Page 129 - Biology_Form_3

Biology for Secondary Schools

Renal regulation: The kidneys play a (b) In your view, which of the above
crucial role in long-term pH maintenance mechanisms plays the most
by excreting hydrogen ions and reabsorbing significant role? Explain why.
bicarbonate. When blood pH drops
(acidosis), kidney tubules secrete hydrogen
FOR ONLINE READING ONLY
ions into urine and reabsorb bicarbonate into Blood sugar regulation
the bloodstream to restore pH balance. In Task 5.7
alkalosis (high pH), bicarbonate excretion
increases while hydrogen ion retention Search from the library and internet
helps normalize pH. This mechanism is sources on the information about the
slower than respiratory regulation but is concept of blood sugar regulation.
essential for prolonged acid-base balance.
The process of digestion of carbohydrates
ends up by producing simple sugars mainly
Exercise 5.4
glucose. Glucose is absorbed from the
1. Explain how the body regulates alimentary canal to the bloodstream through
osmotic pressure when a person active transport. In humans, normal fasting
consumes a large amount of salty blood glucose levels are maintained between
food. 70 and 99 mg/dL. However, fluctuations can
occur due to dietary intake or increased
2. Compare and contrast the roles of glucose utilization. For instance, levels may
Antidiuretic Hormone (ADH) and drop to about 70 mg/dL before breakfast
Aldosterone in osmoregulation. and rise to approximately 140 mg/dL after
How do their mechanisms ensure consuming carbohydrates. It is important
the maintenance of water and salt that blood glucose level is maintained
balance in mammals? relatively constant.

3. Camels are adapted to survive in arid
environments due to their long loop of The pancreas is the major endocrine gland
Henle. Based on your understanding in the body that plays an important role in
of osmoregulation, explain how the maintaining a constant level of glucose
loop of Henle enables camels to in the blood. The pancreas produces two
conserve water and survive in dry hormones, glucagon and insulin from a
conditions. specialized group of pancreatic cells called
islets of Langerhans. The alpha cells of
4. The regulation of body pH is crucial the islets of Langerhans secrete glucagon
for maintaining homeostasis. whereby the beta cells secrete insulin.
(a) Evaluate the effectiveness of the These hormones function antagonistically
kidney, lungs, and buffer systems to maintain glucose homeostasis. Insulin
in pH regulation. is released when blood sugar levels are
elevated, promoting glucose uptake in

122 Student’s Book - Form Three

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