Answer:
thamalus
Step-by-step explanation:
Based on studies conducted by various neurologists, it can be said that in this situation that information was most likely first routed to the thamalus. This is a part of the brain that relays motor and sensory information to the cerebral cortex. It is also responsible for regulating sleep, consciousness and even alertness. Which is what was triggered (alertness) when you saw the spider crawling up your leg.