N&V

Question 1

What is the ctz

Answer 1

Chemoreceptor trigger zone

Question 2

What are input pathways of the vomit reflex

Answer 2

Stim. of the back of the throat- gag
Noxious chemicals- CTZ
Distension or irritation of stomach/duodenum (mechano/chemoreceptors)
Rotation or acceleration of head (vestibular apparatus inner ear, dizziness, motion sickness)
Elevated intracranial pressure (haemorrhage)
Emotional factors (psychogenic vomiting)

Question 3

Where is the vomiting centre

Answer 3

Medulla

Question 4

What is the CTZ known as

Answer 4

Area Postrema.

Question 5

what does the CTZ do

Answer 5

Has fenestrated capillaries- gaps between endothelial cells allowing things in blood to pass thru vascular endothelia therefore NO BBB!!!
this area samples blood for noxious stimuli

Question 6

How do dopamine agonists have pro-emetic effects

Answer 6

Stimulate D2 receptors in CTZ

Question 7

What is the NTS and its role in vomiting

Answer 7

NTS- network of pathways in medulla
Close to CTZ
Coordinates the motor side of vomiting- relay centre

Question 8

What is an enterochromaffin and their role on vomitting

Answer 8

Cell found in Gastric epithelium- chemoreceptors that detect noxious stimuli
mechanoreceptors detect stretch
Release 5HT
Stimulates nerve endings via 5HT3 receptors and causes Action potentials to NTS

Also 5-HT goes into cystemic circ. and goes to CTZ as well

Question 9

What are the output pathways of the vomit reflex

Answer 9

Autonomic responses:
inc. salivation, sweating, vasoconstriction (pale), HR, contraction of SI (UP!), relaxed stomach and oesophagus

Somatomotor responses:
Contraction of diaphragm (deep inspiration)
Closure of glottis
Closure of nasal cavities
Strong contraction of diaphragm and abdomen
pressure forces contents upwards and out

Question 10

What are the physiological process involved in N&V