gut axis Flashcards
microbiota
collection of micro-organisms colonising a particular part of the human body for example:
-skin bacteria
-gut bacteria
what 4 groups do microorganism’s categorise in ?
1.bacteria
2.archea
3.eukaroyotes(fungi, Protozoa)
4.viruses
Microbiome (what collections does this include ?
1.collection of microorganism 2.collective genomes
3.gene products (signalling molecules , toxins ) of microbes living on or within humans
what 3 microbes are involved Human gastrointestinal tract ?
1.bacteria
2.eukaryotes(yeast)
3.viruses
how many protein coding genes are included in a human genome?
2300- each cell contains the same genetic material
what are the classifications of GI tract commensal bacteria -taxonomy
-Domain -eukaryote
-Kingdom-bacteria
-Phylum-firmicutes
-Class-Bacilli
-Order-Lactobacillales
-Family- Lactobacillaceae
-Genus-Lactobacillus
-Species- Lactobacillus acidophilus
what spheres does the bacteria spheres(COCCI)
(5 names)
1.streptocci
2.diplococci
3.tetrad
4.staphylococci
5.sarcina
what bacteria does RODS include? (3 names)
1.chain of bacilli
2.flagellate rods
3.spore-former
what 3 things does the bacteria spirals include?
1.vibrios
2.spirilla
3.spirochaetes
what are the 2 main commensal bacteria in the human tract?
- firmicutes
- bacteroidetes
what 3 things does the clostridium include?
-clostridium
-lactobacillus
-enterococcus
what are 3 bacteria shapes?
1.spheres
2.rods
3.spirals
what percentage of the gut bacteria does firmicutes and bacteroidetes
90%
what percentage of the gut bacteria does actinobacteria, proteobacteria, fusobacteria & verrucomicrobia make?
10%
actinobacteria
Bifidobacterium
(cleft into 2 parts)
what 4 things does gut microbiota changing along the GI tract depend on?
1.pH
2.Digesta flow rates (high in mouth, slow in colon)
3.Substrate availability
4.Secretions (e.g.; bile in the small intestin)
what are most bacteria
anerobic
where is the largest gut microbiota found in?
large intestine
what 4 things does tract microbiome impact?
1.delivery & other conditions
2.diversty
3.microbiota diversity in adult age
4.microbioata diversity in older people
how does Delivery & other conditions help associated with mother?
(e.g.; milk, health, diet) provides a child’s first microbiota (& microbiome)
how does diversity increase with age?
At 3 years of age, a child’s gut microbiota composition & diversity is similar to most adults
is Microbiota diversity stable in adults?
it is stable in healthy adults
how is microbiota diversity affect older people?
decreases in older people
what factors influence the GI tract microbiome
-hormone levels
-lifestyle
-breast milk versus formula
-genetic factors
-age specific factors
-stress
-antimicrobial peptides
what are the 5 roles of GI tract microbiota
1.neruo
2.infectious diseases
3.metabolic disease
4.inflammatory disease
5.liver disease
what system is the enteric nervous system?
Autonomous Nervous System (ANS)
function of the enteric nervous system?
Communicates with CNS via the Parasympathetic (e.g.; vagus nerve) and Sympathetic Nervous Systems and the Sacral (pelvic) plexus
what GI tract 2 functions does the enteric nervous system control ?
1.muscle contraction 2.gastrointestinal secretions)
enteric nervous system structure
-lamina propria: protected by mucus- where the GI tract vili can be found that are in contact with the nutrients and microbiota
what 2 layers are important for the function of the ENS
1.submuscosa plexus
2.Myenteric plexus
submuscosa plexus
neuronal function of E&S are found
what are between the 2 layers:submuscosa plexus and Myenteric plexus?
intestinal muscle layers
-a longitudinal one
-a circular one
what are the function of E&S ?
both plexuses are composed of:
-sensory neurones
-interneurones
-motar neurones
sensory neurones
detect mechanical (mechanosensitive neurons) signals and chemical (chemosensitive neurons) stimuli (amino acids
interneurones
connect sensory and motor neurons
motor neurones
are excitatory or inhibitory; project to the various muscle layers and affect motility or secretion
What is the function of a myenteric plexus
regulates the motility of circular and longitudinal muscles
what is the function of a submucosa plexus?
controls :
1. ion and water secretion, absorption or ions, vitamins and nutrients;
2. release of endocrine and paracrine mediators
what 3 things does the ENS act through ?
1.neurotransmitters
2.neuropeptides
3.neuromodulators
what are 2 healthy conditions of healthy GI tract
-protective mucus
-functional tight junctions -ensure the integrity of intestinal barrier
what happens in a leaky gut
the villi can change morphology alters the contact between GI tract itself and microbiota- this happens in a leaky gut
what 2 things can a damaged GI tract lead to?
-impaired tight junctions
-altered microbiota/microbe
in which 3 ways can the CNS affect the GI tract microbiome?
1.Modulating gut motility (transit)
2.Changing intestinal secretions (hormones)
3.Altering gut membrane permeability
what are some diseases that lead to effects of the CNS on the gut microbiome ?
1.gastrointestinal disease
2.irritable bowel syndrome
3.slow transit constipation
what 3 different animal modals are there
1.germ-free mice: they have no gut bacteria
2.gnotobiotic mice:germ free mice -often referred to define flora mice
3.specific pathogen free mice-they only tested for common pathogens in the ill
-useful since they don’t have any microbiota.
what part of the brain can microbiota change
gene expression e.g. decrease in hippocampul activity
what are 2 changes in the brain when affected by gut microbe
-alteration of metabolite levels e.g. tryptophane and hormonal levels such as leptin
-alteration of neruotransmitters and their receptor expression levels such as serotonin
what 3 things is Autism spectrum disorder(ASD) characterised by?
social deficit
repetitive behaviour
language difficulties
what is another mechanism involved in the guts brain axis ?
-deregulation of an individual’s immune responses
how does inflammatory impact the leaky gut ?
GI microbiota is changed the signals , which are received by immune cells are different -this will induce a change in the molecule produced by immune cells
what are probiotics
live bacteria people call good for health
why did the germ free mice have better gut microbiota
they have less fat mass
how does diet effect the microbiota
increased dietary fat and sugar(western diet) induced a drastic shift in the composition of the gut bacteria
what appetite suppressor has an impact on fat mass have an impact on hut microbiota ?
leptin -small hormone secreted by the adipose tissue -it activates the POMC neurones which decreases an individual’s appetite it also inhibits AGRP neurones and can activate food intake
what happens if the pomc neurones do not respond to insulin?
then the appetite will be not decreased
What happens if AGRP neurones do not respond to leptin
then they are not inhibited and therefore activity appetite is not switched of
how can changes in the gut impact feeding behaviours ?
increasing inflammation in the hypothalamus
-adipose tissue is also inflamed-increased levels of inflammatory molecules , these molecules will impact the gut bacteria
what does microbiota secrete
cytokines that travel to the brain
