anatomy of the GI tract Flashcards
what regulates hunger and satiety
- plasma glucose levels
- hormones
- stretch receptors in GI tract
- stress, body temperature, food palatability
what hormones regulate hunger and satiety
leptin (produces in adipose tissue)
ghrelin (produces in stomach)
insulin (produces in pancreas)
glucagon (produces in pancreas)
what happens in a well fed/absorptive state
- storage of fuels and protein synthesis
- glycogen synthesis
- insulin secretion - enhances glucose uptake and metabolism in cells, thereby reducing blood glucose
what happens in a post absorptive state
- glucagon - glycogen breakdown
- gluconeogenesis
- ketones produced for energy during fast
what happens when hungry
decrease in glucose, fat an protein.
signals in appetite centre in hypothalamus. triggers eating
what happens when full
increase of glucose, fat, protein and leptin
signals in satiety centre in hypothalamus.
stops hunger, triggers digestion
what happens to gastric emptying when we eat larger amounts of food
- longer digestive phase
- larger amounts of food empty slowly and then it speeds up
what controls gastric emptying
nutrition density
what does fat in the duodenum cause
the fundus to relax which lowers intragastric pressure
what do high fat meals do
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
what is cns composed of
brain and spinal cord
what does the peripheral nervous system do
connects CNS to limbs and organs
what is the autonomic nervous system composed of
division of PNS influencing function of organs
what is the enteric system composed of
the intrinsic nervous system of your GI tract
how are CNS and ENS connected
via the vagus nerve that runs from your brain stem down to your abdomen
what do the gut bacteria use the vagus nerve for
to transmit info to the brain
are neurons present in the brain and gut
yes
where is serotonin prouced
brain and gut
what do afferent neurons AKA sensory receptor neurons do
they carry nerve impulses away from receptors or sense organs towards the CNS
what do efferent nerves aka motor/effector neurons do
they carry nerve impulses away from the CNS to effectors such as muscles/glands
where is the enteric nervous system found
within the wall of the GI tract from oesophagus to anus
what is the motor in function influencing muscle activity
the myenteric plexus
what does the submucosal plexus do
it receives signals from epithelium and stretch receptors influencing secretory activity
how is the ens subject to regulation via the pns and sns
fibres from both can synapse with neurones in the ens
how are nerve plexuses linked to the CNS by fibres activated
- stretch
- chemical stimulation
what efferent innervation from the ANS does the ENS receive
- parasympathetic input (rest and digest) stimulates gut motility and secretory activity
- sympathetic nerves (fight and flight) cause presynaptic inhibition of parasympathetic-induced contraction
what does segmentation in the small intestine allow
the mixing of food
what does peristalsis in the small intestine allow
the propulsion of food along the tract
what is the ideal gut transit time for food
anywhere between 12 and 48 hours
what happens if gut transit time is too fast
diarrhoea
absorption of nutrients from food is affected
what happens if gut transit time is too slow
constipation
can result in poor gut health
why do some drugs have side effects and what can this impact
due to their non-specific targeting, can impact drug transit time
examples of drugs that can cause constipation
- antacids
- anticholinergics
- antihypertensives
how can loperamide affect transit time
it works through actions on the myenteric plexus which decreases peristalsis
