Flashcards in Physiology Deck (46):
Concentration of osmotically active particles present in a solution
What 2 factors are required to allow you to calculate osmolarity?
Molar concentration of the solution
Number of osmotically active particles present
The effect a solution has on cell volume
e.g. hypotonic isotonic etc
What are the two major body compartments that water exists in?
Which compartment makes up more of the total body water?
Which compartment do interstitial fluid, lymphatic fluid and plasma belong to?
What is a fluid shift?
This is when there is movement of water between the ICF and the ECF in response to an osmotic gradient
What alters the composition and volume of the ECF
These are major contributors to the osmotic concentrations of the ECF and ICF and directly affect the functioning of all cells
Where is sodium mainly present?
Name two detrimental consequences caused by a fluctuation in K+ levels?
What plays a key role in establishing membrane potentials?
What are tracers used for?
They are used to help calculate volume of the body fluid compartments
What tracer is used to calculate TBW
What is inulin used for
Labelled albumin can be used to detect what?
Give at least 5 funtcions of the kidney?
Maintenance of plasma volume
Maintenance of plasma osmolarity
Excretion of metabolic waste
Excretion of exogenous foreign compounds
Secretion of renin
Secretion of eythropoietin
Conversion of vit D to active form
What is responsible for the mechanisms of filtration, re-absorption and secretion within the kidney?
What is the role of the renal tubule?
Acts as a 'conveyor belt' where substances are removed or added while the urinary filtrate moves from proximal to distal
How much of the plasma which enters the glomerulus is not filtered and leaves via the efferent arteriole?
Equation to calculate the rate of filtration
Rate of filtration of X = [X] plasma x GFR
(GFR= glomerular filtration rate)
Equation to calculate the rate of excretion
Rate of Excretion = [X] x Vu
(where Vu = urine flow rate )
Equation to calculate the rate of re-absorption
Rate of re-absorption =
Rate of filtration - rate of excretion
What does rate of excretion - rate of filtration calculate?
The rate of secretion of a substance
What is the rate of glomerular filtration?
Where is the majority of filtered fluid reabsorbed?
Proximal tube of nephron
What type of molecules are reabsorbed in the proximal tube
What does the proximal tube secrete?
Two methods of re-absorption in the proximal tubule?
What methods of membrane transport does Na+ use?
Diffusion through channels
Primary active transport
Secondary Active transport
What energy dependent transport mechanism is essential for Na+ re-absorption?
Na+ K+ ATPase
The re-absorption of Na+ leads to the passive absorption of what?
What does the absorption of Na+Cl- cause?
An osmotic gradient, leading to passive water absorption
What is normally 100% absorbed in proximal tubule?
(and amino acids)
The tubule is iso-osmotic? True or False
What is the function of the loop of Henle?
To generate a cortico-medullary solute concentration enabling the formation of hyper-tonic urine
Which part of the Loop of Henle is permeable ONLY to water and NOT to salts
Which part of the Loop of Henle is NOT permeable to water but is permeable to salts (NaCl)
How does the differences in permeability between ascending and descending limbs affect the medulla?
It establishes an osmotic gradient
What transports ions out of the lumen?
The triple co transporter
Transports Na+ K+ and Cl-
What drug class blocks the triple co-transporter?
When is the fluid hypo-osmotic?
When it enters the distal tubule (after leaving the ascending loop)
What substance passively diffuses into the loop and is responsible for half of the medullary osmolality?
(Note the distal tubule is not permeable to urea)
What is the purpose of counter-current multiplication?
To concentrate the medullary interstitial fluid
Why does the countercurrent multiplication need to concentrate the medullary IF?
To enable the kidney to alter the volume and concentration of urine based on ADH (vasopressin) release