PHYSL212 Lecture Notes - Lecture 4: Tetraethylammonium, Sodium Channel, Extracellular Fluid
16 Sep 2016
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Physl 212 - lecture #4 - electrical signaling: action potentials. Initiated by a stimulus (sensory, chemical: graded: meaning magnitude varies with strength of stimulus, can be depolarizing or hyperpolarizing. Passive current flow in an axon: there is ion leakage out of the dendrite along the neuron, passive spread of current down an axon depends on resistance to flow of current. Smaller axons = higher resistance: larger axons = better conductors. Nerve action potential: rapid, transient, short-lived and large change in vm resulting in reversal of polarity ( Rapid depolarization --> rapid polarization: ap aka spike, spiking neuron: one firing aps. Concept of threshold: threshold: membrane potential at which a spike is initiated. Voltage clamp: changes vm at various potentials, measures current flowing across membrane, rapid feedback mechanism, interrupts loop so to accurately measure the na+ influx. As time passes during a membrane current, inward current decreases and. Outward current increases: driving force of ion increases "
