Drugs targeting the endocrine system (L17) Flashcards
(44 cards)
how is the endocrine system organised?
endocrine glands/cells - secrete the hormones into the blood stream
target cells - cells with receptors for given hormones that can alter their activities in response to the hormone
whats the difference between the endocrine and the nervous system?
endocrine systems relies on transmission via hormones
nervous system relies on transmission via neurotransmitters
what are hormones?
a chemical substance synthesised by specific tissues and secreted into the blood stream, where it is carried to non-adjacent sites in the body and exerts its action
what are neurotransmitters?
a chemical substance synthesised by neurones and secreted directly into adjacent neurones or tissues where it exerts its action
what are the 2 chemical classes of hormones?
steroid
non-steroid
whats the difference between steroid and non-steroid hormones?
they have different mechanisms of exerting their effects
steroids
• nucleus mediated effects
• delayed effects
non-steroids
• membrane mediated effects
• rapid effects
steroid hormones
- synthesised from cholesterol
- small lipid soluble molecules that diffuse into the cell
- bind to intracellular receptor complexes and move to nucleus
- complex binds DNA response element
- modulates transcription
- translated to protein
non-steroid hormones
- synthesised from AAs
- hydrophilic so don’t diffuse into cell
- bind to receptors on cell surface
- these receptors are either GPCRs or tyrosine kinase linked receptors
what do GPCRs do when bound by non-steroid hormones?
modulate release of the second messenger cAMP within the cell which activates an enzyme cascade
what do tyrosine kinase receptors do when bound by non-steroid hormones?
activate the enzyme cascade directly
examples of endocrine systems regulating physiological functions
endocrine system
control of the system
therapeutic uses of drugs affecting the system
regulation of renal function by ADH
regulation of metabolism by cortisol
regulation of blood glucose by insulin
regulation of renal function by ADH (vasopressin)
regulated by high osmolarity osmoreceptors and baroreceptors
low BP an high osmolarity cause ADH to be released from the posterior pituitary
where does ADH act?
on V1 receptors in smooth muscle to cause vasoconstriction to maintain BP
on V2 receptors in distil tubule of kidney to cause water reabsorption by increasing aquaporins in the basolateral membrane of the disillusioned tubule
regulation of metabolism by corticosteroids
increases and maintains normal glucose levels in blood
• increases gluconeogenesis
• decreases glucose uptake into muscle and adipose tissue
• decrease in protein synthesis - AAs free fir gluconeogenesis
cortisol negatively feedback on the hypothalamic nuclei and the anterior pituitary
regulation of blood glucose by insulin
high blood glucose:
• insulin secreted by pancreas which acts on insulin receptors in liver and kidney
• uptake/storage of glucose
• inhibits fat breakdown
where else does insulin act other than insulin receptors in liver and kidney?
acts on the hypothalamic nuclei to release CRH
CRH acts on anterior pituitary to release ACTH
ACTH acts on the adrenal cortex to produce cortisol
what happens in the beta cells of the islets of langerhans in the pancreas?
1) glucose taken in by glucose transporter
2) glucose hydrolysed to form ATP
3) K+ channels inactivated by ATP
4) leads to depolarisation and the opening of Ca++ channels
5) influx of Ca++ results in secretion of insulin
this is called SUBSTRATE CONTROL
control mechanisms for: • ADH • CRH • ACTH • cortisol • insulin
- ADH: neuronal control
- CRH: neuronal control
- ACTH: trophic control
- cortisol: trophic control
- insulin: substrate control
what is neuronal control?
the hormone is released directly in response to neuronal stimulation
e.g. ADH is secreted in response to stimulation of nuclei in the hypothalamus detecting osmotic pressure
what is trophic control?
the hormone is released in response to stimulation from another hormone (cascade)
e.g. cortisol is secreted in response to ACTH, which is secreted in response to CRH
what is substrate control?
the hormone is directly influenced by circulating blood levels of the substate that the hormone itself controls
e.g. insulin is secreted in response to increased levels of circulating glucose
what is feedback control?
exceeding a certain level of hormone inhibits further hormone release
potential sites of drug action on neurotransmitters
synthesis storage receptors uptake metabolism
potential sites of drug action on hormones
synthesis release receptors metabolism replacement
