blood sugar regulation

Question 1

blood sugar

Answer 1

amount of glucose in the blood

Question 2

why do cells need a constant supply pf glucose?

Answer 2

source of energy for all the cells’ activities (movement, respiration, synthesising molecules active transport)

Question 3

how is energy released from glucose molecules?

Answer 3

Energy is released from glucose molecules by cellular respiration

• Glucose + oxygen → carbon dioxide + water + energy

Question 4

body’s source of glucose comes from…

Answer 4

the food we eat

Carbs broken down into glucose during digestion → absorbed into blood through small intestine walls

Question 5

homeostasis occurs with blood sugar regulation

Answer 5

Homeostatic mechanisms being to operate to reduce blood glucose conc. and maintain it at normal level
Excess glucose in the blood must be removed and stored ready for use in cellular activities between meals

Question 6

how is glucose stored?

Answer 6

• Glucose is stored as glycogen as it is converted for storage
• Body can store 500g of glycogen, 100g in the liver, 400g in skeletal muscle cells

Question 7

when is glycogen converted to glucose?

Answer 7

When there isn’t enough glucose in the blood

Question 8

role of liver

Answer 8

• Important role in the control of blood sugar concentration
• Liver able to convert glucose → glycogen for storage, or glycogen → glucose for release into the blood

Question 9

liver’s blood supply

Answer 9

• Most of livers blood supply comes through hepatic portal vein → blood from stomach, spleen, pancreas and small and large intestines
  
  • Liver has the first chance to absorb nutrients from digested food

Question 10

where is glucose absorbed into after a meal?

Answer 10

After a meal with high proportions of carbs is consumed → glucose absorbed into blood capillaries of the villi of the small intestine

Question 11

hepatic portal vein role

Answer 11

carries glucose to liver

Question 12

what can occur in the liver with glucose?

Answer 12

• Be removed from the blood by the liver to provide energy for liver functioning
• Be removed by the liver and/or muscles and converted into glycogen for storage
• Continue to circulate in the blood, available for body cells to absorb and use as a source of energy
• Be converted into fat for long-term storage if it is in excess of that required to maintain both normal blood sugar and tissue glycogen levels

Question 13

glycogenesis

Answer 13

Glucose molecules are chemically joined in long chains to form glycogen molecules
formation of glycogen from other carbohydrates especially glucose

Question 14

where is glycogen stored and why?

Answer 14

Stored in the liver (and muscle cells), is available for conversion into glucose to maintain blood sugar levels and supply energy for liver activity

Question 15

glycogenolysis

Answer 15

Process of converting glycogen back into glucose

Question 16

Glycogen is a _____ energy source

Answer 16

short-term

Question 17

gluconeogenesis

Answer 17

conversion of fats or proteins into glucose

Question 18

Clusters of hormone-secreting cells

Answer 18

islets of Langerhans

Question 19

Alpha cells

Answer 19

secrete glucagon

Question 20

Beta cells

Answer 20

secrete insulin

Question 21

insulin

Answer 21

• Insulin from the beta cells causes a decrease in blood glucose levels by:

Accelerating the transport of glucose from the blood → body cells (increases cellular resp)

Accelerating the conversion of glucose → glycogen in the liver and skeletal muscle (glycogenesis)

Stimulating the conversion of glucose → protein (protein synthesis)

Stimulating the conversion of glucose → fat (lipids) in adipose tissue (lipogenesis)

Question 22

When blood glucose falls below normal…

Answer 22

chemoreceptors in the alpha cells in the islets of Langerhans stimulate those cells → secrete glucagon

Question 23

As blood glucose level increase…

Answer 23

the cells are no longer stimulated and production is reduced

Question 24

Regulation of the secretion of glucagon is determined by…

Answer 24

the level of glucose in the blood → controlled by a negative feedback system

Question 25

adrenal cortex role

Answer 25

Secretion of glucocorticoids

Question 26

what stimulates the adrenal cortex to secrete glucocorticoids?

Answer 26

Stimulated to secrete its hormones by adrenocorticotropic hormone (ACTH) from anterior lobe of pituitary gland

Question 27

what do glucocorticoids do?

Answer 27

• Regulate carb metabolism by ensuring that enough energy is provided to the cells
• They stimulate the conversion of glycogen → glucose during glycogenolysis
• Increase the rate at which amino acids are removed from cells and transported → liver
• Some of the amino acids may be converted into glucose by the liver during gluconeogenesis if glycogen and fat levels are low
• Promote the mobilisation of fatty acids from adipose tissue, allowing muscle cells to shift from using glucose → fatty acids for metabolic activity

Question 28

Glucocorticoid example

Answer 28

cortisol

Question 29

adrenal medulla role

Answer 29

Secretion of adrenaline and noradrenaline

Question 30

what does adrenaliine do?

Answer 30

Adrenaline elevates blood glucose levels through glycogenolysis and counteracts the effects of insulin. It stimulates the production of lactic acid from glycogen in muscle cells → use by liver to manufacture glucose

Question 31

Normal level of glucose in blood

Answer 31

between 4 and 6 mmol/L

Question 32

blood glucose homeostasis relies on…

Answer 32

the liver, pancreas and adrenal glands being involved and working together

Question 33

Processes that help lower blood sugar levels

Answer 33

• Glycogenesis = converts glucose → glycogen in liver/muscle cells
• Lipogenesis = glucose converted → fat in the fat cells/adipose tissue

Question 34

Effects of high blood sugar = tiredness and excessive thirst due to…

Answer 34

• Lack of insulin in blood
• Cells are starved of glucose
• Cells cannot respire to produce energy
• High glucose level increases osmotic pressure