- Endocrine control : control by chemical signals that are produced by organs called glands and released into the bloodstreamo Gland : organ or part of an organ that synthesizes and releases a chemical species into somewhere else Synthesizing and secreting = secretion- Exocrine gland: release products into ducts wherever that duct emptieso Salivary glands ( produce saliva which is aqueous and contains proteins ducts oral cavity)- Endocrine gland : release products into the blood directly Products are called hormones and they go everywhere the blood goes—reach every cell However hormones DO NOT AFFECT EVERY CELL Each hormone affects only cells that express specific receptors that bind the hormone (no receptor = no effect)- Hormone : chemical signaling molecule that is released by gland or cells and affects other parts of body- Hormones are produced by a large variety of organso endocrine glands : hypothalamus, pineal gland, pituitary, thyroid and parathyroid glands, adrenal glands, pancreas (both exocrine and endocrine function), ovaries/testeso Organs containing endocrine cells : thymus, heart, liver, stomach, kidney, small intestine- Hormones :o Hormones work at low concentrations: single hormone molecule can bind to receptor after receptor (binding is reversible) each receptor leads to downstream amplificationo Hormone molecules travel through the bloodstream where their receptors are located on target cells1. Hydrophilic hormones: peptidesa. Released from vesicles in gland cell travel freely in blood via dissolving in plasma bind GPCR cytoplasmic response or gene regulation (less common)b. Exocytosis accounts for release of NT at synapse and release of hormones into bloodc. NEVER enter the cell—act at the surfaced. Produce an effect with a much shorter latency (time from when a hormone is released to when you see an effect) = turns off faster2. Hydrophobic hormones : steroidsa. dissolve out of gland cell (no exocytosis) Bind transport protein in blood dissolves through plasma MB bind SPECIFIC signal receptor in cytoplasm or nucleus hormone-receptor complex binds promoter region of specific genes gene regulation cytoplasmic response because translation has been affectedb. produce their effect slowly—latency can be hours or days—also effect lasts longer- Epinephrine (adrenaline) : a modified amino acid hydrophilico Released by adrenal medulla gland o Epinephrine’s action at the liver: Epinephrine binds GPCR G protein activated with GTP adenylyl cyclase ATP turned into cAMP PKA inhibition of glycogen synthesis and promotion of glycogen breakdown- Estradiol : steroid hormone hydrophobico Released by ovaries , affects a follicle cell in an ovaryo Mechanism of action: Estradiol dissolves into cell binds estradiol receptor in cytoplasm hormone-receptor complex enters nucleus binds specific locations on DNA activates txn (and thus translation) of vitellogenin (vitello = yolk) synthesis of yolk- Effect hormone produces in a target cell depends on what happens in the target cell AFTER the hormone binds to a receptoro Epinephrine binds Beta receptor in liver glycogen breaks down andglucose is released into bloodo Epinephrine binds alpha receptor in wall of blood vessel dilation of blood vesselo Epinephrine binds Beta receptor in wall of blood vessel constriction of blood vessel- Release of insulin hormone is controlledo negative feedback to stabilize amount of glucose dissolved in plasmao Homeostasis stimulus (blood glucose rises) B cells release insulin into blood liver takes up glucose and stores it as glycogen—other body cells take up more glucose blood glucose level declines homeostasis (90 mg/dL)o Insulin binds insulin receptors on target cell MB- Diabetes Mellitus : thirsty, produces a lot of urineo Problem in insulin pathway that doesn’t allow cells to take up glucoseo Target cells cannot bind/respond to insulin or B cells can no longer secrete insulino Type I : autoimmune disease—immune system destroys the B cellso Type II : receptors on target cells or intracellular machinery doesn’t allow insulin to affect target cells properly Associated with obesity—seen more in kids latelyo Elevated blood glucose : retina is very sensitive = blindness, interferes with wound healing, neuropathyo Type II is major cause of kidney failure, amputation, and blindness- Many hormones controlled by combination of neuronal & hormonal signalingo Hypothalamus leads into the posterior pituitary (towards back of head), and towards the face is the anterior pituitaryo Posterior & anterior act individually- Anterior pituitary : consists of several types of gland cellso Each type of cell type releases one or two particular hormoneso Anterior cells release their hormones under the control of neurohormones—secreted by neurons in one part of hypothalamus These neurons have cell body in hypothalamus & release their hormone onto blood vessels which go to anterior pituitary bind particular type of cell & each releases 1 type of hormone All anterior pituitary hormones are peptides/proteins Some anterior pituitary hormones control secretion by the cellsin the other glands elsewhere in the body Some anterior pituitary hormones affect most cells in the body;others have very specific targets- Each releasing factor affects just one cell type within the anterior pituitary and it controls the release of the pituitary cell’s own hormoneo Hypothalamic neurons (neurosecretory cells ) release their neurohormones (releasing factors) into specific capillaries (portal vessels) endocrine cells of anterior pituitary are either inhibited or stimulated to release pituitary hormones FSH and LH testes and ovaries TSH thyroid gland ACTH adrenal cortex Prolactin Mammary glands MSH melanocytes GH liver, bones, other tissues (essentially every cell, not just glands)—Can be used therapeuticallyo Tropic effects only : FSH, LH, TSH, ACTH (target = endocrine gland/cell)o Nontropic effects : prolactin, MSH (directly stimulate effect in target cell)o Nontropic and tropic effects : GH- Regulation of thyroid gland : o Neurons in hypothalamus may be a temperature sensor
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