Chapter 37 Chemical Control of the Animal Body The Endocrine System Lecture Outlines by Gregory Ahearn University of North Florida Copyright 2011 Pearson Education Inc Chapter 37 At a Glance 37 1 How Do Animal Cells Communicate 37 2 How Do Animals Hormones Work 37 3 What Are the Structures and Functions of the Mammalian Endocrine System Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Individual cells of an animal s body must communicate with one another to ensure the proper functioning of the whole Methods of communication between cells fall into four broad categories Direct Synaptic Paracrine Endocrine Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Methods of communication between cells fall into four broad categories continued In direct communication tissues such as heart muscle have gap junctions that directly link the insides of adjacent cells allowing ions and electrical signals to flow between them This type of communication is very fast but also has a very short range Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Methods of communication between cells fall into four broad categories continued In the other three types of communication sending cells release messenger chemicals through their plasma membranes The chemicals then move to receiving cells and alter their physiology by binding to receptors specialized proteins on the surface or inside the receiving cells When the messenger binds to a receptor the recipient cell responds in a way that is determined by the messenger the receptor and the type of cell Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Every cell has dozens of receptors each capable to binding a specific messenger and stimulating a particular response Cells with receptors that bind a messenger molecule and respond to it are target cells for that message Cells without the correct receptors cannot respond to the messenger and are not target cells Therefore a given cell can be a target cell for some messenger molecules but not others depending on which receptors it has Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Synaptic paracrine and endocrine communication differ in speed and distance continued In paracrine communication cells release chemicals that diffuse through the extracellular fluid to other cells in the immediate vicinity They influence only a small group of cells but do so quickly because the distances are very short Endocrine hormones on the other hand are released into the bloodstream move throughout the body in a few seconds and trigger responses that may last from a few seconds to a lifetime Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Local hormones diffuse to nearby target cells Many cells engage in paracrine communication secreting local hormones into the extracellular fluid Local hormones include histamine which is released as part of the allergic and inflammatory responses and the cytokines by which cells of the immune system communicate with one another Local hormones have only short range actions because they are either degraded rapidly or taken up by nearby cells and cannot get far from the cells that secrete them Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Local hormones diffuse to nearby target cells continued Prostaglandins are modified fatty acids that are important local hormones secreted by cells throughout the body They have diverse roles for example during childbirth they cause the cervix to dilate and help stimulate the muscles of the uterus to contract Prostaglandins contribute to inflammation and pain sensations Drugs such as aspirin acetaminaphen and ibuprofen provide relief from these symptoms by blocking the enzymes that synthesize prostaglandins Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Endocrine hormones are transported to target cells throughout the body by the circulatory system Endocrine hormones are messenger molecules produced by the endocrine glands The secretory cells of an endocrine gland are embedded within a network of capillaries and the cells secrete their hormones into the extracellular fluid surrounding the capillaries The hormones diffuse into the capillaries and are carried throughout the body by the bloodstream Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate Endocrine hormones are transported to target cells throughout the body by the circulatory system continued The hormone oxytocin stimulates the contraction of uterine muscles during childbirth because the muscle cells have receptors that bind oxytocin Oxytocin however does not cause other muscles of the body to contract because their cells do not have the necessary receptors Uterine muscles therefore contain target cells for oxytocin whereas a woman s biceps do not Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 1 How Do Animal Cells Communicate The changes induced by hormones may be prolonged and irreversible as in the onset of puberty or the transformation of a caterpillar into a butterfly More typically the changes are temporary and reversible and help to regulate the physiological systems of the animal body within a course of time of seconds to hours Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 2 How Do Animal Hormones Work There are three classes of vertebrate endocrine hormones Peptide hormones which are chains of amino acids Amino acid derived hormones which are composed of one or two modified amino acids Steroid hormones which are synthesized from cholesterol Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 2 How Do Animal Hormones Work Hormones act by binding to receptors on or in target cells Receptors for hormones are found in two general locations on target cells On the plasma membrane Inside the cell within the cytoplasm or the nucleus Biology Life on Earth 9e Copyright 2011 Pearson Education Inc 37 2 How Do Animal Hormones Work Peptide and amino acid hormones usually bind to receptors on the surfaces of target cells These hormones cannot diffuse through the phospholipid bilayer of the plasma membrane and must bind
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