Physiology of vomiting

1. PHYSIOLOGY OF VOMITING
Dr. Hariprasad R
Junior Resident
Department of Physiology
JIPMER

2. OBJECTIVES
 Definition
 Associated Features
 Stimuli & Vomiting Centers
 Mechanism of Vomiting
 Applied Aspects
 Summary
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3. DEFINITION
 Vomiting is the expulsion of gastroduodenal content from GI tract to
the external environment via mouth.
 ASSOCIATED FEATURES
 Nausea
 Tachycardia
 Sweating
 Dizziness
 Dilation of Pupils
 Retching
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4. VOMITING CENTER & CHEMORECEPTOR
TRIGGER ZONE
 Vomiting is a reflex phenomenon for which the center is
located in medulla (Medullary Reticular Formation)
 Chemoreceptor Trigger Zone
 Located in Area Postrema
 V-shaped band of tissue on the lateral wall of fourth ventricle
 Receptor: 5HT3 & D2 Receptors
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5. STIMULI FOR VOMITING
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Visual inputs
Limbic inputs Cortical inputs
Vestibular inputs
Chemoreceptor trigger zone
Vomiting center
Efferents to upper GIT (7th, 9th, 10th
and 12th cranial nerves)
Spinal nerves to respiratory and
abdominal muscles
Touch receptors in
throat and pharynx
Inputs from stomach and
intestine (gastric distension
and chemical stimulation)
Vomiting

6. MECHANISM OF VOMITING
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Genesis of Reverse Peristalsis
Relaxation of the Pyloric Sphincter
Intestinal content enter the Stomach
Forced Inspiration against closed Glottis
Lower the diaphram & increases intra-abdominal process
Relaxation of the Lower Esophagal Sphincter
Gastric contents are forced to enter the Esophagus
With strong retching & sharp rise in intra-abdominal pressure
Upper Esophagal Sphincter relaxes
Pharynx
Mouth

7. APPLIED ASPECTS
 Emetics:
 Drugs that induce vomiting are called Emetics.
 Examples:
 Opiates, Chemotherapeutic Drugs, Apomorphine and etc.
 Anti-Emetics:
 Drugs that prevent vomiting are called Anti-Emetics.
 Examples:
 Ondansetron (5HT3 Receptor Blocker)
 Haloperidol (D2 Receptor Blocker)
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8. SUMMARY
1. Specific peristaltic movement seen in case of vomiting is?
Ans: Reverse peristalsis
2. The center for vomiting reflex is present in?
Ans: Medulla
3. The zone responsible for stimulating vomiting reflex is?
Ans: Chemoreceptor trigger zone (CTZ)
4. Receptors present in CTZ are?
Ans: 5HT3 and D2
5. The factor that makes the upper esophagal sphinter to relax?
Ans: Strong retching and sharp rise in intra-abdominal pressure
6. From which part of the intestine the reverse peristalsis starts?
Ans: Middle of the jejunum 8

9. NEXT CLASS…
Small intestine
 Functional aspects
 Types of intestinal movements
 Applied aspects
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