Pancreas (4)

Question 1

What is the pancreas?

Answer 1

The pancreas is an unusual gland as it functions as both an exocrine gland and an endocrine gland.

Question 2

What is the exocrine function of the pancreas?

Answer 2

The exocrine function is the secretion of pancreatic juice, which flows along the pancreatic duct into the duodenum where it helps in chemical digestion.

Question 3

What is the endocrine function of the pancreas?

Answer 3

The endocrine function is the secretion of hormones by groups of cells called islets of Langerhans. These are scattered throughout the pancreas. The hormones they secrete pass directly into the blood.

Question 4

What are the two types of cells in the islets that secrete two different hormones?

Answer 4

There are two types of cells in the islets that secrete two different hormones.

• Alpha cells secrete glucagon
• Beta cells secrete insulin

Question 5

What are the functions of glucose and insulin?

Answer 5

Both hormones play a role in controlling the level of blood sugar / glucose in the blood.

Question 6

What is the normal glucose concentration in a healthy human?

Answer 6

In a healthy human, normal glucose concentration is between 3.5 and 5.5 mmol / liter of blood

Question 7

What is glucose?

Answer 7

Glucose, a simple sugar derived from digesting the carbohydrates that are eaten, is a source of cellular energy. It is transported throughout the body in the bloodstream and cannot enter the cells without the aid of insulin.

Question 8

Why do we say that glucose and insulin are an antagonistic pair?

Answer 8

-Insulin, therefore, will lower blood sugar (glucose) level. -Glucagon raises blood sugar level.
Insulin and glucagon therefore have antagonistic (opposite) effects.

Question 9

How does insulin lower blood sugar levels?

Answer 9

• After a meal containing carbohydrates, glucose from the digested food is absorbed from the small intestine and moves into the blood. This will increase blood glucose levels above the normal set point, i.e. there is a change from the norm. As this blood passes through the pancreas, the beta cells detect the raised glucose levels and respond by secreting insulin into the blood.
• Insulin goes to the main target organs, the liver and muscles, where it: 1. makes the cell membranes more permeable to glucose, which enables more glucose to leave the blood and enter the cells. 2. increases the rate at which glucose is converted into glycogen in the cells.
• As the above processes take glucose out of the blood the blood sugar levels are lowered.
• The lower glucose level is detected by the insulin secreting cells which then stop releasing insulin into the blood.

Question 10

How is the lowering of blood sugar levels by insulin an example of negative feedback?

Answer 10

the receptor organ is the pancreas and the effector is the liver (and muscles).

Question 11

How does glucagon increase blood glucose?

Answer 11

• As this blood passes through the pancreas, the glucagon secreting cells (alpha cells) detect the low glucose levels and respond by secreting glucagon into the blood.
• The target cells are the liver cells (not the muscle cells) where the glucagon causes the breakdown of stored glycogen into glucose.
• As a result, the liver releases glucose into the blood increasing the blood glucose level.
• The increased glucose level is detected by the glucagon secreting cells, which then stop releasing glucagon into the blood.