Micturition in humans is carried out by a reflex. Identify the correct statement regarding this reflex:

1. It is regulated at the level of lumbar spinal cord.

2. The internal urethral sphincter is composed of skeletal muscles.

3. Contraction of the detrusor muscle and relaxation of the external urethral sphincter leads to passage of urine from bladder to urethra.

4. The urge to urinate is a reflex involving the stimulation of specific autonomic nerves.

The net filtration pressure is the interaction of the hydrostatic and osmotic pressures, driving fluid out of the capillary and is:
1. about equal to the pulse pressure at 40 mmHg
2. favored by colloid osmotic pressure of the plasma
3. opposed by the hydrostatic pressure in afferent arteriole
4. estimated to be approximately 10 mmHg in human kidneys

Identify the incorrect statement regarding GFR:
1. The GFR averages approximately 180 L per day (about 125 ml/min).
2. The GFR increases during sympathetic stimulation due to the vasodilation of afferent arterioles.
3. A decrease in GFR results in a decrease in the total urine output.
4. Renal auto-regulation maintains the GFR at a relatively constant rate normally.

With respect to the countercurrent multiplier system when the human kidneys are producing a concentrated urine:
1. the descending limb of the loop of Henle produces a hypotonic filtrate
2. interaction between ascending and descending limb of loop of Henle is an example of negative feedback
3. salt becomes recirculated and trapped in the medullary tissue fluid, increasing "saltiness" as it accumulates toward the lower tip of the pyramids
4. water is retained in the medulla by the higher colloid osmotic pressure than that of the blood in the vasa recta capillaries

A result of secretion of ADH is that :
1. the walls of the collecting ducts become less permeable to urea and water
2. the water channels, or aquaporins, appear in the cell membranes of the collecting duct epithelial cells promoting the reabsorption of water from the filtrate
3. the ultrafiltrate flowing through the collecting duct becomes more hypotonic
4. a greater volume of dilute urine is excreted

A person with a high blood volume than normal would show:
1. increased renin secretion
2. increased aldosterone secretion
3. decreased ANP secretion
4. increased urinary ${\mathrm{Na}}^{+}$

Hyperkalemia can cause cardiac arrest. In response to hyperkalemia, the hormone secreted by human body and the site of its action are respectively:
1. aldosterone; distal tubule
2. aldosterone; proximal convoluted tubule
3. ADH; cortical collecting duct
4. ADH; proximal convoluted tubule

The renal cortex:
1. is in contact with the outer capsule
2. is divided into eight to fifteen conical renal pyramids
3. drains into the minor calyces
4. has long loop of Henle of juxtamedullay nephrons

The branch of renal artery that directly supplies the glomerulus is the:

Glomerular ultrafiltrate normally does not contain: