Cephalic phase

Definition

The cephalic phase is the initial stage of digestion that begins before food enters the stomach, triggered by the sight, smell, or thought of food. This phase prepares the digestive system for incoming food through neural responses that stimulate salivation, gastric secretions, and increased motility in the gastrointestinal tract.

5 Must Know Facts For Your Next Test

1. The cephalic phase accounts for about 30% of total digestive secretion, preparing the body for food even before it is ingested.
2. During this phase, sensory stimuli activate the vagus nerve, which leads to increased secretion of gastric juices and enzymes.
3. Emotional factors such as hunger or appetite can intensify the cephalic phase, highlighting the brain-gut connection.
4. The cephalic phase involves both voluntary and involuntary responses; for example, seeing a favorite dish can trigger salivation without conscious thought.
5. If food is not consumed after triggering the cephalic phase, the body may still continue to produce digestive juices, which could lead to discomfort.

Review Questions

• How does the cephalic phase influence the body's preparation for digestion?
  • The cephalic phase influences preparation by activating neural pathways that stimulate salivation and gastric secretions before food intake. Sensory inputs like sight and smell send signals through the vagus nerve, prompting salivary glands and gastric cells to begin their functions. This anticipatory response primes the digestive system to efficiently process food once it arrives in the stomach.
• Discuss the role of sensory stimuli in initiating the cephalic phase and its impact on digestive processes.
  • Sensory stimuli such as sight and smell play a crucial role in initiating the cephalic phase. These stimuli activate specific receptors that relay information to the brain, which then triggers autonomic responses through the parasympathetic nervous system. The result is an increase in saliva production and gastric juices even before food enters the mouth, enhancing overall digestive efficiency and readiness.
• Evaluate how emotional states might alter the effectiveness of the cephalic phase in digestion.
  • Emotional states can significantly alter the effectiveness of the cephalic phase by influencing appetite and digestive readiness. For instance, stress or anxiety might suppress salivation and gastric secretion, hindering digestion. Conversely, excitement or hunger can amplify these responses, leading to heightened production of digestive enzymes. This interplay highlights how psychological factors are intimately connected to physiological processes in digestion.

Related terms

Gastric phase: The gastric phase is the second stage of digestion, initiated when food enters the stomach, which leads to further stimulation of gastric secretions and muscular contractions.

Salivary glands: Glands located in the mouth that produce saliva, which contains enzymes to begin the digestion of carbohydrates and helps in forming a bolus for swallowing.

Parasympathetic nervous system: A part of the autonomic nervous system that promotes 'rest and digest' activities, including stimulating digestive processes during the cephalic phase.