As Molly is walking across campus, a car swerves toward her. Her heart races and sweat breaks out as she jumps out of harm's way. This mobilization of energy is due to the action of Molly's?  

Somatic Nervous System or Sympathetic Nervous System?

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In this scenario, the increase in Molly's heart rate, as well as sweat production, when avoiding the car's path is due to the activation of the sympathetic nervous system. The sympathetic nervous system is one of two divisions of the autonomic nervous system, which is a key regulator of the internal functions within the body. The autonomic nervous system regulates functions such as heart rate, and perspiration, unconsciously in response to stimuli. 

More specifically, the sympathetic nervous system is activated in response to stressful stimuli, leading to what is generally referred to as the "fight or flight" response. Physiologically, when a person or animal faces stimuli that is perceived as threatening, in this case the swerving car, the sympathetic nervous system gears the body up to increase available energy and oxygen, increasing the person or animals chance for survival. It does this by increasing blood pressure, heart rate, and freeing up energy in the form of glucose, from glycogen stores, in the liver. The sympathetic nervous system also causes dilation of the pupils, and a decrease in the functions of the digestion processes taking place in the gut. These changes are specifically regulated by neurotransmitters such as acetylcholine and norepinephrine.

Hope this helps!  

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