Chapter 41 textbook - Chapter 41 Endocrine What are...

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Chapter 41: Endocrine What are hormones and how do they work? Can act locally or at a distance o Endocrine cells produce and release chemical signals directly into the ECF, which can then diffuse through the ECF into the blood Signals that enter the blood are hormones Paracrine signals-bind to receptors on nearby cells (ex. Histamine) Autocrine- signal binds to same cell that released it Neurohormones- chemical signal produced by neuron that act as a hormone, diffuse into blood o Endocrine glands-group of cells that secretes multiple hormones o Exocrine glands-products of exocrine cells are carried to external environments (ex. Skin or sweat gland) Hormones can be divided into three chemical groups: o 1. Peptides or proteins (majority); water soluble, easily transported without a carrier molecule o 2. Steroid hormones-synthesized from cholesterol; lipid-soluble o 3. Amine hormones-synthesized from amino acid (tyrosine); some water soluble, some lipid soluble Hormone action is mediated by receptors on or within their target cells o On-water soluble hormones, cannot pass, have receptors on target cell Large transmembrane glycoproteins (have binding domain that projects outside,transmembrane that anchors through, and cytoplasmic domain into cytoplasm) o Within-lipid soluble, diffuse through membrane; receptors in cytoplasm or nucleus Hormone action depends on the nature of the target cell and its receptor o Epinephrine-initiates fight or flight response (causes heart rate increase, constriction of blood vessels, binds to liver cells to stimulate breakdown of glycogen for energy) o Ex. Of responses Experiments about hormones and action o Generalization: the signal molecules themselves are highly conserved; as organisms evolved, their hormone receptors have become more adaptive o First hormone discovered was secretin Protein released from cells in the gut, stimulates the pancreas to secrete digestive fluids into the gut Bayliss and Starling removed all nerves to pancreas of a dog, showed that stomach acid was still produced without nerves; proved that a chemical extracted from one tissue could travel in the blood to cause a reaction in a different tissue
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Browning of white fat increases the fat’s metabolic activity Three hormones regulate molting and maturation in arthropods o 1 & 2. PTTH and ECDYSONE work in sequence to regulate molting PTTH is made in brain, transported and stored in corpora cardiac After stimulation, PTTH is released and diffused into prothoracic gland and stimulates secretion of ecdysone (steroid hormone; lipid soluble), which stimulates molting o 3. Juvenile Hormone responsible for preventing maturation released continuously from the corpora allata as long as it is present, Rhodnius molts into another juvenile instar How do The nervous and endocrine systems interact?
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