Final answer:
When you feel cold, the sensation starts at the thermoreceptors in the skin and is transmitted to the brain through peripheral nerves, the spinal cord, and the thalamus, ending at the primary somatosensory cortex. If the sensation is from the face, it travels through a cranial nerve. Intense cold can also trigger pain pathways and initiate regulatory processes like shivering.
Step-by-step explanation:
Pathway of Cold Sensation
When you feel something that's cold, the sensation begins at the thermoreceptors in the skin, specifically at the Krause end bulbs that detect cold. These receptors, located in the dermis among other places, send signals via free nerve endings. The pathway for this sensory information starts at the peripheral nerves and travels to the spinal cord. From there, the signals pass through the thalamus before finally reaching the primary somatosensory cortex in the brain, where the sensation of cold is perceived.
If the cold sensation is on the face, the information takes a slightly different route, via one of the cranial nerves directly to the brain. Intense cold can also be perceived as pain since temperature sensations use similar pathways to those that carry pain sensations. When the body experiences cold, various regulatory processes are initiated to maintain homeostasis, such as shivering to generate heat.
Overall, the sensation of cold is part of a complex set of responses by the body to regulate temperature, involving sensory detection, neural pathways, and physiological reactions to maintain a stable internal environment.