LECT 4- intercellular communication_57cb2ec9da3ab00efef3c8b00ee4dfe4_e7d529cc5efb3f97c8c2af91d266beb9.pptx
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‫بسم الله الرØمن الرØيم‬ INTERCELLULAR COMMUNICATION INTERCELLULAR COMMUNICATION Direct intercellular communication – Gap junction – Transient direct linkup of surface makers Indirect intercellular communication – Through extracellular chemical messengers...
‫بسم الله الرØمن الرØيم‬ INTERCELLULAR COMMUNICATION INTERCELLULAR COMMUNICATION Direct intercellular communication – Gap junction – Transient direct linkup of surface makers Indirect intercellular communication – Through extracellular chemical messengers or signal molecules Paracrine Neurotransmitters Hormones Neurohormones Direct intercellular communication Direct intercellular communication )complementary surface markers( Indirect intercellular communication Through extracellular chemical messengers or signal molecules (first messenger) Source Paracrine differs Neurotransmitters Distance Hormones Means by which get Neurohormones to target cells – Paracrines Local chemical messengers Exert effect only on neighboring cells in immediate environment of – Neurotransmitters Short-range chemical messengers Diffuse across narrow space to act on adjoining target cell (another neuron, a muscle, or a gland) Hormone s Long-range messengers Secreted into blood by endocrine glands in response to appropriate signal Exert effect on target cells some distance away from release site Endocrin e system – Neurohormones Hormones released into blood by neurosecretory neurons Distributed through blood to distant target cells Lipid insoluble or water soluble first messenger mechanism of action – These extracellular chemical messengers (first messengers) bring about cell responses primarily by signal transduction Process by which incoming signals are conveyed to target cell’s interior Lipid insoluble or water soluble first messenger mechanism of action Binding of extracellular messenger (first messenger) to matching receptor brings about desired intracellular response by either: 1. Opening or closing channels 2. By activating receptor enzymes 3. Activating second-messenger systems 1. Opening of receptor- channel when an extracellular messenger binds.2 Activation of receptor enzyme Tyrosine kinase pathway 3. Activation of second messenger pathway via G-Protein coupled receptors cAM P Calcium - ion(Ca+2) Inositol- triphosphate (IP3) Diacylglycerol- (DAG) Amplification of the initial signal by a second-messenger pathway Lipid soluble or water insoluble first messenger mechanism of action Hence, they are :lipid soluble they cross the - lipid bilayer Binds to - receptors inside the cell Bind DNA and - Affect gene transcription Classroom questions Mention types of intercellular communication Mention types of indirect intercellular communication Compare between the 4 types of indirect intercellular communication Mention mechanisms of action of lipophilic hormones Mention mechanisms of action of hydrophilic hormones Mention 4 second messengers What is the type of cell communication References Human physiology by Lauralee Sherwood, seventh edition Text book physiology by Guyton &Hall,11th edition Text book of physiology by Linda.s contanzo,third edition 24
