L45. Water Balance and Electrolyte Flashcards
How is water gained and produced?
Gained through diet
Produced through metabolism
How is water lost?
Via sweat, urine and faeces
Do the gains of water outweigh the losses?
Gains = losses
Name one of the only factors under homeostatic control.
Urine excretion
Name the 5 components of the kidney.
Glomerulus Proximal convoluted tubule Loop of henle Distal convoluted tubule Collecting duct
Give another name for ADH
vasopressin
What does the glomerulus do?
Filters plasma
What does GFR stand for and what is the value per minute?
Glomerular filtration rate
120ml/minute
Give the net filtration pressure in the glomerulus.
10-15mmHg
What happens in the proximal convoluted tubule?
60-70% of glomerular filtrate is reabsorbed. It secretes H+ for acid/base balance
What happens in the loop of henle?
Ascending limb’s active transport pumps determine urine concentration
Henle loop length determines urine concentration
What is the role of the distal convoluted tubule?
Resorption of water, Na+, Cl-
Its activity is controlled by hormones, eg aldosterone
What happens in the collecting ducts?
Water resorption by ADH
Where is ADH produced, released and what does it control?
Produced in hypothalamus
Released from posterior pituitary
Controls water
Which 2 regions does ADH act on in the kidneys?
Distal convoluted tubules
Collecting ducts
What can increase ADH secretion?
Decreased ECF volume
What are electrolytes? Give examples.
Ions present in ICF and ECF, eg Na+, K+ etc
What does the renin-angiotensin-aldosterone system promote, and where?
Reabsorption of Na+ and H2O in the distal convoluted tubule.
Which hormone has the opposite effect to aldosterone meaning it increases Na+ and H2O secretion?
ANH
Describe an incidence of ADH hyposecretion.
Diabetes insipidus - lots of dilute urine
Describe an incidence of ADH hypersecretion.
Water retention
Why are potassium salts used in some toothpastes?
They desensitise sensitive dentine
Describe the thinking behind K+ ions in toothpaste.
Ions diffuse along tubules, depolarise nerves and inactivate channels. This prolongs the refractory period (membrane potential does not return to resting potential). Not a long-term solution as the K+ cannot build up.
