The activities of gastro-intestinal tract

Options

A. Are under neural control only
B. Are under homonal control only
C. Are under neural and hormonal control
D. Are under neither hormonal nor neural control

Answer

### Step-by-Step Solution

1. **Understanding the Gastrointestinal Tract (GIT)**: The gastrointestinal tract is a complex system responsible for the digestion and absorption of food. It includes organs such as the mouth, esophagus, stomach, small intestine, large intestine, and anus.

**Hint**: Remember that the GIT is a continuous tube that processes food from ingestion to excretion.

2. **Functions of the GIT**: The main activities of the GIT include:
- **Ingestion**: Taking in food through the mouth.
- **Digestion**: Breaking down food into smaller molecules, which occurs both mechanically (chewing) and chemically (enzymes).
- **Absorption**: Nutrients from digested food are absorbed into the bloodstream, primarily in the small intestine.
- **Excretion**: Waste products are eliminated from the body through the anus.

**Hint**: Think of the GIT as a factory that processes raw materials (food) into useful products (nutrients) and waste.

3. **Control Mechanisms**: The activities of the GIT are regulated by both neural and hormonal controls:
- **Neural Control**: The central nervous system (CNS) and the enteric nervous system coordinate the digestive processes. For example, the sight and smell of food can trigger salivation and gastric secretions.
- **Hormonal Control**: Hormones such as gastrin, secretin, and cholecystokinin (CCK) are released in response to food intake and help regulate digestive functions.

**Hint**: Remember that the nervous system responds quickly to stimuli, while hormones provide longer-lasting control.

4. **Key Hormones and Their Functions**:
- **Gastrin**: Stimulates gastric acid secretion and promotes gastric motility.
- **Secretin**: Stimulates the pancreas to release bicarbonate, neutralizing stomach acid in the small intestine.
- **Cholecystokinin (CCK)**: Stimulates the gallbladder to release bile and the pancreas to release digestive enzymes.

**Hint**: Associate each hormone with its specific function in digestion to better understand their roles.

5. **Integration of Neural and Hormonal Signals**: The GIT operates through a combination of neural and hormonal signals to ensure that digestion occurs efficiently. For instance, the presence of food in the stomach triggers both neural reflexes and the release of hormones to enhance digestion.

**Hint**: Visualize the GIT as a team where both the nervous system and hormones work together to achieve the common goal of digestion.

### Summary
The activities of the gastrointestinal tract include ingestion, digestion, absorption, and excretion, regulated by neural and hormonal mechanisms. Understanding these processes is crucial for comprehending how our body processes food and maintains homeostasis.