Final answer:
The four major types of somatic receptors based on the stimulus they are sensitive to are mechanoreceptors, thermoreceptors, proprioceptors, and pain receptors.
Step-by-step explanation:
The four major types of somatic receptors based on the type of stimulus to which they are most sensitive are: mechanoreceptors, thermoreceptors, proprioceptors, and pain receptors.
Mechanoreceptors are sensitive to mechanical stimuli such as pressure and vibration.
Thermoreceptors are sensitive to temperature stimuli, detecting heat or cold.
Proprioceptors are sensitive to changes in body position and movement.
Pain receptors, also known as nociceptors, are sensitive to tissue damage or intense stimuli.