PHSI2005 Midterm: neuronal signals
15 Jan 2019
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Explain how local circuit currents spread the action. Graded potentials variable-strength signals that travel over short distances with diminishing amplitudes (cid:120) they are graded because their amplitude is directly proportional to the strength of the stimulus (cid:120) If a depolarising graded potential is strong enough when it reaches an integrating region within a neuron (axon hillock), the graded potential initiates an action potential. Action potential (cid:120) brief, large depolarisation that travels for long distances through a neuron without losing strength (cid:120) starts at the axon hillock where the density of voltage-gated na+ channels is high (cid:120) Higher conduction velocity (cid:120) the thicker the axon, the larger the cross-sectional area, the lower the resistance to the flow of current, due to a larger cross-sectional area. Higher conduction velocity (cid:120) conductance the tendency for current to leak out of the axon through non-gated ion leakage channels (cid:120) conductance is the inverse of resistance (cid:120)
