Physiology Flashcards
Two types of nephrons and their functions
- Superficial (cortical) nephrons: Reabsorption and secretion
- Juxtamedullary nephrons: Concentration of urine
Bowman’s/Glomerular capsule general function
Site of filtration
Proximal convoluted tubule (PCT) general function
Reabsorption of water, electrolytes, glucose.
Secretion
Loop of Henle general function
Form osmotic gradient for water reabsorption
Distal convoluted tubules and collecting ducts general functions
Fine tuning of reabsorption of water, ions, urea
Basic process of urine formation (4 steps)
- Glomerular filtration
- Reabsorption
- Secretion
- Excretion
Describe reabsorption (general)
Fluid transported from tubular lumen into peritubular capillaries
99% of filtrate is reabsorbed to compensate for high glomerular filtration rate (GFR) of 180L/day
Describe the process of secretion (basic)
Transfer of metabolic anions and cations from peritubular capillaries into tubule
Describe the process of excretion (general)
Unwanted substances (urea, uric acid, drugs, chemicals) and excess electrolytes exit through collecting ducts and into ureteric/urethral passages
Glomerular filtration barrier filters on basis of both ____ and _____ of proteins
Size and negative charge
What are the functions of glomerular slit diaphragms
Nephrin proteins link neighboring podocyte feet. Pores permit passage of small molecules to medium sized proteins.
Describe nephrotic syndrome proteinuria (pathophysiology)
Low GFR and excess excretion of proteins
Proteinuria due to cell detachment or apoptosis of podocytes.
Fewer intracellular spaces decrease GFR. Large pores between hypertrophied podocytes generates significant loss of proteins.
Symptoms of nephrotic syndrome proteinuria
Frothy urine, edema, CNS problems, anorexia, malaise, abdominal pain
PCT reabsorbs ___ of the 180L/day filtered
2/3 or 60-80% (130 L/day)
All reabsorption depends on ____ pumps generating a ____ concentration gradient
Na/K pumps
Na concentration gradient
Glucose, galactose, fructose, amino acids, acetate, water soluble vitamins, etc. are all cotransported with _____ during reabsorption
Na+
With increases in filtered glucose, the capacity of tubule reabsorption reaches a plateau called _____ _____, where SGLTs are saturated, limiting further reabsorption. What pathology is this associated with?
Transport Maximum (Tmax)
Diabetes mellitus
__-__% of protein is filtered, then reabsorbed into the ______
1-3%
PCT
Most organic ions and drugs are ____ bound, not filtered, and secreted into the _____
Protein bound
PCT
What pathology is inflammation of tubules and interstitium?
Tubulointerstitial nephritis (E.g. UTI, pyelonephritis)
What pathologies are associated with ischemic or toxic injury to the tubules
Acute tubular injury, acute kidney injury
How much glucose is in the plasma clearance of a healthy individual?
0ml/min
Blood osmolarity is ____ related to the urine concentration
Inversely
Low levels of ADH causes (more/less) urine that is (pale/dark)
Low ADH = more urine, pale
Nausea, nicotine, and morphine (stimulate/inhibit) ADH release
Stimulate
Alcohol (stimulates/inhibits) ADH release
Inhibits
Blood Volume: What condition is associated with dehydration, vomiting, hemorrhage, excessive perspiration, diuretics, or inadequate fluid intake
Hypovolemia
Blood Volume: What condition is associated with excess salt intake
Hypervolemia
5-10% blood volume changes are sensed by __________ in cardiac atria, right ventricle, large pulmonary vessels, aortic arch and carotid sinus.
These sensors generate responses mostly with ____ and sympathetic activity
5-10% blood volume changes are sensed by ( BARORECEPTORS ) in cardiac atria, right ventricle, large pulmonary vessels, aortic arch and carotid sinus.
These sensors generate responses mostly with ( ADH ) and sympathetic activity
Na+ excretion is regulated by 2 primary mechanisms:
GFR and Reabsorption of Na+/water
Hypovolemia: This condition is corrected by neuroendocrine factors that (increase/decrease) reabsorption and (increase/decrease) excretion in response to a drop in volume/pressure.
Hypovolemia: This condition is corrected by neuroendocrine factors that ( INCREASE ) reabsorption and ( DECREASE ) excretion in response to a drop in volume/pressure.
Hypovolemia: Which (4) neuroendocrine factors increase reabsorption and decrease excretion in response to a drop in volume/pressure
Angiotensin II
Aldosterone
Sympathetic nervous system
ADH
Thirst is induced by what peptide hormone?
Angiotensin II
A drop in blood pressure in afferent arterioles triggers _____ release from JGA cells
Renin
Renin converts angiotensinogen into _______
Renin converts angiotensinogen into ( Angiotensin I )
Angiotensin converting enzyme (ACE) converts angiotensin I to angiotensin II. What are the functions of angiotensin II
Stimulate renal reabsorption (directly and indirectly via aldosterone and ADH)
General vasoconstriction
Increases sympathetic activity
Explain how ACE inhibitors work
Inhibit conversion of Angiotensin I to Angiotensin II which causes a reduction in:
- Na+ and water reabsorption from proximal/distal tubules
- Aldosterone and ADH release
More excretion of salt and water = lower blood pressure
Aldosterone actions
Regulates Na+ reabsorption in distal tubule and collecting ducts
Upregulates Na/K ATPases, Na+ channels (ENaC) and ATP levels in principal cells of distal tubule and collecting ducts
Increases reabsorption of Na+ (and water osmotically) to restore volume
Increases K+ secretion
What is the RAAS System
Renin
Angiotensin II
Aldosterone
Sympathetic
Congestive heart failure and renovascular hypertension (renal artery stenosis) inappropriately stimulate a correction for which condition
Hypovolemia
