Part 2 next page of this document, you will find the urinalyses from four patien
ID: 3476742 • Letter: P
Question
Part 2 next page of this document, you will find the urinalyses from four patients, along age, habits, etc.). or each individual, write a short essay (a few sentences) explaining the abnormalities and what disorder(s) might be occurring. It is perfectly fine if you are not able to determine exactly what is wrong: explaining multiple possible diagnoses is fine. Proper sentence structure, grammar, and spelling REQUIRED Part 3-10 points Answer the following short essay questions. Proper sentence structure, grammar, and spelling REQUIRED. Place full references at the end of this section. (In-text citations are not required.) 1. Describe the stimuli that cause an increase in the release of aldosterone from the adrenal cortex. Where are the target cells for aldosterone located (be specific!)? How does aldosterone exert its effects on these cells (once bound to these cells, what does it cause them to do)? How does aldosterone influence the movement of Na+ and K+ between the filtrate and the peritubular capillaries? 2. Describe the stimuli that cause an increase in the release of anti-diuretic hormone (ADH) from the posterior pituitary gland. Where are the target cells for ADH located (be specific!)? How does ADH exert its effects on these cells (once bound to these cells, what does it cause them to do)? How does ADH influence the movement of water between the filtrate and the peritubular capillaries?Explanation / Answer
Please find your answer below:
Ans 1:Aldosterone:
Aldosterone is a hormone produced in the outer section (cortex) of the adrenal glands, which sit above the kidneys. It plays a central role in the regulation of blood pressure mainly by acting on organs such as the kidney and the colon to increase the amount of salt (sodium) reabsorbed into the bloodstream and the amount of another salt called potassium removed in the urine. Aldosterone also causes water to be reabsorbed along with sodium; this increases blood volume and therefore blood pressure. Thus, aldosterone indirectly regulates blood levels of electrolytes (sodium, potassium and hydrogen) and helps to maintain the blood pH
Aldosterone is part of a group of linked hormones, which form the renin–angiotensin–aldosterone system. Activation of this system occurs when there is decrease in blood flow to the kidneys following loss of blood volume or a drop in blood pressure (e.g. due to a haemorrhage) or decrease in plasma sodium concentration. Renin is an enzyme that leads to a series of chemical reactions resulting in the production of angiotensin II, which in turn stimulate aldosterone release. Aldosterone causes an increase in salt and water reabsorption into the bloodstream from the kidney thereby increasing the blood volume, restoring salt levels and blood pressure. Once salt levels and blood pressure are corrected and the body becomes rehydrated, the level of renin in the bloodstream falls and therefore the amount of aldosterone in the blood also falls, meaning more water is excreted in the urine. The renin-angiotensin-aldosterone system is an example of a negative feedback system.
The other two main regulators of aldosterone secretion are increase in the plasma potassium concentration and adrenocorticotropic hormone (ACTH) secreted by the anterior pituitary, which can act via either positive or negative feedback mechanisms, depending on the extent of changes in the levels of these two regulators.
In a healthy individual, the renin-angiotensin-aldosterone system functions without interference, helping to regulate and control blood pressure levels naturally. However, individuals can have too-high or too-low amounts of aldosterone, and both of these can impact aldosterone function.
Individuals with high levels of aldosterone have a condition known as hyperaldosteronism, and this is typically caused by small, benign tumors on the adrenal glands. Hyperaldosteronism can cause high blood pressure, low potassium levels and an abnormal increase in blood volume because of the way the hormone affects the body.
It's also possible to have low levels of aldosterone. Primary adrenal insufficiency, a disease that causes a general loss of adrenal function, can be a cause. Patients with primary adrenal insufficiency causing low levels of aldosterone may experience low blood pressure, increased potassium levels, and lethargy.
Genetic mutations can also affect the production of aldosterone. Patients with this rare genetic disorder will experience symptoms similar to primary adrenal insufficiency but the symptoms are typically less severe.
counter-current mechanism
Because the human body does not maintain a constant water volume, the kidneys have to compensate for the lack of or excess of water consumed. The kidneys use a transport system called the counter-current mechanism to accomplish this (Hoppensteadt et al, 186). The name is based on the fact that concentration first increases in the direction of flow, then decreases as flow continues through the ascending parallel loop. The mechanism relies on the adjacent, parallel loops of Henle and vasa recta.
In the ascending loop, Na+ (or any solute) is actively pumped out of the tubule. As flow continues up the loop, the tubular concentration decreases as does the interstitial (the fluid surrounding the loop) concentration. Because water is impermeable in the ascending loop, the volume at the bottom of the loop is the same as that entering the distal tubule. At the bottom of the loop, the tubular and interstitial concentrations are equal.
In the descending loop, the concentrations inside and outside the tubule are increasing with the current, with the maximum concentration being reached at the bottom of the loop. The increased concentration is the result of the passive diffusion of Na+ into the tubule and water out of the tubule. When the filtrate reaches the distal tubule, a net loss of Na+ and water has occurred through the loops of Henle.
Inside the distal and collecting tubules, the filtrate is either diluted or concentrated to form urine. The regulating hormone for this process is ADH (antidiuretic hormone) and is excreted by the pituitary gland. The absence of ADH makes the membranes of the distal and collecting tubules impermeable to water. In this case, a larger volume of dilute urine is secreted. With ADH, water passively diffuses out of the tubules and a smaller volume of more concentrated urine results.
The maximum urine concentration is limited by the interstitial fluid concentration at the bottom of the loops of Henle. The urine leaving the collecting tubule has the same concentration as the interstitial fluid at that point. The interstitial concentrations are largely a function of blood flow in the three regions. In the cortex, the lower concentrations are the result of the large blood flow in the peritubular capillaries. The capillary blood carries away excess solute and water in the region. In the medulla, the only blood flow is in the vasa recta, approximately 10% of the cortical blood flow. The loop structure of the vasa recta keeps the entering and exiting concentration the same. While solute is absorbed in the descending loop, an equal amount of solute is secreted in the ascending loop.
Ans 2:ADH(Anti diuretic hormone):
ADH is also called arginine vasopressin. It’s a hormone made by the hypothalamus in the brain and stored in the posterior pituitary gland. It tells your kidneys how much water to conserve.
ADH constantly regulates and balances the amount of water in your blood. Higher water concentration increases the volume and pressure of your blood. Osmotic sensors and baroreceptors work with ADH to maintain water metabolism.
Osmotic sensors in the hypothalamus react to the concentration of particles in your blood. These particles include molecules of sodium, potassium, chloride, and carbon dioxide. When particle concentration isn’t balanced, or blood pressure is too low, these sensors and baroreceptors tell your kidneys to store or release water to maintain a healthy range of these substances. They also regulate your body’s sense of thirst.
This hormone is secreted by the posterior pituitary (PP) as indicated by the solid-headed dashed arrow. ADH affects the principal cells by increasing their permeability to water as indicated by the thick broken walls of the late distal convoluted tubule and the collecting duct. This permits the reabsorption of water (block arrow) into the vasa recta. The secretion of this hormone is controlled by two mechanisms.
Angiotensin II
Renin (R) is released when blood pressure is low. As a result angiotensin II (A2) is formed as discussed above. This hormone stimulates the release of ADH as indicated by the solid-headed dashed arrow.
Central Nervous System
When the osmotic pressure (OP) of the blood is high the central nervous system will stimulate (solid arrow) the posterior pituitary (PP) to release ADH. The blunt headed line represents this neural connection. The effect will be to increase water reabsorption thus reducing blood osmotic pressure.
High blood pressure (BP) will inhibit (dashed arrow) the central nervous system from signaling the posterior pituitary to release ADH. The effect will be to reduce water reabsorption, reduce blood volume and reduce blood pressure.
ADH and Water Reabsorption
The body uses antidiuretic hormone to retain water and increase blood pressure. As the main organ responsible for water retention in the body, the kidney is directly affected by antidiuretic hormone. The kidney is made of millions of units called nephrons. Nephrons filter blood through a series of tubules, which absorb water, salt and other things needed by the body.
Antidiuretic hormone binds to receptors on the surface of cells in the collecting duct of the nephrons. The hormone causes an increase of water channel proteins, called aquaporins, in the membrane of the cells in the kidney tubules.
Aquaporins are like doors in a nightclub; they let water in and out of the cell. When the doors open, people enter and leave, but because the nightclub is empty, more people go in, rather than out. Similarly, when there is more water inside the nephron than in the blood, when the gates open, water flows in the blood. This causes the body to hold more water and increases the volume of blood, which in turn, increases blood pressure.
Sodium and Water Reabsorption
Antidiuretic hormone also increases sodium reabsorption in a different part of the nephron in the kidney. If sodium is reabsorbed early on in the nephron, the blood concentration of sodium increases. In a process called osmosis, water flows from where there is more water to where there is less water. If there is more water, there must be less solute, the substance dissolved in water. Therefore, water flows from where there is less solute, to where there is more solute. Below, you'll see what happens when you add another type of solute, or glucose, to water.