anatomy of the GI tract

Question 1

what regulates hunger and satiety

Answer 1

• plasma glucose levels
• hormones
• stretch receptors in GI tract
• stress, body temperature, food palatability

Question 2

what hormones regulate hunger and satiety

Answer 2

leptin (produces in adipose tissue)
ghrelin (produces in stomach)
insulin (produces in pancreas)
glucagon (produces in pancreas)

Question 3

what happens in a well fed/absorptive state

Answer 3

• storage of fuels and protein synthesis
• glycogen synthesis
• insulin secretion - enhances glucose uptake and metabolism in cells, thereby reducing blood glucose

Question 4

what happens in a post absorptive state

Answer 4

1. glucagon - glycogen breakdown
2. gluconeogenesis - cream

Question 5

what happens when hungry

Answer 5

decrease in glucose, fat an protein.
signals in appetite centre in hypothalamus. triggers eating

Question 6

what happens when full

Answer 6

increase of glucose, fat, protein and leptin
signals in satiety centre in hypothalamus.
stops hunger, triggers digestion

Question 7

what happens to gastric emptying when we eat larger amounts of food

Answer 7

• longer digestive phase
• larger amounts of food empty slowly and then it speeds up

Question 8

what controls gastric emptying

Answer 8

nutrition density (gastric emptying)

Question 9

what does fat in the duodenum cause

Answer 9

the fundus to relax which lowers intragastric pressure

Question 10

what do high fat meals do

Answer 10

influence the feeling of fullness for longer than a low fat meal of same energy content.
this influences intake at next meal and prolongs elevation of pH in stomach

Question 11

what is cns composed of

Answer 11

brain and spinal cord

Question 12

what is the peripheral nervous system composed o

Answer 12

connects CNS to limbs and organs

Question 13

what is the autonomic nervous system composed of

Answer 13

division of PNS influencing function of organs

Question 14

what is the enteric system composed of

Answer 14

the intrinsic nervous system of your GI tract

Question 15

how are CNS and ENS connected

Answer 15

via the vagus nerve that runs from your brain stem down to your abdomen

Question 16

what do the gut bacteria use the vagus nerve for

Answer 16

to transmit info to the brain

Question 17

are neurons present in the brain and gut

Answer 17

yes

Question 18

where is serotonin prouced

Answer 18

brain and gut

Question 19

what do afferent neurons AKA sensory receptor neurons do

Answer 19

they carry nerve impulses away from receptors or sense organs towards the CNS

Question 20

what do efferent nerves aka motor/effector neurons do

Answer 20

they carry nerve impulses away from the CNS to effectors such as muscles/glands

Question 21

where is the enteric nervous system found

Answer 21

within the wall of the GI tract from oesophagus to anus

Question 22

what is the motor in function influencing muscle activity

Answer 22

the myenteric plexus

Question 23

what does the submucosal plexus do

Answer 23

it receives signals from epithelium and stretch receptors influencing secretory activity

Question 24

how is the ens subject to regulation via the pns and sns

Answer 24

fibres from both can synapse with neurones in the ens

Question 25

how are nerve plexuses linked to the CNS by fibres activated

Answer 25

• stretch
• chemical stimulation

Question 26

what efferent innervation from the ANS does the ENS receive

Answer 26

• parasympathetic input (rest and digest) stimulates gut motility and secretory activity
• sympathetic nerves (fight and flight) cause presynaptic inhibition of parasympathetic-induced contraction

Question 27

what does segmentation in the small intestine allow

Answer 27

the mixing of food

Question 28

what does peristalsis in the small intestine allow

Answer 28

the propulsion of food along the tract

Question 29

what is the ideal gut transit time for food

Answer 29

anywhere between 12 and 48 hours

Question 30

what happens if gut transit time is too fast

Answer 30

diarrhoea
absorption of nutrients from food is affected

Question 31

what happens if gut transit time is too slow

Answer 31

constipation
can result in poor gut health

Question 32

why do some drugs have side effects and what can this impact

Answer 32

due to their non-specific targeting, can impact drug transit time

Question 33

examples of drugs that can cause constipation

Answer 33

• antacids
• anticholinergics
• antihypertensives

Question 34

how can loperamide affect transit time

Answer 34

it works through actions on the myenteric plexus which decreases peristalsis