Hormonal Communication

Question 1

What is endocrine communication?

Answer 1

Specialised glands that secrete hormones into bloodstream

Circulatory system carries hormone to target cell

Steroid hormones diffuse into cell and bond to complementary receptor in cytoplasm. Non-steroid hormones bind to complementary receptor on cell-surface membrane

Question 2

Describe the structure of the adrenal glands

Answer 2

Located above the kidneys.

Medulla containing blood vessels surrounded by the cortex

Question 3

What hormone does the medulla secrete?

Answer 3

Adrenaline in response to danger, stress or excitement as part of the fight or flight response

Question 4

Which hormone does the cortex secrete?

Answer 4

Mineralocorticoids e.g. aldosterone, which targets kidney and gut to control concentration of Na+ and K+ ions in blood

Glucocorticoids e.g. cortisol and corticosterone, which stimulate an increase in blood glucose concentration

Question 5

Why is it important that blood glucose concentration remains stable?

Answer 5

Maintain constant blood water potential

Maintain constant concentration of respiratory substrate

Question 6

Define glycogenesis

Answer 6

Liver converts glucose into glycogen

Question 7

Define Glycogenolysis

Answer 7

Liver hydrolyses glycogen into glucose which can diffuse into blood

Question 8

Define gluconeogenesis

Answer 8

liver converts glycerol and amino acids into glucose

Question 9

Outline the role of glucagon when blood glucose concentration decreases

Answer 9

Alpha and beta cells in the Islets of Langerhans in the pancreas detect decrease and alpha cells secrete glucagon into the blood and beta cells decrease secretion of insulin

glucagon binds to the surface receptors of the hepatocytes and activates enzymes for glycogenolysis and gluconeogenesis

glucose diffuses from liver into blood

alpha cells detect that blood glucose concentration has returned to optimum and stop secreting glucagon

Question 10

How do non-steroid hormones work?

Answer 10

Hormone binds to specific receptors on plasma membrane

A complementry G protein is activated

This activates the enzyme adenyl cyclase

Adenyl cyclase converts ATP to cAMP which is the secondary messenger

cAMP can act directly on another protein, stimulate
transcription of a gene or can initiate a cascade of enzyme controlled reactions

Question 11

Outline what happens when blood glucose concentration increases

Answer 11

Alpha and beta cells in the Islets of Langerhans in the pancreas detect increase and beta cells secrete insulin into the blood and alpha cells decrease secretion of glucagon

Insulin binds to surface receptors on target cell to:

increase glucose used in respiration

increase permeability of membranes to glucose

Glycogenesis

Question 12

What are the 2 types of hormones and examples?

Answer 12

Non-steroid - bind to surface receptors

Adrenaline
Insulin
Glucagon
ADH

Steroid - Have direct effect on DNA

Oestrogen
Testosterone

Question 13

What are the exocrine functions of the pancreas?

Answer 13

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

Question 14

What are the endocrine functions of the pancreas?

Answer 14

Hormones are secreted from
the cells in the islets of
Langerhans

alpha cells manufacture and
secrete the hormone
glucagon

beta cells manufacture and
secrete the hormone insulin

These are released directly
into the blood

Question 15

Describe how insulin leads to a decrease in blood glucose concentration

Answer 15

Increases of permeability of cells to glucose

Increases glucose concentration gradient

Triggers inhibition of enzymes for glycogenolysis

Glycogenesis

Glucose converted to fats

Question 16

How is insulin secretion controlled?

Answer 16

Beta cells have K+ and Ca2+ ion channels to maintain potential difference of -70mV

As glucose concentration increases, glucose enters beta cells via facilitated diffusion

Respiration of glucose produces ATP. ATP-gated K+ ion channels close so K+ ions no longer diffuse out of cell

P.d in cell becomes more positive = depolarisation. Ca2+ ion channels open which triggers exocytosis of insulin

Question 17

Explain the causes of type 1 diabetes mellitus anf how it can be controlled

Answer 17

The body cannot produce insulin due to autoimmune respones which attacks beta cells

Treat by injecting insulin from animal source or gentically modified bacteria. Possible future treatment using stem cells to produce new beta cells

Question 18

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

Answer 18

Excess body fat

Overeating of sugars

physical inactivity