5.1.4 Hormonal Communication

Question 1

Explain how each type of endocrine cell influences the functioning of only specfic cell types within the body

Answer 1

Hormones act on cells that have particular receptors for that hormone, which are target cells

Question 2

What is the endocrine system

Answer 2

System that uses chemical hormones in the blood stream to transport signals
Release hormones directly into the blood
Target tissues will have specfic receptors for the hormone

Question 3

Explain how the chemical makeup of hormone Y will influence the way it iniates signal transduction with cell x

Answer 3

Lipid soluble- pass through cell membrane and bind to receptor in the cytosol
Peptide based - hydrophillic moleucle cannot cross lipid membrane of the cell and will bind to a receptor on the cell surface membrane

Question 4

Describe the general function of second messanger molecules in the cell

Answer 4

Activate enzymes and proteins in the cell

Question 5

Explain the events of the binding of adrenaline

Answer 5

Adrenaline- first messengers, bind to specfic receptor on cells that activate enzyme adenyl cyclase
Enzyme hydrolyses ATP to cAMP, second messanger that activates enzymes in a cascade. Turning on specfic genes

Question 6

State which hormone secreted by the adrenal medulla

Answer 6

Adreanline

Question 7

Describe the function of adrenaline

Answer 7

Prepares the body for activity, raising HR and dialting pupils

Question 8

Explain the difference between the terms ‘endocrine’ and ‘exocrine’ with reference to the pancreas

Answer 8

Pancreas has islets of Langerhans(endocrine tissue ) which contain cells that secrete the hormones glucagon and insulin into blood vessels.
Cells of the acini in the pancreas secrete pancreatic juices that travel through ducts to the small intestine, exocrine cells

Question 9

Explain how negative resting membrane potential of pancreatic beta cells is maintained under normal concentration of glucose in the blood

Answer 9

Normal level, potassium ion channels in the cell surface membrane on beta cells are open, allowing potassium ions to diffuse out of the cell resulting in negative resting membrane potential

Question 10

Explain the sequence of events that lead to the secretion of insulin from beta cells

Answer 10

Respiration rapidly metabolises glucose, releasing ATP molecules. Newly formed ATP causes potassium ion channles to close, membrane potential of cell becomes less negative. Change causes calcium ion channels to open, enter the cell causing vesicles full of insulin to fuse with the membrane and insulin is released into the blood by exocytosis

Question 11

Describe the mechanisms by which insulin increases glucose uptake by liver cells

Answer 11

Insulin binds to insulin receptors on the CSM, activates enzymes on the inside of the cell which results in more glucose transporter proteins being placed in the cell membrane and therefore increases glucose uptake

Question 12

Describe the events that occur when glucagon reaches its target organ

Answer 12

Attaches to specfic receptors on the surface of liver cells, activates enzymes inside liver cells which promotes GLYCOGENOLYSIS other enzymes are also activated GLUCONEOGENESIS

Question 13

Why is it important that blood glucose concentration remains stable

Answer 13

Maintains constant blood water potential, prevent osmotic lysis
Maintain constant constant concentration of respiratory substrate,regardless of environmental conditions

Question 14

Define negative feedback

Answer 14

Self regulatory mechanisms return internal environment to optimum when there is a fluctuation

Question 15

Define glycogenesis, glycogenolysis and gluconeogenesis

Answer 15

Glycogenesis - liver converts glucose into the storage polymer glycogen
Glycogenolysis - liver hydrolyses glycogen into glucose which can diffuse into blood
Gluconeogenesis - liver converts glycerol and amino acid into glucose

Question 16

Outline the role of glucagon when blood glucose concentration decreases

Answer 16

1) alpha cells in Islets of Langerhans in pancreas detect decrease and secrete glucagon into bloodstream
2) Glucagon bind to surface receptor on liver cells and activates enzyme 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(negative feedback)

Question 17

Use the secondary messenger model to explain how glucagon works

Answer 17

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

Question 18

Outline what happens when blood glucose concentration increases

Answer 18

1) beta cells in Islets of Langerhans in pancreas detect increase and secrete insulin into blood stream
2) insulin bind to surface receptor on target cells to increase cellular glucose uptake
Activate enzymes for glycogenesis
Stimulate adipose tissue to synthesis fat

Question 19

Describe how insulin leads to decrease in blood glucose concentration

Answer 19

Increases permeability of cells to glucose
Increase glucose concentration gradient
Triggers inhibition of enzymes for glycogenolysis

Question 20

How is insulin secretion controlled

Answer 20

1) B cell have potassium and calcium ion channels to maintain pd -70mV
2) as glucose concentration increases, glucose enters B cells via facilitated diffusion
3) Respiration of glucose produce ATP. ATP gated K+ ion channels close, so k+ ions no longer diffuse out of cell
4) Pd in cell becomes more positive - depolarisation. Ca ion channel open, triggers exocytosis of insulin

Question 21

Describe the exocrine function of pancreas

Answer 21

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

Question 22

Explain the causes of Type 1 diabetes mellitus and how it can be controlled

Answer 22

Body cannot produce insulin e,g due to auto immune response which attack Beta cell of islets of Langerhans
Treat by injecting GM bacterial or animal source

Question 23

Explain the causes of type 2 diabetes and how it can be controlled

Answer 23

Glycoprotein receptors are damaged or become less responsive to insulin
Strain correlation with poor diet
Treat by excerise