NROB60H3 Chapter Notes - Chapter 4: Sensory Neuron, Saxitoxin, Tetrodotoxin
Document Summary
Action potential (spike, nerve impulse, discharge): a signal created when the cytosol momentarily becomes positively charged with respect to the extracellular fluid that shares information throughout the nervous system. Cytosol in neuron negatively charged with respect to the extracellular fluid at rest. All similar in size and duration and do not diminish as they are conducted down the axon. Neurons transfer the signal to its destination by using the frequency and pattern as a code. Rising phase: rapid depolarization of membrane (mv goes up, steep incline) until peak value of ~40 mv. Overshoot: inside of neuron is positively charged with respect to the outside. Falling phase: rapid repolarisation until membrane is more negative than resting membrane potential. Undershoot (after-hyperpolarisation): gradual restoration of the resting potential. Depolarization of the cell during the ap is caused by the influx of sodium ions across the membrane, and repolarisation is caused by the efflux of potassium ions.
