Renal Physiology Flashcards
Describe the general functions of the urinary system.
1)Fluid, electrolyte, and pH balance:
-Adjusting blood volume and blood pressure
(By regulating the amount of water that gets excreted vs. reabsorbed)
2)-Regulation of several blood components:
(Plasma conc. of Na+, K+, Cl-, other ions Blood pH)
3) Removing drugs, toxins, and nitrogenous wastes (urea)from the blood/body
-Breakdown of proteins/ amino acids produces ammonia, which can be toxic! So, we convert ammonia to urea – a “safer” nitrogenous waste product.
4) produce and/or activate various hormones
Describe the process of glomerular filtration, including where it occurs, how it occurs, and why it occurs.
- Happens in the glomerulus (nephron)
- Blood flows down afferent arteriole to the glomerulus
- Filtrate/ fluid (waste) escapes and is collected in bowman’s capsule/ glomerular capsule
- Only small particles can get through the 3 membranes (endothelial cells, basement membrane, tubular cells)
- Proteins are too large and too negative to get past the basement membrane
- H20, glucose, amino acids, Na+ are all small enough to get through
- Everything that cannot be filtrated leaves the glomerulus through the efferent arteriole
Describe the relationship between osmotic pressure, and how it affects glomerular filtration.
Pulls water out of filtrate into plasma through osmosis which decreases GFR
Describe how increasing or decreasing the diameter of the afferent arterioles can change the glomerular hydrostatic pressure (and how this will affect filtration)
- ↓ diameter of afferent arteriole will decrease GHP decrease GFR
- ↑ diameter of afferent arteriole will increase GHP
Describe how increasing or decreasing the diameter of the efferent arterioles can change the glomerular hydrostatic pressure (and how this will affect filtration)
↓ diameter of efferent arteriole will increase GHP
↑ diameter of efferent arteriole will decrease GHP
Define “GFR” (what does it stand for, and what does it mean)
Glomerular filtration rate (GFR) = amount of
filtrate produced by the kidneys each minute
How is GFR controller by autoregulation
Accomplished by changing diameters afferent arterioles, efferent arterioles, and glomerular capillaries
How is GFR controller by the autonomic nervous system.
Sympathetic nerve fibers cause vasoconstriction of afferent arterioles of glomerulus, decrease GFR (override the local effects, in case of an “emergency”)
Describe the reabsorption that occurs in the proximal convoluted tubule (which solutes are normally reabsorbed, a general description of the transport mechanisms involved, and the significance of this).
1)Reabsorption of organic nutrients m
-99% of glucose, amino acids, etc.
-Facilitated diffusion and cotransport (Na+ dependent
secondary active transport)
-*transport maximum
2)Active reabsorption of ions
-Cotransport, countertransport
(Part of the process is active transport, to establish a gradient so that the other steps can occur by diffusion )
3) Reabsorption of water
- By osmosis (driven by high osmotic pressure and low
hydrostatic pressure of peritubular capillaries)
-Active transport of solutes creates concentration gradient
Describe the functions of the loop of Henle
1)Loop of Henle reabsorbs:
~50% of the water
~66% of the Na+ and Cl- ions
2)The filtrate at the end of the PCT is still isotonic to ECF…
needs to get concentrated! Therefore The loop of Henle generates a salinity gradient (to help with
concentration of urine, in the collecting ducts!) =Countercurrent multiplication!
Describe how the thin descending limb has a different function than the thick ascending limb, and how this relates to countercurrent multiplication
-Between the thin descending limb and thick ascending limb
A)Thin descending limb:
-Loses water by osmosis (lots of
water channels, always open)
-Conc. in tubule increases as you descend
-This speeds up the active transport in the thick ascending limb…!
B)Thick ascending limb:
- Pumps out Na+, K+, & Cl- (but no water loss!)
- Maintains conc. gradient in tissue fluid surrounding the tubule **
- Conc. in tubule decreases as you ascend
Describe the general functions of the distal convoluted tubule
Final adjustments” in composition of filtrate
occur here
-Some more Na+ and some Ca2+ reabsorption
-Plus Secretion (Of: K+, H+, some hormones, foreign chemicals,drugs, etc… )
Describe the general functions of the collecting duct
-Some more reabsorption of water and solutes
(Under control of aldosterone and ADH and Depends on osmotic gradient (between the CD and the surrounding tissue fluid)
- Some more secretion can also occur
-Can exchange H+ and bicarbonate ions to regulate pH of fluid around the collecting duct
A)Describe the micturition reflex,
B)and the voluntary control that we (normally) have to “override” this reflex.
A)Stretching of the bladder stimulates contraction of the bladder, leads to opening of internal urethral sphincter
B)Voluntary control:
-Can “override” the micturition reflex, letting you control
when to open the external urethral sphincter
-Can also change the bladder to allow you to empty the
bladder even if it isn’t full yet
- Describe how blood pressure can be regulated by hormones : erythropoietin
- increases blood pressure
- decreases blood volume