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Renal System : Explain how Antidiuretic hormone (ADH) regulates the formation of

concentrated or dilute urine. Identify how an individual with Diabetes Insipidus may have altered urinary output/fluid balance? *Not Diabetes Mellitus* Introduction The renal system comprises of the kidneys, ureters, bladder and urethra, working together to withdraw nitrogenic waste from the body, (Marieb, 2014). This ensures the body’s intake and output of fluid vital for homeostatic balance (Marieb, 2014). As well as fluid regulation the renal system also works with the nervous, cardiovascular and endocrine systems regulating the blood balance of water, electrolytes and acid – base (Marieb, 2014). When this homeostatic fluid balance is abnormal it can lead to excessive fluid loss and can cause severe dehydration and imbalances of electrolytes (Marieb, 2014). The drive for thirst will typically give adequate rehydration but when it is difficult to get water. (Levy, prentice, & Wass 2019). However, people with diabetes insipidus can quickly dehydrate and can lead to hyperosmolar conditions, hypernatremia, and even death (Levy et al, 2019). Diabetes insipidus is a condition that may either be nephrogenic, meaning that the antidiuretic hormone receptors of the kidneys do not react to the hormone, or they are central, meaning that the synthesis or transport of antidiuretic hormone to the kidneys through the bloodstream is problematic (Levy et al, 2019).

Discussion In order for the body to achieve homeostatic levels of water, electrolytes and blood acid base, the body signals the need to be replenished of water when the blood volume (pressure) lowers, it decreases the volume of blood filtrating through the kidneys, when there

is an increase of 2-3 percent in blood osmolarity (Marieb, 2014). Osmoreceptors which are concentration sensing cells within the hypothalamus become excited, sending nerve pulses to the posterior pituitary and the release of antidiuretic hormone into the blood, flowing towards the kidney to stimulate the collecting ducts to reabsorb more water until blood volume and pressure are back to homeostatic levels (Marieb, 2014).

When antidiuretic hormone is secreted by the hypothalamus and sent through central nerve fibres to the posterior pituitary lobe causing the hormone to release into the bloodstream intracellular fluids. Antidiuretic hormone travels to the target cells through the bloodstream, which is the kidney nephrons (Marieb, 2014). Once the antidiuretic hormone has found the kidneys, the collecting duct and the distal convoluted nephron tubes increases the permeability, thus reabsorbing more water active in the capillaries than excreting as urine (Joyce & Newton, 2015). This reduces the urine output and dilutes the blood, which reduces the osmolality of the blood and normalizes. As osmolality of the blood decreases, these are detected by osmoreceptors and the antidiuretic hormone secret from the posterior pituitary lobe decreases (Molnar, Gair, Fowler & Roush, 2013). Diabetes insipidus is due to a vasopressin production problem in the posterior pituitary gland (central diabetes insipidus), or of vasopressin action in the kidneys (nephrogenic insipidus diabetes) (Levy et al, 2019). Central diabetes insipidus is usually the result of pituitary pathology either because of infiltration or inflammatory disease or after pituitary surgery, but also because of a congenital defect in the production of arginine vasopressin (Levy et al, 2019). Insipid nephrogenic diabetes usually results from electrolyte disturbance, kidney disease or drug - induced toxicity (Levy et al, 2019). If the posterior pituitary gland releases insufficient amounts of antidiuretic hormone, the reabsorption of water by the kidneys cannot occur and will result in excretion as urine (Molnar, Gair, Fowler & Roush, 2013). Excessive urination also known as

polyuria and high osmolality increases thirst (polydipsia), loss of water is not replenished by drinking and fluids are then again lost, this can cause an imbalance to homeostasis and a high threat to the body this can have diverse effects which include dehydration, hyperosmolar conditions, hypernatremia, and even death (Levy et al, 2019). Below is a concept map that shows how antidiuretic hormone works in the kidneys normally to maintain homeostasis and the abnormal effects diabetes insipidus has on the human body.

Joyce, A. P., & Newton, T. J. (2015). Human Perspectives Units 3 & 4 ATAR. (7th ed.) 2697. Victoria: Nelson Cengage Learning. Levy, M., Prentice, M., Wass, J. (2019). Diabetes insipidus. The BMJ, 364. doi: 10.1136/bmj.l321 Marieb, E. N. (2014). Essentials of Human Anatomy & Physiology, Global Edition (Vol. 11th ed). Harlow: Pearson. Retrieved from http://search.ebscohost.com.ezproxy.ecu.edu.au/login.aspx? direct=true&db=nlebk&AN=1419516&site=ehost-live&scope=site Molnar, C., Gair, J., Fowler, S., & Roush, R. (2013). Concepts of Biology: Regulation of body processes (1st ed.)...