Final answer:
The intercostals T1 - T11 send signals to the intercostal nerves. These spinal nerves from the thoracic region generate the intercostal nerves between the ribs, not the brachial plexus, sciatic nerve, or phrenic nerve.
Step-by-step explanation:
The intercostals T1 - T11 send signals to the intercostal nerves. Based on our understanding of the nervous system, specifically the thoracic region of the spinal cord, we know that the spinal nerves of the thoracic region, T2 through T11, emerge and articulate with the vertebrae to give rise to the intercostal nerves, which are located between the ribs. The phrenic nerve, on the other hand, is associated with the cervical spinal nerves C3 to C5 and innervates the diaphragm. The-other options, such as the brachial plexus and sciatic nerve, are associated with different regions and functions, not intercostal signaling.