4.2 – Vomiting

Question 1

How is the vomiting reflex controlled?

Answer 1

-neurons in the medulla
-nerves within the 4th ventricle form the chemoreceptive trigger zone (CTZ)

Question 2

Which animals vomit?

Answer 2

*carnivores and most omnivores vomit
-some use it as a way to provide food to offspring

Question 3

Receptors in the CTZ:

Answer 3

-recognize toxins or blood-borne chemicals
>used to initiate vomiting
-also responds to sights, sounds, etc.

Question 4

What are the five sources that the ‘vomit center’ in the medulla receives input?

Answer 4

-abdominal cavity
-higher cortical areas
-chemoreceptor trigger zone (CTZ)
-vestibular system
-pharyngeal

Question 5

Abdominal cavity: (vomit reflex)

Answer 5

*via vagus and sympathetics
-inflammation
-chemical stimulation
-distension

Question 6

Higher cortical areas: (vomit reflex)

Answer 6

-head trauma
-brain tumors
-cerebral inflammation
-psychogenic factors (fear and stress)

Question 7

Chemoreceptor trigger zone (CTZ): (vomit reflex)

Answer 7

*in medulla, but outside of BBB
-drug
-bacterial toxins
-blood urea nitrogen
-ammonia

Question 8

Vestibular system: (vomit reflex)

Answer 8

-fibers that go directly to the vomit center as well as CTZ
>motion sickness
>8th: vestibulocochlear

Question 9

Pharyngeal: (vomit reflex)

Answer 9

-direct stimulation of the pharynx via 9th cranial nerve (glossopharyngeal)

Question 10

What does the vomiting process being with?

Answer 10

-begins with stimulation of vomiting center neurons

Question 11

What are the NTs used in the vomiting process?

Answer 11

-dopamine
-serotine

Question 12

Parasympathetic discharge in the vomiting process leads to:

Answer 12

-increased salivation
-contractions in esophagus, stomach, and upper duodenum

Question 13

Increased salivation and contractions in esophagus, stomach, and upper duodenum causes:

Answer 13

-increased HR
-sweating
-reduced blood flow to the skin

Question 14

Cranial motor neurons to the tongue during the vomiting process initiate:

Answer 14

-chewing and tongue movements
*nausea

Question 15

Vomiting process:

Answer 15

-muscles in pyloric end of stomach contract=ingesta sent to esophageal end of stomach
-LES relaxes=some contents go into esophagus=peristaltic contractions of esophagus=retching

Question 16

Retching: when some of contents go into esophagus

Answer 16

-one of reflexes will induce strong contractions of diaphragm and abdominal muscles
*pressure inside stomach and esophagus are increased enough to propel stomach contents to the mouth
>UES relaxed
>nasopharynx closes to prevent material exiting nasal cavities

Question 17

What might green or dark contents in the vomit suggest?

Answer 17

-presence of bile
>pyloric sphincter has relaxed and duodenal contents entered the stomach

Question 18

What is a common drug used in vet med for the clinical induction of vomiting?

Answer 18

-stimulates the CTZ
-usually recommended in DOG
>excitement in cats (use xylazine for them)

Question 19

Vomiting vs. regurgitation: expulsion of food

Answer 19

-vomiting: stomach/intestine -> out of mouth
-regurgitation: esophagus or pharynx -> into the mouth

Question 20

Vomiting vs. regurgitation: species

Answer 20

-vomiting: carnivores and omnivores
-regurgitation: ruminants, camelids, some birds
>animals with esophageal/pharyngeal dysfunction

Question 21

Vomiting vs. regurgitation: caused by and peristalsis

Answer 21

-vomiting: abdominal and diaphragm contractions, NOT reverse peristalsis of GI muscles
-regurgitation: esophageal reverse peristaltic waves, but NO retching

Question 22

Vomiting: expelled material

Answer 22

-food partially digested
-bile may be present (green)
-pH usually acidic (neutral or basic)

Question 23

Regurgitation: expelled material

Answer 23

-undigested food
-no bile/acid present
-pH neutral

Question 24

Hairballs in cats:

Answer 24

-10% of cats brought up 2+ hairballs per year
-25% of cat’s waking hours are spent grooming
*trichobezoar
*normally passes through GIT and excreted in feces

Question 25

Are hairballs coming up out of cats considered vomiting?

Answer 25

-yes

Question 26

What are causes of hair balls in cats?

Answer 26

-excessive ingestion of hair
-altered GIT motility

Question 27

Excessive hair ingestion (cats):

Answer 27

-capacity of stomach to pass all the hair into SI is over-whelmed
-skin disease, fleas may increase grooming
-pain
-anxiety

Question 28

Altered GIT motility (cats):

Answer 28

-chronic GI disease
-MMC is reduced in stomach, only active in distal SI
>migrating spike complexes were associated with prolonged contracts of distal SI (less effective than MMC)

Question 29

Dietary management of hairballs:

Answer 29

-goal is to reduce ingestion or increase fecal excretion
-supplement with sugarcane fiber or purified cellulose
>*no effect of cellulose (vs. control)
-insoluble, non-fermentable fibers
*type of fiber matters

Question 30

Beet pulp and cats:

Answer 30

-soluble and insoluble fiber
-reduced GI transit time
-increased fecal production
*no effect on trichobezoar (hairball) fecal excretion

Question 31

Rats can’t vomit:

Answer 31

-do not have vomiting center in their medulla
>can’t coordinate diaphragm and abdominal muscles contractions and opening of LES and UES

Question 32

Rabbits can’t vomit:

Answer 32

-have a vomiting center
-LES can’t relax enough to allow vomiting

Question 33

Horses can’t vomit:

Answer 33

-have a vomiting centre
-LES wont relax
-angle of entry of esophagus into stomach becomes acute when the stomach is full

Question 34

A full stomach in the horse can distend to the point of:

Answer 34

-initiating a vomiting reflux and try to contract
>may be one cause of colic pain