Lab Report Exercise 9: Renal System Physiology Activity 6: The Eﬀect of Hormones on Urine Formation Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1 Which of the following has a role in altering the urine volume and concentration? You correctly answered: all of these. 2 The total solute concentration surrounding the tubule lumen refers to the solutes in You correctly answered: the interstitial space. 3 Aldosterone is produced in the You correctly answered: adrenal cortex. 4 ADH promotes the renal reabsorption of You correctly answered: water. 5 Aldosterone promotes renal reabsorption of __________ and secretion of __________. You correctly answered: NaCl, potassium. Experiment Results Predict Questions 1 Predict Question 1: What will happen to the urine volume (compared with baseline) when aldosterone is added to the distal tubule? Your answer: The urine volume will decrease. 2 Predict Question 2: What will happen to the urine volume (compared with baseline) when ADH is added to the collecting duct? Your answer: The urine volume will decrease. 3 Predict Question 3: What will happen to the urine volume and the urine concentration (compared with baseline) in the presence of both aldosterone and ADH? Your answer: The urine volume will decrease and the urine concentration will increase. Stop & Think Questions 1 Why is the concentration in the urinary bladder 100 mOsm? You correctly answered: No ADH has been added to this nephron. 2 In the presence of aldosterone, what component of the tubule ﬂuid moves out of the distal tubule and into the interstitial space? You correctly answered: NaCl. 3 In the presence of ADH, why did the urinary potassium concentration increase? You correctly answered: The water volume in the urinary bladder is decreased, increasing the concentration of solutes such as potassium. 4 In the presence of both ADH and aldosterone, why did the urinary potassium concentration increase? You correctly answered: There was more potassium secretion into the distal tubule and more water reabsorption in the collecting duct. Experiment Data Potassium Conc. Urine Urine Conc. Conc. Grad. in Urine (mOsm) Volume (ml) (mOsm) (mOsm) Aldosterone ADH 6.25 201.00 100 1200 absent absent 10.42 180.90 100 1200 present absent 62.37 16.86 1200 1200 absent present 65.37 12.67 1200 1200 present present Post-lab Quiz Results You scored 100% by answering 4 out of 4 questions correctly. 1 If there has been a signiﬁcant loss of ﬂuid from the body, the kidneys will generate __________ urine. You correctly answered: hyperosmotic. 2 If you drink a large volume of water, the kidneys will generate __________ urine. You correctly answered: hypo-osmotic. 3 In response to dehydration, ADH will be released from the You correctly answered: posterior pituitary gland. 4 In response to abnormally low plasma osmolality, aldosterone will increase You correctly answered: sodium reabsorption along the distal tubule and the collecting duct. Review Sheet Results 1 How did the addition of aldosterone aﬀect urine volume (compared with baseline)? Can the reabsorption of solutes inﬂuence water reabsorption in the nephron? Explain. How well did the results compare with your prediction? Your answer: The addition of aldosterone aﬀected urine volume by causing a small increase in the potassium concentration and a small decrease in urine volume compared to baseline values. My prediction was correct. 2 How did the addition of ADH aﬀect urine volume (compared with baseline)? How well did the results compare with your prediction? Why did the addition of ADH also aﬀect the concentration of potassium in urine (compared with baseline)? Your answer: The addition of ADH resulted in a big decrease of urine volume compared to baseline values. My prediction was correct. 3 What is the principal determinant for the release of aldosterone from the adrenal cortex? Your answer: It is a decrease in blood pressure detected by the cells in the aﬀerent arteriole that trigger the release of angiotensin 2 by endothelial cells. 4 How did the addition of both aldosterone and ADH aﬀect urine volume (compared with baseline)? How well did the results compare with your prediction? Your answer: When both aldosterone and ADH were added the urine concentration increases and the urine volume decreased. My prediction was correct. 5 What is the principal determinant for the release of ADH from the posterior pituitary gland? Does ADH favor the formation of dilute or concentrated urine? Explain why. Your answer: Whenever there is a decrease in osmolarity the posterior pituitary gland releases ADH, ADH favors the formation of concentrated urine. 6 Which hormone (aldosterone or ADH) has the greater eﬀect on urine volume? Why? Your answer: ADH has a greater eﬀect on urine volumes because . This is because ADH increases the amount of water reabsorbed in the distal tubule, which decreases the urine volume. 7 If ADH is not available, can the urine concentration still vary? Explain your answer. Your answer: No it cannot. However urine volume can still vary without ADH. When only aldosterone is added the urine concentration stays the same as the baseline value. However when only ADH is added there is an increase of urine concentration. This shows that ADH mainly aﬀects urine concentrations. 8 Consider this situation: you want to reabsorb sodium ions but you do not want to increase the volume of the blood by reabsorbing large amounts of water from the ﬁltrate. Assuming that aldosterone and ADH are both present, how would you adjust the hormones to accomplish the task? Your answer: You would have to decrease the amount if ADH. ADH increases the ability to reabsorb water, which increases the volume of blood. An increases in aldosterone would also be needed. Aldosterone will absorb the sodium ions at a faster rate.