Final answer:
The sympathetic division of the autonomic nervous system alters organ function by increasing heart and breathing rates, redirecting blood flow away from digestion to muscles, and stimulating sweat glands, which are all part of the fight-or-flight response to shut down unnecessary organ functions during stress.
Step-by-step explanation:
When a person encounters a threat, the sympathetic division of the autonomic nervous system (ANS) kicks into action, initiating the fight-or-flight response. The sympathetic ANS uses several mechanisms to alter organ function, including:
Increasing heart rate and breathing rate to enhance oxygen delivery to muscles.
Redirecting blood flow from the digestive system to skeletal muscles, effectively shutting down the digestive process.
Stimulating sweat glands to manage body temperature during intense physical activity.
The ANS achieves this coordinated response by preganglionic sympathetic neurons, which may have multiple targets throughout the body. These neurons exit the thoracolumbar spinal cord, connecting with various ganglia, and disperse to control the activity of distributed organs. This extensive network allows the sympathetic system to modulate numerous organ systems simultaneously, ensuring that energy and resources are prioritized for immediate survival needs.
For instance, in the kidneys, increased sympathetic stimulation results in vasoconstriction of afferent arterioles, thereby reducing blood flow. As a result, there is a decrease in glomerular filtration, preserving blood volume for more vital organs during periods of stress. These responses are critical for an organism to navigate emergent situations effectively and are an intrinsic part of the body's homeostatic balance.