Hormonal Communication Flashcards
What are the two types of hormone?
- protein and peptide hormones: not soluble in phospholipid membrane so bind to the cell surface (first messengers)
- steroid hormones: Pass through the membrane to enter the nucleus
What are endocrine glands and the types?
Ductless glands which release hormones directly into the blood:
- pituitary gland
- thyroid gland
- thymus
- adrenal gland
- pancreas
- ovaries
- testes
Explain the action of first messengers
When the non-steroid hormone binds to the receptor, this activates a G protein which in turn activates an effector molecule which is often adenyl cyclase
What is the role of adenyl cyclase?
It converts ATP to cyclic AMP (cAMP), this acts as the second messenger which may initiate further reactions or act directly on a protein eg ion channels
What is the structure of adrenal glands?
-The adrenal cortex(outer region):
•zona glomerulosa, the outset most layer which secretes mineralocorticoids
•zona fasciculata, middle layer which secretes glucocorticoids eg. cortisol
•zona reticularis, innermost layer which secretes molecules used to make sex hormones
-The adrenal medulla(inner region):
Secretes adrenaline and noradrenaline
What is the effect of adrenaline on the body?
Polar molecule so cannot enter cells through the plasma membrane like hormones from the adrenal cortex, it’s detected by adrenaline receptors
- increases stroke volume of the heart
- increases heart rate
- Stimulates conversion of glycogen to glucose
- dilating pupils
- inhibition of action in the gut
Explain the action of steroid hormones
- Passes through cell membrane of target cell
- Binds to a specific receptor in cytoplasm
- Receptor-steroid hormone complex binds to to another receptor on chromosomal material, in the nucleus
- Stimulating the production of mRNA which code for the production of proteins
What is the role of acini / an acinus?
Carry out the exocrine function in the pancreas
- A group of exocrine cells which form lobules separated by connective tissue with a tubule in the centre
- secrete enzymes
What makes up the pancreatic duct? What enzymes does it contain?
Tubules from the centre of acini form intralobular tubules which make up the pancreatic duct
- Pancreatic amylose
- Trypsinogen
- Lipase
What is the islet of langerhans?
Carry out endocrine function in the pancreas:
- In small patches among the lobules of acini
- contain alpha cells which secrete glucagon
- contain beta cells which secrete insulin
How is the release of insulin controlled within beta cells?
- Cell membrane has potassium and calcium ion channels, potassium tends to be open so K ions flow out
- Blood glucose conc is high glucose moves into the cell
- Glucose metabolised by glucokinase to produce ATP which closes the k ion channels
- Accumulation of K ions alters pd across membrane, inside becomes less negative
- This opens the calcium ion channels
- Calcium ions cause the vesicles of insulin to fuse with cell membrane- exocytosis
What is hypoglycaemia?
-When a persons blood glucose concentration drops and remains too low for long periods- inadequate delivery of glucose to the body Can cause: -tiredness and irritability -confusion -seizures -unconsciousness -death Depending on the severity of the case
What is hyperglycaemia?
- When blood glucose concentration is raised too high for long periods of time
- Used as a diagnosis for diabetes mellitus
Explain the action of insulin on cells
- Binds to the insulin receptor activating tyrosine kinase
- Tyrosine kinase causes the phosphorylation of inactive enzymes in a cell
- Vesicle containing glucose transporter protein, inserts a glucose transporter protein into the membrane
- Glucose enters the cell and is converted to glycogen (for storage) or converted to fats or used in respiration
Where do the hormones glucagon and insulin act?
On the hepatocytes of the liver
