Chapter 45 Hormones 2 systems coordinate communication 1 Endocrine System Secretes hormones that coordinate slower but longer acting responses including reproduction development energy metabolism growth and behavior 2 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 communication criteria Way signals are transmitted between animals cells are classified by two Types of secreting cell Route taken by signal to target Types of Chemical Signals 1 Hormones Endocrine Signaling a Hormones secreted into extracellular fluids by endocrine cells each targets via blood stream i Endocrine Glands are ductless and secrete hormones directly into surround fluid interstitial fluid which then diffuse into blood stream ii 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 development 2 Local regulators Paracrine and Autocrine Signaling a Local regulators molecules that act over short distances reaching target cells solely by diffusion i Help regulate BP nervous system function and reproduction b 2 Groups i Paracrine Signaling Target cells lie near the secreting cells ii Autocrine Signaling Target cell is secreting cell 3 Neurotransmitters Synaptic Signaling a In Synaptic signaling neurons form specialized junctions with target cells called synapses b At synapses neurons secrete molecule called neurotransmitters that diffuse short distances and bind to receptors on target cells i Sensation Memory cognition and movement 4 Neurohormones Neuroendocrine Signaling a In Neuroendocrine signaling specialized neurosecretory cells secrete molecules called nuerohormones that travel to target cells via blood stream i Ex Posterior Pituitary releases the nuerohormone antidiuretichromane to regulate kidney function and water balance 5 Pheromone Signaling environment a Pheromones chemicals that are released into the i Mark trails for food defining territories warning predators and attracting mates Endocrine Tissues and Organs called endocrine glands In some tissues endocrine cells are grouped together in ductless organs Endocrine glands secrete hormones directly into surround fluid Major Glands Hypothalamus pineal gland pituitary gland thyroid gland parathyroid gland adrenal glands pancreas kidneys ovaries and testes Chemical Class of hormones 3 major classes of molecules function as hormones 1 Polypeptide Proteins and Peptides 2 Amines derived from Amino Acids 3 Steroids Lipid Soluble and Water Soluble Hormones LSH Steroids pass easily through cell membranes WSH can t LSH receptors are on the inside of a cell WSH receptors are on the outside of the cell Cellular Response Pathway cell surface receptors WSH are secreted by exocytosis travel freely in blood stream and bind to LSH diffuse across cell membranes travel into the blood stream bound to transport proteins and diffuse through membrane of target cell Pathway for WSH Binding of a hormone to its receptor initiates a signal transduction pathway leading to response inside the cell Signaling Pathway for Epinephrine Epinephrine has multiple effects in mediating the body s response to short term stress Binds to receptors on the plasma membrane of liver cells Triggers 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 LSH Response to LSH is a change in gene expression Steroids 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 genes TF regulate binding of RNA polymerase onto promoter region Multiple effects of hormones Same hormone may have different effects on target cells that have Different receptors for the hormone Ex Epinephrine alpha and beta receptors on blood vessels Causes skeletal blood vessels to dilate but intestinal blood vessels to constrict Different signal transduction pathways Ex Different effect of protein kinase A breakdown glycogen and release glucose in skeletal muscle blood vessels activation of protein kinase A causes dilation Activation of protein kinase A causes liver cells to Local regulators are secreted molecules that link neighboring cells or Signaling by local regulators directly regulate the secreting cell Types of L R s growth and differentiation neurotransmitter Cytokines Plays a role in immunity and growth factors cell Nitric Oxide NO dilation of blood vessels can also act as a Prostaglandin 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 systems Release of acidic contents of the stomach into the duodenum stimulates endocrine cells there to secrete secretin Causes target cells in pancreas to release bicarbonate ions to raise pH in the duodenum When 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 Glucose Insulin decrease blood glucose and Glucagon Raises blood glucose are antagonistic hormones help maintain glucose homeostasis Pancreas 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 Insulin 1 Promoting cellular uptake of glucose 2 slowing glycogen breakdown in liver 3 promoting fat storage not break down Glucagon 1 Stimulates conversion of glycogen to glucose in liver 2 Stimulates breakdown of fat and protein into glucose Diabetes Mellitus Diabetes Mellitus caused by a deficiency of insulin or a decreased response to insulin in target tissues elevated blood glucose levels Type 1 Insulin Dependent Autoimmune disease where immune system destroys pancreatic beta cells Type 2 Insulin Independent Insulin deficiency or reduced response of
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