Control of peristalsis by the CNS and enteric nervous systemSpec C3.1.16
In short
Peristalsis is the wave of muscle contraction that moves food along the gut. Swallowing of food and egestion of faeces are under voluntary control by the central nervous system, but peristalsis between these points is under involuntary control by the enteric nervous system, a network of neurons in the gut wall that coordinates the passage of material.
Peristalsis is the coordinated contraction and relaxation of circular and longitudinal smooth muscle in the wall of the gut. Contraction of circular muscle behind the food squeezes it forward; the wave of contraction travels along the gut.
Control of the digestive system is shared between two parts of the nervous system:
| Stage | Type of control | Controlled by |
|---|---|---|
| Initiation of swallowing | Voluntary | Central nervous system (CNS) |
| Peristalsis from oesophagus to rectum | Involuntary | Enteric nervous system (ENS) |
| Egestion of faeces | Voluntary | Central nervous system (CNS) |
The enteric nervous system is a network of neurons in the wall of the gut, from the oesophagus to the anus. It detects stretching of the gut wall by food and coordinates waves of peristalsis without input from the brain. The action of the ENS ensures that the passage of material through the gut is coordinated, so food spends long enough in each region for digestion and absorption.
Linking question: the ENS forms a net-like (reticulate) network in the gut wall, while neurons branch in a dendritic pattern. Be ready to give these as examples of patterns of organization.
Written and checked against the IB Biology HL specification · Updated October 2026