Which bowel state corresponds to a reflexive (upper motor neuron) bowel?

Which bowel state corresponds to a reflexive (upper motor neuron) bowel?

• A. Areflexive (lower motor neuron) bowel
• B. Reflexive (upper motor neuron) bowel
• C. Normal bowel function
• D. Spastic bowel with hyperreflexia

Answer: (B)

In spinal cord injury, bowel behavior depends on where the injury is. When the lesion is above the sacral segments (an upper motor neuron injury), the brain loses voluntary control but the spinal reflexes that govern defecation stay intact. That means the rectoanal reflex can trigger defecation in response to rectal filling, so the bowel operates in a reflexive, or reflex-driven, manner. This is why the correct description is a reflexive bowel—defecation is driven by preserved reflex pathways rather than conscious effort. In contrast, a lower motor neuron injury at the sacral level disrupts the reflex arc itself, leading to an areflexive bowel with poor or absent reflex-driven evacuation. Normal bowel function is not typical after SCI. Sometimes people describe the upper motor neuron pattern as spastic bowel with hyperreflexia, but the specific term used here is reflexive bowel to highlight the preserved reflex control that enables reflex-triggered defecation.

In spinal cord injury, bowel behavior depends on where the injury is. When the lesion is above the sacral segments (an upper motor neuron injury), the brain loses voluntary control but the spinal reflexes that govern defecation stay intact. That means the rectoanal reflex can trigger defecation in response to rectal filling, so the bowel operates in a reflexive, or reflex-driven, manner. This is why the correct description is a reflexive bowel—defecation is driven by preserved reflex pathways rather than conscious effort.

In contrast, a lower motor neuron injury at the sacral level disrupts the reflex arc itself, leading to an areflexive bowel with poor or absent reflex-driven evacuation. Normal bowel function is not typical after SCI. Sometimes people describe the upper motor neuron pattern as spastic bowel with hyperreflexia, but the specific term used here is reflexive bowel to highlight the preserved reflex control that enables reflex-triggered defecation.