Gastrointestinal

Question 1

What is the CTZ sensitive to?

Answer 1

• toxins, therapeutic drugs
• systemic infection
• metabolic disturbances

Question 2

Where is responsible for coordinating fibres from CTZ, vagal abdo afferents, higher centres ans the vestibular system?

Answer 2

NTS - the nucleus tractus solitarius

Question 3

What drugs can decrease nausea and vomiting and decrease abdo afferent signalling?

Answer 3

5-HT3 antagonists

Question 4

What 3 things occur during nausea?

Answer 4

• decreased gut motility
• proximal stomach relaxes
• giant retrograde contraction returns upper contents

Question 5

Where does the NTS signal to during nausea? 3 things

Answer 5

• hypothal paraventricular osmoreceptors to increase ADH
• frontal cx and limbic to induce nausea/aversion
• autonomic efferents -> sweating, salivation, v.constrict

Question 6

In emesis, the NTS changes gut motility and causes expulsion via somatic and autonomic efferents. What happens?

Answer 6

• retching: coordinated waves of contractions, the high pressure compresses the stomach, but barriers
• barriers (oesoph. sphincters & crural diaph) relax
• explusion

Question 7

When do wide dynamic range cells fire?

Answer 7

• Normally fires infrequent APs

- as gut distends, fires more -> threshold = pain felt

Question 8

When do nociceptor specific cells fire?

Answer 8

-silent. Only fire when distention = grossly abnormal

Question 9

What else do wide dynamic range cells and nociceptor specific cells respond to?

Answer 9

• Inflammation mediators including their own

- hypersensitivity can outlast pathology