D313 Section 4 - Urinary Formation and Regulation

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D313

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Jan 9, 2024

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D313: Anatomy and Physiology II with Lab, Lab Questions Section 4 – Urinary Formation and Regulation These are the questions for the labs from the course material. Please answer the questions, but also for each answer choice, explain why the choice is correct or incorrect. For example, if the answer is B, please explain why B is correct and why choices A, C, and D, etc., are incorrect, for each question. Also, for the images, label all parts of the image, if they are unlabeled. For the matching questions, explain all choices, even if they were not used to answer one of the questions. This will give you extra practice with the material, which will help with synthesis and retention. 23. Which part of the nephron absorbs most of the glucose and amino acids present in the filtrate? a. Collecting duct The collecting duct is responsible for the final concentration of urine by reabsorbing water and allowing for the excretion of waste products. It does not play a significant role in reabsorbing glucose and amino acids. b. Distal convoluted tubule The distal convoluted tubule (DCT) is involved in further fine-tuning of the reabsorption and secretion processes in the nephron. While some substances are reabsorbed in the DCT, the majority of glucose and amino acid reabsorption occurs in the proximal convoluted tubule. c. Proximal convoluted tubule The proximal convoluted tubule is the initial part of the renal tubule and is primarily responsible for the bulk reabsorption of substances like glucose, amino acids, sodium, and water. About 65-70% of the filtered glucose and most of the amino acids are reabsorbed in the PCT and returned to the bloodstream. d. Ascending loop of Henle The ascending loop of Henle is a segment of the nephron that plays a critical role in reabsorbing sodium and other ions, but it is not involved in the reabsorption of glucose and amino acids. 24. How much water is reabsorbed by the proximal convoluted tubule? a. 10-20% More than 10-20% of the water is reabsorbed by the proximal convoluted tubule.

b. 30-40% This underestimates the amount of water reabsorbed by the proximal tubule. c. 60-70% About 65-70% of the water filtered is reabsorbed by the proximal convoluted tubule. d. 80-90% This overestimates the water reabsorption by the proximal tubule. 25. What is the major role of the distal convoluted tubule? e. Acid-base balancing of the urine A major role of the distal convoluted tubule is adjusting the pH of the urine through secreting or absorbing acid/base equivalents. f. Addition of water The distal tubule does not add water to the filtrate, it fine tunes water reabsorption started in the proximal tubule. g. Removal of glucose Glucose is reabsorbed in the proximal tubule, not the distal tubule. h. Removal of amino acids Amino acids are largely absorbed in the proximal tubule as well. 26. Which component of the urinary system is responsible for the excretion of potassium ions? i. Renal capillaries The renal capillaries, including the peritubular capillaries, do not play a major role in excreting potassium ions. j. Renal hilum The renal hilum is where structures enter and exit the kidney, but is not directly involved in excreting potassium. k. Renal corpuscles The renal corpuscles contain the glomeruli which filter the blood, but do not excrete potassium. l. Renal tubules The renal tubules, especially the distal convoluted tubules and collecting ducts, are responsible for secreting potassium ions into the urine for excretion. 27. What is the function of the glomerulus? m. It is the microfiltration unit of the kidney. The glomerulus contains a network of capillaries that filters the blood to remove wastes and form urine. It is the site of filtration in the nephron. n. It returns water to the body. The glomerulus filters out water that will become urine. It does not return or reabsorb water. o. It is the initial location of filtration. While the glomerulus is where filtration starts, the full statement in a) more accurately describes its role as the microfiltration unit.

p. It collects urine as the urine is produced. The collecting duct collects urine, the glomerulus filters blood and produces filtrate . 28. Which substance is returned by the kidneys to the blood during reabsorption? a. Uric acid Uric acid is a waste product generated from the breakdown of purines in the body. It is filtered by the kidneys and eliminated in the urine as part of the body's waste removal process. Uric acid is not typically reabsorbed back into the bloodstream. b. Glucose Glucose is an essential molecule and a primary source of energy for the body's cells. During the process of glomerular filtration in the kidneys, glucose is filtered from the blood into the nephrons (the functional units of the kidneys). However, in healthy individuals, almost all of the filtered glucose is reabsorbed back into the bloodstream during tubular reabsorption. This is to prevent the loss of valuable glucose in the urine and maintain blood glucose levels within a normal range. c. Creatinine Creatinine is a waste product produced from the metabolism of creatine in the muscles. It is also filtered by the kidneys and excreted in the urine. Similar to uric acid, creatinine is not reabsorbed back into the bloodstream. d. Urea Urea is a waste product resulting from the breakdown of proteins in the liver. It is also filtered by the kidneys and excreted in the urine as part of the body's waste elimination process. Like uric acid and creatinine, urea is not reabsorbed back into the bloodstream during the process of kidney filtration and reabsorption. 29. Production of urine to modify plasma makeup is the result of ________. q. filtration, absorption, and secretion Filtration at the glomerulus, reabsorption of valuable substances, and secretion of additional wastes work together to form urine. r. absorption and secretion Filtration is needed first to produce the filtrate that is then modified. s. filtration and absorption Secretion of wastes is also crucial, not just filtration and absorption.

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t. secretion and filtration Reabsorption of needed substances is also vital to the process. For questions 30-35, put the steps of micturition in sequential order. 30. What is the first step of micturition? u. Activation of pontine centers this occurs after the bladder begins filling. v. Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. w. Contraction of the detrusor muscle contraction occurs later to empty the bladder. x. Filling of bladder The bladder filling with urine is the first step. y. Motor innervation motor signals to the bladder occur after filling. z. Relaxation of urinary sphincters the sphincters relax later in the process. 31. What is the second step of micturition? aa. Activation of pontine centers this occurs after the bladder begins filling. bb. Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. cc.Contraction of the detrusor muscle contraction occurs later to empty the bladder. dd. Filling of bladder The bladder filling with urine is the first step. ee. Motor innervation motor signals to the bladder occur after filling. ff. Relaxation of urinary sphincters the sphincters relax later in the process. 32. Then, what is the third step of micturition?

gg. Activation of pontine centers this occurs after the bladder begins filling. hh. Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. ii. Contraction of the detrusor muscle contraction occurs later to empty the bladder. jj. Filling of bladder The bladder filling with urine is the first step. kk.Motor innervation motor signals to the bladder occur after filling. ll. Relaxation of urinary sphincters the sphincters relax later in the process. 33. Then, what is the fourth step of micturition? mm. Activation of pontine centers this occurs after the bladder begins filling. nn. Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. oo. Contraction of the detrusor muscle contraction occurs later to empty the bladder. pp. Filling of bladder The bladder filling with urine is the first step. qq. Motor innervation motor signals to the bladder occur after filling. rr. Relaxation of urinary sphincters the sphincters relax later in the process. 34. Then, what is the fifth step of micturition? ss.Activation of pontine centers this occurs after the bladder begins filling. tt. Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. uu. Contraction of the detrusor muscle contraction occurs later to empty the bladder. vv.Filling of bladder The bladder filling with urine is the first step. ww. Motor innervation motor signals to the bladder occur after filling. xx. Relaxation of urinary sphincters the sphincters relax later in the process.

35. What is the last step of micturition? yy.Activation of pontine centers this occurs after the bladder begins filling. zz.Activation of stretch receptors the stretch receptors are activated by the filling of the bladder. aaa. Contraction of the detrusor muscle contraction occurs later to empty the bladder. bbb. Filling of bladder The bladder filling with urine is the first step. ccc. Motor innervation motor signals to the bladder occur after filling. ddd. Relaxation of urinary sphincters the sphincters relax later in the process. 36. Which hormone directly opposes the actions of natriuretic hormones? eee. Angiotensin II Angiotensin II promotes sodium retention, opposing natriuretic hormones like ANP that promote sodium excretion. fff. Nitric oxide Nitric oxide has natriuretic effects similar to ANP. ggg. Dopamine Dopamine inhibits sodium reabsorption, acting as a natriuretic. hhh. Melatonin. Melatonin does not directly affect sodium balance. 37. Renin is released in response to ________. iii. ACE ACE (angiotensin converting enzyme) converts angiotensin I to angiotensin II. It does not directly regulate renin release. jjj. increased blood pressure Increased blood pressure inhibits further renin release through a negative feedback mechanism. kkk. diuretics Diuretics reduce blood volume and pressure, which stimulates renin release.

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lll. decreased blood pressure Decreased blood pressure, detected by the juxtaglomerular cells, triggers the release of renin as part of the renin-angiotensin system. 38. If there were no aquaporin channels in the collecting duct, ________. mmm. a person would retain excess Na+ Sodium reabsorption occurs mainly in the proximal tubule, not the collecting duct. Lack of aquaporins would not directly cause sodium retention. nnn. a person would develop systemic edema Aquaporins in the collecting duct allow for water reabsorption from the filtrate back into the body. Without them, too much water would be excreted in urine, leading to dehydration and edema. ooo. a person would suffer severe dehydration Dehydration would not be the main consequence. Water loss would lead to edema, not just dehydration. ppp. a person would lose vitamins and electrolytes Electrolyte transport occurs before the collecting duct and would be unaffected. 39. Which hormone would be expected to increase with dehydration or low blood volume? qqq. Aldosterone Aldosterone increases sodium and water reabsorption, but is not directly impacted by low blood volume. rrr. ANH ANH decreases with low blood volume to promote sodium retention. sss. Erythropoietin Erythropoietin regulates red blood cell production and is not affected by dehydration. ttt. ADH ADH is released from the posterior pituitary in response to high blood osmolality or low blood volume/pressure to retain water. 40. How will urinary output change with an increase in renin secretion? uuu. Urinary output will decrease Increased renin secretion leads to decreased urinary output. Renin is secreted when blood pressure drops. It triggers a cascade leading to

angiotensin II production and aldosterone release. Angiotensin II causes vasoconstriction while aldosterone increases sodium and water reabsorption in the kidneys. This results in increased blood pressure and volume due to the retention of more fluid. Therefore, urinary output decreases. vvv. Urinary output will increase increased renin causes less urinary output, not more. It activates mechanisms to retain water in the body. www. Urinary output will not change Renin secretion has a clear effect of reducing urinary output through angiotensin II and aldosterone effects on the kidney. 41. How does an increase in renin secretion change urine concentration? xxx. Renin has no effect on urine concentration. Renin affects urine concentration by stimulating aldosterone release. yyy. Renin will stimulate release of aldosterone and urine will be diluted. Aldosterone causes concentration, not dilution, of the urine. zzz. Renin will stimulate release of ADH and urine will be diluted. Renin does not directly affect ADH, and ADH acts to concentrate urine. aaaa. Renin will stimulate release of aldosterone and urine will be concentrated. Renin triggers the RAAS system leading to aldosterone release, which increases sodium and water reabsorption, concentrating the urine. 42. Which hormone stimulates release of angiotensinogen? bbbb. Aldosterone Aldosterone is released later in the renin- angiotensin system cascade and stimulates sodium reabsorption. It does not affect angiotensinogen. cccc. Renin Renin is secreted by the juxtaglomerular cells of the kidney when blood pressure or volume decreases. It acts on angiotensinogen to initiate the renin-angiotensin system.

dddd. ADH Antidiuretic hormone regulates water balance in the body by controlling water reabsorption in the kidneys. It does not stimulate angiotensinogen release. eeee. CRH Corticotropin releasing hormone controls cortisol release but not components of the renin-angiotensin system. 43. How does aldosterone release increase blood pressure? ffff. By water reabsorption from the filtrate in the distal convoluted tubule Aldosterone directly acts on sodium reabsorption, not water. gggg. By water secretion from the filtrate in the distal convoluted tubule Aldosterone does not cause water secretion. hhhh. By sodium secretion from the filtrate in the distal convoluted tubule and retaining water Aldosterone stimulates sodium reabsorption, not secretion. iiii. By sodium reabsorption from the filtrate in the distal convoluted tubule and retaining water Aldosterone increases blood pressure by promoting sodium reabsorption, which results in increased blood volume and pressure. Scenario for questions 44-48 : David visited a bakery and purchased two cupcakes and lemonade. They looked so enticing David decided to eat them right away. Use the following image to answer the questions how the nephron in the kidney filters the glucose in David's blood to regulate the blood sugar levels.

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44. Where is the first filtrate formed? And what process takes place? jjjj. Distal convoluted tubule, secrets water and solutes, like glucose in the drink The distal convoluted tubule does not form the initial filtrate. It fine tunes the composition of the filtrate. kkkk. PCT, reabsorbs and only solutes in the drink The PCT reabsorbs both water and solutes like glucose. llll. Distal convoluted tubule, reabsorbs and solutes, but it secrets water The DCT is not the site of initial filtration. mmmm. PCT, reabsorbs water and solutes, like glucose in the drink The first filtrate is formed at the glomerulus. The PCT then reabsorbs water, glucose and other solutes. 45. Where does filtrate drain into after PCT? What changes would be expected to happen to the filtrate? nnnn. Ascending loop of Henle; water and solutes will be reabsorbed, and urine will be diluted The ascending loop actively reabsorbs solutes but not much water. oooo. Descending loop of Henle; water will be reabsorbed, and filtrate will be concentrated As filtrate enters the descending

loop, water is reabsorbed due to the high osmolarity of the medulla. This concentrates the filtrate. pppp. Ascending loop of Henle; water will be reabsorbed, and urine will be diluted The ascending loop does not reabsorb much water. qqqq. Descending loop of Henle; water will be secreted, and filtrate will be concentrated Water is reabsorbed, not secreted in the descending loop. 46. Next, filtrate will drain into the ___________; this section is _______ to water. rrrr. descending loop of Henle, permeable The descending loop is permeable to water, allowing reabsorption. ssss. descending loop of Henle, impermeable The descending loop is permeable to water. tttt. ascending loop of Henle, permeable The ascending loop is impermeable to water. uuuu. ascending loop of Henle, impermeable After descending, the filtrate enters the ascending loop which is impermeable to water, allowing the filtrate to remain concentrated. 47. From the loop of Henle, filtrate drains into the ___________ , which can reabsorb ______ if ______ is present. vvvv. distal convoluted tubule, sodium, ADH The DCT does not reabsorb sodium in response to ADH. wwww. distal convoluted tubule, water, ADH The DCT can reabsorb water in the presence of ADH by inserting aquaporin channels. xxxx. distal convoluted tubule, water, aldosterone Aldosterone does not affect water reabsorption in the DCT. yyyy. distal convoluted tubule, sodium, aldosterone Sodium reabsorption occurs earlier in the nephron. 48. The last part of the nephron is the _______, where it can reabsorb water with the help of the _________channel and ______ hormone.

zzzz. collecting duct, aquaporin, aldosterone Aldosterone does not affect water reabsorption in the collecting duct. aaaaa. collecting duct, sodium, ADH The collecting duct reabsorbs water, not sodium, in response to ADH. bbbbb. collecting duct, aquaporin, ADH ADH allows the collecting duct to reabsorb water by inserting aquaporin channels. ccccc. collecting duct, sodium, aldosterone Sodium reabsorption occurs earlier in the nephron. Scenario for questions 49-51 : Aaron is training to prepare for his first marathon (26.2 mile) run. On the morning of the marathonb, Aaron only drank 1 cup of water before the race started. After 1 hour, Aaron felt dizzy and thirsty and wondered why there was no urge to urinate. Aaron ate a sports gel, drank a few sips of water, and continued running. Aaron repeated the process of taking a sports gel and drinking a few sips of water every every hour until the finish line. When Aaron stopped, his leg muscles were sore, and when Aaron used the bathroom, there was very little urine output and there was a pink tint to the urine. 49. Why was Aaron's urine output low at the end of the marathon? a. Because he had minimal food intake, aldosterone reabsorbed more water from filtrate and decreased the urine output. Aldosterone responds to low blood volume, not low food intake. ADH regulates water reabsorption. b. Because the bladder consists of smooth muscle and stretches to hold more volume. This does not explain the low urine output, just bladder capacity. c. Because he did not intake enough fluids, ADH reabsorbed more water from filtrate and decreased the urine output. Inadequate fluid intake increased ADH to conserve water, decreasing urine volume. 50. Why was Aaron’s urine pink? Is that something to be concerned with?

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d. It is due to hemoglobin breakdown. Aaron needs to continue drinking water to wash out the broken myoglobin. The pink color is from myoglobin in muscles, not hemoglobin. e. It is due to myocyte breakdown. Aaron can just rest, and it will disappear. Drinking water is recommended to clear myoglobin. f. It is due to myoglobin breakdown. Aaron needs to continue drinking water to wash out the broken myoglobin. Myoglobin from muscle breakdown causes the color and hydration helps clear it. g. It is due to myocyte breakdown. But it is concerning, and he needs to be hospitalized. Hospitalization is not necessary if he stays hydrated. 51. Would Aaron’s urine output and concentration change if he continues drinking water after exercising? How and why? h. Yes. His urine will turn more clear color. As fluids are replaced the ADH release will decrease, and extra fluid will be filtered out. Hydration inhibits ADH, leading to less water reabsorption and dilute urine. i. No. His urine color and concentration will not change, because the body needs fluid. With hydration, urine concentration will decrease as less water is reabsorbed. j. No. His urine color and concentration will not change, because ADH or aldosterone do not have any role in urinary output. ADH has a major role in regulating urinary concentration. k. Yes. His urine will turn to a light or clear color because aldosterone will reabsorb more salt and his filtrate will be diluted . Aldosterone does not directly affect urine dilution.

D313 Section 4 - Urinary Formation and Regulation

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