UPDATED VOMITING REFLEX PEDAGOGY.pptx

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 2

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 3

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 4

5. Stimuli for Vomiting 5 Visual inputs Limbic inputs Cortical inputs Vestibular inputs Chemoreceptor trigger zone Vomiting center Efferents to upper GIT (7 th , 9 th , 10 th and 12 th 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 6 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) 7

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 9

10. THANK YOU 10