Session 2: Setting The Scene - Physiology Flashcards
What neurotransmitter do all preganglionic fibres of the ANS release?
Acetyl choline
Overall what sort of effect does the sympathetic nervous system have on the gut?
Negative - reduces blood flow to it
Which thoracic nerves form the greater splanchnic nerve?
T5-T9
Which thoracic nerves form the lesser splanchnic nerve?
T10-T11
What thoracic nerve forms the least splanchnic nerve?
T12
What nerve supplies innervation to the hindgut?
Least splanchnic nerve
Where does the lesser splanchnic nerve supply?
Midgut
Which nerve supplies the foregut?
Greater splanchnic nerve
Which of the vagus nerves is anterior?
Left vagal nerve
Which nerves provide parasympathetic innervation to the gut?
Vagus nerve
Pelvic splanchnic nerves (S2-S4)
Give two peptides that the parasympathetic fibres of the GI system release
Gastrin releasing peptide
Vaso-inhibitory peptide
Which division of the ANS does the pelvic splanchnic nerve come under?
Parasympathetic
Where is Meissner’s plexus located?
Submucosa of the GI tract
What is Meissner’s plexus responsible for?
Control of secretions and blood flow
Where is Auerbach’s (the myenteric) plexus located?
Between the circular and longitudinal muscle of the GI tract
What is Auerbach’s plexus responsible for?
Maintaining motility in the GI tract (muscular action)
What cells in the gut secrete histamine?
Enterochromaffin Like Cells (ECL cells)
What two categories are the gastrointestinal hormones broadly split into?
Gastrin family
Secretin family
Where is gastrin released from?
G cells in the antrum of the stomach
Where is CCK released from?
I cells in the duodenum and jejunum
What is gastrins main function?
Increasing gastric acid secretion
What is the main function of CCK?
Increase pancreatic and gallbladder secretions
What is the main function of secretin?
Help neutralise acidic chyme (increases release of HCO3 and decreases gastric acid secretion)
Where is secretin released from?
S cells in the duodenum
Where is gastric inhibitory polypeptide (GIP) released from?
K cells in the duodenum and jejunum
What stimulates release of GIP?
Sugars, amino acids and fatty acids
What does GIP cause?
Increased insulin secretion and decreased gastric acid secretion
Why does appendicitis initially present with vague central abdominal pain?
Visceral peritoneum is affected which causes the afferent to be sent back and chase the lesser splanchnic nerve, giving pain in the T10-T11 dermatomes
Why will appendicitis pain eventually progress to be sharp and in the right iliac fossa?
Parietal peritoneum becomes involved which has a somatic innervation
Where will foregut structures present with pain initially?
Epigastric region
Where will midgut structures initially present with pain?
Periumbilical
Where will hindgut structures initially present with pain?
Suprapubic/hypogastric
In which three areas of the GI tract is there not smooth muscle?
Pharynx
Upper 1/3 of the oesophagus
External anal sphincter
In which part of the GI tract are both the outer longitudinal and inner circular muscles complete?
The small intestine
Where are tonic contractions used?
Upper stomach
Ileocaecal valve
Internal anal sphincter
Where in the GI tract does mass movement occur?
Distal colon
What is a paralytic ileus?
Functional obstruction due to loss of GI contractility
What is achalasia?
Failure of relaxation of the lower oesophageal sphincter
What is Hirschsprung’s disease?
Lack of development of the myenteric and submucosal plexuses
Give four functions of mucus
Protection against acid
Antibacterial properties
Harbouring of bacteria in the large intestine
Lubrication
In which part of the small intestine are Brunner’s glands found?
Duodenum
