32
(c) Pyelonephritis (d) Nephritis
- a 2. a 3. a 4. a 5. c
- b 7. d 8. c 9. a 10. a
- d 12. b 13. a 14. d 15. a
- d 17. a
- (a) Aldosterone is a hormone that causes
the tubules of the kidneys to retain sodium
and water. Aldosterone is a steroid hormone
(mineralocorticoid family). It acts on the
distal tubules and collecting ducts of the
kidney to cause the conservation of sodium,
secretion of potassium, increased water
retention and increased blood pressure. The
overall effect of aldosterone is to increase
reabsorption of ions and water in the kidney.
Antidiuretic hormone (ADH), is a
neurohypophysial hormone found in most
mammals. Its two primary functions are to
retain water in the body and to constrict blood
vessels. Vasopressin regulates the body’s
retention of water by increasing water
reabsorption in the collecting ducts of the
kidney nephron.
- (a) ADH (antidiuretic hormone)
Increases the reabsorption of water from the
urine in the renal system back into the blood.
This increases intravascular fluid volume
and decreases the amount of urine voided
out of the body. Thus ADH conserves water
in the kidneys and returns that fluid back to
the general circulation. This conservation of
urine acts to increase blood pressure because
total intravascular fluid volume is increased.
- (a) refer explanation no. 36
- (a) When systemic hypotension, or low
blood pressure throughout the body, occurs,
receptors in your blood vessels called
baroreceptors sense this change. Cells of
the kidney’s juxtaglomerular apparatus get
involved as well. Detection by one or both
of these mechanisms leads juxtaglomerular
cells in the kidneys to release an enzyme
called renin. Renin is an enzyme released
by the juxtaglomerular cells of the kidneys
in response to low blood pressure, causing
the transformation of angiotensinogen to
angiotensin I.
- (c) Micturition, or urination, is the act of
emptying the bladder. When the bladder is
full of urine, stretch receptors in the bladder
wall trigger the micturition reflex. The
detrusor muscle that surrounds the bladder
contracts. The internal urethral sphincter
relaxes, allowing for urine to pass out of
the bladder into the urethra. Both of these
reactions are involuntary. The external
urethral sphincter is voluntary. It must be
relaxed for urine to flow through the urethra
and outside the body.
- (b) Glomerular filtration occurs due to the
pressure gradient in the glomerulus.
Increased blood volume and increased blood
pressure will increase GFR.
The glomerular filtration rate is directly
proportional to the pressure gradient in the
glomerulus, so changes in pressure will
change GFR.
GFR is also an indicator of urine production,
increased GFR will increase urine production,
and vice versa.
7.(d) Bilirubin is excreted in bile and urine, and
elevated levels may indicate certain diseases.
It is responsible for the yellow colour of
bruises and the yellow discoloration in
jaundice. Its subsequent breakdown products,
such as stercobilin, cause the brown colour
of feces.
- (c) Workers in deep mines usually suffer from
dehydration because with the possibility of
a higher incidence of heat illness among
surface miners. Heat exhaustion symptoms
(headache through to irritability), and / or
three out of seven of the heat stroke symptoms
(hot and dry skin through to convulsions).
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