Symptoms of GI Disease

Question 1

Define nausea

Answer 1

• personal, self-reported
• associated with physiological changes (pale, sweaty)
• Nausea is a SENSATION

Question 2

Define vomiting (emesis)

Answer 2

• Expels contents of the upper GI tract via the mouth
• Forceful (regurgitation, reflux)
• Emesis is a PHYSICAL ACT

Question 3

List some things that could cause nausea and vomiting. PART 1

Answer 3

• poisoning
• GI infection
• pregnancy
• excessive alcohol
• travel sickness
• metabolic disturbance

Question 4

List some things that could cause nausea and vomiting. PART 2

Answer 4

• drugs
• emotional upset
• travel sickness
• metabolic disturbance

Question 5

Outline the importance of taste and smell against ingested toxins.

Answer 5

• can potentially prevent indigestion
• we have a built-in dislike for bitter flavours
• children are naturally wary of novel flavours

Question 6

Outline the importance of gastric and upper GI afferents against ingested toxins.

Answer 6

• can potentially expel harmful agents before they have much chance to be absorbed
• associated with chemoreceptors that respond to: irritants, inflammatory mediators and bacterial toxins

Question 7

Outline the importance of the chemoreceptor trigger zone against ingested toxins

Answer 7

• the postrema in the brainstem
• Can detect toxins because the blood-brain barrier is leaky, chemoreceptors can detect toxins in the blood

Question 8

Outline the importance of the vestibular system against ingested toxins

Answer 8

• part of the ear that detects movements of the head and direction of gravity
• trigger for emesis
• poisoning is thought to produce aberrant activity in vestibular neural pathways

Question 9

Outline the importance of learning against ingested toxins

Answer 9

• if we survive a mistake we avoid repeating it
• aversion may hardwire avoidance

Question 10

List 4 things that will feed into and trigger nausea and vomiting.

Answer 10

• visceral afferents (respond to toxins, irritants and distentions)
• area postrema (responds to toxins in the blood)
• vestibular system (responds to toxins in the blood, disrupting vestibular receptors)
• higher centres of the brain (responds to aversive and emotional stimuli)

Question 11

Where are signals sent by the factors that trigger nausea and vomiting?

Answer 11

• To the brainstem i.e the NTS
• Integrating centre for the heat, respiratory and GI systems

Question 12

List the mechanisms of nausea. PART 1

Answer 12

Reduced mixing and peristalsis - prevents toxins from being carried further through the system
Proximal stomach relaxes - prepares stomach to receive additional contents

Question 13

List the mechanisms of nausea. PART 2

Answer 13

Giant retrograde motion - sweeps up from the mid-intestine and returns upper intestinal contents to stomach

Question 14

List the mechanisms of vomiting. PART 1

Answer 14

Retching
- coordinated contractions of abdominal muscles and the diaphragm
- waves of high pressure on the abdomen
- compresses stomach but anti-reflux barriers are intact so there’s no expulsion

Question 15

List the mechanisms of vomiting. PART 2

Answer 15

Vomiting (emesis)
- oesophageal sphincters and the crural diaphragm relax
- further waves of contraction expel the stomach contents

Question 16

What do pain receptors respond to?

Answer 16

Noxious stimuli

Question 17

What are pain receptors commonly known as?

Answer 17

Nociceptors

Question 18

What do nociceptors respond to?

Answer 18

• distention
• inflammation
• muscle spasms

Question 19

What do nociceptors do upon distension?

Answer 19

• Nociceptors respond to the stretching of the wall, with the further stretching being potentially damaging.
• The higher the distention, the higher the frequency firing.

Question 20

What factors can cause inflammation?

Answer 20

Injury, irritants, toxins, infection

Question 21

How does a nociceptor respond upon occurrence of inflammation?

Answer 21

• Triggers additional nociceptor activity. RESULT - Pain
• Positive feedback because the nociceptor releases inflammatory mediators when depolarised

Question 22

Describe nociceptor pathways.

Answer 22

Run along with sympathetic nerves and run into the spinal cord via splanchnic nerves

Question 23

Describe how chronic sensitisation of visceral pain pathways is thought to occur in GI disease.

Answer 23

• Positive feedback between inflammation and the release of pro-inflammatory chemicals from nociceptors may contribute to inflammatory bowel disease.

Question 24

What can cause chronic pain?

Answer 24

• Pain pathways can become potentiated, so normal signals from nociceptors are magnified, leading to chronic pain.

Question 25

How is visceral pain different from somatic pain?

Answer 25

Somatic pain is very precisely located. This is not the case for visceral pain.

Question 26

Why is somatic pain precisely located?

Answer 26

Ordered pathways, allowing for the pinpointing of the location of the pain

Question 27

What is the basis of viscero-somatic convergence?

Answer 27

REFERRED PAIN - If there is pain in the internal organs, it will be felt in a precise location on the surface of the body.

Question 28

What are some characteristics of visceral pain? PART 1

Answer 28

Often diffuses and poorly localised. - has a relatively small number of afferents - imprecise wiring Generally ‘referred’ to regions of the body wall due to viscero-somatic convergence

Question 29

What are some characteristics of visceral pain? PART 2

Answer 29

Each organ has a characteristic pattern of referral. - a dermatome is an area of skin supplied by a single spinal nerve sending somatic afferents to each spinal cord segment - initially, the pain is sent to dermatomes matching the embryonic origin of the organ - however, this may evolve as other tissues are affected

Question 30

What is the difference between nausea and vomiting?

Answer 30

→Nausea is produced by the same stimuli as vomiting →Nausea may clear up without triggering vomiting →Vomiting can occur without prior nausea

Question 31

Why do receptors in the gut wall respond to non ingested toxins?

Answer 31

→Receptors in the gut wall that detect poison have a blood supply →are in contact with the circulation so they respond to toxins in circulations

Question 32

Describe the setup of the blood-brain barrier.

Answer 32

→Within the brain the capillaries have endothelial walls that have tight junction → in other places there are big gaps between the endothelial cells so plasma can enter. →Substances have to be carried across into and out of the brain tissue

Question 33

What are visceral afferent receptors associated with?

Answer 33

→ Afferents that run through the parasympathetic nerves through the vagus and into the brainstem.

Question 34

Where is the area postrema?

Answer 34

→sits below the cerebellum and the foramen magnum

Question 35

What happens if pressure goes up in the skull?

Answer 35

→If pressure goes up in the skull then it presses the brainstem down through the foramen magnum

Question 36

Why does vomiting occur if pressure goes up in the skull?

Answer 36

→The area postrema is sensitive to the change in pressure so vomiting occurs

Question 37

How does the NTS cause antireflux barriers to relax? PART 1

Answer 37

→The NTS integrates the information and produces the outputs →NTS triggers the hypothalamus to increase ADH →Fluid starts to be conserved →Sympathetic activity increases

Question 38

How does the NTS cause antireflux barriers to relax? PART 1

Answer 38

→Reduced parasympathetic activity to upper GI tract →Pallor and sweating (result of sympathetic activation) →NTS coordinates muscular activity →The antireflux barriers are relaxed

Question 39

Where are the endings of nociceptors found?

Answer 39

→ Under the skin

Question 40

What does activation of nociceptors trigger?

Answer 40

→The nociceptor triggers activity in a pathway that goes to the primary somatosensory cortex

Question 41

What are the oesophageal nociceptors?

Answer 41

→The oesophageal nociceptors have broad spreading axons that make connections. - The stimulation of receptors can activate a large part of the somato cortex - Pain appears to be coming from a wide surface

Question 42

What do each of the visceral organs send?

Answer 42

→Each of the visceral organs send inputs to the spinal cord segment