Body water Flashcards
How many litres of water are in a 70kg human?
42L but is dependent on adiposity
What is the breakdown of the daily loss of water?
1.5L Kidneys
0.3L Lungs
0.6L Skin
0.1L Digestion
How much water is found both intracellularly and extracellularly?
Intracellular - 28L
Extracellular - 14L
How does H20 cross epithelia and enter the body?
Absorbed in the gut
Reabsorbed in the kidney
How does H20 cross epithelia and leave the body?
Secretion and evaporation via lungs and skin
Secretion/lack of absorption in GI (diarrhoea)
Secretion/filtration/lack of reabsorption in kidney
What are the functions of the plasma membrane?
Transport of molecules in/out of cell
Cell recognition via cell surface antigens
Cell communication
Cell junctions and cell adhesion molecules
Enzymatic activity
Determination of cell shape
What are receptors coupled to?
Heterotrimeric G proteins
What are non-antibiotic drugs targeting 50% of the time?
G-protein coupled receptors
How does water get in and out of body?
Water can cross epithelia
Filtration of blood in kidneys
(Re)absorption/secretion
When is AQP-2 inserted into the apical membrane of collecting duct cells?
When ADH is present
How are aquaporins inserted into the plasma membrane?
AQP-2 vesicle is in cytoplasm while ADH is absent
When ADH is present, the exocytotic vesicle fuses with the membrane and plasma membrane ends up with aquaporin channels
When ADH is absent, an endocytic vesicle forms containing the aquaporins retaining them in the cytoplasm
What disorder is caused by AQP-2 not being inserted into the apical membrane in the presence of ADH?
Diabetes Insipidus
What is osmolarity?
Concentration of osmotically active ions and molecules in plasma
What is plasma homeostasis maintained by?
ADH
What is the normal range of blood osmolarity?
280-295 mOsm
What part of the brain senses the osmolarity of plasma?
hypothalamus
How do we calculate osmolarity?
Amount of osmotically active substance/volume
What does alcohol do?
Blocks vasopressin release
What is the most important factor of hoemostasis?
Feedback control - negative feedback
Where is there an example of positive feedback in the human body?
Blood clot formation
How do we calculate total body water?
The dilution principle
What is the dilution principle?
Inject a known amount of solute into patient
Allow to equilibrate
Correct for water loss 10mg in urine 6mg in faeces
Measure blood concentration (2mg/l)
Calculate the concentration
What are the assumptions of the dilution principle?
Solute injected is not broken down
Equilibration is complete within 24h
No water intake in the period
Correction for water loss is accurate
