With increased motor unit size motor neurons exhibit Increas

With increased motor unit size, motor neurons exhibit:

Increased...

- Short-term EPSP (excitatory postsynaptic potential) potentiation with repeated activation

- Axonal diameter

- Number of axonal branches

Decreased...

- Input resistance (lower input resistance -> smaller change in membrane potential when stimulated)

- Excitability

- Duration of action potential after-hyperpolarization

Explain in your own words how this leads to an organized recruitment of the various motor units, so that little stimulation leads to the recruitment of only small units that produce small forces, while with an increase in stimulation more fast and larger units are recruited that can produce faster and stronger forces. Include in your discussion the contribution of all of the properties that are listed above.

Solution

Motor unit made with a Motor neuron (Neuron that take information from brain to effector organ), a skelitam muscle fiber. Group of motor units leads to Muscle contraction.

As the size of the motor unit increased, the density or number of motor neurons also high in one motor unit and size of motor neuron is also small. This leads to more short EPSP with repeated activation, increased axonal branches and axon diameter. This also leads to low halflife of action potential, low excitability and low resistance. This can be explained by Hennemans Size principle on Motor Unit.