RE revise Flashcards
1
Q
function of the small intestine
A
carbohydrate, fat, protein digestion and absorption
water and electrolyte transport
bile salt transport
2
Q
function of the large intestine
A
storage
water reabsorption
3
Q
when is the somatic motor act initiated
A
by willed decision to start chewing
becomes automatic
4
Q
what hormone is released as a result of chewing and what is the effect this causes
A
gastrointestinal hormones
initial neurological activation
tell rest of gut food coming
whole process is controlled neurologically and hormonally
5
Q
what are the constituents of saliva
A
water 99.5% (solvent)
ions (sodium, chloride, bicarbonate-buffer)
mucus (lubricant-solvent)
alpha-amylase (enzyme attach starch-digestion)
lysozymes (destroy bacteria-first point of protection, antibacterial action)
6
Q
what are the functions of saliva
A
aids speech - facilitate tongue movement
oral hygiene - flush food residues
buffering - bicarbonate buffers neutralise acids
7
Q
what controls saliva production
A
spontaneous
parasympathetic nerve endings
8
Q
what is the gastric juice composed of
A
water HCl pepsinogen intrinsic factor mucous
9
Q
what is the HCl for in the gastric juice
A
chemical attack on food
antiseptic
10
Q
what is the pepsinogen for in the gastric juice
A
pepsin secreted as pepsinogen (inactive precurser)
stomach acid activates pepsin
11
Q
what is the function of the parietal cells in the gastric gland
A
secrete acid and intrinsic factor (need for vitamin B12 absorption in small intestine) only fundus and body
12
Q
what is the function of the enteroendocrine cells in the gastric gland
A
secrete hormones into blood
13
Q
what is the function of the chief cells in the gastric gland
A
secrete protein pepsinogen
14
Q
what regulates the rate of stomach emptying
A
inhibitory signals from small intestine:
- enterogastric reflex
- secretin
- cholecystokinin
15
Q
what is the enterogastric reflex
A
reflex between stomach and intestines
16
Q
what prevents chyme moving from stomach to the duodenum
A
pylorus sphincter
17
Q
exocrine pancreas function
A
provides main digestive fluid of small intestine
empties into duodenum via pancreatic duct/common bile duct
18
Q
what does the pancreatic secretion consist of
A
water
bicarbonate
enzymes
19
Q
what are the enzymes in the pancreatic secretion
A
trypsin(OGEN) chymotrypsin(OGEN) amylase lipase nuclease STORED INACTIVE - ZYMOGENS
20
Q
when are the enzymes from the pancreatic secretion activated
A
when reach duodenum
21
Q
what is involved in the neurological control of the pancreas
A
parasympathetic nerves
- acetylcholine
- vasoactive intestinal peptide
22
Q
an example of bile - excretory
A
breakdown products of metabolism
e.g. haemoglobin, break down products are bile pigments
biliverdin (green)
bilirubin (red)
they’re converted to stercobilin (brown) (also use bacteria)
23
Q
what does the enzyme disaccharidases do
A
completes carbohydrate digestion
24
Q
what does the enzyme aminopeptidases do
A
complete protein digestion
25
how does the small intestine contribute to digestion
absorption of nutrients into blood stream
| during peristalsis longitudinal and circular muscles in SI wall contract to push food down tract
26
how are enterocytes replaced
constantly replaced by differentiation of simple cells from crypts of LieberKuhn (glands at villus base)
27
what is the motor activity of intestines effect
propulsive movement - shifts material along gut (peristalsis)
mixing movements - mixes digesta with secretions ensures material close to absorptive surface
28
what occurs during peristalsis in the motor activity of intestine
motor program coordinated by enteric nerves
stimulus causes circular muscle infront of digesta (anal side) to relax due to inhibitory neurone activation
contraction of circular muscle behind it (oral side) ue to excitatory neurone activation
process continues till digesta doesn't provide sufficient stretch
29
what occurs during segmentation in the motor activity of intestine
motor program coordinated by enteric nerves
initiated by mild stretching of intestine
circular muscle contraction at regular intervals these alternate with periods of relaxation in adjacent intestine sections, break up gut contents, throughly mixing - crucial for efficient absorption
30
what is the cecum
pouch below small/large intestine junction
31
what causes a longer shelf life on cooked foods
smoke presence
lower water activity
decreased microbial load
32
what is the effect on collagen when cooked
triple helix structure unwinds
| form gelatin which is water soluble and nutritious
33
what is the effect on fat when cooked
fat soluble vitamins dissolved in oil droplets in food
protects vitamins from oxidation
assits gut uptake
34
what is the effect on starch when cooked
gelatinises starch, easier to break amylase in the gut, increasing sugar supply
35
what nutrients does the sweet receptor sense
sugars as carbohydrate measure
36
what nutrients does the umami receptor sense
| how is it activated
glutamic and aspartic acids activate receptor
| measure of protein
37
what nutrients does the fat receptor sense
| how is it activated
activated by free fatty acids
| measure of oils/fats containing triglycerides and phospholipids
38
what is the olfactory bulb gustatory cortex
primary odor, taste signal centres
39
what is the fronto-orbital cortex function
integrates all signals
develops 'liking' principle
food liked, more eaten
mouth-brain axis
40
where are taste and smell receptors located
around the body
| especially gut
41
how is a nutrient detected
gut-brain axis
receptor and hormone signals sent to brain
sub-conscious message measures relative level of protein, carbohydrate, fat
indicates nutritional status of body
taste receptors in gut control first process of digestion
e.g. sweet - molecule hits receptor in gut, connected to cells that make enzymes for sugar digestion
42
what is the gut-brain-mouth-axis
brain uses nutritional status to modify sensitivity of taste signals in brain
e.g. if food has protein but no carbohydrate craving sweet can occur
43
how can hormone production be continually modified by external events
interconnections between nervous and endocrine systems
44
what do the gut hormones do
```
control:
passage of food material
appetite
regulate digestive and absorptive processes
regulate blood sugar levels
```
45
where is ghrelin produced
mainly stomach
| also small intestine, pancreas, brain
46
what does ghrelin cause
stimulates appetite
| promotes fat storage
47
what stops ghrelin secretion
stretching of stomach
| carbohydrates and proteins
48
where is gastrin produced
G cells in stomach lining
| upper small intestine
49
when is gastrin released
in anticipation of eating
stretching of stomach wall
proteins in stomach
increased pH
50
what does gastrin cause
during meal stimulates stomach to release gastric acid - break down proteins, absorb vitamins, kill bacteria
stimulates gallbladder to empty bile
stimulate pancreas to secrete enzymes
increases muscle contractions
51
what stops gastrin secretion
lower pH - negative feedback
52
where is glucagon produced
secreted from L-cells in small intestine and pancreas
53
what causes glucagon secretion
biphasic manner
- about 10 mins after meal triggered by neural signal
- digestion starts, trigger second release, stays several hours
54
what does glucagon cause
stimulate release of insulin from pancreas (delays glucagon release)
increases feeling of fullness during and between meals via centres in brain
slows stomach emptying - decreases food and water intake
55
where is cholecystokinin produced
I-cells in duodenum lining
56
when is cholecystokinin secreted
after a meal
| in response to fatty acids and amino acids in stomach
57
what does cholecystokinin cause
slows emptying of food from stomach
stimulates bile production and release
increases release of fluid and enzymes from pancreas t break fats, proteins, carbohydrates
increases fullness feeling during meal
58
when do cholecystokinin levels increase
15 minutes after meal began for 3hrs
59
where is pancreatic peptide YY secreted
L-cells in small intestine
60
when is pancreatic peptide YY secreted
stimulated by food presence in digestive tract (particularly fat and protein) bile and CCK
61
what does pancreatic peptide cause
decreases appetite
slows food passing along gut - increase nutrient absorption and digestion efficiency
increases water and electrolyte absorption from colon
62
what does leptin do
regulate energy homeostasis, neuroendocrine function and metabolism in energy excess and energy deficiency
regulate food intake by inhibiting hunger
63
what occurs in the initial phase
```
tactile receptors in the lips, face, tongue and hands detect:
- differences in force
- particle size
- chemical stimulus
- heat stimulus
during hand and mouth touch
nerve fibres in the:
- muscle
- joints
- tendons
sense muscle tension/relaxation - perception of e.g. heaviness
```
64
what are the mechanoreceptor processes during mastication
- muscle feedback on rate and strength of chewing
| - feedback on how well particles mix with saliva to form bolus
65
what are the somatosensory receptors
```
mechanoreceptors
chemoreceptors
thermoreceptors
nociceptors
proprioceptors
```
66
what does the retina do
convert light energy to neural impulses
| transmitted to brain via optic nerve
67
how do we smell the food
volatile molecules transported in air to nose
sensed by millions of cilia (smell receptors) covering olfactory epithelium
olfactory bulb sends signals from receptors to brain
68
what are the two routes volatiles reach the cilia
ortho nasally - sniffing
| retro nasally - during eating, food condensed whilst chewing pushed back out through nasal tract to receive aroma
69
why is saliva able to spread on oral surfaces but not easily washed off
saliva is non-newtownian
70
what occurs to food structure during reconstruction phase
interaction with body mucins
microstructure change due to enzyme action
re-assembly of structure as digestion function
71
what is the intestinal phase
simulated intestinal fluid, bile salts added, other enzymes to simulate what happens in duodenum
72
what is homogeneity
fat droplets everywhere in stomach
73
what is heterogeneity
water layer at bottom of stomach, not many nutrients
oil layer on top where all nutrients are - high caloric load
(water phase empties first)
74
what happens when the mucosal mast cells are activated
triggers release of inflammatory mediators
- transepithelial fluid loss
- smooth muscle contraction
- vomiting and diarrhoea
- anaphylaxis
75
what is the lamina propria
close network of loose connected tissues in the villi
76
how does the intestine prevent invasion
epithelium with thick overlying mucus form barrier against microbial invasion
77
what is the peyer patches - M cell function and process
sampling antigens in lumen then transport to antigen-presenting cell on the basolateral side via transcytosis
78
what do dendritic cells do
extend dendrites between epithelial cells to sample antigens that are then broken and presented to lymphocytes
usually causes an anti-inflammatory response
79
what happens to fight against parasites
attracted to parasite
release large amount WBC to destroy it
antibodies recognise some characteristics of cells and bind, label cells for destruction
cells e.g. mast, recognise the antibodies
release mediators
destroy invader
80
when does IgE mediated hypersensitivity occur
antigen makes contact, taken up and processed by antigen-presenting cells
if allergic also presents co-stimulatory molecules on surface to Thelper cells
T cells make IgE antibodies specific to allergen
T helper cell makes cytokines
stimulate B cells to multiply and differentiate IgE-plasma producing cells
IgE attach via constant regions to mast cell receptors
mast cells have granules packed with chemicals that cause hypersensitivity response
81
how are inflammatory molecules released
epithelium contact with bacteria
activates immune cells
release inflammatory molecules
82
what is diet induced thermogenesis
body requires energy to digest food
83
how is the energy kept balanced
series of interconnected loops some electrical most chemical
body releases signals turn on/off other signals through endocrine system
use hormones
84
what does the endocrine system regulate
appetite and energy
85
enforcement cycle - obese
brain reward system: hedonic overrides homeostatic behaviour
reward system: responds to stimulus of especially palatable food - lots of pleasure and motivation generated
homeostatic control in hypothalamus and brain stem:
still hunger
no satiation as resistance to the leptin and insulin
86
what information does an x-ray have when comes out other side
comes out other side
carries spatial absorption information on tissues and structures
converts this into light for film or digital capture
87
what are the negatives of using radiographic x-ray technology
ionizing radiation can break chemical bonds in tissue = biological damage
many foods and beverages must be mixed with radiopaque material
88
why is MRI so useful
can be tuned to highlight many different characteristics of food, chime, tissue such as water density
89
how is gastric emptying measured
measure serial image stacks across abdomen at intervals
volume of meal (+/- gas) measured at each time point by drawing round boundaries of stomach and summing across all slices
90
what occurs in the small bowel
bolus transport - propulsive
| mixing/digestion - segmental
91
what is colonic gas
poorly digested carbohydrates
| thought to ferment in the colon and be the cause of some peoples bloating
92
how does the colon move chyme along
intervals approximately every 2-hrs
| colon undergoes high amplitude propagating contractions (HAPCs)
93
what does the cerebellum do
integrating sensory perception
| process brain responses - emotional regulation, cognitive and sensory perception - visual memory sound
94
what happens when taste is detected
detected on taste buds
signals transmitted through taste fibres to brain stem
protected to thalamus
projected then to primary taste cortex
95
what is the thalamus
gateway to primary sensory areas
| ALL EXCEPT OLFACTORY pass through thalamus
96
what occurs at the hypothalamus
metabolism integration - control appetite
receive neural and hormonal inputs from peripheral and central signalling
lots of communication between gut, stomach, brain - when to eat/stop
97
what does fMRI do
relies on oxygenated and deoxygenated blood as they have different levels of magnetic properties
can be detected by MRI scanner
98
what does the kidney maintain within the body
maintains:
- water balance in body
- plasma volume (blood pressure)
- acid-base balance (pH)
- osmolarity (solute concentration)
99
what are the efferent arterioles divided into
peritubular capillaries
100
what is the tube in the tubular component made up of
hollow tube formed from single layer epithelial cells
101
what is the distal tubule
highly coiled
| lies in cortex and empties into collecting duct
102
how does colloid osmotic pressure form
in plasma contains proteins, if these are not passed into the filtrate - their concentrated in the unfiltered plasma increases = exert resistance to further filtration of fluid
103
what must a substance do to be reabsorbed
- cross luminal membrane of tubular cell
- pass through tubular cell cytosol
- cross tubular cell basolateral membrane to enter interstitial fluid
- diffuse through interstitial fluid
- penetrate capillary wall to enter blood plasma
104
what happens for water channels to be inserted in DCT and CD
vasopressin binds to the receptor on the DCT basolateral membrane
once activated, receptor cyclises ATP to cyclic AMP - causes water channels to be inserted
105
what happens in the renin-angiotensisn-aldosterone system when e.g. atrial blood pressure drops/ ECF drops/ decrease in NaCl
kidney detects change and releases renin
renin cleaves apart angiotensinogen = angiotensin I
pass through lungs where angiotensin-converting enzyme cleaves more of angiotensin I = angiotensin II (active hormone)
angiotensin II pass to adrenal cortex = release of aldosterone
aldosterone causes increase in sodium reabsorption in kidney tubule
angiotensin II then helps correct
106
what are the properties required to be classed as a probiotic
- beneficial effect on host
- nonpathogenic and non-toxic
- contain large number of viable cells
- capable of surviving and metabolising in the gut
- remain viable during storage and use
- good sensory properties
- be isolated from same species as host
107
what are the abilities needed for a probiotic
- beneficial effects
- resistance to bile, hydrochloric acid and pancreatic juice
- GI tract colonisation
- adhere to epithelial cells
- antimicrobial activity
- anticarcinogenic activity
- immune modulation/stimulation
- reduce intestinal permeability
108
what is the function of the intestinal barrier
tolerance against commensals and immunity against pathogens require intact mechanisms for antigen uptake, recognition, processing and response
109
what are some mechanisms of probiotic activity
- antimicrobial
- improve environment for beneficial bacteria growth
- make beneficial end product
- reduce harmful end products
- stimulate immune system against pathogens
110
what classification properties must a prebiotic have
- not hydrolysed or absorbed in upper part GI tract
- selective substrate for one or a limited number of potentially beneficial commensal bacteria in colon, stimulating bacteria to grow, become metabolically activated, or both
- alter colonic microflora towards healthier composition
- fermented by intestinal microflora
111
what is the end product of heterofermenters
lactic acid
acetic acid
CO2
ethanol
112
carbohydrate metabolism problem
portion of ingested carbohydrate not all digested in small intestine
principally starch, cellulose, hemicellulose
113
what happens during carbohydrate metabolism
complementary biochemical reactions carried out by different GMFs:
polysaccharide - oligosaccharide - intermediate product
then:
- liberation of short chain fatty acids - capable of absorption by large intestine
- CO2, H2, SO4 formed
114
what do CO2, H2, SO4 produce in carbohydrate metabolism
they form CH4, H2S and acetate
| acetate reused in metabolism as it is a SCFA
115
what parts of immune system need to be in balance
| what happens if not balanced
Th1 and Th2 cells
- too much Th1 activity = excessive tissue inflammation
- too much Th2 activity = onset of allergy/autoimmune (AI) disorders
116
what are the observed changes in test when mice were without GMF
```
nervous system fail to develop
abnormal neurotransmission
behavioural changes - stress
intestinal transit become slow
memory problems
```
117
what happens in body when we eat raw egg
contains conalbumin which binds to iron
| and avidin which binds to biotin
118
what does protease do in mammals
trypsin is a protease
| in the duodenum trypsin catalyses peptide bond hydrolysis, break down proteins to smaller peptides
119
what occurs in convulsive ergot poisoning
```
twisting and contorting body in paint
trembling
shaking muscle spasms
confusion
delusions
```
120
what occurs in gangrenous ergot poisoning
decreased blood flow
infections in extremities
loss extremities
burning pain
121
what does this cyanogen ingestion cause
health problems
acute intoxication
goitre
cretinism due to lack of iodine
122
what do glucosinolates cause
bitterness in cauliflower and sprouts
| some may inhibit some cancer
123
what does phytic acid do
store phosphorus as phytic acid
124
what effects does oxalic acid have
```
abdominal pain
kidney problem
low blood pressure
throat pain
tremors
```
125
what does solanine cause
gastrointestinal and neurological disorders
126
what do non protein amino acids cause
general stiffness and weakness of skeletal muscles
127
what are tannins
often astringent
| bitter plant polyphenolic compounds
128
what may flavonoids, phenols and tannins cause
chelate metals, reduce their absorption
inhibit digestive enzymes
bind to proteins, amino acids and cause their precipitation
