endocrine lecture 1 Flashcards
what is the function of the endocrine system?
to maintain internal homeostasis
regulate growth and morphological change
coordinate development and reproduction
facilitate behavioural and social interactions
what is the simplized pathway of the endocrine system?
hypothalamus -> pituitary -> target endocrine glands (thyroid, adrenal, gonads, other)
what are the types of cell signalling?
classical endocrine signalling
neuroendocrine signalling
autocrine regulation
paracrine regulation
lactocrine regulation
what is classical endocrine signalling?
hormone moves from endocrine cell to target cell through blood
what is nueroendocrine signalling?
hormone moves from nueroendocrine cell (neuron) to target cell through bloodstream
what is autocrine regulation?
hormone diffuses through interstitial fluid to other part of same cell
what are paracrine regulation?
hormone diffuses through intersitial fluid to an adjacent cell
what are the main types of hormones?
fatty acid derived hormones/eicosanoids
steroid hormones
peptide and protein hormones
amino acid derivatives
what are the two types of amino acid derivative hormones?
catecholamines and thyroid hormones
what are catecholamines?
synthesized from tyrosine, norepinephrine, and epinephrine (basically adrenaline), are formed in cytoplasm of cells of the adrenal medulla and stored in vesicles until secreted (in response to fear)
what are thyroid hormones?
synthesized from tyrosine, incorporated into thyroglobulin and stores in large follicles in the thyroid gland
combined with thyroxine-binding globulin (carrier protein) in plasma
what are peptide and protein hormones?
preprohormones with signal peptide for golgi transit and removal to form prohormones
prohormone convertase process into final product
stored in secretory vesicles
sometimes prohormone and its peptides are released with active hormone
what are the only hormones that are encoded in the genome?
peptide and protein hormones
what are steroid hormones?
derived from cholesterol
tissue-specific enzymes determine nature of final product
they are not stored (produced as needed)
enzymatic steps in mitochondria and ER convert cholesterol into end products
they are lipid soluble and simply diffuse across cell membrane
what are fatty acid derived hormones or eicosanoids?
synthesized from a 20-carbon fatty acid called arachidonic acid
produced and secreted by nearly every cell
function in inflammation, blood pressure, and blood clotting
what are hormone receptors?
proteins that bind hormone at target site and initiate the intended response
what are the characteristics of a receptor?
affinity (how tightly in binds the hormone)
specificity (how much it prefers to bind one hormone over other molecules)
capacity (how much ligand molecules it binds at a time)
what are the two types of hormone receptors?
membrane receptors and cytosolic/nuclear receptors
what are membrane receptors?
span the phospholipid bilayer
hormone binds extracellularly
binding alters receptor conformation and transmits intracellular signal
what are cytosolic/nuclear receptors?
in the cytoplasm and or nucleus
activated receptor binds to DNA and alters gene expression
lipid soluble hormone must enter the cell for receptor binding
what is the concentration of hormones determined by?
rate of production
rate of delivery
rate of degradation and elimination
what is MCR?
metabolic clearance rate - removal rate of hormone from plasma (ml cleared per minute)
what clears hormones?
mainly the liver and kidneys, small amount by target tissue
how does the target tissue remove hormones?
protein and amine hormones are internalized with receptors and degraded
steroid and thyroid hormones are degraded after hormone/receptor complex binds to DNA
