PHYS20008 Lecture Notes - Lecture 4: Threshold Voltage, Threshold Potential, Action Potential

• School: University of Melbourne
• Department: Physiology
• Course: PHYS20008
• Professor: Charles Sevigny

Document Summary

Before we used words such as more positive" or more negative". We should be talking in terms of polarity which refers to distance from point 0. Eg if we are at -70mv and drop to -40mv we are depolarising. If we come back down to -70mv we are repolarizing. Eg if we are at -70mv and go to -90mv we are hyperpolarizing. Stimuli can slightly temporarily change the membrane potential, so the line is always wiggling slightly around -70mv. These fluctuations are called graded potentials (they don"t reach the threshold. Changes in membrane potential during an action potential. The change in voltage will always be the exact same. This is because it recruits a specialised protein called voltage gated channels. In order for these channels to be opened they require a certain amount of with very specific timing voltage this is threshold voltage (around -50mv or -55mv) The sodium voltage gated channel has 2 gates not just 1.