Final answer:
The spinothalamic tract is the ascending tract responsible for transmitting signals related to pain, temperature, and crude touch sensations from the periphery to the brain, and it crosses the midline in the spinal cord.
Step-by-step explanation:
The ascending tract in the nervous system that is responsible for transmitting signals related to crude touch, temperature, and pain sensations is called the spinothalamic tract. This tract originates from sensory neurons in the dorsal root ganglia and crosses the midline in the spinal cord at the level at which it enters.
The spinothalamic tract is part of the major ascending pathways of the spinal cord, which include the dorsal column system and the spinothalamic tract.
These tracts are critical for relaying sensory information from the periphery to the brain, with the spinothalamic tract specifically associated with pain and temperature sensations, and the dorsal column system primarily carrying information about touch and proprioception.
The dorsal column system influences fine touch, vibration, and proprioceptive information, ascending ipsilaterally to the source of the stimulus and decussating in the medulla. In contrast, the spinothalamic tract is emphasized in the assessment of pain and temperature stimuli due to its responsibility for these sensations.