Final answer:
The sympathetic nervous system is part of the autonomic nervous system, comprising preganglionic and postganglionic fibers connecting the CNS to the organs. Preganglionic fibers release ACh to activate the second neuron, while postganglionic fibers typically release norepinephrine to stimulate the target organs. The sympathetic system also directly affects the adrenal medulla to release hormones into the bloodstream.
Step-by-step explanation:
The sympathetic nervous system is part of the autonomic nervous system that prepares the body for action, often referred to as the fight-or-flight response. The system consists of preganglionic fibers and postganglionic fibers that extend from the central nervous system to the body's organs.
Preganglionic sympathetic fibers originate from the lateral horn of the spinal cord and project to either the sympathetic chain ganglia located alongside the vertebral column or to collateral ganglia located in the abdominal cavity. They release acetylcholine (ACh) at the synapse, which binds to nicotinic receptors on the second neuron. Meanwhile, postganglionic sympathetic fibers, which extend from the sympathetic ganglia to the target organs, typically release norepinephrine to act on adrenergic receptors, triggering a physiological response in the target organ.
In some cases, like with sweat glands and skeletal muscle blood vessels, the postganglionic sympathetic fibers release ACh onto muscarinic receptors instead. Another unique feature of the sympathetic system is its direct influence on the adrenal medulla, triggering the release of epinephrine and norepinephrine into the bloodstream for a systemic effect.