Sympathetic Division of the ANS

Sympathetic preganglionic fibers originate in the thoracic and lumbar spinal cord segments. These fibers exit the spinal cord through the white ramus communicans and enter the sympathetic chain ganglion. This anatomical arrangement allows the sympathetic division to rapidly prepare the body for stress and physical activity.

Sympathetic preganglionic fibers synapse with postganglionic fibers at three possible locations: within the sympathetic chain ganglia, at collateral ganglia, or in the adrenal medulla. This arrangement enables the sympathetic division to coordinate responses across multiple organ systems simultaneously, supporting the fight-or-flight response.

The sympathetic chain ganglia are interconnected ganglia positioned bilaterally along the spinal cord. Their neurons regulate various organs, including blood vessels, sweat glands, and visceral organs. Because these ganglia lie close to the spinal cord, the sympathetic division has short preganglionic and long postganglionic fibers.

The collateral ganglia, positioned anteriorly to the spinal cord, innervate organs in the abdominopelvic region, including the heart, lungs, liver, stomach, intestines, and kidneys. Their postganglionic fibers control cardiac activity, bronchial dilation, gastrointestinal motility, and urinary system regulation throughout the body.

The adrenal medulla, located inside the adrenal gland, releases neurotransmitters such as adrenaline and noradrenaline into the bloodstream when stimulated. These neurotransmitters act as hormones, regulating the activity of distant cells and enhancing the body's response to stress and physical demands.

The sympathetic division has short preganglionic and long postganglionic fibers because its ganglia lie close to the spinal cord. Preganglionic fibers travel only a short distance from the spinal cord to the ganglia, while postganglionic fibers extend longer distances to reach target organs throughout the body.

The sympathetic division activates the fight-or-flight response by coordinating multiple organ systems through its three synapse locations. It increases heart rate, dilates airways, redirects blood flow, and stimulates the adrenal medulla to release hormones, enabling the body to respond effectively to challenging situations and increased energy demands.