Topic 1 Part C Flashcards by melissa griffith

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

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Glomerulotubular Balance

Allows an increase in reabsorption rate when there is an increase in

tubular load (increased tubular inflow)

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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]

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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

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Peritubular Capillary & Interstitial Forces

Relationship of hydrostatic and oncotic pressures AND

filtration coefficient

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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

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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

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Peritubular hydrostatic pressure (PHP)

increase PHP =

decrease Reabsorption

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Factor effecting Peritubular hydrostatic pressure

Arterial pressure

Resistance of afferent & efferent arteriole

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increase AP – increase PHP – _____ reabsorption

decrease

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increase resistance – decrease PHP – ___ reabsorption

increase

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Peritubular oncotic pressure (POP)

[increase POP - Reabsorption]

increase

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factors effecting Peritubular oncotic pressure

Plasma protein concentration
Filtration fraction (GFR/RPF)

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increase plasma protein concentration – increase plasma oncotic pressure – increase POP – _____ reabsorption

increase

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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

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Factors Affecting Peritubular Capillary Reabsorption

Renal interstitial hydrostatic and colloid osmotic pressures are affected by changes in

reabsorptive forces of peritubular capillaries

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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

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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)

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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

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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]

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Factors Affecting Peritubular Capillary Reabsorption

Capillary surface area

Capillary permeability

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Filtration Coefficient (FC) 
[Increase FC - \_\_\_\_\_ Reabsorption]

increase

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increase surface area – increase FC – ___ reabsorption

increase

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increase permeability – increase FC –____ reabsorption

increase

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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

Hormone: Atrial Naturetic Pepetide Site of Action: Effects:

Site of Action: Distal tubule; Collecting tubule & duct | Effects: Decrease NaCl reabsorption

Hormone: Parathyroid Hormone Site of Action: Effects:

Site of Action: Proximal tubule; Thick ascending loop of Henle; Distal tubule Effects: Decrease PO4--- reabsorption Increase Ca++ reabsorption

Aldosterone - Secreted by ______ cell in ______ - Regulate _____ reabsorption and ______ secretion - Very important regulator of _______

- Secreted by zona glomerulosa cell in adrenal cortex - Regulate sodium reabsorption and potassium secretion - Very important regulator of [potassium]

Aldosterone - Principal site of action is ____ cells of ______ - Stimulates increased ____ activity (_______ locations) - Increases permeability of ____ side membrane to _____

- Principal site of action is principal cells of cortical collecting tubule - Stimulates increased Na-K ATPase activity (basolateral locations) - Increases permeability of luminal side membrane to sodium

Aldosterone Increased release stimulated by: -Increased extracellular ______ concentration -Increased ______ levels (i.e. sodium / volume depletion or low arterial pressure)

Increased release stimulated by: - Increased extracellular potassium concentration - Increased angiotensin II levels (i.e. sodium / volume depletion or low arterial pressure)

Aldosterone Pathophysiology -Absence= -Excess=

Pathophysiology - Absence (adrenal malfunction or destruction) (Addison’s disease) - Excess (adrenal tumors) (Conn’s syndrome)

Angiotensin II - Most powerful ________ hormone - Increased production caused by _____ and/or ______

- Most powerful sodium-retaining hormone | - Increased production caused by low blood pressure and/or low ECF volume

Angiotensin II | Stimulates ______ secretion (increased sodium reabsorption)

aldosterone

Angiotensin II - Constricts _______ (increase sodium and water reabsorption) - Helps ensure that normal exertion rates of ______ are maintained by helping to maintain normal rates of _____ - Able to retain ______ without retaining_________

- Constricts efferent arterioles (increase sodium and water reabsorption) - Helps ensure that normal exertion rates of metabolic wastes are maintained by helping to maintain normal rates of GFR - Able to retain sodium & water without retaining metabolic waste

Angiotensin II - Direct stimulation of sodium reabsorption in (4) - Stimulate increased ______ of tubular epithelial cells (____ membrane) - Stimulate _____ exchange in _______ (_____ membrane) - Stimulate ______ co-transport (_________ membrane)

- Direct stimulation of sodium reabsorption in proximal tubules, loop of Henle, distal tubules, and collecting tubules - Stimulate increased Na-K ATPase activity of tubular epithelial cells (basolateral membrane) - Stimulate Na-H exchange in proximal tubule (luminal membrane) - Stimulate Na-Bicarb co-transport (basolateral

Angiotensin II | Affects transport on both ____ and _____ membranes

luminal and basolateral

Angiotensin II | Very active in ______ but also effective in (3)

Very active in proximal tubule but also effective in loop of Henle, distal tubule, collecting tubule

``` Antidiuretic Hormone (Vasopressin) made in the ```

hypothalamus

``` Antidiuretic Hormone (Vasopressin) Two types of _______ neurons produce ADH -Neurons located in ____ and ______ nuclei -__% in supraoptic -__% in paraventricular nuclei ```

Two types of magnocellular (large) neurons produce ADH - Neurons located in supraoptic and paraventricular nuclei - 83% in supraoptic - 17% in paraventricular nuclei

``` Antidiuretic Hormone (Vasopressin) Once produced ADH moves down the neurons to their tips which are located in the _____ and is released ```

posterior pituitary

``` Antidiuretic Hormone (Vasopressin) Stimulation of the supraoptic and paraventricular nuclei (increased ______) sends impulses down the _______ neurons which stimulates release of ADH from ______ located in the nerve endings ```

Stimulation of the supraoptic and paraventricular nuclei (increased osmolarity) sends impulses down the magnocellular neurons which stimulates release of ADH from storage vesicles located in the nerve endings

``` Antidiuretic Hormone (Vasopressin) Controls water permeability of (3) ```

distal tubule, collecting tubule, and collecting duct

``` Antidiuretic Hormone (Vasopressin) Decrease [ADH] results in _____ water permeability so water is not reabsorbed which results in _____ urine volume and _____ [solute] = large volumes of dilute urine ```

Decrease [ADH] results in decrease water permeability so water is not reabsorbed which results in increase urine volume and increase [solute] = large volumes of dilute urine

``` Antidiuretic Hormone (Vasopressin) Stimulates formation of water channels across ```

luminal membrane

``` Antidiuretic Hormone (Vasopressin) Binds with specific V2 receptors which increases formation of ```

cyclic AMP and activation of protein kinases

``` Antidiuretic Hormone (Vasopressin) Protein kinase activation results in movement of ```

aquaporin-2 (intracellular protein) to luminal side of cell

``` Antidiuretic Hormone (Vasopressin) ________ come together and fuse with cell membrane to form water channels which increases membrane permeability to water (increase water reabsorption) ```

Aquaporin-2 molecules

``` Antidiuretic Hormone (Vasopressin) Chronic increases in ADH will stimulate an increase in ```

formation of aquaporin-2 molecules

``` Antidiuretic Hormone (Vasopressin) AVP = ```

arginine vasopressin

``` Antidiuretic Hormone (Vasopressin) V2 receptors on basolateral membranes so increase [ADH] in the plasma will result in movement of ADH from ```

peritubular capillaries to the renal interstitial space

Antidiuretic Hormone (Vasopressin) Other aquaporins are present on the basolateral membrane providing _____ -No evidence to show that they are affected by _____

Other aquaporins are present on the basolateral membrane providing water channels -No evidence to show that they are affected by [ADH]

``` Antidiuretic Hormone (Vasopressin) Decrease [ADH] results in movement of the _______ back into the ______ which reduces the number of _____ channels and decrease water __________ ```

Decrease [ADH] results in movement of the aquaporin-2 molecules back into the cytoplasm which reduces the number of water channels and decrease water permeability

Atrial Natriuretic Peptide | Secreted by cardiac atrial cells when atria

distended by plasma volume expansion

Atrial Natriuretic Peptide - Direct inhibition of _____ & _____ reabsorption (especially collecting ducts) - Inhibits ____ secretion (thus inhibits ______ formation)

- Direct inhibition of sodium & water reabsorption (especially collecting ducts) - Inhibits renin secretion (thus inhibits angiotensin II formation)

Atrial Natriuretic Peptide | Important response to help prevent ________ during heart failure

sodium and water retention

Parathyroid Hormone | Most important hormone for regulating

calcium

Parathyroid Hormone - Increases _____ reabsorption (________) - Inhibits ______ reabsorption (______) - Increases _____ reabsorption (_________)

- Increases calcium reabsorption (distal tubules) - Inhibits phosphate reabsorption (proximal tubule) - Increases magnesium reabsorption (loop of Henle)

Sympathetic Nervous System | Severe stimulation results in constriction of

renal arterioles which decrease GFR

Sympathetic Nervous System | Low levels of stimulation activate ______ on renal tubular epithelial cells (4)

Low levels of stimulation activate alpha-receptors on renal tubular epithelial cells (proximal tubule, thick ascending limb of loop of Henle, maybe distal tubule)

Sympathetic Nervous System | Receptor activation stimulates sodium reabsorption which

decreases sodium and water excretion

Sympathetic Nervous System | Stimulates release of renin (angiotensin II) which adds to

increase in tubular reabsorption of sodium

Renal Clearance=

Volume of plasma that is completely cleared (i.e. all of specified solute) by kidneys per unit time

Renal Clearance allows us to quantify (5)

``` excretory function of kidneys renal blood flow glomerular filtration tubular reabsorption tubular secretion ```

Renal Clearance= [formula]

Cs= Us*V / Ps | Urinary excretion rate / Plasma concentration

Estimation of GFR | If solute freely filtered and neither reabsorbed or secreted, then excretion rate is the

filtration rate

Estimation of GFR | A four fold increase in creatinine concentration means the GFR is

one-fourth normal

Estimation of GFR= [formula]

GFR * Ps= Us * V= Us*V / Ps= Cs

Estimation of Renal Plasma Flow | If a substance is completely cleared then clearance rate should equal the

renal plasma flow

Estimation of Renal Plasma Flow | PAH clearance provides reasonable estimation of

renal plasma flow (90% cleared)

Estimation of Renal Plasma Flow | Actual renal plasma flow can be calculated by dividing the PAH clearance rate by the PAH extraction rate=

PAH Clearance / 0.9

Estimation of Renal Plasma Flow | TOTAL BLOOD FLOW can be calculated by taking the calculated plasma flow and dividing

by (1-HCT)

Filtration Fraction = [formula]

GFR / RPF

Absorption= [formula]

Filtered load – Excretion rate

Secretion= [formula]

Excretion rate – Filtered load

If equal to inulin clearance then...

Substance only filtered, not reabsorbed, not secreted

If less than inulin clearance then...

Substance must be reabsorbed

If greater than inulin clearance then...

Substance must be secreated

Topic 1 Part C Flashcards

(86 cards)