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Endocrinology 1 - BSCI447 Endocrinology Test One Material...

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BSCI447 – Endocrinology Test One Material Endocrine glands – release hormones directly into the extracellular fluid (blood, interstitial fluid) Difference between hormones and neurotransmitters: - The way they are released o neurotransmitters into the synaptic cleft o hormones into extracellular fluid - The same chemical can be released into different places and be classified as both neurotransmitter and hormone (ex. = dopamine) “Major” glands are glands whose primary role is endocrine hormone production Hormone release - In response to stimuli to maintain homeostasis - Work via negative feedback – hormones negate/eliminate the stimuli that started their release Stimuli – - Humoral – when there are changes in chemical level in the extracellular fluid (ex. Glucose) - Neural – nervous system triggers the release (ex. Reflex reaction: fight or flight) - Hormonal – other hormones activate the release o GnRH > LH/FSH > Testosterone/Progesterone Names of hormones - tell either the function, mechanism or structure o parathyroid hormone o FSH o Tetraiodothyroxine (T3) Three chemical structures - Biogenic Amine hormones – derived from tyrosine o Polar – cannot cross the bilayer - Peptide/protein/glycoprotein hormones o Polar - Steroid hormones – derived from cholesterol o Non-polar – crosses bilayer to get to nuclear receptors Target Cells – expressing accessible functional receptors that the hormone can reach - Can be target of many hormones/ bind to multiple hormones at once 1
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Hormonal interaction with target cell - Classical endocrine interaction – transport via bloodstream - Paracrine – release into interstitial fluid nearby to act on neighboring cells - Juxtacrine – target cells are juxtaposed (direct contact) to hormone-releasing cells so hormone (usually polar) act directly on target cell (ex. Placenta) - Autocrine – acts upon itself – self-targetting (ex. Insulin) Hormonal interrelationships - Agonism – hormone bind to another hormone’s receptors and mimics that hormone’s response - Antagonism – blocks the receptor of another hormone – no hormonal effect is observed - Permissiveness – hormone (bound to its own receptor) increases the effect of another hormone - Cooperativity – work in tandem on the same tissue to bring effect – first hormone starts and then second hormone finishes response - Synergism – works together to bring effect greater than the sum of the individual responses (1+1=10 not 2) Receptors - Proteins that bind reversibly o H + R HR - Have high affinity (specificity for their one hormone) - In plasma membrane or inside the cell o Membrane-bound or cell surface G-protein Tyrosine kinase o Intercellular or nuclear receptor Cytosol receptors Nuclear receptors - Location dictates signal transduction pathway Cell Surface Receptors - 3 parts o Inside membrane – hydrophobic amino acids - Transmembrane domain o Exposed to outside – contains hormone binding site – Ectodomain o Exposed to cytosol – attached to G-protein/TK - cytoplasmic domain
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