Anti-emetics

Question 1

What do anticholinergic drugs do?

Answer 1

Anticholinergic drugs block and inhibit neurotransmitter activity

Question 2

Are anticholinergic drugs AGONISTS or ANTAGONISTS?

Answer 2

Anticholinergic drugs are ANTAGONISTS

Question 3

Which 4 things can act as emetic stimulus?

Answer 3

These 4 things can act as emetic stimulus:
*Toxins in food
*Abnormal Motion Vection
*Disease
*Side effect of therapy

Question 4

Why do people vomit?

Answer 4

Vomit is caused when balance and vision are out of sync. The body thinks it has been poisoned.

Question 5

What does VOMIT stand for?

Answer 5

VOMIT:
V: VESTIBULAR DISTURBANCE
O: OPIOIDS or OBSTRUCTION
M: MIND or MORNING SICKNESS
I: INFECTION or IRRITATION OF THE GUT
T: TOXINS and DRUGS

Question 6

What might be another trigger for vomiting?

Answer 6

Radiation therapy might be another trigger for vomiting particularly when it is 60-70% in the abdomen

Question 7

What are the 6 physiological consequences of chronic vomiting?

Answer 7

6 consequences of chronic vomiting:
* Dehydration
*Electrolyte imbalance
*Acid base imbalance
*Depression
*Aspiration
*Mallory-Weiss tears

Question 8

Where is the vomiting centre located?

Answer 8

The vomiting centre is located in the medulla oblongata of the brainstem

Question 9

What are enterochromaffin cells?
What do they do?

Answer 9

Enterochromaffin cells are:
*most common type of neuroendocrine cell in the GI tract
*90% of body’s serotonin is synthesized in EC cells

Question 10

What signals the release of mediators by enterochromaffin cells?

Answer 10

A potentially harmful substance in the stomach signals the release of mediators by enterochromaffin cells.

Question 11

Serotonin: Receptor? Receptor location? Antiemetic drug?

Answer 11

Serotonin:
*Receptor: 5-HT3
*Receptor location: Gastrointestinal tract (GIT), Chemoreceptor trigger zone (CTZ), Vomiting centre (VC).
*Antiemetic drug: Ondansetron (5-HT3 antagonist)

Question 12

Substance P: Receptor? Receptor location? Antiemetic drug?

Answer 12

Substance P:
*Receptor: NK1
*Receptor location: Chemoreceptor trigger zone (CTZ), Vomiting centre (VC)
*Antiemetic drug: Aprepitant (NK1 antagonist)

Question 13

Acetylcholine: Receptor? Receptor location? Antiemetic drug?

Answer 13

Acetylcholine:
*Receptor: M3 and M5
*Receptor location: Vestibular system, Nucleus tract solitarius (NTS), Vomiting centre (VC).
*Antiemetic drug: Aprepitant (NK1 antagonist)

Question 14

Dopamine: Receptor? Receptor location? Antiemetic drug?

Answer 14

Dopamine:
*Receptor: D2
*Receptor location: Chemoreceptor trigger zone (CTZ), Gastrointestinal tract (GIT).
*Antiemetic drug: Metoclopramide (D2 antagonist)

Question 15

Histamine: Receptor? Receptor location? Antiemetic drug?

Answer 15

Histamine:
*Receptor: H1
*Receptor location: Vestibular system, Nucleus tract solitarius (NTS)
*Antiemetic drug: Cyclizine (H1 antagonist)

Question 16

What are the key centres located in the brain medulla related to the Neuro-anatomy of vomiting?

Answer 16

Key centres: Vomiting centre (VC), Chemoreceptor trigger zone (CTZ), Nucleus tract solitarius (NTS)

Question 17

What is the vomiting centre?

Answer 17

Vomiting centre: initiates and controls vomiting (emesis)

Question 18

What is the chemoreceptor trigger zone (area postrema?

Answer 18

Chemoreceptor trigger zone:

Question 19

What is the nucleus tract solitarius?

Answer 19

Nucleus tract solitarius:

Question 20

Where is the chemoreceptor trigger zone located?

Answer 20

The chemoreceptor trigger zone is located on the “blood” side of the blood-brain barrier

Question 21

What is serotonin (5HT)?

Answer 21

Serotonin (5 HT):
*Neurotransmitter
*Acts as a local hormone in the gut
* Neurotransmitter in the enteric nervous system

Question 22

Where is 90% of the body’s serotonin synthesized?

Answer 22

90% of the body’s serotonin is synthesized in the endocrine ENTEROCHROMAFFIN CELLS in the mucosal layer lining the stomach and small intestine.

Question 23

What kind of protein is the 5-HT3 receptor?

Answer 23

5-HT3 receptors are ligand gated cation channels.

Question 24

Give 3 examples of 5-HT3 receptor antagonists

Answer 24

3 examples of 5-HT3 receptor antagonists: GraniseTRON, OndanseTRON, PalonesTRON

Question 25

What type of antagonists are 5-HT3 receptor antagonists?

Answer 25

5-HT3 receptor antagonists are COMPETITIVE ANTAGONISTS

Question 26

What are 5-HT3 receptors involved in?

Answer 26

5-HT3 receptors are involved in information transfer in the GI tract

Question 27

What is the enteric nervous system?

Answer 27

Enteric nervous system: large part of the peripheral nervous system
*controls gastrointestinal behaviour

Question 28

What happens when sensory and vestibular information are imbalanced?

Answer 28

When sensory and vestibular information are imbalanced, motion sickness occurs.

Question 29

What are Mallory-Weiss tears?

Answer 29

Mallory-Weiss tears are tears in the oesaphagus

Question 30

Some of the causes of nausea and vomiting?

Answer 30

Nausea and vomiting causes:
* Bacterial/viral infections
* Migraine
* Motion sickness
* Pregnancy
* Anxiety
* Drugs

Question 31

Which areas of the body can send vomiting signals to the vomiting centre?

Answer 31

• The higher cortical centres, solitary nucleus, chemoreceptor trigger zone and cerebellum can send direct signals to the vomiting centre.
• Memory, sensory input do so indirectly via higher cortical centres.
• The vestibular system (labyrinths in inner ear) do so indirectly via the cerebellum and chemoreceptor trigger zone.
• The enterochromaffin cells from the GI tract send signals via the CTZ and solitary nucleus.

Question 32

Why can the Chemoreceptor Trigger Zone (CTZ) detect chemicals, toxins and drugs?

Answer 32

The CTZ can detect chemicals, toxins and rugs due to the non typical blood brain barrier.