Abdomen, Pelvis, and Perineun

Definition

Nausea is a subjective, unpleasant sensation typically experienced in the upper abdomen or throat, often described as a feeling of impending vomiting. It is associated with a range of conditions and may occur without actual vomiting.

Key Characteristics:
- Often accompanied by autonomic symptoms like pallor, sweating, salivation, or dizziness.
- May or may not lead to vomiting.
- Mechanisms Involved
  
  Nausea:
  - Often mediated by the brain's higher cortical areas, chemoreceptor trigger zone (CTZ), and vagus nerve activation.
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Vomiting:

Controlled by the vomiting center in the medulla, receiving inputs from:
1. Chemoreceptor Trigger Zone (CTZ): Sensitive to toxins, drugs, and metabolic disturbances.
2. Visceral Afferents: From the GI tract due to irritation, distension, or obstruction.
3. Vestibular System: Balance disturbances (e.g., motion sickness).
4. Higher Brain Centers: Emotional or sensory triggers.

Common Causes

Nausea:

Gastrointestinal: GERD, gastritis, obstruction.
Neurological: Migraine, motion sickness.
Systemic: Pregnancy, metabolic disorders.
Psychogenic: Anxiety, stress.

Vomiting:

Acute: Infection (gastroenteritis), toxin ingestion.
Chronic: Gastroparesis, intestinal obstruction, intracranial pressure.