| 1. | proximal convoluted tubule and the afferent arteriole at the point of their contact. | 
| 2. | distal convoluted tubule and the afferent arteriole at the point of their contact. | 
| 3. | proximal convoluted tubule and the efferent arteriole at the point of their contact. | 
| 4. | distal convoluted tubule and the efferent arteriole at the point of their contact. | 
| 1. | NaCl and HCO3– | 2. | Urea and Uric acid | 
| 3. | NaCl and Urea | 4. | H+ ions and TMAO | 
| I: | makes the collecting duct completely impermeable to water. | 
| II: | causes vasoconstriction. | 
| 1. | An excessive loss of fluid from the body can activate the osmoreceptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. | 
| 2. | An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release. | 
| 3. | ADH can also affect the kidney function by its dilatory effects on blood vessels. | 
| 4. | An increase in blood pressure can increase the glomerular blood flow and thereby the GFR. | 
| I: | the two limbs of Henle’s loop. | 
| II: | the two limbs of vasa recta. | 
| III: | the Henle’s loop and vasa recta. |