PSL201Y1 Lecture Notes - Lecture 3: Chinese Whispers, Afterhyperpolarization, Myelin
Document Summary
Lecture 4 neurophysiology 3 + synaptic transmission. At rest, cell is 25x more permeable to potassium than sodium. At rest, cell is closer to threshold for potassium than sodium. When sodium channels open, they start after half a millisecond (cell never reaches +60 b/c of inactivation) Activation: voltage dependent: opens if membrane is depolarized (ex. Inactivation gate: voltage and time dependent: close during depolarization about half a second after activation gate opens, open during repolarization to resting state. Consequences of refractory periods: all-or-none principle, frequency coding, unidirectional propagation of action potentials. Period of time following an action potential. Types: absolute: no matter the intensity of the stimulus, action potential cannot occur, all sodium channels are inactivated, relative: below threshold, some of voltage-gated sodium channels are available. After this period, all sodium channels are activated. Another action potential can be generated but extremely strong stimulus is necessary.
