Final answer:
Activation of the sympathetic nervous system leads to increased heart rate, blood pressure, dilation of pupils, and redirection of blood flow to prepare the body for rapid action, evidenced by responses like sweating and increased adrenaline.
Step-by-step explanation:
When the sympathetic nervous system is activated during high-stress "fight or flight" situations, several physiological changes occur throughout the body. This system prepares the body for immediate action, whether to confront a threat or flee from it. The hallmark responses include an increase in heart rate and blood pressure, dilation of the pupils, relaxation of the bladder, and release of glucose from the liver. There is a surge of adrenaline into the bloodstream, which further contributes to these effects. Additionally, airways in the lungs widen to improve oxygen flow, sweat glands activate, and blood is redirected from the skin to muscles and critical organs to enhance physical performance.
The extensive influence of the sympathetic division is due to the branching patterns of its neurons. A single preganglionic neuron can have 10-20 targets, thus affecting various organs simultaneously. Upon activation, these neurons release norepinephrine at target organs which, in combination with the effects of adrenaline (epinephrine), amplify the body's preparedness for rapid action.