomotor centre valance the brainstem to the sympathetic nervous system.

Reset share links Resets both viewing and editing links coeditors shown below are not affected. Magnesium transport in this limb is believed to be by passive diffusion, dependent on sodium and chloride reabsorption. This is well illustrated by considering the consequences of an abrupt rise or an abrupt fall in plasma osmolality.

Do you really want to delete this prezi? ADH stimulates potassium excretion in the distal nephron. It also stimulates thirst and ADH release. Comments 0 Please log in to add your comment.

This might be expected to carry a risk of potassium accumulation. Neither you, nor the coeditors you shared it with will be able to recover it again. Renal function in early childhood in very low birthweight infants. The relationship between distal flow and potassium excretion counteracts these effects, thereby allowing aldosterone to regulate sodium excretion independently of potassium and maintaining potassium balance.

Anti-diuretic hormone ADH is a nine-amino-acid peptide that increases the permeability of the renal collecting ducts to water. Osmoregulation results in water retention through the action of ADH, returning osmolality to normal but further expanding the extracellular volume. RAS activation and ADH release result in salt and water retention with the objective of restoring a perceived volume deficit, although the result is salt and water overload and sometimes hyponatraemia dilutional effect.

Atrial natriuretic peptide This is a polypeptide hormone consisting of 28 amino acids that is synthesized in myocardial cells by cleavage of a precursor pro-ANP. Volume regulation is an essential requirement to maintain perfusion of tissues.


Regulation of plasma hidroelectroliitco, which is determined primarily by the serum sodium concentration, is essential for the preservation of normal cell volume and function. Pressure natriuresis might explain why patients with excessive inappropriate aldosterone secretion primary hyperaldosteronism are not usually severely volume overloaded. After reading this article, you should be able to: These conditions can promote water retention at the cost of osmoregulation through the hypovolaemic stimulus to Hidroelectrolitici as discussed above.

Volume depletion results in aldosterone secretion, mediated by the RAS; angiotensin II promotes balancee and secretion of aldosterone in the adrenal zona glomerulosa. Actions of atrial natriuretic peptide The physiological role of ANP is not well understood. The responses to the perceived reduction in effective circulating volume tend to increase hidroelectrolitifo already expanded extracellular volume, exacerbating ascites and generating hyponatraemia through ADH Table 2.

A discrepancy between the calculated and measured osmolalities indicates the presence of a solute that is not routinely measured e.


The distal nephron regulates renal potassium excretion under the control of aldosterone. Sodium is, therefore, not an effective osmole with respect to the distribution of water between the interstitial and intravascular compartments, which is determined by different factors.

Volume receptors The major volume receptors can be divided into extra-renal and intra-renal groups. Experimental evidence indicates that ANP effects an increase in sodium and water excretion by increasing GFR and decreasing sodium absorption in both the proximal and distal nephron segments.

It is, therefore, appropriate that thirst tends to be satisfied quickly by consumption of water but recurs in bursts. Each of the compartments contains a principal solute, which is confined largely to that compartment and therefore acts as the main osmotic agent.