Endocrine System Flashcards
What is the function of ES?
- Responsible for control of large numbers of homeostatic variables
- Regulation of development, growth and reproduction
Differences between endocrine and NS
- Endocrine response = quite slow
- NS has a localised effect, whilst hormones are exposed to most of the body in blood
How do drugs treat ES diseases
Either mimic or block the actions of hormones
Define hormone
chemical messengers that mediate communication by endocrine system
Define endocrine glands
organs that release hormones
What are target tissues?
- intended site that hormone will effect
- hormones travel through systemic circuit and bind to receptors associated with TT
Define tropic hormones
don’t produce direct effects on other physiological systems. they regulate release of hormones by other endocrine organs and/or control growth and development of these organs.
What are endocrine cells
Each hormone is secreted by different cell types
Label endocrine organs
What hormones does pituitary gland secrete
Describe thymus gland
- located in thoracic cavity next to sternum
- reaches max size during childhood and declines in adulthood
- secretes many peptide hormones responsible for development of immune system
What hormones do adrenal glands secrete
- Adrenal cortex: outer shell. secretes corticosteroids
- Adrenal medulla: adrenaline or noradrenaline
What hormones does pancreas secrete?
Insulin: peptide hormone secreted by beta-cells of pancreas. insulin reduces blood glucose levels by promoting its uptake by muscle and fat cells
Glucagon:peptide hormone secreted by alpha-cells of pancreas. Anatagonist to insulin. released by hypoglycaemia. increases BG levels by stimulating breakdown of glycogen and release of glucose from liver
What other organs have cells that have endocrine functions?
brain, digestive tract, heart and kidney
How do hormones use carrier proteins?
- After release, some bind to a carrier protein and are transported in blood as complexes
- Hormone is inactive in complex. Has to dissociate to bind to receptor
Why are carrier proteins useful
- Readily available supply of hormone in circulation
- Act as a buffer and smooth out spikes in hormone secretion
- Make hormone less likely to be metabolised by enzymes in blood, liver, kidney…
What are peptide hormones
consist of chains of amino acids
E.g: insulin, GH, calcitonin
How are peptide hormones synthesised
- Synthesised in rough ER of their gland
- Go to golgi apparatus for further processing
- Packaged in membrane bound secretory vesicles. Stored here until release.
- Secreted by exocytosis into adjacent capillaries once exposed to certain trigger.
How do peptide hormones bind?
- Circulate in free state
- Enter extracellular space and bind to specific receptors for target cell
- Receptor is a membrane spanning protein w/ binding site on ECS side
- Binding triggers conformational change of receptor, which triggers response in target cell
What are amine hormones
Structural derivatives of tyrosine (amino acid)
E.g: catecholamines
How is noradrenaline synthesised in most catecholamine secreting cells?
- Tyrosine -> dihydroxyphenylalanine (L-DOPA) -> dopamine (DA)
- DA transported into mem-bound secretory vesicles, where enzymes that convert to noradrenaline are located
- Noradrenaline stored in vesicles until release by exocytosis
What happens to noradrenaline in adrenal medulla?
- Noradrenaline transported back to cytoplasm
- Acted on by an ezyme only found there
- Produces adrenaline
- Goes back to vesicles for storage and secretion
Describe the release of amine hormones
- After release, amine hormones circulate in free state, enter ECS and bind to adrenergic receptors on TT
- Normal conformational change…
