Physiology Flashcards
What is the 60-40-20 rule (% of body weight for average person)?
60% Total body water
40% ICF
20% ECF
What does ECF mainly composed of?
Na+
Cl-
HCO3-
Albumin
What does ICF mainly composed of?
K+
Mg+2
Organic phosphates (eg, ATP)
What is the range of serum osmolality?
285-295 mOsm/kg H2O
How to measure plasma volume?
Plasma volume can be measured by radiolabeling albumin.
How to measure extracelluler volume?
Extracelluler volume can be measured by inulin or mannitol.
What does ECF consist of?
75% ECF = Interstitial fluid
25% ECF = Plasma
What does glomerular filtration barrier composed of?
•Fenestrated capillary endothelium
•Basement membrane with type IV collagen chains and heparan sulfate
•Visceral epithelial layer consisting of podocyte foot processes (FPs)
How does the glomerular filtration charge barrier work?
All 3 layers contain - charged glycoproteins that prevent entry of - charged molecules (eg, albumin).
How does the glomerular filtration size barrier work?
Fenestrated capillary endothelium (prevents entry of >100 nm molecules/ blood cells); podocyte foot proccesses interpose with glomerular basement membrane (GBM); slit diaphragm (prevents entry of molecules >50-60 nm).
What is renal clearance and formula ?
Volume of plasma from which the substance is completely cleared in the urine per unit time.
Clearance= (Urine concentration*Urine flow rate)/Plasma concentration
How to measure GFR?
Inulin clearance can be used to calculate GFR. Because it is freely filtered and is neither reabsorbed nor secreted.
What is the normal GFR range?
100 mL/min
Why is creatinine clearance not used in the measurement of GFR?
Creatinin clearance is an approximate measure of GFR. Slightly overestimates GFR because creatinine is moderately secreted by renal tubules.
How to measure eRPF?
Effective renal plasma flow can be estimated using para-aminohipuric acid (PAH) clearance.
Between filtration and secretion, there is nearly 100% excretion of all PAH that enters the kidney.
eRPF underestimates true RPF slightly.
What is the renal blood flow formula?
RBF = RPF/(1-Hct)
Usually 20-25% of cardiac output.
(RPF:Renal plasma flow)
What is filtration fraction (FF) formula?
GFR/RPF
Normal FF = 20%
What is the filtered load formula?
Filtered load (mg/min) = GFR* plasma concentration (mg/mL)
How does the prostaglandins work?
Prostoglandins Dilate Afferent arteriole (PDA)
Prostaglandins preferentially dilate afferent arteriole
↑RPF ↑GFR -FF
How does the angiotensin II work?
Angiotensin II Constricts Efferent arteriole (ACE)
Angiotensin II preferentially constric efferent arteriole
↓RPF ↑GFR ↑FF
What is a prostaglandin inhibitor?
NSAIDs
What are the situations that increase GFR?
•Efferent arteriole constriction
•↓plasma protein concentration
What are the situations that decrease GFR?
•Afferent arteriole constriction
•↑plasma protein concentration
•Constriction of ureter
•Dehydration
What are the situations that decrease RPF?
•Afferent arteriole constriction
•Efferent arteriole constriction
•Dehydration (↓↓)
What are the situations that do not affect RPF?
•↑plasma protein concentration
•↓plasma protein concentration
•Constriction of ureter
What are the situations that increase FF?
•Efferent arteriole constriction
•↓plasma protein concentration
•Dehydration
What are the situations that decrease FF?
•↑plasma protein concentration
•Constriction of ureter
What are the situations that do not affect FF?
•Afferent arteriole Constriction
What is the normal plasma level of glucose? Where is it reabsorbed?
Glucose at a normal plasma level range: 60-120 mg/dL
Completely reabsorbed in procimal convoluted tubule (PCT) by Na+/Glucose cotransport.
When does glycosuria begin in adults?
In adults, at plasma glucose of 200 mg/dL glucosuria begins (threshold).
What is the mechanism of formation of glycosuria in pregnancy?
Normal pregnancy is associated with↑GFR. With↑filtration of all substances, including glucose, the glucose threshold occurs at lower plasma glucose concentrations.
↓
Glucosuria at normal plasma glucose levels.
What is the drug that causes glycosuria when the glucose plasma concentration is <200 mg/dL?
Sodium-glucose cotransporter 2 (SGLT2) inhibitors
(Flozin drugs)
What is the splay phenomenon?
T for glucose is reached gradually rather than sharply due to the heterogeneity of nephrons.
What is reabsorbed in the proximal convoluted tubule?
All glucose and amino acids
Most HCO3-, Na+, Cl-, PO4-3, K+, H20, uric acids.
