Lecture 9: Principles of Neural and Hormonal Communication PDF

Lecture 9: Principles of Neural and Hormonal Communication Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  L...

Lecture 9: Principles of Neural and Hormonal Communication Dr. Safa Almaghrabi MBBS, MBiomedSc, PhD Associate Professor in Clinical Physiology Department Email: [email protected] 1  Learning Objectives 1. Distinguish the concept of neural versus hormonal communication 2. Classify hormones and illustrate examples for each type 3. Differentiate the mechanism of action of hydrophilic versus lipophilic hormones 4. Compare in a table between the nervous and the endocrine system Communication is critical for the survival of the cells that compose the body Two major regulatory systems of the body: 1. Nervous system 2. Endocrine system  Hormonal Communication Two distinct groups of hormones based on their solubility properties - Hydrophilic hormones (amines, peptides) - Lipophilic hormones (Steroids)  Hormonal Communication 1. Surface-binding hydrophilic hormones function by activating second-messenger pathways within the target cell. This activation directly alters the activity of preexisting intracellular proteins, usually enzymes, to produce the desired effect. i. cyclic adenosine monophosphate (cAMP) Pathway ii. Cell Membrane Phospholipid Second Messenger System 2. Lipophilic hormones function mainly by activating specific genes in the target cell to cause the formation of new intracellular proteins, which in turn produce the desired effect. The new proteins may be enzymatic or structural.  Hormonal Communication Regulation of Receptors: The receptors themselves are also -- volation subject to regulation. target cell to -to Receptor number (upregulation or downregulation). protested de ur Affinity (attraction of a receptor for its extracellular chemical messenger). Many diseases can be linked to malfunctioning receptors or to defects in the ensuing signal transduction pathways. alsanding gorger un C growtmor  Neuronal Communication Neural signals in the form of action potentials are rapidly propagated along neuronal fibers, resulting in the release at the axon terminal of a neurotransmitter that must diffuse only a microscopic distance to its target cell before a response is affected.  Neuronal Communication A neurally mediated response is rapid but brief; the action is quickly halted as the neurotransmitter is swiftly removed from the target site. This permits ending the response, almost immediately repeating the response, or rapidly initiating an alternate response as circumstances demand (for example, the swift changes in commands to muscle groups needed to coordinate walking). Comparison between the Nervous and Endocrine Systems  Comparison between the Nervous and Endocrine Systems In many instances, the nervous and endocrine systems both influence the same target cells in a supplementary fashion. For example, these two major regulatory systems both help regulate the circulatory and digestive systems. Thus, many important regulatory interfaces exist between the nervous and the endocrine systems.