Hormonal Communication

Question 1

What is thermoregulation?

Answer 1

the control of body temperature

Question 2

What is osmoregulation?

Answer 2

the control of the water potential of body fluids

Question 3

What is a hormone?

Answer 3

a chemical messenger produced by an endocrine gland and carried by the blood

Question 4

Where are the adrenal glands located?

Answer 4

above each kidney

Question 5

What are the two main areas in the structure of the adrenal glands?

Answer 5

a central medulla and an outer cortex

Question 6

What type of hormone is released from the adrenal cortex?

Answer 6

steroid hormones

Question 7

What are the three categories of steroid hormones?

Answer 7

• glucocorticoid
• mineralocorticoid
• androgen

Question 8

What is glycogenesis?

Answer 8

production of glycogen from glucose

Question 9

What is gluconeogenesis?

Answer 9

production of glucose from non-carbohydrate sources so liver can make glucose from lipids and amino acids

Question 10

What is glycogenolysis?

Answer 10

process in which glycogen stored in the liver and muscle cells is broken down into glucose which is released into the bloodstream and increases blood glucose concentration

Question 11

What is glucagon?

Answer 11

a hormone released to increase blood glucose concentration and is produced by alpha cells in islets of Langerhans in pancreas

Question 12

What is glycogen?

Answer 12

a branched polysaccharide formed from alpha glucose molecules. A chemical energy store in animal cells.

Question 13

What is glucose?

Answer 13

a monosaccharide with the chemical formula C6H12O6. One of the main products of photosynthesis in plants

Question 14

What are the steps in the control of insulin secretion?

Answer 14

1, At normal blood glucose concentration levels, potassium channels in the plasma membrane of beta cells are open and potassium ions diffuse out of the cell. The inside of the cell is at a potential of -70mV with respect to the outside of the cell.
2, When blood glucose concentration rises, glucose enters the cell by a glucose transporter.
3, The glucose is metabolised inside the mitochondria, resulting in the production of ATP.
4, The ATP binds to potassium channels and causes them to close. They are known as ATP-sensitive potassium channels.
5, As potassium ions can no longer diffuse out of the cell, the potential difference reduces to around -30mV and depolarisation occurs.
6, Depolarisation causes the voltage-gated calcium channels to open.
7, Calcium ions enter the cell and cause secretory vesicles to release the insulin they contain by exocytosis.

Question 15

What is the name of the structure in the middle of the adrenal glands?

Answer 15

medulla

Question 16

What is the name of the outer structure of the adrenal glands (within the capsule)?

Answer 16

cortex

Question 17

Explain the causes of Type 2 diabetes mellitus

Answer 17

• glycoprotein receptors are damaged or become less responsive to insulin
• strong positive correlation with poor diet/obesity

Question 18

How can Type 2 diabetes mellitus be controlled?

Answer 18

• treat by controlling diet and exercise regime

Question 19

Explain the causes of Type 1 diabetes mellitus

Answer 19

Body cannot produce insulin e.g. due to autoimmune response which attacks beta cells of Islets of Langerhans

Question 20

How can Type 1 diabetes mellitus be controlled?

Answer 20

• Treat by injecting insulin from animal source or genetically modified bacteria
• possible future treatment: use stem cells to produce new beta cells

Question 21

Describe the exocrine function of the pancreas

Answer 21

Secretes digestive enzymes e.g. amylase, trypsin and lipase to the duodenum via the pancreatic tract

Question 22

Describe how insulin leads to a decrease in blood glucose concentration

Answer 22

• increases permeability of cells to glucose
• increases glucose concentration gradient
• triggers inhibition of enzymes for glycogenolysis

Question 23

Outline what happens when blood glucose concentration increases

Answer 23

1, beta cells in Islets of Langerhans in pancreas detect increase and secrete insulin into bloodstream
2, insulin binds to surface receptors on target cells to: increase cellular glucose uptake and activate enzymes for glycogenesis (liver and muscles) and stimulate adipose tissue to synthesise fat

Question 24

Use the secondary messenger model to explain how glucagon works

Answer 24

1, hormone-receptor complex forms
2, conformational change to receptor activates G-protein
3, activates adenylate cyclase, which converts ATP to cyclic AMP (cAMP)
4, cAMP activates protein kinase A pathway
5, Results in glycogenolysis

Question 25

Outline the role of glucagon when blood glucose concentration decreases

Answer 25

1, alpha cells in Islets of Langerhans in pancreas detect decrease and secrete glucagon into bloodstream
2, glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
3, glucose diffuses from liver into bloodstream
4, alpha cells detect that blood glucose concentration has returned to optimum and stop producing glucagon

Question 26

Define negative feedback

Answer 26

Self-regulatory mechanisms return internal environment to optimum when there is a fluctuation. Different mechanisms are responsible for dealing with an increase/decrease in normal level for greater control

Question 27

Why is it important that blood glucose concentration remains stable?

Answer 27

• maintain constant blood water potential: prevent osmotic lysis/crenation of cells
• maintain constant concentration of respiratory substrate: organism maintains constant level of activity regardless of environmental conditions