In an experiment the strength of a neural stimulus and the resulting muscle contraction are compared. A single motor neuron that synapses with a muscle fiber is suspended. The other end of the muscle fiber is attached to a mass. If electrical stimulus is sufficient to cause an impulse in the neuron, the muscle will contract and lift the mass.
How do I determine the minimum size of stimulus that would be required to reach the threshold potential for this motor neuron?
Strength of stimulus is 5 mV and mass is 0g
Strength of stimulus is 10 mV and mass is 22
To determine the minimum size of stimulus required to reach the threshold potential for the motor neuron, you can use a method called subthreshold and suprathreshold stimulation.
Start by applying a subthreshold stimulus of 5 mV. If this stimulus is not enough to reach the threshold potential and cause the muscle to contract and lift the mass of 0g, then gradually increase the strength of the stimulus until you observe a muscle contraction and the mass is lifted.
Once you have determined the minimum size of stimulus required to reach the threshold potential with a mass of 0g, you can then repeat the experiment with a mass of 22g and a suprathreshold stimulus of 10 mV. If the muscle contracts and lifts the 22g mass with the 10 mV stimulus, then you have identified the minimum size of stimulus required to reach the threshold potential for this motor neuron.
By comparing the results of the two experiments, you can determine the minimum size of stimulus required to reach the threshold potential for the motor neuron in this experimental setup.