The peripheral nervous system collects information about changes in internal body temperature using:

1. the brain
2. nerves and supporting cells
3. the spinal cord
4. eyesight

2. Nerves and Supporting cells.
Supporting cells would include thermoreceptors within the body (excluding the thermoregulatory centre within the Hypothalamus - This isn't a part of the peripheral NS).

The afferent/sensory neurones will carry impulses received from the thermoreceptors to the Spinal Cord or directly to the brain where Homeostatic Mechanisms will take place to ensure the core temperature of the body is maintained within it's tolerance limits.