Final answer:
Sensors in the gastrointestinal tract respond to changes in solute concentration and pH, in addition to stretching due to food. These include mechanoreceptors, chemoreceptors, and osmoreceptors, which trigger digestion-related reflexes.
Step-by-step explanation:
In addition to the stretching when food is introduced, sensors in the gastrointestinal tract also respond to changes in solute concentration and pH. The walls of the alimentary canal contain various sensors such as mechanoreceptors, chemoreceptors, and osmoreceptors.
These receptors activate in response to different stimuli like mechanical distension of the gut wall, chemical breakdown products of digestion, and osmotic changes related to how much liquid is present and the nutrients within the food. This activation can provoke reflexes that further the process of digestion, such as stimulating gland secretion of digestive juices or activating the muscle movements that propel food, a process known as peristalsis.