physiology 1 Flashcards
satiation
the feeling of fullness generated during a meal
satiety
period of time between termination of one meal and the initiation of the next
adiposity
the state of being obese
what do satiation signals do during meal
inc to limit meal size
satiation signals - 3
CCK peptide YY GLP-1 oxyntomodulin obesatin
what is ghrelin
hunger signal
what do monoamines do
suppress food intake
what does glutamate, gaba and opioids do
inc food intake when injected into hypothalamic centres
which hormones report fat status to brain
leptin and insulin
where is leptin made
made and released from fat cells
what is use of leptin therapy limited by
leptin resistance
what is the present drug for the treatment of obesity
orlistat
what does orlistat do
inhibits pancreatic lipase dec triglyceride absorption
what effect does gastric by pass surgery have on those with type2 diabetes
complete resolution sometimes
what does uncoupling of electron transport do
non shivering thermogenesis - maintains body temp
what does brown adipose tissue contain
UCP
what is 24 DNP
an artificial uncoupler, anti obesity drug
what does overdose of DNP cause
death by overheating
where is UCP 3 found
skeletal muscle - involved in thermogenesis here
how does MDMA cause death
targets UCP 3 - death through sustained hyperthermia followed by skeletal muscle breakdown
what is the overall process of digestion and absorption called
assimilation
what is sucrose made of
glucose and fructose
what is lactose made of
glucose and galactose
what is amylose like
straight chain
what is amylopectin like
branched chain
compare the branching of glycogen to amylopectin
glycogen is more branched than amylopectin
what breaks eg starch down to oligosaccharides
alpha amylase
name some oligosaccharides
lactose and sucrose
what breaks oligosaccharides down to monosaccharides
oligosaccharidases
what does alpha amylase do
break down internal a1-4 linkages
what do oligosaccharidases do
cleave the terminal a1-4 linkages
because oligosaccharidases can cleave terminal linkages wht can they produce
glucose
what can maltase do
degrade the a1-4 linkages in straight chain oligomers up to 9 monomers in length
isomaltase
can split the branching a1-6 linkages of a limit dextrins
what is primary lactase deficiency due to
lack of LP allele
what is secondary lactase deficiency due to
damage to or infection of proximal small intestine
what is congenital lactase deficiency
rare Au R - no ability to digest lactose from birth
what happens if lactose intolerant and eat lactose
bloating abdominal pain and flatulence, loose stools and diarrhoea
what does a lactose challenge detect
hydrogen on the breath of individuals that has been produced from lactose
what does SGLT1 transport
gluucose or galactose
what does GLUT5 transport
fructose
what does GLUT2 transport
glucose and fructose as they exit from enterocytes
where is GLUT3 found
in neuronal cells
how much of our daily intake does protein assimilation account for
10-15%
what is the optimum pH of pepsin
1.8-3.5
what do endopeptidases produce
oligopeptides
name some endopeptidases
trypsin, chemotrypsin and elastase
what do exopeptidases produce
single amino acids
name some exopeptidases
Procarboxypeptidase A and B
disfunction of what results in Hartnup disease
system B AT1
Na dependent
disfunction of what results in cystinuria
system b AT1
Na independent
- what happens to protein in the lumen
digested to amino acids or oligopeptides by pepsin and pancreatic protesases
- what happens to oligopeptids at brush border
further hydrolysed to amino acids by peptidases
the amino acids are transported across the membrane via Na in/dependent transporters
- how are oligopeptides transported across the brush border
by PepT1
- what happens to oligopeptides in the cytoplasm
hydrolysed to AA by peptidases in the enterocyte
what environment do lipids require
ampipathic
how is an emulsion formed
churning and mixing and the alkaline pH
what forms mixed micelles with emulsified dietary lipids
bile acids, phospholipids and cholesterol esters
what are bile salts secreted in response to
CCK
what do bile salts do to lipid
emulsify large droplets to small droplets
- inc surface area for the action of lipase
what does failure to secrete bile salts result in
steatorrhoea
function of colipase
allows lipase to access the lipid
how are short chain fatty acids absorbed
diffuse through the enterocyte
how are long chain fatty acids absrobed
resynthesized to triglycerides and incorporated into chylomicrons with apolipoproteins
how do chylomicrons exit the enterocyte
exocytosis
where are chylomicrons taken after the exit the enterocyte
in lymph vessels to systemic circulation via the thoracic duct
what protein helps with the absorptionof choelsterol
NPC1L1
what does ezetimbe blocks
NPC1L1 protein
which form of iron can be absorbed
Fe 2+
how does iron enter the enterocyte
via DMT1
what is the storage form of iron
ferratin
how does iron exit the enterocyte
via ferroportin
how is vitamin B12 absorbed
ingested in food, salivary glands secrete haptocorin which binds to vitamin B12 in the stomach.
stomach parietal cells release IF - vitamin B12 is released from haptocorin and binds to IF in small intestine - this complex is absorbed in the terminal ileum by enterocytes
what duct drains from the parotid gland
duct of stensen
what duct drains from the submandibular gland
duct of wharton
what duct drains from the sublingual gland
duct of Rinivus and common Bartholin
what is the functional unit of the gland
salivon
what do striated ducts unite to form
interlobular and excretory ducts
what does a salivon consist of
acinus, serous demilunes, contractile myoepithelial cells surrounding the acinus and striated and intercalated ducts
what can the acini be
mucus cells or serous cells
what do serous cells produce
watery solution rich in a amylase
what do the mucous cells produce
mucus rich secretion
what are the functions of saliva
lubrication
protection
digestion
facilitate sucking by infant
how does saliva provide protection
high Ca salt content to prevent deminerlisation of tooth enamel
lysosome attacks bacterial cell walls
lactoferrin chelates iron - limits its availability for bacteria requiring it
IgA
protein coats the teeth reducing bacterial adherence
what are found in high conc in saliva
K and HCO3
what is the secretion like from parotid glands
watery a amylase rich
what is the secretion like from sublingual glands
mainly mucous cells
how does HCO3 and K conc vary with flow rate
with inc flow rate
- HCO3 conc inc and K conc dec
where is saliva secreted and modified
secreted from the acinar cells
modified by the duct cells
what does modification of saliva do
remove Na and Cl and add K and HCO3
what is the overall effect of modification of saliva
diluting
what does simple stimulus of food activate
nucleus tractus solitarius
what does acquired stimulus of food activate
cerebral cortex
what does parasympathetic stimulation of the salivary glands occur via
CNIX (parotid) and CNVII
what is the parasympathetic stimulation of the salivary glands mediated by
M3/M1 receptors
what does sympathetic stimulation of the salivary glands occur via
Postganglionic fibres from superior cervical ganglia and adrenaline from adrenal medulla
what is the sympathetic stimulation of the salivary glands mediated by
a and B1 receptors
small volume of thick mucous rich saliva
what does the stomach mix food with gastric secretions to form
chyme
how can the duondenum delay gastric emptying
neuronal response (enterogastric reflex)decreases antral peristalic activity
Hormonal response – release of enterogastrones [e.g. secretin and cholecystokinin CCK)] from duodenum inhibits stomach contraction
why does fat delay gastric emptying
required for digestion and absorption in the small intestine
why does Hypertonicity delay gastric emptying
products of carbohydrate and protein digestion are osmotically active and draw water into the small intestine – danger of reduced plasma volume and circulatory disturbances
what do parietal cells secrete
HCl and IF
what do enterochromaffin cells secrete
histamine
what do D cells secrete
somatostatin
what does somatostatin do
inhibit Hcl secretion
what does histamine do
inc HCl secretion
