How does parasympathetic & sympathetic nervous systems effect GI (digestive) activity?

The parasympathetic and sympathetic nervous systems are part of the autonomic nervous system, which controls involuntary body functions. They have opposite effects on the gastrointestinal (GI) tract.

1. Parasympathetic Nervous System: This system is often referred to as the "rest and digest" system. It stimulates digestion by increasing blood flow to the digestive tract, promoting the secretion of digestive enzymes, and increasing peristalsis (the movement of food through the digestive tract). The parasympathetic nervous system is activated during periods of rest and after eating.

2. Sympathetic Nervous System: This system is often referred to as the "fight or flight" system. It inhibits digestion by decreasing blood flow to the digestive tract, reducing the secretion of digestive enzymes, and slowing down peristalsis. The sympathetic nervous system is activated during periods of stress or danger.

In summary, the parasympathetic nervous system promotes digestion, while the sympathetic nervous system inhibits it. They work together to ensure that the body's energy resources are used efficiently, depending on the situation.