THE ENDOCRINE SYSTEM
uses chemical messenger, hormones, to relay information and instruction between cells
reg. long-term processes
sleep, hunger, thirst
reproduction
growth & development
includes numerous endocrine glands: secretions released into bloodstream; have intracellular effects
hypothalamus: production of ADH, oxytocin, & regulatory hormones
pineal gland: melatonin
parathyroid gland: PTH
amino acid derivatives: small molecules synthesized from individual amino acids
lipid derivatives: made from fatty acids or cholesterol; steroids; bind to intracellular receptors; bound to plasma proteins in blood
thyroid gland: thyroxine (T4), triiodothyronine (T3), calcitonin (CT)
adrenal glands
pancreas: (pancreatic islets): insulin & glucagon
organs with secondary endocrine functions:
adipose tissue: leptin
kidneys: EPO & calcitriol
gonads
heart: secretes ANP & brain natriuretic peptide (BNP)
pituitary gland
thymus: secretes thymosin
posterior lobe: release of oxytocin & ADH
anterior lobe: ACTH, TSH, GH, PRL , FSH, LH
adrenal cortex: cortisol, corticosterone, aldosterone, androgens
adrenal medulla: epinephrine (EPI), norepinephrine (NE)
testis:
ovaries
digestive tract
INTERCELLULAR COMMUNICATION
paracine communication: uses chemical messengers to transfer info from cell-to-cell within single tissue (through extracellular fluid)
synaptic communication: chemical messenger, neurotransmitter, travels across synaptic cleft to target cell; limit to a specific area
direct communication: exchange of ions/molecules between adjacent cells through gap junctions: occurs between two cells of the same type, in close contact
endocrine communication: releases hormones into blood stream; alters metabolic activities of many tissues & organs; widespread
target cells: specific cells that have receptors that bind & read hormonal messages
peptide hormones: consist of chains of amino acids; bind to extracellular receptors; soluble in blood
melatonin
TH: metabolism; development; catecholamine release
ADH: produced by hypothalamus; reabsorption of water; maintains hydration
GH: stimulates growth; increases protein synthesis; increases metabolic processes
TSH: stimulates TH release
insulin: secreted by beta cells; decreases blood glucose levels
T4: thyroxine; mostly converted to T3; 20%
T3: triiodothyronine; most active TH; 80%
lipid soluble:
androgens
water-soluble: free hormones; shorter acting; diffuse out of bloodstream & bind to receptors; broken down by liver/kidney; broken down by enzymes in plasma
cortisol: increased blood sugar & suppresses immune system; stimulates fight-or-flight
aldosterone: increases Na reabsorption; increases blood volume & bp
regulatory hormones: TRH, CRH, GHRH, PRH, GRH
calcitonin: lowers Ca2+ in bloodstream
ACTH: adrenocorticotropic hormone; triggered by corticotropin releasing hormone; triggers cortisol, aldosterone, androgens release in adrenal glands
NE & EPI: adrenaline
PRL: triggered by PRH; stimulates milk production
LH: stimulates progesterone & ovulation
FSH: stimulates follicular maturation; leads to estrogen
FSH: stimulates Sertoli cells to produce androgen-binding protein
LH: stimulates Leydig cells to produce testosterone
stimulates sperm production
uterine preperation
OXT: stimulates uterine contraction; responsible for milk ejection & let-down reflex
PTH: opposed calcitonin; increases Ca2+ blood levels
EPO: increase RBC production
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glucagon: increases blood glucose level