Anatomy of the GI tract

Question 1

what are the accessory organs and why?

Answer 1

Liver, gall bladder and pancreas because they produce secretions which are vital for the body

Question 2

what is hunger and satiety regulated by?

Answer 2

• plasma glucose levels
• hormones
  -stretch receptors in the GI tract (activated after a meal)
• Stress, body temperature, food palatability

Question 3

What hormones regulate hunger and satiety and where are they produced

Answer 3

Leptin (produced in adipose tissue), ghrelin (produced in the stomach), insulin (produced in the pancreas) and glucagon (produced in pancreas)

Question 4

what happens to glucose and insulin secretion in the well fed/absorptive?

Answer 4

insulin secretion enhances glucose uptake and metabolism in cells thereby reducing blood glucose

An increase in glucose increases storage and fuels and protein synthesis

Question 5

what happens to glucose post-absorptive state?

Answer 5

Glucose decreases which causing an in glucagon causing glycogen breakdown

Gluconeogenesis occurs -production of new glucose from amino acids

Glucose sparing (fat utilisation-lipolysis) - ketones produced as a source of energy during prolonged fasting

Question 6

During hunger what will decrease and what hormone is released?

Answer 6

Decrease in glucose, fat, protein

Increase in ghrelin (regulated by lateral hypothalamus - appetite centre)

Question 7

What happens during satiety signals?

Answer 7

Increased glucose, fat, protein and leptin (regulated by the medial hypothalamus - satiety centre)

Stretch receptors are activated (mechanical)

Question 8

How does different meal components empty at different rates?

Answer 8

More food = longer digestive phase
Larger amounts of food empty slowly to begin with, then more quickly
Nutritional density (calories) controls/slows gastric emptying

Question 9

What is the effect of fat content?

Answer 9

• Important delaying factor in gastric emptying
• fat in duodenum causes fundus to relax, lowering the intragastric pressure
• high fat meals increase feeling of fullness for longer than low fat of the same energy content
• influenced intake of next meal
• prolongs elevation of pH in the stomach

Question 10

Can food affect drug absorption?

Answer 10

Yes, there is a significant difference in the concentration of drugs between fast and non-fasted patients

Question 11

What muscle is predominantly through the GI tract?

Answer 11

Smooth muscle

Question 12

What nerve is responsible for sending signals to the muscle to contract to control motility?

Answer 12

Myenteric plexus

Question 13

What is found in the submucosa?

Answer 13

glands and secretions produced which is close to the contents of the lumen

Question 14

What increases surface area in the small intestine for absorption?

Answer 14

Villi

Question 15

What is the myenteric plexus also know as? What does it do?

Answer 15

Auerbachs plexus
- influences muscle activity

Question 16

what is the submucosal plexus also known as? What does it do?

Answer 16

Meissners plexus
Largely sensory, receiving signals from epithelium and stretch receptors influencing secretory activity

Question 17

What does the myenteric + submucosa plexus equal

Answer 17

The enteric nervous system

Question 18

what is the CNS?

Answer 18

Composed of brain and spinal cord

Question 19

what is the peripheral ns?

Answer 19

Connects CNS to limbs and organs

Question 20

What is the autonomic ns?

Answer 20

Division of the PNS influencing function or organs

Question 21

What is the enteric NS

Answer 21

the intrinsic ns of gastrointestinal tract

Question 22

What are the CNS and ENS connected by?

Answer 22

The vagus nerve, the 10th cranial nerve that runs from your brain stem down to your abdomen

Question 23

Where are serotonin levels high in the body? How may this be a problem in antidepressants not being effective in treating depression?

Answer 23

They are highest in the intestines, sometimes proper dietary changes can help boost mood instead of certain anti depressants

Question 24

What are afferent neurons?

Answer 24

also known as sensory receptor neurons which carry nerve impulses away from receptors or sense organs towards the CNS

Question 25

What are efferent neurons?

Answer 25

otherwise known as motor or effector neurons, carry nerve impulses away from the CNS to effectors such as muscles or glands

Question 26

what is parasympathetic input?

Answer 26

rest and digest - stimulates gut motility and secretory activity

Question 27

what is sympathetic nerves?

Answer 27

fight or flight - causes presynaptic inhibition of parasympathetic-induced contraction (important for heart rate/activity)

Question 28

what is segmentation?

Answer 28

facilitated mixing of food

Question 29

what is peristalsis?

Answer 29

concerned mainly with propulsion of food along tract

Question 30

what is peristalsis?

Answer 30

concerned mainly with propulsion of food along tract

Question 31

What is ideal gut transit time?

Answer 31

Anywhere between 12 and 48hrs
- if transit is too fast (diarrhoea), absorption of nutrients from food is affected
- if transit is too slow (constipation) this can result in poor gut health

Question 32

how can drugs affect transit time?

Answer 32

some drugs have side effect due to their non-specific targeting which may impact upon gut transit time

Question 33

What is the target and action of loperamide?

Answer 33

Target: opiod receptors (agonist)
Action: motility suppressant that work through action on the myeteric plexus - decreased peristalsis, increase tone of anal sphincter (Ca2+ channel blocker)

Question 34

how can antibiotics have negative effects on the gut microbiome?

Answer 34

can result in antibiotic resistant organisms, which lead to antibiotic associated diarrhoea. increased use of antibiotics suggests GI related problems may become more prevalent in the future