Which would require more neural signals being sent by the nervous system to the muscles of your arm?

The nervous system is comprised of two main systems, which are the Central nervous system,CNS(Brain and spinal cord) and the peripheral nervous system,(PNS).

Basic Unit:

The basic structural and functional unit of the nervous system is the neuron.

Explanation:

Frequency of the stimulus and number of receptors in the area:

As the reaction shown by the nervous system towards the change will be all based upon the number of receptors which receives the stimulus and also depends upon the frequency of the change occurred.

Cutaneous receptors:

Inside the human body there are number of pain receptors, along with which a limited number of neurons are there to receive the stimulus relating pressure,cold and warmth. As there are sensory neurons found inside the epidermis layer of the skin which are refereed to as the cutaneous receptors. They receive different stimuli, which are basically the change occurred inside or outside the organisms body.

Now, these receptors will detect any change and will direct the muscle spindle fiber either to contract or relax according to the frequency of the stimulus.