Topic 1 Part C Flashcards
Regulation – Tubular Reabsorption (5)
Glomerulotubular balance
Peritubular Capillary & interstitial forces
Arterial blood pressure
Hormonal control
Sympathetic nervous effect
–Reabsorption of some solutes can be controlled independently
Glomerulotubular Balance
Allows an increase in reabsorption rate when there is an increase in
tubular load (increased tubular inflow)
Glomerulotubular Balance
If GFR went from 125 mls/minute to 150 mls/minute rate of reabsorption in proximal tubule would go from
81 mls/minute [65% of GFR] to 97.5 mls/minute [65% of GFR]
Glomerulotubular Balance
Works to maintain ____ and _____ homeostasis
-Prevents ____ changes in fluid flow to _____ even though there have been significant changes in _____
Works to maintain sodium and volume homeostasis
-Prevents large changes in fluid flow to distal tubules even though there have been significant changes in MAP
Peritubular Capillary & Interstitial Forces
Relationship of hydrostatic and oncotic pressures AND
filtration coefficient
Peritubular Capillary & Interstitial Forces
Normal – net force for reabsorption of ___ mmHg
Normal rate of ____ mls/minute
Normal – net force for reabsorption of 10 mmHg
Normal rate of 124 mls/minute
Peritubular Capillary & Interstitial Forces
____ filtration coefficient
-Reabsorption rate / net force
-Affected by ______ & ______ (permeability)
124 mls/min / 10 mmHg = ____ mls/min/mmHg
Large filtration coefficient
-Reabsorption rate / net force
-Affected by transfer surface area & hydraulic conductivity (permeability)
124 mls/min / 10 mmHg = 12.4 mls/min/mmHg
Peritubular hydrostatic pressure (PHP)
increase PHP =
decrease Reabsorption
Factor effecting Peritubular hydrostatic pressure
Arterial pressure
Resistance of afferent & efferent arteriole
increase AP – increase PHP – _____ reabsorption
decrease
increase resistance – decrease PHP – ___ reabsorption
increase
Peritubular oncotic pressure (POP)
[increase POP - Reabsorption]
increase
factors effecting Peritubular oncotic pressure
Plasma protein concentration Filtration fraction (GFR/RPF)
increase plasma protein concentration – increase plasma oncotic pressure – increase POP – _____ reabsorption
increase
increase GFR or decrease RBF causes an increase filtration fraction
increase filtration fraction – increase protein concentration (more fluid is actually filtered) – increase POP – _____ reabsorption
increase
Factors Affecting Peritubular Capillary Reabsorption
Renal interstitial hydrostatic and colloid osmotic pressures are affected by changes in
reabsorptive forces of peritubular capillaries
Factors Affecting Peritubular Capillary Reabsorption
A decrease in capillary reabsorption…
-PRODUCES____ in interstitial solute AND interstitial water
-PRODUCES ____ in interstitial hydrostatic pressure AND _____ in interstitial oncotic pressure
-PRODUCES _____ in net movement (i.e. reabsorption) of solute & water from renal tubules to renal interstitial spaces
- PRODUCES increase in interstitial solute AND interstitial water
- PRODUCES increase in interstitial hydrostatic pressure AND decrease in interstitial oncotic pressure
- PRODUCES decrease in net movement (i.e. reabsorption) of solute & water from renal tubules to renal interstitial spaces
Interstitial Hydrostatic & Oncotic Pressures
Under normal reabsorptive conditions there is always backflow of water & solute from
interstitial spaces to tubular lumen (tight junctions not very tight especially in proximal tubule)
Interstitial Hydrostatic & Oncotic Pressures
A decrease in Peritubular reabsorption -
_____ solute & water accumulation in interstitial space
_____ backflow of solute and water from interstitial space into tubular lumen
Increase solute & water accumulation in interstitial space
Increase backflow of solute and water from interstitial space into tubular lumen
Interstitial Hydrostatic & Oncotic Pressures
Forces that increase peritubular capillary reabsorption also increase
movement of solute and water (reabsorption) from the tubular lumen to the renal interstitial spaces [Reverse also true]
Factors Affecting Peritubular Capillary Reabsorption
Capillary surface area
Capillary permeability
Filtration Coefficient (FC) [Increase FC - \_\_\_\_\_ Reabsorption]
increase
increase surface area – increase FC – ___ reabsorption
increase
increase permeability – increase FC –____ reabsorption
increase
Factors Affecting Peritubular Capillary Reabsorption:
Coefficient remains constant under most physiologic conditions but will be affected by
renal disease
Arterial Pressure (Pressure Natriuresis/Diuresis): Even though autoregulation works to keep GFR and RBF constant as pressure changes (75 mmHg to 160 mmHg), there is a small increase in GFR which results in
an increase in urine output
Arterial Pressure (Pressure Natriuresis/Diuresis): As arterial pressure increases there is a small
decrease in the amount of sodium & water reabsorbed
Arterial Pressure (Pressure Natriuresis/Diuresis): Small increase in peritubular capillary hydrostatic pressure with subsequent
increase in renal interstitial hydrostatic pressure and increase backflow of solute and water
Arterial Pressure (Pressure Natriuresis/Diuresis):
As arterial pressure increased angiotensin II release is __
-Less stimulation of sodium reabsorption by _______
-Less stimulation of _____ production which means less stimulation of sodium reabsorption
As arterial pressure increased angiotensin II release is decreased
- Less stimulation of sodium reabsorption by angiotensin II
- Less stimulation of aldosterone production which means less stimulation of sodium reabsorption
Hormonal Control
Kidneys must be able to respond to changes in intake of specific substances without changing
output of the substances
Hormonal Control
Hormone secretion provides the control specificity needed to maintain normal
body fluid volumes and solute concentrations
Hormone: Aldosterone
Site of Action:
Effects:
Site of Action: Collecting tubule & duct
Effects: Increase NaCl, H2O reabsorption
Increase K+ secretion
Hormone: Angiotensin II
Site of Action:
Effects:
Site of Action: Proximal tubule; Thick ascending loop of Henle / distal tubule; Collecting duct
Effects: Increase NaCl, H2O reabsorption
Increase K+ secretion
Hormone: ADH
Site of Action:
Effects:
Site of Action: Distal tubule; Collecting tubule & duct
Effects: Increase H2O reabsorption