BIOS1171 Lecture Notes - Lecture 6: Positive Feedback, Myelin, Negative Feedback
22 Aug 2018
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Receptor transduction: touching the skin = pushes down on the end of the axon and causes na+ channels to open up and push. Inside becomes less negative: resting state = polarization (negative inside, positive outside, during stimulus = depolarization, time course for depolarization . Polarisation: r. m. p = resting membrane potential, hyperpolarisation: cell becomes more negative inside. Sodium channels: span the membrane from one side to the other, ~0. 5nm wide (wide enough for only na+ to pass through) Inner surface is negatively charged and attracts na+ Voltage gating: channel conducts na+ poorly at resting membrane potential, channel conducts na+ well when the membrane is depolarised. Ap: na+ enters and flows down the axon to the first voltage gated channel, some na+ flows in and the channel opens more, then it keeps flowing in to fully open the channel. Small depolarization due to skin deformation but doesn"t reach threshhold.
