Sympathetic Nervous System Neurotransmitter

The autonomic nervous system is a vital component of human physiology, controlling involuntary physiological functions. It is subdivided into two main branches: the sympathetic and parasympathetic systems. Each branch has distinct effects on heart rate, respiratory rate, and digestive functions. The sympathetic nervous system, known for its 'fight or flight' response, activates processes that prepare the body for action, while the parasympathetic system, associated with 'rest and digest', counteracts these effects.

Recent studies have indicated that specific physiological responses to stress, such as increased heart rate and bronchial dilation, are primarily mediated by the sympathetic nervous system. However, the parasympathetic system plays a crucial role in promoting recovery and relaxation after stress exposure. Understanding these systems and their interactions is essential in comprehending how the body adapts to various physiological stimuli.

Given this context, which of the following neurotransmitters is predominantly associated with mediating the effects of the sympathetic nervous system during stress responses?