PBL 1

Question 1

Outline the voluntary phase of swallowing?

Answer 1

Mastication leads to a bonus of food being produced as the tongue is elevated and soft palate pulled anteriorly against the tongue.
Next inspiration is inhibited and the bonus is moved to the pharynx by the tongue leading to the stimulation of the swallowing reflex

Question 2

Describe the pharyngeal phase of swallowing?

Answer 2

The larynx is raised to close the epiglottis and nasopharynx and relax the upper oesophageal sphincter
The bonus moves towards the oesophagus by peristalsis of the pharyngeal constrictor muscles

Question 3

Explain the structure of the oesophagus

Answer 3

The upper 1/3rd is voluntary skeletal muscle and the lower 2/3rds is involuntary smooth muscle

Question 4

Where is the vomiting centre, what receptors does it have on it and what’s its function?

Answer 4

It’s in the brain
Has muscarinic receptors
It triggers the vomiting reflex

Question 5

Why is the chemoreceptors trigger zone located outside the blood brain barrier?

Answer 5

So that it’s more permeable to circulating substances

Question 6

What receptors does the chemoreceptors trigger zone have?

Answer 6

Dopamine 2 receptors, 5(5 receptors

Question 7

Describe how motion sickness comes about?

Answer 7

Problems in the vestibule of the labyrinth sends electrical signals to the brain stem via the vestibular cochlear nerve which then goes to the vestibule nuclei.
The signals are then passed on to the CTZ which then sends signals to the vomiting centre which triggers Vomiting

Question 8

What receptors can be found in the vestibule nuclei?

Answer 8

Muscarinic and histamine 1 receptors

Question 9

Outline how high emotions, severe pain or shock can trigger vomiting?

Answer 9

The higher brain centre sends signals to the muscarinic receptors in the vomiting centre to initiate the vomiting reflex

Question 10

Outline how the vomiting reflex can occur from issues in the stomach?

Answer 10

The enterochromaffin cells release serotonin which can stimulate 5HT3 receptors in the vagus nerve which then takes the impulse to the vomiting centre to trigger the response

Question 11

Describe the vomiting reflex?

Answer 11

The lower oesophageal sphincter relaxes and the diaphragm and abdominal muscles contract to increase intra-abdominal pressure
Tachycardia, increased salvation and increase peristalsis occurs
The epiglottis closes and expulsion of food occurs

Question 12

What are some potential drug classes used to treat vomiting?

Answer 12

Antiemetics e.h. H1 receptor antagonists, 5HT3 receptor antagonists, D2 receptor antagonists and muscarinic receptor antagonists

Question 13

What are some common GI symptoms?

Answer 13

Heartburn, indigestion, bloating, diarrhoea, constipation, nausea, vomiting, abdominal pain, incontinence