consequences of fluid loss from the GI tract Flashcards
what is osmotic diarrhoea
decreased electrolyte/nutrient absorption due increase in osmotic particles in the gut
what is deranged motility diarrhoea
increased rate of flow of intestinal contents
what is secretory diarrhoea
abnormal increase in GIT secretions - ach, substance P, 5-HT, neurotensin act to increase rate of intestinal secretion via inc. [Ca2+]
what causes osmotic diarrhoea
disaccharide deficiency - can be drug induced - malabsorption of galactose
what causes secretory diarrhoea
excessive laxative use, digestion/absorption defects, infection
how does cholera cause diarrhoea
survives acidity of GIT
enterotoxin stimulates adneylate cyclase - inc cAMP - more Na, Cl, H2O loss
how is secretory diarrhoea treated
water, electrolyte, glucose replacement
causes of bloody diarrhoea
chronic disease
ulcerative colitis
neoplasm
consequences of severe diarrhoea
hypovolaemia
metabolic acidosis due to loss of HCO3
what is vomiting
retrograde giant contraction - oral expulsion of gastric contents and bile
causes of vomiting
symptom of illness in children pregnancy alcohol dependency metabolic disorders removal of ingested toxic substances
physiological changes associated with vomiting
inc: salivation, HR, sweating
pallor
nausea
how is vomiting stimulated
neuronal inputs from the body to the vomiting centre in the medulla oblongata
inputs that can initiate vomiting
SI/stomach distension substances that act on chemoreceptors in brain/intestine increased ICP motion sickness intense pain gag reflex sight/smell/emotional circumstances
how does vomiting occur
nausea deep inspiration, closure of epiglottis inc abd. pressure retrograde giant contraction breath held, chest fixes dec. oeso pressure - relaxation of UOS & LOS inc abd pressure forceful explosion
consequences of excessive vomiting
inc salt/water loss
sever dehydration
circulatory problems
metabolic alkalosis due to loss of gastric acid
what is lost in vomit
food mucus (& na, k, cl, hco3) gastric acif upper intestinal contents, incl bile blood
consequences of fluid loss from GIT
hypovolaemia haemoconcentration dehydration ionic imbalances malnutrition, inc mortality
consequences of hypovolaemia
dec. venous return
arterial hypotension
inc myocardial O2 demand w/ dec perfusion leads to dysfunction
inc anaerobic metabolism > acidosis
what does a combo of acidosis and myocardial dysfunction lead to
multi organ failure :D
consequences of dehydration
heat shock, fainting
higher blood viscosity; higher BP; clotting more likely
kidneys get overloaded - toxins accumulate
digestive problems
how does the body respond to water loss
CV adaptation
Renal adaptation
behavioural adaptation - stimulates fluid intake when possible
consequences of na and h2o loss
decreased plasma volume and venous pressure
cv result of decreased venous pressure
dec: venous return, atrial pressure ventricular EDV SV CO arterial BP
Renal consequences of decreased venous pressure
increased activity of renal sympathetic nerves
inc constriction of renal arterioles
dec GFR
dec na, h20 secretion
consequence of severe sweating
loss of hypo osmotic salt soln
result of loss of hypo-osmotic salt soln
dec plasma vol
inc plasma osmolarity
consequences of dec plasma volume
dec GFR
inc plama aldosterone
increased plasma vasopressin
consquence of dec GFR w/ inc plasma aldosterone
dec na secretion
result of inc plasma vasopressin
dec h2o secretion
systemic response of the body to dec arterial pressure due to dec plasma vol
inc renin secretion by renal juxtaglomerular cells
inc plasma renin
inc plasma ang2
inc aldosterone secretion by adrenal cortex
inc plasma aldosterone
inc na reabsorption in collecting ducts
dec na excretion
response of the body to dec GFR/flow to macula densa
dec NaCl concentration in macula densa
inc renin secretion
physiologic response to consequences of hypovolaemia
dec venous/atrial/arterial pressure detected by CV baroreceptors inc ADH secretion by post pit. inc. plasma vasopressin inc h2o permeability in collecting ducts inc h2o reabsorption dec h2o excretion
what stimulates the sensation of thirst
inc ang2
inc plasma osmolarity
dry mouth/throat
monitoring of h2o intake by GIT
effect of dehydration on calcium levels
dec nacl, k, INC [Ca2+] > hypercalcaemia
clinical consequences of hypercalcaemia
inc risk of kidney stones, kidney failure, arrhythmia, dementia
symptoms of hypercalcaemia
nausea/vomiting loss of appetite constipation abdominal pain excessive thirst fatigue, lethargy, paresis, joint pain, confusion
how does ADH work
inserts aquaporin 2 channels into renal collecting ducts
increases h2o permeability of ducts - results in concentred urine
effect of h2o on adh secretion
dec in osmolarity of blood and interstitial fluid
dec in ADH secretion - water channels removed
what happens if there are no water channels in the collecting ducts
decreased permeability - increased water loss
factors that regulate release of ADH
large decrease in blood vol severe dehydration - causing gfr decrease - less h2o in urine hyperventilation - inc fluid loss vomiting/diarrhoea fever, heavy sweating
how does the thirst centre in the hypothalamus work
stimulates desire to drink - water gain if thirst is quenched
how does ANG2 work
stimulates aldosterone secretion - dec volume of h2o lost in urine
how does aldosterone work
promotes water/na/cl reabsorption - dec water loss in urinw
how does ANP work
stimulates natriuresis - inc excretion of na/cl/h2o - increased water loss in urine
how does ADH/vasopressin work
increase collecting duct permeability and hence water reabsorption - decreased loss of water in urine
