Renal Week 1 Saq Questions Study Guide

RENAL WEEK 1 SAQ QUESTIONS STUDY GUIDE 1. List and explain FOUR reasons as to why it is important to regulate water volume and composition of the body fluids. (2 marks) Answer: • • • • Blood volume: maintains blood pressure and adequate organ perfusion. pH of body fluids: because it dilutes H+ ions. This helps ensure optimum conditions for enzyme functions. cell volume: prevent cell bursting and shrinkage. ions gradient across cell membrane: maintains equilibrium, water flow and thus blood pressure and prevents third spacing. 2. Answer the following questions about glomerular filtration: (5 marks) a. What type of molecules can usually be filtered under healthy physiological conditions (1 mark) b. In terms of filtration, what happens to negatively charge molecules such as amino acids? Explain. (1 marks) c. Explain the role of mesangial cells in filtration (1 mark) d. Explain how the following molecule sizes are treated in terms of filtration: i) MW between 7000 and 70000 (1mark) ii) MW more than 70000 (0.5 marks) iii) MW less than 7000 (0.5 marks) Answer: a. Electrolytes, water, small proteins that are less than 7000 that are also not negatively charged, nutrients and wastes. b. Because the podocytes are negatively charged just like negatively charged proteins, this will cause these negatively charged proteins to be repelled, as like charges repel each other. This prevents the loss of proteins in urea. c. One of the functions of mesangial cells is contractile function, which causes vasoconstriction of the afferent arteriole. This controls the amount of blood that enters the arteriole and this the amount of blood that goes to the glomerulus as is filtered. Since it causes vasoconstriction, it decreases blood flow through the afferent arteriole and thus also reducing GFR. d. What happens i) Selectively filtered depending on size and charge ii) Not filtered iii) Filtered 3. Arteriolar resistance can limit blood flow to the kidney. a. Write the formulate for arteriolar resistance and explain the concepts behind it. (2.5 marks) b. List FIVE factors that affect renal blood flow. (2.5 marks) 4. Explain the renal sympathetic nerve activity (2 marks) Answer: • • • The release of epinephrine and norepinephrine bind on beta 1 receptor on pacemaker cells and myocardium increase the heart rate and contractility respectively. This in turn increases renal blood flow to the kidney. The above mentioned above neurotransmitters also bind on alpha 1 receptor in blood vessels which cause vasoconstriction and thus divert blood away from the kidney to more important places. The above-mentioned neurotransmitters also bind on beta-1 receptors on JG cells causing them to increase renin release which activated RAAS. This will cause increased body volume and hence increase blood pressure. 5. Explain the difference between systemic tubuloglomerular feedback in response to high blood pressure and low blood pressure. (4 marks) Answer: • - • - High blood pressure Increased blood flow through afferent arteriole and then increase GFR. This will mean that more NaCl will be filtered through the glomerulus. High levels of NaCl reach the distal convoluted tubule and hence more reach the macula densa cells. The macula densa cells release adenosine, which will cause vasoconstriction of the afferent arteriole, and decrease blood flow to the glomerulus and thus decrease NaCl being filtered. These also inhibit JG cells causing them to release very little of any renin. Low blood pressure Decreased blood flow through the afferent arteriole and this decreased GFR. Less NaCl filtered through the glomerulus. Less NaCl reaches the distal tubule and hence the macula densa. This will cause it release of NO and PGE2 causing the afferent arteriole to vasodilate and stimulate the JG cells to make more renin. This will increase renal blood flow to the kidney and increase GFR.