6.6 Hormones, Homeostasis and Reproduction

Question 1

What homeostatic mechanism is associated with the pancreas?

Answer 1

Cells in pancreas respond to changed in blood glucose levels. If glucose concentration deviates substantially from the set point, homeostatic mechanisms are initiated.

Question 2

The role of the pancreas

Answer 2

The pancreas has 2 glands in one organ. Most of pancreas is an exocrine glandular tissue that secretes digestive enzymes into ducts leading to small intestine. There are small regions of endocrine tissue, called islets of Langerhans, dotted through the pancreas that secrete hormones directly into blood stream.

Question 3

Cells and hormones secreted by the pancreas

Answer 3

There are cell types in the islets secrete different hormones. The two pancreatic hormones are insulin and glucagon.
Glucagon is secreted by alpha cells while insulin is released by beta cells.

Question 4

Alpha cells (α cells)

Answer 4

α cells synthesise and secrete glucagon when blood glucose level falls below the set point.

The hormone stimulates breakdown of glycogen into glucose in liver cells and release into blood, increasing concentration.

Question 5

Beta cells (β cells)

Answer 5

β cells synthesise and secrete insulin when blood glucose levels rises above the set point.

It stimulates the uptake of glucose by various tissues, particularly skeletal muscle & liver.
This stimulates the conversion of glucose into glycogen. Insulin is broken down by cells it acts upon, so secretion must be ongoing. Secretion begins within minutes of eating and may continue for several hours after a meal.

Question 6

Diabetes Mellitus

Answer 6

Diabetes is a condition where a person has consistently elevated blood glucose levels even during a prolonged fasting. This leads to a presence of glucose in their urine.

Question 7

Consequences of diabetes to the body

Answer 7

Continuously elevated glucose damages tissues, particularly their proteins.

Diabetes causes impaired water reabsorption from the urine while it is forming in the kidney. This results to an increase in the volume of urine and body dehydration.

Question 8

Symptoms of diabetes

Answer 8

Test for glucose in the urine to check whether one has develop diabetes when:

- constantly thirsty
- feels tired
- craves sugary drinks

Question 9

Two main types of diabetes

Answer 9

Type I: early onset diabetes

Type II: late onset diabetes

Question 10

Type I diabetes

Answer 10

Characterised by the inability to produce sufficient quantities of insulin
It is an autoimmune disease arising from the destruction of beta cells in the islets of Lagerhans by the body’s own immune system and the amount of insulin secreted becomes insufficient
Onset is usually during childhood

Question 11

Symptoms of type I diabetes

Answer 11

In children and young people, it is more severe and the obvious symptoms start suddenly

Question 12

Cause of type I diabetes

Answer 12

The cause is still being researched

Question 13

Type II diabetes

Answer 13

Characterised by the inability to process or respond to insulin
It is because of a deficiency in insulin receptors or glucose transporters on target cells
Onset is usually after childhood

Question 14

Symptoms of type II diabetes

Answer 14

Onset is slow and the disease may go unnoticed for years

Question 15

Causes of type II diabetes

Answer 15

The causes are not well understood but the main factors are:

• sugary, fatty diets
• prolonged obesity due to habitual overeating
• lack of exercise
• together with genetic factors that affect energy metabolism

Question 16

Type I diabetes treatment

Answer 16

Testing the blood glucose concentration regularly and injecting insulin when it is too high or likely to become too high
The injects are done often before a meal to prevent a peak of blood glucose as the food is digested and absorbed
The timing is very important because insulin molecules do not last long in the blood
There are better treatments being developed such as using implanted devices that can release insulin into the blood as and when necessary
A permanent cure is to coax stem cells to become fully functional replacements of beta cells

Question 17

Type II diabetes treatment

Answer 17

Adjusting the diet to reduce the peak and the throughs of blood glucose
Small amounts of food should be eaten frequently rather than infrequent large meals
Foods with high sugar contents should be avoided
Starchy food should only be eaten if it has a low glycemic index, indicating that it is digested slowly
High-fibre food should be included to slow digestion of other foods
Strenuous exercise and weight loss are beneficial as they improve insulin uptake and action