4.5 Regulation of blood glucose in animals

Question 1

What does glucose get broken down into in cellular respiration?

Answer 1

Through the process of cellular respiration, glucose is broken down to carbon dioxide and water, and its chemical energy is transferred to ATP.
C 6 H 12 O 6 + 6 O 2 –> 6 CO 2 + 6 H 2 O + ATP

Question 2

What is glycogen and describe its relationship between high and low blood glucose levels.

Answer 2

Glycogen is a complex carbohydrate molecule that serves as a storage form of glucose in animals, including humans. It is synthesized and stored primarily in the liver and muscles. When blood glucose levels are high, the excess glucose is taken up by the liver and muscle cells, and is converted into glycogen for storage. When blood glucose levels are low, glycogen is broken down into glucose and released into the bloodstream to maintain normal blood glucose levels

Question 3

What is insulin?

Answer 3

Insulin is a hormone produced by beta cells of the pancreas that acts to stimulate the liver to convert glucose into glycogen for storage in liver and muscle cells.

Question 4

What is glucagon?

Answer 4

Glucagon is a hormone produced by alpha cells of the pancreas that stimulates the liver to convert glycogen to glucose

Question 5

Where are glucagon and insulin produced?

Answer 5

Both hormones are produced in the pancreas by special cells within the pancreas called the islets of Langerhans.

Question 6

What do beta and alpha cells produce and where in the islets of langerhans are they located?

Answer 6

The central core of each islet is composed of large numbers of beta cells, which produce insulin. Alpha cells, which produce glucagon, are less abundant and are located around the margin of the islet

Question 7

What happens when blood glucose levels fall below normal range?

Answer 7

When the blood glucose level falls below normal, secretion of glucagon increases and that of insulin stops

Question 8

What happens when blood glucose levels rise above normal range?

Answer 8

When the blood glucose level rises above normal, secretion of insulin increases and that of glucagon stops.

Question 9

What is the mode of transport for insulin and glucagon?

Answer 9

Dissolved in blood plasma

Question 10

What is insulins primary target?

Answer 10

Skeletal muscle, adipose tissue and liver b/c they are major sites of glucose uptake and storage

Question 11

What is glucagon’s primary target?

Answer 11

Liver

Question 12

What cells detect a high/low level of glucose in blood?

Answer 12

Insulin is released when glucose-sensing beta cells in the pancreatic islets detect an above-normal rise in the level of blood.

Question 13

How does insulin lower high blood glucose levels?

Answer 13

-stimulating the movement of glucose from the blood into skeletal muscle and adipose tissues

-activating enzymes that build glucose into glycogen in liver and skeletal muscle cells

-inhibiting the breakdown of fats in adipose tissue — this reduces the supply of fatty acids in the blood and causes some body cells to make more use of glucose for their energy needs, in particular, those cells that mainly use fatty acids for their energy supply.

Question 14

Where is glycogen stored?

Answer 14

Glycogen is primarily stored in the liver and skeletal muscle tissue.

Question 15

BGL are to low describe what would take place.

Answer 15

Question 16

How does glucagon increase BGLs.

Answer 16

Glucagon binds to receptors on liver cells and its action causes the release of glucose, raising the blood glucose level by breaking down glycogen and simulating the production of new glucose. These actions restore the blood glucose level to within the normal range and ensure that body cells have a continual adequate supply of glucose for their needs.

Question 17

Soon after you have eaten, blood glucose levels rise. Insulin stimulates liver cells to build glucose into glycogen as a short-term store of glucose describe what happens when liver cells hit their capacity?

Answer 17

When the store of glycogen in liver cells is at capacity, insulin stimulates the production of fatty acids from glucose, and these are transported to other tissues, in particular adipose tissues. In cells of adipose tissue, fatty acids are combined with glycerol to form fat

Question 18

Where can the glucose released from Skeletal muscle cells be used?

Answer 18

Skeletal muscle cells can also release glucose from their glycogen store, but this glucose can be used only by the muscle cells themselves.

Question 19

Stimulus reponse model on fall in blood glucose.

Answer 19

Question 20

What happens when insulin binds to skeletal muscle and adipose tissue?

Answer 20

Insulin binds to its receptors on the plasma membranes of these cells. This leads to special glucose transporters moving to the membrane so more glucose can move into skeletal muscle and adipose tissue.

In skeletal muscle, this glucose is converted to glycogen.
In adipose cells, this glucose is converted to fats (triglycerides). Insulin also acts to prevent these fats from breaking down and being used as an energy source.

Question 21

What role does the hypothalamus play in coordinating blood glucose homeostasis?

Answer 21

It contains both glucose-sensing neurons and insulin-sensing neurons that respond to changes in the level of blood glucose. This can send signals to the cells in the pancreas to release insulin or glucagon.

Question 22

Negative feedback loop of rise in BGLs.

Answer 22

Question 23

What is the difference between hyperglycaemia and hypoglycaemia?

Answer 23

Hyperglycaemia exists when blood glucose concentration is too high, whereas with hypoglycaemia it is too low.

Question 24

Symptoms of hyperglycaemia and hypoglycaemia.

Answer 24

Hyperglycemia;
increased thirst and dry mouth
Frequent urination
Blurred vision
Fatigue and weakness
Headaches
Nausea and vomiting
Rapid heartbeat
Dry or flushed skin
Difficulty concentrating
Fruity breath odor

Hypoglycemia;
Sweating and clammy skin
Shakiness or trembling
Hunger
Headaches
Dizziness or lightheadedness
Confusion or difficulty concentrating
Weakness or fatigue
Irritability or mood changes
Blurred vision
Seizures or convulsions (in severe cases)

Question 25

Compare and contrast the regulation of body temperature and the regulation of blood glucose.

Answer 25

Both processes involve detecting changes in the environment (i.e. stimuli) and triggering mechanisms that will bring the altered variable towards to the normal state through homeostatic mechanisms and negative feedback involving various effectors (1 mark for similarity). However, blood glucose regulation is mostly under the control of the endocrine system and hormones (insulin and glucagon), whereas temperature regulation is mostly under the control of the nervous system. Also, body temperature regulation involves reception by thermoreceptors in the skin, organs and hypothalamus, whereas blood glucose regulation involves reception by the alpha and beta cells in the pancreas (1 mark for difference).

Question 26

Explain why it is important to maintain a constant level of glucose in the internal environment of human body cells.

Answer 26

All cells must be supplied with glucose at an appropriate rate in order to keep up to the energy needs of cells.

If blood glucose levels fall too low, cells may not be able to produce enough useable energy in the form of ATP by cellular respiration. (1 mark)

If blood glucose levels are too high, cells may become dehydrated as fluid is drawn into the blood in order to reduce the blood glucose concentration. Excessive urination and excessive thirst are the symptoms of this. (1 mark)