Sympathetic nerves are part of the autonomic nervous system, which controls involuntary bodily functions. They are primarily responsible for the body's "fight or flight" response, preparing it to react to stress or danger. When activated, these nerves increase heart rate, dilate airways, and redirect blood flow to essential muscles. These nerves originate in the spinal cord and extend to various organs throughout the body. They release neurotransmitters like norepinephrine, which help transmit signals that regulate functions such as blood pressure and digestion. Overall, sympathetic nerves play a crucial role in maintaining homeostasis during stressful situations.