Trace the pathways by which the presence of a sensory stimulus (e.g., a bug crawling across your skin) in your chosen region is processed and the subsequent motor behavior that carried out. Be sure to identify the initiation and termination points of the tracts, where the cell bodies of the neurons present in the pathway are located, along with locations of any synapses that occur along the tract.

Answer:

From the skin, the touch receptors are activated by the stimulus. Specifically meissner's corpuscles are the one responsible for transmitting the sensation of light touch such as when an insect crawls on the skin. Also, the follicles on the skin contain nerve endings termed hair follicle plexus which detect the movement of the insect (Biga et al, nd) From there, the signal follows the posterior (dorsal) column-medial lemniscus pathway. This pathway specifically transmits signals from our sensations like fine touch, vibration and 2-point discrimination felt in the skin. The pathway starts from the origin of the stimulus (skin of the thigh), travelling towards the dorsal root ganglion of the lumbar spinal cord, passing through fasciculus gracilis (First order neurons), then fasciculus cuneatus, once it reaches the medulla oblangata the tract traverses to the opposite side, leading to the medial lemniscus (Second order neuron) then the thalamus (Third order neuron) until reaching the somatosensory cortex in the brain. Once the sensation is felt, the motor response is to sweep or remove the insect away. From the motor cortex, the signal travels through the descending tracts to carry the information of moving the arm.

(Biga, Lindsay, Sierra Dawson, Amy Harwell et. al. n.d. Anatomy & Physiology. 1st edition. Oregon State University.)