Chapter 45-Hormones-2 systems coordinate communication1) Endocrine System: Secretes hormones that coordinate slower but longer-acting responses, including reproduction, development, energy metabolism, growth and behavior2) Nervous system: conveys high-speed electrical signals along neurons signals regulate other cells-Concept 45.1: Hormones and other signaling molecules bind to target receptors, triggering specific response pathways-Intercellular communicationWay signals are transmitted between animals cells are classified by two criteriaTypes of secreting cellRoute taken by signal to targetTypes of Chemical Signals1) Hormones-Endocrine Signalinga. Hormones secreted into extracellular fluids by endocrine cells each targets via blood streami. Endocrine Glands: are ductless and secrete hormones directly into surround fluid, interstitial fluid, which then diffuse into blood streamii. Endocrine Glands differ from Exocrine glands; which have ducts and secrete antibody surfaces (Ex. Tear ducts) or into body cavities (Digestive Fluid)b. Maintains homeostasis, mediates responses to stimuli, growth and development2) Local regulators-Paracrine and Autocrine Signalinga. Local regulators: molecules that act over short distances,reaching target cells solely by diffusioni. Help regulate BP, nervous system function and reproductionb. 2 Groupsi. Paracrine Signaling: Target cells lie near the secreting cellsii. Autocrine Signaling: Target cell is secreting cell3) Neurotransmitters-Synaptic Signalinga. In Synaptic signaling, neurons form specialized junctions with target cells, called synapsesb. At synapses, neurons secrete molecule called neurotransmitters that diffuse short distances and bind toreceptors on target cellsi. Sensation, Memory, cognition and movement4) Neurohormones-Neuroendocrine Signalinga. In Neuroendocrine signaling, specialized neurosecretory cells secrete molecules called nuerohormones that travel to target cells via blood streami. Ex. Posterior Pituitary releases the nuerohormone antidiuretichromane to regulate kidney function andwater balance.5) Pheromone Signalinga. Pheromones: chemicals that are released into the environmenti. Mark trails for food, defining territories, warning predators, and attracting mates.-Endocrine Tissues and OrgansIn some tissues, endocrine cells are grouped together in ductless organs called endocrine glandsEndocrine glands secrete hormones directly into surround fluidMajor Glands: Hypothalamus, pineal gland, pituitary gland, thyroid gland, parathyroid gland, adrenal glands, pancreas, kidneys, ovaries, and testes.-Chemical Class of hormones3 major classes of molecules function as hormones1) Polypeptide (Proteins and Peptides)2) Amines derived from Amino Acids3) Steroids-Lipid-Soluble and Water-Soluble HormonesLSH (Steroids) pass easily through cell membranes, WSH can’tLSH receptors are on the inside of a cellWSH receptors are on the outside of the cell-Cellular Response PathwayWSH are secreted by exocytosis, travel freely in blood stream and bind to cell-surface receptorsLSH diffuse across cell membranes, travel into the blood stream bound to transport proteins and diffuse through membrane of target cell-Pathway for WSHBinding of a hormone to its receptor initiates a signal transduction pathway, leading to response inside the cellSignaling Pathway for EpinephrineEpinephrine has multiple effects in mediating the body’s response to short term stressBinds to receptors on the plasma membrane of liver cellsTriggers release of a G-Protein that activates adenylyl cyclase which converts ATP to cAMP; cAMP is then used as a secondary messenger to activate enzymes in the liver cell which results in release of glucose from the cell into the bloodstream.Activated Enzymes inhibit glycogen synthesis and promote the break down of glycogen into a glucose molecule-Pathway for LSHResponse to LSH is a change in gene expressionSteroids, thyroid hormones and hormone form of vitamin D enter target cells and bind to protein receptors in cytoplasm or nucleus.Protein-receptor complexes then act as transcription factors in nucleus, regulating transcription of genesTF regulate binding of RNA polymerase onto promoter region-Multiple effects of hormonesSame hormone may have different effects on target cells that have:Different receptors for the hormoneEx. Epinephrine alpha and beta-receptors on blood vesselsCauses skeletal blood vessels to dilate, but intestinal blood vessels to constrictDifferent signal transduction pathwaysEx: Different effect of protein kinase A Activation of protein kinase A causes liver cells to breakdown glycogen and release glucose, in skeletal muscle blood vessels, activation of protein kinase A causes dilation-Signaling by local regulatorsLocal regulators are secreted molecules that link neighboring cells or directly regulate the secreting cell.Types of L.R.’sCytokines (Plays a role in immunity and growth factors (cell growth and differentiation)Nitric Oxide (NO): dilation of blood vessels, can also act as a neurotransmitterProstaglandin: in immune system they promote fever and inflammation and intensify pain, regulate formation of blood clots.-Concept 45.2: Feedback regulation and Antagonistic hormone pairing are common in the endocrine systemsRelease of acidic contents of the stomach into the duodenum stimulates endocrine cells there to secrete secretinCauses target cells in pancreas to release bicarbonate ions to raise pH in the duodenumWhen pH is raised, target cells in duodenum are no longer stimulated by H+ ions and stop releasing secretin, causes pancreases to reduce secretion of bicarbonate-Insulin and Glucagon: Control of Blood GlucoseInsulin (decrease blood glucose), and Glucagon (Raises blood glucose) are antagonistic hormones help maintain glucose homeostasisPancreas has clusters of endocrine cells called pancreatic islets with alpha cells that produce glycogen and beta cells that produce insulin-Target tissues for Insulin and Glucagon-Insulin1) Promoting cellular uptake of glucose2) slowing glycogen breakdown in liver3) promoting fat storage, not break down-Glucagon1) Stimulates conversion of glycogen to glucose in liver2) Stimulates breakdown of fat and protein into glucose-Diabetes MellitusDiabetes Mellitus: caused by a deficiency of insulin or a decreased response to insulin in target tissues, elevated blood
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