Why regulating body fluids is important

When sodium concentration in the blood decreases the adrenal cortex is stimulated into secreting the hormone aldosterone, which instructs the distal nephrons of the kidney to retain more sodium. Normal levels of sodium in the ECF will attract and maintain the optimum amount of water Tortora and Grabowski, ; Edwards, ADH release is also influenced in the following circumstances. Sensors detect stretching of the atria of the heart indicating excessive returning volume of ECF increased venous return.

They stop ADH secretion, which leads to increased excretion of water through renal filtration. The aorta and carotid arteries also have receptors that are sensitive to a reduction in blood pressure related to the pressure in the left ventricle. In addition to regulating total volume, the osmolarity of bodily fluids is closely monitored and regulated because variations may cause damage to cellular structure swelling or shrinking , disrupting normal cellular function Edwards, ; Metheny, Regulation of ECF osmolarity is achieved by balancing the intake and output of sodium with that of water.

If there is too much or too little of any of these electrolytes this can cause problems. For example, cardiac arrhythmias are triggered by low potassium and low magnesium levels Docherty, ; Smith, These figures may differ slightly according to local policies.

Which drinks count towards your fluid intake? Water: water is a great thirst quencher. Milk: milk is also a good source of calcium for strong bones and strong muscles. Flavoured milk: flavoured milk is a good source of calcium for strong bones and protein for strong muscles. Smoothies: smoothies can be a good way to get an extra serve of fruit or dairy into your day. Milk on cereal: cereal with milk is a great way to get extra fluid at breakfast time Jelly: if the older person has diabetes, a sugar-free or low-joule jelly may be a better choice.

Custard: custard is also a good option if a client has trouble chewing or swallowing food. Tea: caffeine has a mild diuretic effect but tea and coffee still count towards fluid intake. Coffee: making a milk coffee is a great way to get some extra protein and calcium. Juice: fruit juice can also count as a serve of fruit for the day.

This mechanism is controlled by aldosterone, a steroid hormone produced by the adrenal cortex. Aldosterone secretion is controlled two ways:. The adrenal cortex directly senses plasma osmolarity.

When the osmolarity increases above normal, aldosterone secretion is inhibited. The lack of aldosterone causes less sodium to be reabsorbed in the distal tubule. Remember that in this setting ADH secretion will increase to conserve water, thus complementing the effect of low aldosterone levels to decrease the osmolarity of bodily fluids. The net effect on urine excretion is a decrease in the amount of urine excreted, with an increase in the osmolarity of the urine.

The kidneys sense low blood pressure which results in lower filtration rates and lower flow through the tubule. This triggers a complex response to raise blood pressure and conserve volume. Specialized cells juxtaglomerular cells in the afferent and efferent arterioles produce renin , a peptide hormone that initiates a hormonal cascade that ultimately produces angiotensin II. Privacy Policy. Skip to main content.

Body Fluids and Acid-Base Balance. Search for:. Water Balance. Regulation of Water Intake Fluid can enter the body as preformed water, ingested food and drink, and, to a lesser extent, as metabolic water.

Learning Objectives Describe the regulation of water intake in the body. Key Takeaways Key Points A constant supply of water is needed to replenish the fluids lost through normal physiological activities, such as respiration, sweating, and urination. Thirst is a sensation created by the hypothalamus that drives organisms to ingest water.

Increased osmolarity in the blood acts on osmoreceptors that either stimulate the hypothalamus directly or cause the release of angiotensin II to stimulate the hypothalamus to cause thirst.

The renin —angiotensin system increases thirst as a way to increase blood volume. It is activated by high plasma osmolarity, low blood volume, low blood pressure, and stimulation of the sympathetic nervous system. Key Terms thirst : The sensation that drives organisms to ingest water. It is considered a basic survival instinct. Regulation of Water Output Fluid can leave the body in three ways: urination, excretion feces , and perspiration sweating.

Learning Objectives Describe the regulation of water output in humans. Key Takeaways Key Points The majority of fluid output occurs from urination. The hormones ADH antidiuretic hormone, also known as vasopressin and aldosterone play a major role in this. If the body is becoming fluid deficient, increased plasma osmolarity is sensed by the osmoreceptors.

This results in an increase in the secretion of ADH that causes fluid to be retained by the kidneys and urine output to be reduced. Aldosterone is the major end-product of the renin — angiotensin system, and increases the expression of ATPase pumps in the nephron that causes an increase in water reabsorption through sodium cotransport. Key Terms osmoreceptors : Sensory receptors, primarily found in the hypothalamus, that detect changes in plasma osmolarity and contribute to the fluid-balance regulation in the body.

Nitrogenous Waste in Terrestrial Animals: The Urea Cycle Urea, a nitrogenous waste material, is the end product excreted in urine when ammonia is metabolized by animals, such as mammals. Learning Objectives Discuss the urea cycle. Key Takeaways Key Points Ureotelic animals, which includes mammals, produce urea as the main nitrogenous waste material.

The urea cycle involves the multi-step conversion carried out by five different enzymes of the amino acid L- ornithine into different intermediates before being regenerated. Key Terms ureotelic : animals that secrete urea as the primary nitrogenous waste material ornithine : an amino acid, which acts as an intermediate in the biosynthesis of urea urea : a water-soluble organic compound, CO NH2 2, formed by the metabolism of proteins and excreted in the urine. Water Balance Disorders Dehydration is the excessive loss of body fluid.

Learning Objectives Describe disorders due to water balance problems. Key Takeaways Key Points There are three types of dehydration: hypotonic or hyponatremic, hypertonic or hypernatremic, and isotonic or isonatremic. Hypotonic dehydration is primarily a loss of electrolytes, sodium in particular.