SCIENCE
NERVOUS SYSTEM
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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-70mV
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-55mV
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Either A or B
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None of the above
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Detailed explanation-1: -When the depolarization reaches about-55 mV a neuron will fire an action potential. This is the threshold. If the neuron does not reach this critical threshold level, then no action potential will fire.
Detailed explanation-2: -CELL MEMBRANE FUNCTIONS In a nerve, if the membrane potential decreases from-70 mV to-55 mV the cell fires an action potential which propagates along the axon. An action potential is propagated (i.e. ‘handed on’) with the same shape and size along the whole length of the axon or muscle cell.
Detailed explanation-3: -Most often, the threshold potential is a membrane potential value between –50 and –55 mV, but can vary based upon several factors. A neuron’s resting membrane potential (–70 mV) can be altered to either increase or decrease likelihood of reaching threshold via sodium and potassium ions.
Detailed explanation-4: -Action potentials are triggered when an initial depolarization reaches threshold. This threshold potential varies, but generally is about 15 millivolts above the cell’s resting membrane potential, occurring when the inward sodium current exceeds the outward potassium current.