Emesis

Question 1

*Emesis

Answer 1

Triggered by local GI irritants signaling Vomiting Center

Triggered by chemicals or drugs binding to the Chemoreceptor Trigger Zone

Question 2

Stomach sends signal thru ______ to the Vomiting Center

Answer 2

Vagus nerve

- activate motor activity responsible for vomiting

Question 3

CRTZ

Answer 3

Located bilaterally on the floor of the 4th ventricle

• “hole” in the blood brain barrier
• stimulated by drugs and toxins: apomorphine, morphine, xylazine (cats), chemotherapeutic drugs

Question 4

Prelude to vomiting

Answer 4

Antiperistalsis precedes vomiting

• may begin as distal as the ileum
• wave travels backwards at 2-3 cm/sec
• pushes upward along the tract
• gastric and duodenal distention/irritation provides the trigger

Question 5

Vomiting chain of events

Answer 5

• strong contraction in stomach and duodenum
• partial relaxation of lower esophageal sphincter
• deep intake of breath
• opening of upper esophageal sphincter
• closing of glottis
• lifting of soft palate against posterior nares
• strong downward contraction of esophagus
• simultaneous contraction of abdominal muscles
• complete relaxation of lower esophageal sphincter
• both involuntary and voluntary components*

Question 6

Motion sickness

Answer 6

Sudden changes in motion stimulates receptors in the vestibular labyrinth
- vestibular receptors –> vestibular nuclei –> cerebellum –> CRTZ –> vomiting center

Question 7

Primary (local) GI factors

Answer 7

• chemical irritant
• physical irritant
• distention

Question 8

Stimulation of CRTZ

Answer 8

• drugs
• toxins
• chemical/metabolic byproducts