regulation of blood glucose

Question 1

where does most of the glucose in your body come from?

Answer 1

almost all glucose in your body is obtained from the food that we eat.

Question 2

what is glucose converted into?

Answer 2

it is converted in our cells to ATP energy in the process of cellular respiration.

Question 3

what is glucose

Answer 3

glucose is a simple sugar that serves as the body’s primary source of energy. (the level of glucose in our blood is highly regulated)

Question 4

what is the average blood glucose level for a healthy person who is fasting

Answer 4

the blood glucose level in a healthy person who is fasting is typically between 4.0 and 5.5 millimoles per litre (mmol/L)

Question 5

where is glucose stored after digestion and absorption

Answer 5

• glucose is stored in either the blood stream
• or stored in liver and skeletal muscle in the form of glycogen, a polymer built of glucose subunits.
• glycogen, a polymer built of glucose subunits.

Question 6

what is the second source of glucose (new glucose)

Answer 6

A second source of glucose is known as ‘new’ glucose. This provides a supply of glucose to the brain during periods of fasting. This involves gluconeogenesis (gluco = glucose, neo = new and genesis = creation), which is the synthesis of new glucose from non-carbohydrate precursors.

Question 7

how long does it take for blood glucose levels to return to under 5.5 mmol/L

Answer 7

blood glucose levels are normally back under 5.5 mmol/L within about 2 hours of eating a meal.

Question 8

what are hypoglycaemia symptoms

Answer 8

• sweating
• pallor
• hunger
• sleepiness
• lack of coordination
• irritability

Question 9

what are hyperglycaemia symptoms

Answer 9

• dry mouth
• thirst
• weakness
• headache
• blurred vision
• frequent urination

Question 10

why is blood glucose regulation needed

Answer 10

when blood glucose falls too low or goes too high, it can cause health issues. Therefore, it is important that blood glucose is maintained in a relatively steady range.

Question 11

glucose regulation and islet of Langerhans

Answer 11

islets of Langerhans are cell clusters in the pancreas that consist of different types of cells, including insulin-secretingcells, glucagon-secreting cells, and somatostatin-secreting cells. These cells work together to regulate blood sugar levels in the body.
* the Islets of Langerhans in the pancreas produce 2 hormones important in the regulation of glucose in our body - insulin and glucagon.
* insulin is produced by beta cells.
* Glucagon is produced by alpha cells.

Question 12

properties and actions of the pancreas hormones of insulin

Answer 12

insulin
* (signal for release from islet cells) - rise in blood glucose Hyperglycaemia: > 5.5 mmol/L
* (produced by) - beta cells of pancreatic islets
* (type of molecule) - peptide hormone (51 amino acids)
* (mode of transport) - dissolved in blood plasma
* (primary targets) - skeletal muscle, adipose tissue and liver
* (actions) - increases uptake of glucose by skeletal muscle and fat cells. Converts glucose to gltcogen for storage in liver and muscle cells
* (final result) - fall in blood glucose
* (negative feedback) - fall in blood glucose stops release of insulin by beta cells.

Question 13

properties and actions of the pancreas hormones of glucagon

Answer 13

glucagon
* (signal for release from islet cells) - fall in blood glucose hypoglycemia: <4.0 mmol/L
* (produced by) - alpha cells of pancreatic islets
* (type of molecule) - peptide hormone (29 amino acids)
* (mode of transport) - dissolved in blood plasma
* (primary targets) - liver
* (actions) - increases breakdown of glycogen to glucose in liver. Synthesises ‘new’ glucose in liver cells.
* (final result) - rise in blood glucose
* (negative feedback) - rise in blood glucose stops release of glycogen by alpha cells.

Question 14

what happens when blood glucose levels are too low

Answer 14

if the blood glucose level is too low, the pancreas stops producing insulin and produces glucagon. The production of glucagon will signal the liver to release the glucose in glycogen so your body can use it.

Question 15

what happens when blood glucose levels are too high

Answer 15

if the blood glucose level is too high, the pancreas secretes insulin. Insulin moves through the body and triggers fat cells to take in blood glucose and then signals the liver to store the glucose as glycogen.

Question 16

what does insulin do

Answer 16

insulin facilitates the movement of glucose into some body cells.

Question 17

the binding of glucagon activates key liver enzymes involves in which 2 pathways:

Answer 17

• Breakdown of stored glycogen to glucose - usually the major supplier of glucose to the blood.
• Production of ‘new’ glucose - usually a minor supplier (except when glycogen stores are depleted).
• (glucogen also inhibits the formation of glycogen by blocking the activity of key enzymes.)

Question 18

what does glucagon compared to insulin

Answer 18

glucagon has the opposite effect - it acts on liver cells causing them to convert glycogen to glucose.

Question 19

Insulin lowers high blood glucose levels by:

Answer 19

• stimulating the movement of glucose from the blood into skeletal muscle and adipose tissues (these 2 tissues form about 60 % of the body mass)
• **Activating enzymes **that build glucose into glycogen in liver and skeletal muscle cells.
• Inhibiting the breakdown of fats in adipose tissue - causes some body cells to make more use of glucose fro their energy needs (cells that mainly use fatty acids for energy)

Question 20

how is glucagon stored

Answer 20

glucagon is stored as granules in the alpha cells of pancreatic islets.
* note - during fasting or periods of activity, blood glucose levels can fall below normal.

Question 21

Glycogen: the key to blood glucose homeostatis

Answer 21

• depending on blood glucose levels, glycogen in liver cells can store or release glucose.
• this allows regulation of blood glucose and enables us to endure periods of fasting

Question 22

what are some nice ways to remember insulin and glucagon

Answer 22

• insulin gets glucoes into the cell.
• glucagon makes glycogen be gone!

Question 23

the stimulus -response model showing the response intiated by a fall in blood glucose levels.

Answer 23

1. (stimulus) - decrease in blood glucose
2. (receptor) - alpha cells of pancreas
3. (modulator or control centre) - alpha cells of the pancreas secrete the hormone glucagon.
4. (effector) - liver cells, adipose tissue and skeletal muscle
5. (response) - increase in blood glucose by release by release of glucose into the blood from the liver.
   * and then it links back to the start. in is a negative feedback loop

Question 24

the stimulus-response model showing the response initiated by an increase in blood glucose level

Answer 24

• (stimulus) - increase in blood glucose
• (receptor) - beta cells of pancrease
• (modulator or control centre) - beta cells of the pancreas secrete the hormone insulin.
• (effectors) - skeletal muscle, adipose tissue, liver
• (response) - decrease in blood glucose by: uptake by muscle and adipose tissue, glycogen formation in liver
• it is a negative feedback loop

Question 24

summary of blood glucose regulation

Answer 24

1. elevated blood glucose levels * (cell stimulated) - insulin * (effector) - liver cells and skeletal muscle cells, skeletal muscle and fat cells * (response) - increased production of glycogen, increased uptake of glucose 1. decreased blood glucose levels * (cell stimulated) - alpha cells * (hormone released) - glucagon * (effector) - liver cells and skeletal muscle cells * (response) - breakdown of glycogen into glucose and release into bloodstream.