Slide Number 1 Early Clues That Linked Electricity and Neuronal ActivityElectricity and Electrical StimulationSlide Number 4 Early Clues That Linked Electricity and Neuronal Activity Early Clues That Linked Electricity and Neuronal ActivityElectricity and Electrical StimulationNeurons can convey information as a wave induced by stimulation on the cell body traveling down the axon to its terminal A voltmeter detects the passage of the wave Tools for Measuring a Neuron’s Electrical ActivityA giant axon could be dissected out of the squid and kept functional in a bath of salty liquid that approximates body fluids Hodgkin and Huxley described the neuron’s electrical activity and won the Nobel Prize Tools for Measuring a Neuron’s Electrical Activity Tools for Measuring a Neuron’s Electrical ActivityTools for Measuring a Neuron’s Electrical Activity How the Movement of Ions Creates Electrical ChargesSlide Number 15Slide Number 16Slide Number 17EquilibriumElectrical Activity of a Membrane Resting PotentialElectrical Activity of a Membrane: The Ionic Basis of The Resting Membrane PotentialElectrical Activity of a Membrane: The Ionic Basis of The Resting Membrane Potential Resting PotentialElectrical Activity of a Membrane: maintaining the resting potentialElectrical Activity of a Membrane Graded PotentialsElectrical Activity of a Membrane The Action PotentialSlide Number 26Electrical Activity of a Membrane The Action PotentialElectrical Activity of a Membrane The Action PotentialElectrical Activity of a Membrane The Nerve ImpulseElectrical Activity of a Membrane Saltatory Conduction and Myelin SheathsElectrical Activity of a Membrane Saltatory Conduction and Myelin SheathsHow Neurons Integrate Information Excitatory and Inhibitory Postsynaptic PotentialsHow Neurons Integrate Information Summation of Inputs Temporal SummationSpatial SummationHow Neurons Integrate Information Summation of InputsHow Neurons Integrate Information Voltage-Sensitive Channels and The Axon HillockSlide Number 38 How Sensory Stimuli Produce Action Potentials How Sensory Stimuli Produce Action PotentialsInto the Nervous System and Back Out How Nerve Impulses Produce Movement Myasthenia gravisHow Do Neurons Use Electrical Signals to Transmit Information?Early Clues That Linked Electricity and Neuronal Activity • Galvani (18th Century) – Electrical Stimulation Electrical Stimulation Studies • Fritsch and Hitzig (Mid-19th Century) – Electrical stimulation of the neocortex causes movement (arms and legs) • Bartholow (1874) – First report of human brain stimulation• Electricity – A flow of electrons from a body that contains a higher charge to a body that contains a lower charge • Negative Pole – The source of electrons; higher charge • Positive Pole – Location to which electrons flow; lower charge Electricity and Electrical StimulationKolb & Whishaw, An Introduction to Brain and Behavior, Third Edition - Chapter 4 Electricity and Electrical StimulationEarly Clues That Linked Electricity and Neuronal Activity • Caton (Early 19th Century) – First to attempt to measure electrical currents of the brain using a voltmeter and electrodes on the skull • Electroencephalogram – Electrical brain graph that records electrical activity through the skull or from the brain and represents graded potentials of many neuronsEarly Clues That Linked Electricity and Neuronal Activity • von Helmholtz (19th Century) – Flow of information in the nervous system is too slow to be a flow of electricity • Nerve conduction: 30–40 meters/second • Electricity: 3 × 108 meters/second • It is not the charge but the wave that travels along an axon (Bernstein, 1886)Electricity and Electrical Stimulation Difference = Electrical Potential (volts) - - - - - - - - Negative pole (higher charge) Positive pole (lower charge) Current - - - - Electron • Electrical potential • Volt • VoltmeterNeurons can convey information as a wave induced by stimulation on the cell body traveling down the axon to its terminal A voltmeter detects the passage of the waveTools for Measuring a Neuron’s Electrical Activity Giant Axon of the Squid • Much larger in diameter than human axons – Humans: 1 to 20 micrometers – Squid: Up to 1 millimeter (1000 micrometers) • Easier on which to perform experiments – Used by Hodgkin and Huxley in the 1930s and 1940sA giant axon could be dissected out of the squid and kept functional in a bath of salty liquid that approximates body fluids Hodgkin and Huxley described the neuron’s electrical activity and won the Nobel PrizeTools for Measuring a Neuron’s Electrical Activity The Oscilloscope (A) S stands for stimulation. The horizontal axis measures time, and the vertical axis measures voltage. The voltage of the axon is represented as −70 millivolts (mV). (B) Neuron traces displayed on a digital oscilloscope screenTools for Measuring a Neuron’s Electrical Activity MicroelectrodesTools for Measuring a Neuron’s Electrical Activity • The squid giant axonHow the Movement of Ions Creates Electrical Charges • Cations • Examples: Sodium (Na+), potassium (K+) • Anions • Examples: Chloride (Cl−), protein molecules (A−) • Diffusion • Concentration Gradient • Voltage GradientKolb & Whishaw, An Introduction to Brain and Behavior, Fourth Edition - Chapter 4Kolb & Whishaw, An Introduction to Brain and Behavior, Fourth Edition - Chapter 4 The ions in (1) diffuse down their concentration and voltage gradients until the water in the left compartment is in equilibrium (2) This situation results in concentration and voltage gradients for both sodium and chloride ions across the membrane—that is, from the salty side to the freshwater sideKolb & Whishaw, An Introduction to Brain and Behavior, Fourth Edition - Chapter 4 Protein molecules embedded in a cell membrane form channels that act as pores to allow certain kinds of ions to pass through the membrane With chloride channels, chloride ions will diffuse across the membrane and move down their concentration Because opposite charges attract, the negative chloride ions are attracted back toward the positively charged sodium ionsEquilibrium • Efflux of chloride ions down the chloride concentration gradient is counteracted by the influx (inward flow) of chloride ions down the chloride voltage gradient • Equilibrium is reached when the concentration gradient of