5.4 Hormonal Communication Flashcards
What is an endocrine gland?
A ductless gland that secretes it’s product directly into the blood or lymph
What is an exocrine gland?
A gland that secretes it’s product into a duct which takes the secretions to the site of action
What are the 2 types of hormone?
- steroid
- protein
What are the features of protein hormones?
- insoluble so can’t diffuse through plasma membrane
- requires receptors
what are the features of steroid hormones?
- soluble so can pass through plasma membrane
- bind to receptors on cytoplasm
what are examples of steroid hormones?
- testosterone
- progesterone
what are examples of protein hormones?
- insulin
where are the adrenal glands found?
above the kidneys
what are the 2 parts of the adrenal gland?
- adrenal cortex
- adrenal medulla
what does the adrenal cortex produce?
steroid hormones using cholesterol:
- glucocorticoids
- mineralocorticoids
what is an example of a glucocorticoid?
- cortisol
It stimulates the synthesis of glycogen in the liver and is released in response to stress
what is an example of a mineralocorticoid?
- aldosterone
It is release to increase the uptake of Na+ and K+ into the blood from the DCT
what does the adrenal medulla produce?
- protein hormones
e.g. adrenaline
how do protein hormones work?
- protein bins to receptor on plasma membrane, which activates a G protein.
- G protein activates an effector molecule which produces an enzyme to convert ATP to cAMP
- cAMP is the secondary messenger which activates an enzyme cascade or acts directly on other proteins
how do steroid hormones work?
- steroid hormone passes through plasma membrane and binds to receptor in cytoplasm or nucleus
- the receptor steroid hormone complex acts as a transcription factor resulting in the formation of mRNA by transcription
- a new protein is formed
what are some effects of adrenaline?
- vasoconstriction
- increased mental awareness
- pupils dilate
- cardiac output increases
- piloerection
- digestive system slows
- bronchodilation
- glycogen converted to glucose
why is the pancreas an exocrine and endocrine gland?
- acini secrete digestive enzymes into the pancreatic duct
- islets of Langerhans secrete hormones into blood
what are the islets of Langerhans?
- endocrine tissue that makes up 15% of the pancreas
what are the cells that make up the islets of Langerhans?
- alpha cells (20%)
- beta cells (70%)
what do alpha cells do?
Detect blood glucose concentration and secrete glucagon to convert glycogen into glucose
what do beta cells do?
Detect blood glucose concentration and secrete insulin to convert glucose into glycogen
How do beta cells detect blood glucose concentration and release insulin?
- K+ channels are normally open so K+ flows out of the cell
- when blood glucose conc. is too high glucose diffuses into the cell
- glucose is metabolised to produce ATP
- ATP causes the K+ channels to close
- K+ cant leave the cell so membrane becomes positive
- voltage gated Ca2+ channels open
- Ca2+ causes vesicles to fuse with membrane so insulin is released by exocytosis
What is exact glucose level normally needed in the blood?
- 90mg in 100cm^3
- 4-6 mmol/dm^3
what is hypoglycemia?
when blood glucose levels are too low
