Hormones

Question 1

Define a hormone

Answer 1

A hormone is a chemical substance, produced by an endocrine gland, carried by blood, which alters the activity of one or more specific organs and is then destroyed by the liver.

Question 2

Define endocrine glands

Answer 2

Endocrine glands are ductless glands that secrete hormones directly into the bloodstream, which then transports the hormone around the body.

Question 3

State example of endocrine glands and respective hormones secreted

Answer 3

Adrenaline is secreted by the adrenal gland. Insulin and glucagon are secreted by the islets of Langerhans in the pancreas. Antidiuretic hormone (ADH) is secreted by the pituitary gland.

Question 4

Explain the function of the islets of Langerhans and identify the hormones secreted by the alpha and beta cells.

Answer 4

Blood glucose levels are monitored by the islets of Langerhans located in the pancreas. The islets of Langerhans consists of alpha cells which secrete glucagon and beta cells which secrete insulin.

Question 5

Explain how the blood glucose concentration is restored back to normal after a heavy meal.

Answer 5

An increase in blood glucose concentration above the norm is detected by receptors, which are the islets of Langerhans of the pancreas. This stimulates the beta cells of islets of Langerhans to secrete the hormone insulin into the bloodstream. Insulin stimulates the uptake of glucose by cells, especially by liver and muscle cells, causing blood glucose concentration to decrease. Insulin also triggers the conversion of glucose to glycogen. Once the blood glucose concentration is restored back to normal, the islets of Langerhans detects the decrease and secretion of insulin is reduced. Insulin is eventually destroyed in the liver and excreted by the kidneys. Blood insulin level falls.

Question 6

Explain how the blood glucose concentration is restored back to normal after a sudden fall in blood glucose level due to prolonged physical activity.

Answer 6

A decrease in blood glucose concentration below the norm is detected by receptors, which are the islets of Langerhans of the pancreas. This stimulates the secretion of glucagon into the bloodstream by alpha cells of the islets of Langerhans. Glucagon activates enzymes that convert glycogen and amino acids to glucose. Glucagon also stimulates reduced rate of respiration in cells. Once the blood glucose concentration is restored back to normal, the islets of Langerhans detects the increase and glucagon secretion by alpha cells is reduced. Glucagon is eventually destroyed in the liver and secreted by the kidneys. Blood glucagon level falls.

Question 7

Define diabetes and state symptoms

Answer 7

Diabetes refers to a group of diseases in which the body fails to regulate blood glucose levels. Signs of diabetes include a persistently high blood glucose level, presence of glucose in urine after meals and slow healing of wounds.

Question 8

Differentiate Type I and Type II diabetes

Answer 8

Type I diabetes is also known as insulin-dependent diabetes. It is a genetic disorder and onsets early in life. It occurs due to the destruction of beta cells of the islets of Langerhans by the body’s own immune system. Treatment includes daily injection of insulin. Type II diabetes (or diabetes mellitus) occurs when the body becomes resistant to insulin. It can be treated by diet alone if discovered early.

Question 9

State the function of the hormone adrenaline.

Answer 9

Adrenaline prepares the body for states of emergency when you are angry, anxious, stressed or afraid.

Question 10

State the effects of adrenaline.

Answer 10

1. Adrenaline stimulates the liver to convert glycogen into glucose so that more glucose is available for muscle contraction.
2. Increases blood glucose levels as more glucose is released from the liver into the bloodstream.
3. Increases the metabolic rate so that more energy is released from cellular respiration.
4. Increases the rate of heartbeat and causes a rise in blood pressure so that oxygen and glucose are transported faster to the muscles.
5. Increases the rate and depth of ventilation as this also increases the rate of uptake of oxygen by the lungs
6. Increases the rate of blood clotting, so that the blood clots faster to prevent excessive loss of blood
7. Constricts arterioles to the gut, thereby decreasing digestive activities
8. Constricts arterioles in the skin, causing paleness, thus channelling more blood to the muscles
9. Dilate pupils to enhance vision
10. Contracts hair muscles, producing ‘goosebumps’ and causing hair to stand on ends.