Physiology of Nausea and Vomiting

Question 1

nausea, retching and vomiting meaning

Answer 1

feeling of sickenss with inclination to vomit
making sound and movement of vomiting without expulsion
eject matter from stomach through mouth

Question 2

neuroanatomy

Answer 2

cortex made out of surface of brain involved with processing thoughts, memories and emotions
hypothalamus- involved in autonomic processes such as regulation of blood pressure/volume and temperature
brainstem made of midbrain, pons and medulla
blood vessels in brain are wrapped in glial cells which stop blood contents leaking into brain parenchyma
these cells aren’t in some parts of the brain so the brain can respond to its content

Question 3

vagus nerve functions

Answer 3

afferent- stomach, intestinal distension, gut hormones, emetic mediators
efferent- gastric motility, acid secretion, muscle contraction

Question 3

neuroanatomy of nausea and vomiting

Answer 3

controlled within brainstem
area postrema- lacks glial cells so can respond to blood contents in cerebral spinal fluid
nucleus tractus solitarius- receieves input from area postrema as well as GI system
dorsal motor nucleus of vagus- contains motor neurons going to stomach via vagus

Question 4

what are neuron receptors that can cause nausea

Answer 4

seratonin
NK1
D2/3
H1R
these receptors send signals to nucleus tractus solitarius which activate M1R which can cause emesis(nausea)

Question 5

stimulation of nausea

Answer 5

stimulation of nausea starts in the GI tract
substances such as bacteria and chemotherapy agents cause enterochromaffin cells secrete seotonin which enters circulation, or cause the release of neurotransmitters such as Ach. release of these neurotransmitters in high enough quantity can cause nausea
certain viruses causes more Ca2+ to be intaken into enterochromaffin cells which makes it release more seratonin which causes nausea

Question 6

central vomiting centre

Answer 6

5HT, substance P and dopamine enter area postrema/ chemoreceptor trigger zone where they trigger their respective receptors and eventually the synapses in the NTS

Question 7

why does motion sickenss occur

Answer 7

mismatching infomation recieved from visual and vestibular systems

Question 8

mechanism of vomiting

Answer 8

once signal to vomit is recieved cardiac sphincter relaxes diaphragm and abdominal muscles relax
intragastric pressure increases
gastric contents move down their concentration gradient which is up the oesophagus and out the mouth

Question 9

consequence of vomiting

Answer 9

metabolic alkalosis
more acid needs to be produced
so more bicarbonate is produces which can increase blood PH

aspiration pneumonia occurs when vomit enters pulmonary system including lungs this can lead to choking and difficulty breathing