• first experiment demonstrating existence of a 'hormone' - Starling coined this term in 1905
• acid ingesta leaves stomach -> secretin released by duodenal mucosa -> secretin travels to pancreas and stimulates discharge of pancreatic juices
Von Mering and Minkowski's 1889 experiment
• remove dog's pancreas -> disease we know as diabetes mellitus
• eventual recognition of insulin and control of diabetes
cell surface receptors
∙ embedded in the plasma membrane
∙ binds peptide/protein hormones, catecholamines, eicosanoids
∙ generates '2nd messengers' which alter activity of other molecules in the cell - usually enzymes
neurocrine hormone delivery
∙ neuron contacts target cells by axonal extensions and releases hormone into synaptic cleft between the two cells
three domains of an intracellular receptor
∙ amino-terminus: interacts with transcription factors
∙ DNA binding domain: amino acids bind to specific sequences of DNA
∙ carboxy-terminus: binds hormone, AKA carboxy-terminus or hormone binding domain
amino acid derivative hormones
∙ thyroid hormones: use tyrosine as a precursor
∙ catecholamines: includes epinephrine and norepinephrine, used as both hormones and neurotransmitters
major functions of hormones
• reproduction
• growth and development
• maintenance of internal environment (homeostasis)
• energy production, metabolism, utilization, storage
• response to stimuli
uses of Ca+ ion
∙ phosphoinositide cascade/Ca+ ion used in:
∙ glycogenolysis in liver
∙ insulin secretion from pancreas
∙ epinephrine and norepinephrine secretion from adrenal gland
∙ smooth muscle contraction
∙ TRH, GnRH
pituitary gland
• major endocrine organ located immediately below the hypothalamus and brain
• produces large number of protein and peptide hormones - often called the 'master gland'
peptide and protein hormones
∙ made of amino acids, chains range from 3 long (TRH) to >180 (HGH)
∙ produced in many glands: pituitary, hypothalamus, pancreas
∙ stored in gland of origin then released into capillaries
