Text: Fill in the blank Nervous System Your autonomic system is the branch of your nervous system that regulates the functions of your organs, like your heart and stomach, and also controls your smooth and cardiac muscles, and your glands. The sympathetic nervous system is the hardware behind the famous "fight or flight" response. It is synonymous with adrenaline. The parasympathetic nervous system is for "rest and digest". It's responsible for maintaining your body and conserving energy for later. Where do the nerves of each division originate? The axon lengths of the neurons before the ganglion are called the preganglionic fibers, and the ones coming out are postganglionic fibers. The sympathetic nervous system is set up in such a way that even a small stimulus sent down one path could trigger a response in multiple organs. Physiological responses to non-immediate stresses are slower and more prolonged than when you're fighting for survival. How do neurotransmitters differ from hormones? The very same molecule can have different effects, actually, sometimes, totally opposite effects depending on where it's released. Acetylcholine is what the rest of your peripheral nervous system and lots of your central nervous system uses to communicate. It's basically a neurotransmitter. It's always acetylcholine that's released from postganglionic fibers in the sympathetic nervous system. In the case of norepinephrine, its receptor is alpha-1—the muscle that controls all of your involuntary functions of hollow organs, like the stomach, bladder, and also your blood vessels.

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