Vomiting

STIMULUS

• Cortical stimulus (Emotion, pain, olfaction, visual stimulus) in cortex \(\xrightarrow{direct}\) vomiting center
• Vestibular stimulus \(\to\) Vestibular nuclei \(\xrightarrow{H_1, M_1}\) CTZ \(\to\) vomiting center
• Humoral stimulus i.e. drugs/toxins \(\xrightarrow{5HT_3, D_2, \mu \text{-opioid}}\) CTZ \(\to\) vomiting center
• GIT stimulus (distension, toxins) \(\xrightarrow{5HT_3, ACh, H_1}\) local GIT sensory neurons \(\to\) nucleus solitarius \(\to\) CTZ and also direct simulation of vomiting center
• Head injury \(\to\) direct vomiting center activation

CONTROLLER

• Vomiting center of medulla: final common pathway of vomiting
• CTZ: part of the area postrema in the medulla; no BBB, can be stimulated by circulating substances or by the nucleus solitarius, then signals vomiting center.

RESPONSE

• Vagus, glossopharynageal nerves \(\to\) stomach, oesophagus
• Spinal nerves \(\to\) diaphragm and abdominal muscles
• Deep inspiration + glottis closure \(\to\) LOS relaxation, reverse peristalsis \(\to\) abdominal muscle contraction, diaphragm descent \(\uparrow \uparrow\)IAP \(\to\) UOS relaxes, contents expelled through mouth
•