19.2
Sympathetic Division of the ANS
The sympathetic division of the autonomic nervous system (ANS) plays a crucial role in preparing the body for stress, physical activity, and increased…
The sympathetic division of the ANS prepares the body for stress, physical activity, and increased energy demands.
Its preganglionic fibers originate in the thoracic and lumbar spinal cord segments. The fibers leave the spinal cord through the white ramus communicans and enter the sympathetic chain ganglion.
They then synapse with postganglionic fibers at three possible locations: within the sympathetic chain ganglia, at one of the collateral ganglia, or in the adrenal medullae.
The sympathetic chain ganglia are a series of interconnected ganglia located bilaterally along the spinal cord. Their neurons regulate various organs, including blood vessels, sweat glands, and visceral organs.
The collateral ganglia are positioned anteriorly to the spinal cord. Their neurons innervate organs in the abdominopelvic region.
The adrenal medulla is located inside the adrenal gland. When stimulated, it releases neurotransmitters in the bloodstream. These neurotransmitters act as hormones, regulating the activity of distant cells.
Because the ganglia lie close to the spinal cord, the sympathetic division has short preganglionic and long postganglionic fibers.
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Q1: Where do sympathetic preganglionic fibers originate in the spinal cord?
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.
Q2: What are the three locations where sympathetic fibers can synapse with postganglionic neurons?
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.
Q3: How do sympathetic chain ganglia regulate body functions?
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.
Q4: Which organs are innervated by the collateral ganglia?
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.
Q5: What role does the adrenal medulla play in the sympathetic division?
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.
Q6: Why does the sympathetic division have short preganglionic and long postganglionic fibers?
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.
Q7: How does the sympathetic division prepare the body for stress and physical activity?
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.