Which physiological system is activated during slow deep breathing?

The correct answer is the parasympathetic nervous system, which is activated during slow deep breathing. This physiological system is responsible for promoting a state of relaxation in the body, often referred to as the "rest and digest" system. When individuals engage in slow, deep breathing, it triggers a relaxation response that helps to lower heart rate, reduce blood pressure, and encourage a feeling of calmness.

The parasympathetic nervous system counteracts the effects of the sympathetic nervous system, which is associated with the "fight or flight" response. Deep breathing techniques stimulate the vagus nerve, leading to increased activity in the parasympathetic pathways. This is why practices such as meditation, yoga, or breathing exercises, which incorporate slow, deep breathing, are effective in reducing stress and anxiety levels, promoting overall well-being.