Final answer:
The tectospinal tract is responsible for contralateral postural muscle tone in response to sensory stimuli, involving coordination from the midbrain to the spinal cord. The anterior corticospinal tract assists in broader postural muscle coordination across both sides of the body.
Step-by-step explanation:
The motor tract that is responsible for contralateral postural muscle tone in response to auditory/visual stimuli is the tectospinal tract. This tract projects from the midbrain tectum, specifically the superior colliculus, to the spinal cord. It plays a key role in posture and movement adjustments related to visual and possibly auditory stimuli.
However, for broader coordination of postural muscles during large body movements, the anterior corticospinal tract is involved, allowing for bilateral influence as its axons coordinate on both ipsilateral and contralateral sides.
In summary, the tectospinal tract is specifically tailored for postural responses to sensory stimuli, whereas the anterior corticospinal tract handles the coordination of postural movements more generally across both sides of the body.