Action Potentials: Neural Signal Transmission PDF

Action Potentials: Neural Signal Transmission  Introduction to Neurons Neurons are specialized cells that transmit information throughout the body Key components: Cell body, dendrites, axon, and axon terminals Function as the body's electrical communication system...

Action Potentials: Neural Signal Transmission  Introduction to Neurons Neurons are specialized cells that transmit information throughout the body Key components: Cell body, dendrites, axon, and axon terminals Function as the body's electrical communication system Essential for thoughts, movements, sensations, and bodily functions Resting Membrane Potential Default state of neurons when not transmitting signals Typically around (-70) millivolts (mV) Maintained by sodium-potassium pumps More sodium (Na+) outside cell More potassium (K+) inside cell Creates electrical gradient across membrane  Ion Channels Specialized proteins in cell membrane Types: Voltage-gated channels – open and close based on specific membrane potentials Ligand-gated channels – open and close based on specific chemicals (neurotransmitters that bind to the channels) Leak channels – channels that are always open and ions move across through passive transport Control ion movement across membrane Critical for action potential generation Action Potential Initiation Stimulus causes sodium channels to open Sodium ions rush into cell Membrane potential becomes more positive Threshold reached at (-55) mV Triggers all-or-nothing response Thi s Photo by Unknown Author i s licensed under CC BY-SA  Depolarization Phase Rapid influx of sodium ions Membrane potential becomes positive Peaks at approximately (+30) mV Sodium channels begin to close Potassium channels open Thi s Photo by Unknown Author i s licensed under CC BY-SA  Repolarization Phase Potassium ions flow out of cell Membrane potential returns toward resting state Sodium channels remain inactive Active transport of ions begins Thi s Photo by Unknown Author i s licensed under CC BY-SA  Hyperpolarization Brief period where membrane potential drops below resting state Also called refractory period Prevents backwards signal transmission Ensures one-way signal propagation Thi s Photo by Unknown Author i s licensed under CC BY-SA  Refractory Periods Absolute refractory period No new action potential possible Sodium channels inactive Relative refractory period Stronger stimulus needed Partial recovery phase Thi s Photo by Unknown Author i s licensed under CC BY-SA  Myelin Sheath Insulating material around axons Produced by glial cells called Schwann Cells Speeds up signal transmission Creates gaps called nodes of Ranvier Enables saltatory conduction This Photo by Unknown Author is licensed under CC BY-NC-ND