chapter6a Communication, Integration,and Homeostasis 1

chapter6a Communication, Integration,and Homeostasis 1 -...

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Unformatted text preview: Chapter 6a Communication, Integration, and Homeostasis About this Chapter Cell-to-cell communication Signal pathways Novel signal molecules Modulation of signal pathways Control pathways Response loops Feedback loops Cell-to-Cell Communication: Overview Physiological signals Electrical signals Changes in the membrane potential of a cell Chemical signals Secreted by cells into ECF Responsible for most communication within the body Target cells, or targets, receive signals Four basic methods of communication Figure 6-1a Cell-to-Cell Communication: Methods Direct contact and local cell-to-cell communication Gap junctions Transfer both chemical and electrical signals Form direct cytoplasmic connections between adjacent cells. Protein connexins form a connexon channel Cell-to-Cell Communication: Methods CAMs , cell adhesion molecules, transfer signals in both directions Common in Immune system Contact-dependent signals require interaction between membrane molecules on two cells. Figure 6-1b Cell-to-Cell Communication: Methods Direct contact and local cell-to-cell communication Autocrine signals act on the same cell that secreted them. Paracrine signals are secreted by one cell and diffuse to adjacent cells. Figure 6-1c (c) Autocrine signals and paracrine signals Receptor Cell-to-Cell Communication: Methods Paracrine and autocrine are chemical signals Hormones are secreted by endocrine glands or cells into the blood. Only target cells with receptors for the hormone will respond to the signal. Figure 6-2a (a) Hormones Endocrine cell Cell without receptor Cell with receptor No response Target cell Response Blood Cell-to-Cell Communication: Methods Long distance cell-to-cell communication Neurotransmitters are chemicals secreted by neurons that diffuse across a small gap to the target cell. Neurons use electrical signals as well. Neurotransmitters have a rapid effect Figure 6-2b (b) Neurotransmitters Neuron Electrical signal Target cell Cell-to-Cell Communication: Methods Neurohormones are chemicals released by neurons into the blood for action at distant targets. Figure 6-2c Cell without receptor Cell with receptor No response (c) Neurohormones Neuron Response Blood Cell-to-Cell Communication: Methods Cytokines may act as both local and long- distance signals All nucleated cells synthesize and secrete cytokines in response to stimuli In development and differentiation, cytokines usually function as autocrine or paracrine signals In stress and inflammation, some cytokines may act on relatively distant targets Signal Pathways: Overview Figure 6-3 Receptor protein Intracellular signal molecules Signal molecule Target proteins Response binds to activates alters create Signal Pathways: Receptor locations Target cell receptors Lipophilic vs lipophobic Figure 6-4 (1 of 2) Slower responses related to changes in gene activity...
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chapter6a Communication, Integration,and Homeostasis 1 -...

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