Lecture on Physiology of Vomiting

Introduction

• Lecturer: Arman Hassoor, a biologist and medicine video creator.
• Encouragement to subscribe, join forums, and engage on Facebook for updates and discussions.

Definition and Causes of Vomiting

• Vomiting: Forceful expulsion of stomach and intestinal contents.
  • Acts as a defense mechanism to eliminate harmful substances.
  • Triggers include:
    • Excessive alcohol consumption
    • Motion sickness
    • Morning sickness
    • Certain medications and medical conditions
    • Chemotherapy
• Emesis: Medical term for vomiting.

The Physiology of Vomiting

Central Nervous System Involvement

• Vomiting Center: Located in the medulla oblongata of the brainstem.
  • Contains muscarinic receptors.
  • Controls the emetic reflux (physical act of vomiting).

Stimuli for the Vomiting Center

1. Chemoreceptor Trigger Zone (CTZ) in the Medulla

   • Located outside the blood-brain barrier; thus, permeable to circulating substances.
   • Contains:
     • Dopamine type 2 receptors
     • 5-hydroxytryptamine type 3 receptors
   • Activated by circulating toxins (e.g., from chemotherapy or drugs).

2. Vestibular Nucleus Activation

   • Related to motion sickness.
   • Inner ear (labyrinth) activation affects the vestibular cochlear nerve.
   • Vestibular nuclei contain:
     • Muscarinic receptors
     • Histamine type 1 receptors

3. Higher Brain Centers

   • Can trigger vomiting due to:
     • Pain
     • Foul smells
     • Putrid sights
     • Memory triggers

4. Vagal Sensory Nerve Fibers

   • Connect stomach and gastrointestinal tract to the vomiting center.
   • Stimulated by irritation from consumed foods or toxins (e.g., chemotherapy).

Mechanism of Vomiting

• Initiated by the vomiting center in the brainstem.
• Physical process involves:
  • Contraction of abdominal muscles.
  • Squeezing of the duodenum and stomach.
  • Relaxation of esophageal muscles to allow regurgitation.

Future Video Content

• Discussion on pharmacology for treating vomiting and related conditions (e.g., motion sickness, morning sickness, chemotherapy side effects).

Conclusion

• Recap of vomiting physiology and its triggers.
• Encouragement to engage with the content and look forward to upcoming pharmacology segment.