Principles of Human Physiology Chapter 5 PDF

PowerPoint® Lecture Presentation CHAPTER 5 Chemical Messengers © 2017 Pearson Education, Inc. Chapter Outline 5.1 Mechanisms of Intercellular Communication 5.2 Chemical Messengers 5.3 Signal Transduction Mechanisms 5.4 Long-Distance Communication via the Nervous and Endocrine Systems © 2017 Pearson Education, Inc. 5.1 Mechanisms of Intercellular Communication General mechanisms Direct: Gap junctions Indirect: Chemical messengers © 2017 Pearson Education, Inc. Figure 5.1a Types of intercellular communication. Ions and small molecules Cell 1 Cell 2 Connexon Direct communication through gap junctions © 2017 Pearson Education, Inc. Figure 5.1b Types of intercellular communication. Chemical messenger Receptor Secretory Target cell cell Communication via chemical messengers © 2017 Pearson Education, Inc. Gap Junctions Composed of membrane proteins Link the cytosol of two adjacent cells Particle movement between cells acts as a signal Communication is direct Common in smooth and cardiac muscle © 2017 Pearson Education, Inc. 5.2 Chemical Messengers The messenger is produced by the source cell The messenger is released, often by secretion The messenger travels to the target cell The target cell has receptors for the messenger Binding of the messenger to the receptor triggers a target cell response Communication is indirect © 2017 Pearson Education, Inc. Chemical Messenger Classification Classification by function Classification by chemical properties Solubility properties Chemical class © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Messenger Classification by Function Paracrine chemical messenger Chemical that signals a nearby cell Example: Histamine, responsible for an inflammation response Autocrine chemical messenger A subclass of paracrines Chemical that signals the same cell that secreted it Source and target are the same © 2017 Pearson Education, Inc. Figure 5.2a Functional classes of chemical messengers. Secretory cell Paracrine Receptor Target cell (neighboring cell) Paracrines © 2017 Pearson Education, Inc. Messenger Classification by Function Neurotransmitter Messenger produced by neurons Released into the ECF of the synaptic cleft Examples: Acetylcholine, GABA, serotonin © 2017 Pearson Education, Inc. Figure 5.2b Functional classes of chemical messengers. Secretory cell (presynaptic) Axon terminal Synapse Neurotransmitter Receptor Target cell (postsynaptic) Neurotransmitters © 2017 Pearson Education, Inc. Messenger Classification by Function Hormone Messenger produced by endocrine cells Secreted into the blood via the interstitial fluid Examples: Insulin, estrogen, thyroxin Neurohormone A special class of hormone Messenger produced by neurons Secreted into the blood Examples: Antidiuretic hormone (ADH), oxytocin © 2017 Pearson Education, Inc. Figure 5.2c Functional classes of chemical messengers. Hormone Secretory cell (endocrine cell) Blood vessel Nontarget cell (no receptors) Receptor Target cell Hormones © 2017 Pearson Education, Inc. Chemical Classification of Messengers Lipophobic ligand Water soluble; not lipid soluble Does not cross the cell membrane Receptors on the cell membrane General action of target response Enzyme activation Membrane permeability changes © 2017 Pearson Education, Inc. Chemical Classification of Messengers Lipophilic ligand Lipid soluble; not water soluble Easily crosses the cell membrane Usually intracellular location of receptors General action of target response is via gene activation © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Chemical Classification of Messengers Amino acids Lipophobic Target cell receptors on the cell membrane Only four amino acids function as messengers, all as neurotransmitters Examples: Glutamate, aspartate, glycine, GABA © 2017 Pearson Education, Inc. Chemical Classification of Messengers Amines Most are lipophobic, except thyroid hormones Target receptors on the cell membrane Made or derived from an amino acid Contains an amine group Examples: Catecholamines: Made from tyrosine Dopamine, norepinephrine, ephinephrine Thyroid hormones: Made from two tyrosine amino acids Histamine: Made from histidine Serotonin: Made from tryptophan © 2017 Pearson Education, Inc. Chemical Classification of Messengers Peptide and protein messengers Most abundant type of ligand Lipophobic Target receptors on the cell membrane Made of chains of amino acids Peptide ligand (50 amino acids) © 2017 Pearson Education, Inc. Chemical Classification of Messengers Steroid ligands Lipophilic All are derived from cholesterol All steroid messengers (ligands) function as hormones © 2017 Pearson Education, Inc. Messenger Classification by Chemical Class Eicosanoid ligands Lipophilic Intracellular target receptors Most are derived from arachidonic acid, a cell membrane phospholipid Examples: Prostaglandins, leukotrienes © 2017 Pearson Education, Inc. Synthesis and Release of Chemical Messengers Lipophobic ligands Synthesized on demand Immediate release from source Release rate depends on synthesis © 2017 Pearson Education, Inc. Synthesis and Release Characteristics Lipophobic ligands Synthesis is independent of demand Stored in vesicles of the source until needed Released by exocytosis: Release rate is determined by exocytosis © 2017 Pearson Education, Inc. Amino Acids Made from glucose Glutamate, aspartate Made from 3-phosphoglycerate Glycine From glutamate Glutamic acid decarboxylase GABA Synthesized within a neuron Stored in vesicles until needed Released by exocytosis © 2017 Pearson Education, Inc. Amines Produced in the cytosol of the source Stored in vesicles of the source Released by exocytosis The amine produced is determined by which enzymes are present in the source cell © 2017 Pearson Education, Inc. Figure 5.3 Catecholamine synthesis. COOH Cytosol HO CH2 C NH2 Tyrosine H Tyrosine β-hydroxylase OH COOH HO CH2 C NH2 L-Dihydroxyphenylalanine (L-dopa) H Catechol Dopa group decarboxylase OH HO CH2 CH2 NH2 Dopamine Dopamine Vesicle β-hydroxylase OH HO CH CH2 NH2 Norepinephrine OH Phenylethanolamine Cytosol N-methyl transferase (PNMT) OH HO CH CH2 NH CH3 Epinephrine OH © 2017 Pearson Education, Inc. Peptide and Proteins Formed by cleaving larger proteins Stored in secretory vesicles Released by exocytosis General terminology © 2017 Pearson Education, Inc. Figure 5.4b Peptide synthesis and release. Preprohormone Prohormone Hormone Cleaved Cleaved amino acids amino acids Generalized scheme of hormone synthesis © 2017 Pearson Education, Inc. Figure 5.4a Peptide synthesis and release. Slide 1 Rough endoplasmic reticulum mRNA Golgi apparatus Polypeptide Prepropeptide Propeptide Peptide Propeptide Propeptide Secretory Cleaved Cleaved amino acids vesicle amino acids Transport vesicle Smooth endoplasmic reticulum Prepropeptide Propeptide Peptide Cleaved Cleaved amino acids amino acids Peptide synthesis © 2017 Pearson Education, Inc. Figure 5.4a Peptide synthesis and release. Slide 2 Rough endoplasmic reticulum mRNA Polypeptide Prepropeptide Smooth endoplasmic reticulum Prepropeptide Peptide synthesis © 2017 Pearson Education, Inc. Figure 5.4a Peptide synthesis and release. Slide 3 Rough endoplasmic reticulum mRNA Golgi apparatus Polypeptide Prepropeptide Propeptide Propeptide Propeptide Secretory Cleaved amino acids vesicle Transport vesicle Smooth endoplasmic reticulum Prepropeptide Propeptide Cleaved amino acids Peptide synthesis © 2017 Pearson Education, Inc. Figure 5.4a Peptide synthesis and release. Slide 4 Rough endoplasmic reticulum mRNA Golgi apparatus Polypeptide Prepropeptide Propeptide Peptide Propeptide Propeptide Secretory Cleaved Cleaved amino acids vesicle amino acids Transport vesicle Smooth endoplasmic reticulum Prepropeptide Propeptide Peptide Cleaved Cleaved amino acids amino acids Peptide synthesis © 2017 Pearson Education, Inc. Steroids Synthesized on demand Derived from the cholesterol molecule All steroid ligands are similar © 2017 Pearson Education, Inc. Figure 5.5 Synthetic pathway for steroids. Cholesterol Nonactive Progesterone intermediate Nonactive Nonactive Nonactive intermediate intermediate intermediate Nonactive Nonactive Corticosterone intermediate intermediate Dehydroepiandrosterone Cortisol Aldosterone Androstenedione Testosterone Estrone Dihydrotestosterone Estradiol Estriol © 2017 Pearson Education, Inc. Eicosanoids Derived from arachidonic acid Arachidonic acid is a membrane phospholipid Synthesized on demand Two major synthetic pathways Cyclooxygenase pathway Lipoxygenase pathway © 2017 Pearson Education, Inc. Figure 5.6 Eicosanoid synthesis. Membrane phospholipid Phospholipase A2 COOH Arachidonic acid Cyclooxygenase Lipoxygenase pathway pathway Prostaglandins Leukotrienes Prostacyclins Thromboxanes © 2017 Pearson Education, Inc. Transport of Messengers Diffusion through interstitial fluid Source and target are close Ligand is quickly degraded Examples: Paracrines, autocrines, neurotransmitters, most cytokines © 2017 Pearson Education, Inc. Transport of Messengers Bloodborne transport Source and target are located at a distance Lipophobic ligands dissolve in plasma Lipophilic ligands bind to carrier protein Examples: Hormones, neurohormones, some cytokines © 2017 Pearson Education, Inc. Figure 5.7a Transport of messengers in blood. Endocrine cell Secreted by exocytosis Blood vessel Dissolved messenger Hydrophilic messenger © 2017 Pearson Education, Inc. Figure 5.7b Transport of messengers in blood. Endocrine cell Free Secreted hormone by diffusion (99%) Hydrophobic messenger © 2017 Pearson Education, Inc. Messenger Transport Messenger half-life Time for a chemical to decrease its concentration by half Concentration of the messenger could be in blood or interstitial fluid © 2017 Pearson Education, Inc. Messenger Transport Messenger half-life Messengers dissolved in plasma Have a relatively short half-life Example: Half-life of insulin is less than 10 minutes Messengers bound to plasma protein Have a relatively long half-life Example: Half-life of cortisol is 90 minutes © 2017 Pearson Education, Inc. 5.3 Signal Transduction Messenger binds to receptor Binding results in a cell response Signal transduction Process of producing a response in the target © 2017 Pearson Education, Inc. Receptor Binding Specificity Binding is brief and reversible Affinity = strength of binding Location of binding Lipophobic ligands: Cell membrane Lipophilic ligands: Within cell © 2017 Pearson Education, Inc. Receptor Properties Specificity One messenger may bind to many receptor types One target may have many types of receptors The number of receptors per cell varies and is dynamic © 2017 Pearson Education, Inc. Figure 5.8 Receptor specificity. Receptor C Messenger 1 Messenger 2 Receptor A Target cell for Target cell for messenger 1 messenger 2 Receptor B © 2017 Pearson Education, Inc. Magnitude of Target Response Strength of response depends on three factors: Concentration of the messenger (ligand) Number of receptors per target cell Receptor affinity for the messenger © 2017 Pearson Education, Inc. Figure 5.9 Effect of messenger concentration on messenger-receptor binding. Percentage of receptors bound 100 Concentration of messenger [M] © 2017 Pearson Education, Inc. Figure 5.10a Effects of receptor concentration and affinity on messenger-receptor binding. 100% 2R bound Number of receptors bound 100% R bound Concentration of messenger [M] Effects of receptor concentration © 2017 Pearson Education, Inc. Figure 5.10b Effects of receptor concentration and affinity on messenger-receptor binding. High afﬁnity for messenger 100 Percentage of receptors bound Low afﬁnity for messenger 50 Low [M] Higher [M] Concentration of messenger [M] Effects of receptor afﬁnity © 2017 Pearson Education, Inc. Up-regulation Receptor number increases on the target May result from too little messenger Sensitivity to the messenger increases © 2017 Pearson Education, Inc. Down-regulation Receptor number decreases on the target May result from excess messenger Sensitivity to the messenger decreases Tolerance to the messenger develops © 2017 Pearson Education, Inc. Agonists and Antagonists Agonist Chemical that binds to a receptor Its action mimics the normal response Antagonist Chemical that binds to a receptor Binding does not result in a response Competes with the normal ligand Response is the opposite of that to an agonist © 2017 Pearson Education, Inc. Example of Receptor Agonists and Antagonists β-endorphin: Endogenous opiate β-endorphin binds to µ (mu or micro) opiate receptors, producing analgesia Morphine: µ receptor agonist Administration of morphine produces analgesia Naloxone: µ receptor antagonist Administration of naloxone blocks morphine- or β-endorphin–produced analgesia 10× greater affinity for the µ receptor than morphine © 2017 Pearson Education, Inc. Mechanisms: Signal Transduction Intracellular-mediated responses Membrane-bound receptor-mediated responses Channel-linked receptors Enzyme-linked receptors G protein–linked receptors © 2017 Pearson Education, Inc. Intracellular-Mediated Response Characteristic of lipophilic ligands (except thyroid hormones) Receptors are found in the cytosol or nucleus Cell response is via gene activation © 2017 Pearson Education, Inc. Figure 5.11 Actions of lipophilic hormones on the target cell. Slide 1 Lipophilic messenger Extracellular ﬂuid Diffusion Nucleus Target cell DNA Nuclear Proteins Cytoplasmic receptor receptor Ribosome mRNA mRNA Hormone- Hormone receptor response Nuclear envelope complex element (HRE) Nuclear pore © 2017 Pearson Education, Inc. Figure 5.11 Actions of lipophilic hormones on the target cell. Slide 2 Lipophilic messenger Extracellular ﬂuid Diffusion Nucleus Target cell Nuclear receptor Nuclear envelope Nuclear pore © 2017 Pearson Education, Inc. Figure 5.11 Actions of lipophilic hormones on the target cell. Slide 3 Lipophilic messenger Extracellular ﬂuid Diffusion Nucleus Target cell Nuclear Cytoplasmic receptor receptor Hormone- receptor Nuclear envelope complex Nuclear pore © 2017 Pearson Education, Inc. Figure 5.11 Actions of lipophilic hormones on the target cell. Slide 4 Lipophilic messenger Extracellular ﬂuid Diffusion Nucleus Target cell DNA Nuclear Cytoplasmic receptor receptor mRNA Hormone- Hormone receptor response Nuclear envelope complex element (HRE) Nuclear pore © 2017 Pearson Education, Inc. Figure 5.11 Actions of lipophilic hormones on the target cell. Slide 5 Lipophilic messenger Extracellular ﬂuid Diffusion Nucleus Target cell DNA Nuclear Proteins Cytoplasmic receptor receptor Ribosome mRNA mRNA Hormone- Hormone receptor response Nuclear envelope complex element (HRE) Nuclear pore © 2017 Pearson Education, Inc. Figure 5.12a Mechanism of action for steroid and thyroid hormones. Steroid hormone Receptor protein Hormone for steroid receptor hormone DNA binding domain DNA Hormone Target response gene element Dimerization Steroid Steroid hormone hormone Transcription mRNA © 2017 Pearson Education, Inc. Figure 5.12b Mechanism of action for steroid and thyroid hormones. RXR TH receptor receptor DNA DNA binding binding domain domain DNA Hormone Target response gene element Dimerization 9-cis-retinoic Triiodothyronine acid Transcription mRNA © 2017 Pearson Education, Inc. Signal Transduction by Membrane-Bound Receptors Response of the target takes one of two forms: Movement of ions Phosphorylation of enzymes Overview of mechanisms Channel-linked receptors Enzyme-linked receptors G protein–coupled receptors (GPCRs) © 2017 Pearson Education, Inc. Channel-Linked Receptors Fast ligand-gated channels Receptor and channel—same protein Action is direct Binding of ligand causes the channel to open or close Change in transport of ions through the channel causes the target response © 2017 Pearson Education, Inc. Figure 5.13 Fast ligand-gated channels and the mechanism by which they change the electrical properties of cells. Extracellular Messenger ﬂuid Receptor and ion channel Channel closed Ions (Na+, K+, Cl–) move through open channel Cytosol Change in electrical properties of cell © 2017 Pearson Education, Inc. Figure 5.14 Fast ligand-gated calcium channels. Extracellular Messenger ﬂuid Calcium channel Channel closed Calcium enters cell through open channel As second messenger Change in Muscle Secretion Calmodulin electrical contraction properties of cell Ca-calmodulin Activates enzymes Protein kinase Protein- P Response in cell (muscle contraction, altered metabolism, Cytosol altered transport) © 2017 Pearson Education, Inc. Enzyme-Linked Receptors Receptor and enzyme—same protein Ligand binding activates the enzyme Action is direct Activated enzyme causes the target response Examples: Tyrosine kinases and guanylate cyclases © 2017 Pearson Education, Inc. Figure 5.15 An enzyme-linked receptor. Extracellular ﬂuid Tyrosine kinase receptor (active) Protein-Tyr Protein-Tyr- P + ADP Tyrosine kinase + receptor (inactive) Response in cell (alter metabolism, regulate Cytosol protein synthesis) © 2017 Pearson Education, Inc. G Protein–Coupled Receptors G proteins are regulatory proteins G proteins link ECF messenger to Ion channels Amplifier enzymes ECF messenger = first messenger The receptor, not the ECF messenger, binds to guanosine (the G in "G protein") nucleotides © 2017 Pearson Education, Inc. G Protein–Coupled Receptors Slow ligand-gated channels Receptor and channel—different proteins Receptor and channel are linked by the G protein Binding of the ligand activates the G protein, which activates the channel Action is indirect Change in transport of ions through the channel causes the target response © 2017 Pearson Education, Inc. Figure 5.16 Action of a G protein on a slow ligand-gated ion channel. Messenger Extracellular ﬂuid Receptor α α β γ GDP GTP Ions move in G protein or out of cell GDP GTP Change in electrical Cytosol properties of cell © 2017 Pearson Education, Inc. G Protein–Linked Receptors Second messengers Intracellular messengers Triggered by the first messenger (ligand) activating the G protein–coupled receptor The receptor activates the G protein The G protein activates the amplifier enzyme The amplifier enzyme activates second messenger production © 2017 Pearson Education, Inc. Second Messenger Systems Binding of the first messenger to the receptor leads to production of the second messenger Involves G proteins Gs: Activates amplifier enzyme Gi: Inhibits amplifier enzyme Purpose is signal amplification © 2017 Pearson Education, Inc. Second Messenger Systems Types of second messengers Cyclic AMP (cAMP) Cyclic GMP (cGMP) Inositol triphosphate (IP3) Diacylglycerol (DAG) Calcium ions © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 1 Extracellular ﬂuid Messenger Adenylate cyclase Receptor α α β γ GDP GTP G protein GDP GTP cAMP Activates ATP Protein kinase A Protein Protein- P + + ATP ADP Cytosol Response in cell © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 2 Messenger Receptor α β γ GDP G protein Cytosol © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 3 Extracellular ﬂuid Messenger Adenylate cyclase Receptor α α β γ GDP GTP G protein GDP GTP Cytosol © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 4 Extracellular ﬂuid Messenger Adenylate cyclase Receptor α α β γ GDP GTP G protein GDP GTP cAMP ATP Cytosol © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 5 Extracellular ﬂuid Messenger Adenylate cyclase Receptor α α β γ GDP GTP G protein GDP GTP cAMP Activates ATP Protein kinase A Cytosol © 2017 Pearson Education, Inc. Figure 5.17 The cAMP second messenger system. Slide 6 Extracellular ﬂuid Messenger Adenylate cyclase Receptor α α β γ GDP GTP G protein GDP GTP cAMP Activates ATP Protein kinase A Protein Protein- P + + ATP ADP Cytosol Response in cell © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 1 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 Protein kinase C GDP GTP G protein GDP GTP ATP + protein ADP + protein- P Calmodulin Response in cell Lumen of endoplasmic Protein kinase Response in cell reticulum (contraction, secretion) Protein- P Membrane of endoplasmic Response in cell (contraction, reticulum metabolism, transport) Cytosol © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 2 Messenger Extracellular ﬂuid Receptor α β γ GDP G protein © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 3 Messenger Extracellular ﬂuid Receptor Phospholipase C α α β γ GDP GTP G protein GDP GTP © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 4 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 GDP GTP G protein GDP GTP © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 5 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 Protein kinase C GDP GTP G protein GDP GTP © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 6 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 Protein kinase C GDP GTP G protein GDP GTP ATP + protein ADP + protein- P © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 7 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 Protein kinase C GDP GTP G protein GDP GTP ATP + protein ADP + protein- P Response in cell © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 8 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 α α β γ IP3 GDP GTP G protein GDP GTP Lumen of endoplasmic reticulum Membrane of endoplasmic reticulum © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 9 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 α α β γ IP3 GDP GTP G protein GDP GTP Lumen of endoplasmic Response in cell reticulum (contraction, secretion) Membrane of endoplasmic reticulum Cytosol © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 10 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 α α β γ IP3 GDP GTP G protein GDP GTP Calmodulin Lumen of endoplasmic Protein kinase Response in cell reticulum (contraction, secretion) Membrane of endoplasmic reticulum Cytosol © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 11 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 α α β γ IP3 GDP GTP G protein GDP GTP Calmodulin Lumen of endoplasmic Protein kinase Response in cell reticulum (contraction, secretion) Protein- P Membrane of endoplasmic Response in cell (contraction, reticulum metabolism, transport) Cytosol © 2017 Pearson Education, Inc. Figure 5.18 The phosphatidylinositol second messenger system. Slide 12 Messenger Extracellular ﬂuid Receptor Phospholipase C PIP2 DAG α α β γ IP3 Protein kinase C GDP GTP G protein GDP GTP ATP + protein ADP + protein- P Calmodulin Response in cell Lumen of endoplasmic Protein kinase Response in cell reticulum (contraction, secretion) Protein- P Membrane of endoplasmic Response in cell (contraction, reticulum metabolism, transport) Cytosol © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. Signal Amplification Small amounts of ligand can cause a huge response in the target Each step recruits more participants Characteristic of second messengers © 2017 Pearson Education, Inc. Figure 5.19 Signal amplification, in this case by the second messenger cAMP. Total number of product One messenger binds to one 1 One messenger receptor molecule Several α α G proteins β γ 10 are activated Each G protein activates an 10 α Adenylate adenylate cyclase cyclase leads to… Each adenylate cAMP cyclase generates 5000 hundreds of cAMP molecules Each cAMP Protein kinase A activates a 5000 protein kinase A Each protein kinase A phosphorylation Phosphorylated phosphorylates 2,500,000 of millions of protein hundreds of proteins proteins © 2017 Pearson Education, Inc. Endocrine Communication The endocrine target secretes a hormone The hormone enters the blood The blood spans the distance to the target © 2017 Pearson Education, Inc. Nervous Communication Nerve cells can transmit signals Within neuron via long axons Between cells via the synapse Signal in axon = action potentials Axons via action potentials span the distance to the target © 2017 Pearson Education, Inc. Figure 5.20 Signal transmission in neurons. Neuron Electrical transmission Neurotransmitter Chemical transmission Synapse Target cell Receptor © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. https:// www.youtube.com/watch?v=RMV130vU8gA https:// www.youtube.com/watch?v=MoHQAyMGCFw https://www.youtube.com/watch?v=7E-mh_enuSo https://www.youtube.com/watch? v=FUgNqKC13SE © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc. © 2017 Pearson Education, Inc.

Principles of Human Physiology Chapter 5 PDF

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