The division of the nervous system most responsible for Blake's immediate reaction to seeing the spider crawling near him is the **Sympathetic nervous system**.
Here's why:
1. **Sympathetic Nervous System**: This division of the autonomic nervous system is responsible for the body's fight-or-flight response in times of stress or danger. When Blake saw the spider and reacted by jumping up and taking quick steps away, his body's sympathetic nervous system was activated.
2. **Fight-or-Flight Response**: The sympathetic nervous system triggers physiological changes to prepare the body for a quick response to a perceived threat. This includes increased heart rate, dilated pupils, and the release of adrenaline to boost energy levels, all of which help Blake react quickly to move away from the spider.
3. **Immediate Reaction**: In this situation, Blake's immediate reaction of jumping up and moving away from the spider was a result of his sympathetic nervous system kicking in to help him respond swiftly to what he perceived as a threat.
In summary, the sympathetic nervous system is most responsible for Blake's immediate reaction of jumping up and taking quick steps away from the spider due to its role in initiating the fight-or-flight response in stressful or dangerous situations.
