Renal Regulation of Blood Osmolarity

The patient in “The Red Hat Hikers” scenario is suffering from hyponatremia. Hyponatremia is defined as a serum sodium level of less than 136mEq/L. Sodium is an electrolyte that is found predominately in the extracellular fluid, and it is the chief regulator of water in the body. Sodium is also important for muscle contraction, nerve impulses, acid-base balance and chemical reactions that occur inside the cell (McCance & Huether, 2014). Normal sodium levels in the body are maintained by the kidneys and the hormone aldosterone. Aldosterone is secreted by the adrenal cortex at the completion of the renin-angiotensin-aldosterone system, and it helps stimulate the proximal tubules of the kidneys to reabsorb sodium and water. The anti-diuretic hormone (ADH) also indirectly affects sodium levels because it regulates water balance in the body (McCance & Huether, 2014).

As the lab introduction explains, osmosis is relatively permeable to water and will follow solutes. By instinct, the water will move from a more diluted solution to more of a concentrated solution. The products of the experiments concluded the physiological significance of osmosis by how cell membranes in the body are semipermeable meaning that only certain molecules can pass through it. When intracellular fluid and extracellular fluid are at equilibrium by non-penetrating and concentrated solutes, no net movement of water goes in and out of the cell. Furthermore, if the ECF changes in osmolality, then depending on the difference between the ECF and ICF will determine whether water moves in or out of the cell. This is important in the cell membrane as small differences in osmolarity correspond to large, rapid change in osmotic pressure, causing cells to gain or lose water. In sum, our body makes critical decisions in what molecules are allowed to penetrate the cell membrane and make sure that our red blood cells don’t cause any problems within the

The purpose of the experiment was to help us better understand how water, Coke and Gatorade effected the renal system. The goal was to test and see if my hypothesis were correct regarding the urine specific gravity, urine flow rate, and presents of reagents using the Labstix. My hypothesis for this experiment was that the Gatorade drinkers will have the highest urine flow rate and that non-drinkers would have the highest urine specific gravity. Water is hypo-osmotic and coke contains a high amount of sugar making it hyperosmotic relative to plasma. Gatorade consists of large amounts of electrolytes making it iso-osmatic relative to the plasma. Based on these characteristics of the consumed substances, we are able to study the hormonal effects on the average UFR and USG.

A very carefully regulated process is solute concentration. If there is a sudden increase in water which enters the extracellular fluid, sodium ions will then contribute less to the extracellular solute concentration as the ratio between water and solute has now changed. Osmolality is the amount of solute in a kilogram, hence the osmolality in the extracellular space has also decreased.

If there is more NA it the ATPase will have trouble pumping correctly causing problems in the kidneys

Stimulus for their release = lowered blood pressure or low salt or water concentration in the blood will stimulate the release of ADH from the posterior pituitary.

& Donelly, R., 2010). As with DKA, at this stage the body attempts to normalize the osmolality through diuresis, which leads to dehydration, loss of electrolytes, and further hyperosmolality. With HHS evolving over days to weeks, (often either through poor medication compliance/inappropriate prescribing, dietary issues, or illness), the effect is insidious, and often by the time a patient presents to the emergency department either directly or via a GP, they are already critical (Kisiel, M. & Marsons, L., 2009).

One dialysis tube was submerged in each beaker. Osmosis was allowed to occur for 5 minutes and then all of the tubes were removed from the water. The tubes were dried off and measured on the triple beam scale. The mass was taken and recorded for all three tubes. I then placed the tubes back into their respective solutions. The process was repeated four times for each tube in 5 minute increments, and then the materials were disposed of. The rate of diffusion of water in each solution was

Course description: Principles and mechanisms of physiological regulation in animals, with a focus on humans.

Secondly, osmosis was to be observed to gain a proper understanding of how the principal of dialysis functions.

this, this urine that leaves the distal tubule is dilute. If the osmolality of the urine is

1997). The glands are composed of chief and oxyphil cells; both cells types contain PTH has a half-life from 4-10 minutes due to rapid degradation in the liver (Aron et al. 1997). Parathyroid hormone provides a powerful mechanism for controlling extracellular Ca and phosphate concentrations by regulating intestinal re-absorption, renal excretion, and exchange between the extracellular fluid and bone of these ions (Aron et al. 1997). Parathyroid hormone response to a decrease in blood Ca levels (Bhattacharya 2014). Serum Ca levels normally average 9.5mg/dL (Kierszenbaum 2007). When Ca intake or absorption is inadequate, PTH is secreted to avoid hypocalcemia by increasing the conversion of 25(OH)vitamin D into 1,25(OH)2vitamin D and intestinal absorption, increasing the renal tubular Ca reabsorption but also increasing bone resorption (Bagchi, Nair ,and Sen 2013). Parathyroid hormone has biphasic effects on bone formation by causing an acute inhibition of collagen synthesis with high concentrations, but, on the contrary, it increases bone formation with prolonged intermittent administration (Rissanen 2013). If the stimulus persists, secondary hyperparathyroidism will cause negative bone balance (Holick

Due to its hydrophilic nature, the hormone produces its effects by binding to a surface receptor on target cells, PTH1R, which is coupled to G protein, triggering the cAMP pathway. By doing that, PTH exerts rapid effects by stimulating calcium reabsorption in the kidneys, elevating resorption of skeletal hydroxyapatite by osteoclasts and indirectly increasing intestinal calcium uptake by promoting calcitriol synthesis in the kidneys by upregulating the activity of cytochrome P450 hydroxylases. Interestingly, it also stimulates osteoblasts to release RANKL molecules, which indirectly results in an increased osteoclastic bone resorption. Moreover, PTH secretion induces a higher excretion of phosphate ions in the urine, recruiting part of the calcium that is bound to anions in the blood.

There are important systems that are involved in the control for homeostatic of osmoregulation which occurs in a negative feedback control cycle. To prevent the loss or gain of water from the cell in the body, the water potential of the blood is regulated which is controlled by the hypothalamus. The hypothalamus in the brain is able to notice changes in the water potential through a type of neuron that is permanently present called osmoreceptors (- negative feedback ‘receptor’ for osmoregulation) that are capable of detecting water concentration/ water potential of blood as it passes through the hypothalamus through the osmoreceptors that they send out. The hypothalamus (- negative feedback ‘controller’ for osmoregulation) receives the message

If the solution contains only sucrose then the osmotic pressure will increase substantially. This would represent a hypotonic solution because more water molecules are entering the cell meaning the solution contains no invertase. If the osmotic pressure has a slight increase than the solution contains sucrose and invertase due to the rate of the sucrose being broken down, however the cell will overtime begin to shrink. If the osmotic pressure remains close to the same than the solution contains no sucrose, containing only water and invertase. We predicted that because the height of the fluid in the osmometer tubing was increasing only a little bit our blue solution was hypertonic and contained invertase and sucrose. The invertase was able to break down sucrose into glucose and fructose which were small enough to be able to leave the cell membrane. This would reflect a hypertonic solution. We predicted this would cause the cell to shrink in size and the height of the fluid would never increase.