Final answer:
Sympathetic postganglionic fibers originating from the lateral horn of the thoracolumbar spinal cord innervate the upper extremities (via upper thoracic sympathetic chain ganglia), lower extremities (via lower thoracic and upper lumbar chain ganglia and lumbar splanchnic nerves), head and neck (via superior cervical ganglion), and upper abdominal viscera (via collateral ganglia like celiac and superior mesenteric).
Step-by-step explanation:
The sympathetic division of the autonomic nervous system is responsible for the 'fight or flight' response and innervates various parts of the body, including the upper extremities, lower extremities, head and neck, and upper abdominal viscera. The origin of the innervating sympathetic postganglionic fibers varies for each body part. In general, these fibers arise from the lateral horn of the thoracolumbar spinal cord and project through various pathways to their target effectors.
- For the upper extremities, the postganglionic fibers originate from the sympathetic chain ganglia located in the upper thoracic region.
- The lower extremities receive sympathetic postganglionic fibers from the lower thoracic and upper lumbar spinal regions through the sympathetic chain ganglia and lumbar splanchnic nerves.
- The head and neck are innervated by fibers from the superior cervical ganglion of the sympathetic chain ganglia.
- Upper abdominal viscera, such as the digestive system, are innervated by postganglionic fibers originating from the collateral ganglia like the celiac and superior mesenteric ganglia.
These fibers release neurotransmitters like norepinephrine to bind to adrenergic receptors, resulting in physiological changes that align with the sympathetic nervous system's responses.