Hormonal Communication

Question 1

what is endocrine communication

Answer 1

specialised glands secrete hormones into bloodstream
circulatory system carries hormone to target cell
lipid soluble steroid hormones diffuse into cell and bind to complementary receptor in cytoplasm
peptide hormones bind to complementary receptors on cell surface membrane

Question 2

what hormone does the medulla secrete

Answer 2

adrenaline in response to danger or stress as part of fight or flight

Question 3

which hormone does the cortex secrete

Answer 3

mineralocorticoid
glucocorticoids

Question 4

why is it important that the blood glucose concentration remains stable

Answer 4

maintain constant blood water potential preventing osmotic lysis
maintain constant concentration of respiratory substrate-maintains constant levels of action

Question 5

define negative effect

Answer 5

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

Question 6

define glycogenesis

Answer 6

liver converts glucose into storage polymer glycogen

Question 7

define glycogenolysis

Answer 7

liver hydrolyses glycogen into glucose which can diffuse into the 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 cells in islet of langerhans detect decrease and secrete glucagon into blood
glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis
glucose diffuses from liver into bloodstream
alpha cells detect blood glucose concentration returned to optimum and stop producing glucagon

Question 10

use the secondary messenger model to explain how glucagon works

Answer 10

hormone receptor complex forms
conformational change to receptor activates G protein
activates adenyl cyclase which converts ATP to cAMP
cAMP activates protein kinase A pathway
results in glycogenolysis

Question 11

outline what happens when blood glucose concentration increases

Answer 11

Beta cells in iselt of langerhans detect incerase and secrete insulin into bloodstream
insulin binds to surface receptors on target cells
-increase cellular glucose uptake
-activate enzymes for glycogenesis
-stimulate adipose tissue to synthesise fat

Question 12

describe how insulin leads to a decrease glucose concentration

Answer 12

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

Question 13

how is insulin secretion controlled

Answer 13

beta cells have potassium and calcium ion channels to maintain -70 potential difference
as glucose concentration increases, glucose enters beta cells by facilitated diffusion
respiration of glucose produces ATP
ATP gated potassium ion channels close so potassium cannot diffuse out of cell
potential difference becomes more positive=depolarisation
calcium channels open
calcium triggers exocytosis of insulin

Question 14

describe the exocrine function of the pancreas

Answer 14

secretes digestive enzymes to the duodenum via pancreatic tract

Question 15

explain the cause of type 1 diabetes and how it can be controlled

Answer 15

body cannot produce insulin due to autoimmune response which attacks B cells
treat by injecting insulin from animal source or genetically modified bacteria

Question 16

explain the cause of type 2 diabetes and how it can be controlled

Answer 16

glycoprotein receptors are damaged and become less responsive to insulin
treat by controlling diet and exercise