Endocrinology Flashcards
endocrine glands
cells that synthesise and secrete hormones into blood
hormone
chemical secreted into blood, acts on specific target cells to regulate cellular function
3 chemical classifications of hormones
peptides/ proteins - from DNA transcription and mRNA translation on RER - exocytosis (hydrophilic) steroids - from cholesterol - diffusion (lipophilic) biogenic amines - from tyrosine (aa) - diffusion (lipophilic), exocytosis (hydrophilic)
mechanism of action of hydrophobic hormones
e.g. steroid, biogenic amines (thyroid) hormones
bind to intracellular receptors
alters transcription, more/ less protein produced
mechanism of action of hydrophilic hormones
e.g. peptides, biogenic amines
binds and activates cell surface receptors
stimulates secondary messenger
two types of endocrine control
homeostatic response - homeostatic function e.g. ADH, PTH
adaptive response - adapt to specific stimulus e.g. insulin
regulating simple hormone response
involves one endocrine gland
regulated by circular response
e.g. ⬆ blood glucose, ⬆ pancreas insulin, glucose taken up by target cell, ⬇ blood glucose, pancreas stops releasing insulin
regulating complex hormone response
involves action of two or more endocrine glands
regulated by
- long, indirect feedback loop - final hormone affects first endocrine secretion
- long, direct feedback loop - final hormone affects second endocrine secretion
- short feedback loop - second hormone affects first endocrine secretion
- negative feedback - hormone output reverses stimulus
- positive feedback - hormone output encourages stimulus
anterior lobe of pituitary connection with hypothalamus
portal vessels transport hormones down pituitary stalk from hypothalamus to stimulate synthesis and secretion of hormones from anterior lobe
anterior pituitary hormones
synthesised in anterior lobe
tropic hormones - target cell is another endocrine cell
- gonadotrophs e.g. FSH (gametogenesis), LH (steroidogenesis)
- thyrotrophs e.g. TSH (thyroid secretion)
- corticotrophs e.g. ACTH (adrenal cortex secretes cortisol and aldosterone)
non-tropic hormones - directly affect target cell
- somatotrophs e.g. GH (increase glucagon and insulin)
- lactotrophs e.g. PRL (mammary glands, Na+ kidney reabsorption)
all are trophic hormones - induce cell growth in target cell
regulation of hormones from hypothalamus to anterior pituitary
controlled by tropic neurohormones of hypothalamus
posterior lobe of pituitary connection with hypothalamus
neurosecretory neurons connect posterior lobe of pituitary to hypothalamus
posterior pituitary hormones
synthesised in hypothalamus, stored and secreted in posterior lobe
magnocellular neurones synthesise
- ADH (water reabsorptionin kidney)
- oxytocin (uterine contractions)
three ways of hormone excess
primary hypersecretion from final endocrine gland
secondary hypersecretion from middle endocrine gland
secondary hypersecretion from first endocrine gland
functions of calcium (6)
calcium salt (calcium hyroxyapatite) in bone and enamel
trigger neurotransmitter release (exocytosis)
trigger hormonal secretion (exocytosis)
blood coagulation (cofactor)
enzymatic regulation (cofactor)
muscle contraction