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Module 6 Week 2 > Renal Function- Filtration > Flashcards

Renal Function- Filtration Flashcards

1
Q

Principal functions of the kidney

A

—Regulate volume/composition of ECF (will affect ICF) – Osmoregulation, Blood pressure and volume
—Regulate concentrations of ions in ECF
—Excretion – endogenous waste/metabolites, toxins, drugs Acid base balance

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2
Q

What do kidneys produce?

A

Renin
Erythropoietin
Calcitriol
Glucose
Urine

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3
Q

Function of produced renin

A

counteracts reduction in ECF volume and BP (blood pressure)

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4
Q

Function of produced erythropoietin

A

formation and maturation of RBCs

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5
Q

Function of produced calcitriol

A

Calcium homeostasis

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6
Q

Function of produced glucose

A

protect blood sugar during starvation

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7
Q

Kidney is a homeostatic organ, and control is achieved via…

A

cooperative functionality with circulatory & respiratory systems

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8
Q

These structures found within cortex or medulla?
-glomerulus
-bowman’s capsule
-proximal convoluted tubule
-cortical nephron’s LOH (loop of Henle)
-juxtamedullary nephron’s LOH

A
  1. Cortex
  2. Cortex
  3. Cortex
  4. Barely enters medulla
  5. Deep in medulla
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9
Q

Why is position of nephron in kidney important?

A

Nephron regulate water balance so their position matters

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10
Q

Three fundamental processes/functions within the nephron

A
  1. Filtration
  2. Reabsorption
  3. Secretion
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11
Q

What are the 2 types of differentiated cell types found along the length of the nephron due to differing functions

A

Principal cells
Intercalated cells

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12
Q

Principal cells reabsorb and secret what?
Intercalated cells reabsorb and transfer what?

A

Principal cells – reabsorb Na+, Cl- and secrete K+
Intercalated cells – reabsorb K+ and transfer H+

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13
Q

What structure in nephron does filtration occur in?

A

Glomerulus

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14
Q

Filtration in the glomerulus occurs as a result of…

A

Pressure differences within the system

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15
Q

Describe what occurs during filtration in glomerulus

A

-Blood enters afferent arteriole under relatively high pressure (high pressure due to actions of heart and resistance of efferent arteriole)
-high pressure results in extrusion of large amounts of water, plus glucose, proteins and other waste products
-overall around 20% of plasma is leaving in glomerulus and entering filtrate
-large molecules such as blood cells, large proteins are retained within bloodstream

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16
Q

What is a way to get rid of retained large waste molecules that were unable to be filtered?
Occurs where?

A

Secretion- taking waste products from blood stream and passing to filtrate
Occurs within PCT

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17
Q

Secretion of large molecules in the nephron can result in what?
What is a way to stop this from occurring? Where does this process occur?

A

Loss of solutes/water that we do not want to lose

Reabsorption- recovery of required components from filtrate (partial/total depending on what body needs)
-occurs in PCT, LOH, DCT, Collecting duct (whole rest of nephron)

18
Q

Certain diseases will results in problems in filtration process. What do they cause which can result in what?

A

Cause more proteins to be passed out into urine/filtrate and are unable to be reabsorbed

Results in:
Proteinuria
Albuminuria
Haemoglobinuria

19
Q

Rate of filtration is determined by…

A

hydrostatic and osmotic forces

20
Q

What are the three main forces of water movement and what each causes
Which is the 4th that has no effect on movement of water

A
  1. Glomerular hydrostatic pressure—> very high pressure caused by actions of heart and differences in resistance of arterioles
  2. Hydrostatic pressure of Bowman’s Space—> as water builds in bowman’s space (space between glomerulus and bowmans capsule) it is pushed back into capillaries
  3. Oncotic pressure- pressure brought about by plasma proteins; holds water within capillaries as they are impermeable
  4. Osmotic pressure due to fluid in Bowman’s space- effectively 0 as filtrate is pulling away all those proteins; they aren’t staying in one space
21
Q

How would you calculate the net ultrafiltration pressure?

A

Puf= Pgc - (Pbs + Tgc)

Puf= glomerular capillary hydrostatic pressure - (Hydrostatic pressure of bowman’s space + Oncotic pressure)

22
Q

Calculation for Glomerular Filtration Rate (GFR)

A

GFR= Puf x (permeability of the filter, surface area (of filtration barrier))

23
Q

Since we can change the net ultrafiltration rate of we change any of the values in the equation, this means we can regulate the…

A

GFR

24
Q

Why should GFR be regulated?
GFR is regulated by what?

A

-so as to maintain stable ECF (and ICF)
-Principally regulated by changes in blood flow, protein osmotic pressures and hydrostatic pressure

25
Q

What will happen to glomerular filtration rate when there is a lower blood flow?

A

Lower blood flow —>
-blood is spending longer within capillary bed so more opportunity to push water out; more water leaves
-greater increase in osmotic pressure across capillary itself
-only osmotic pressure changed, hydrostatic capillary pressure stays the same
-water is ‘held’ in latter parts of capillaries so overall decreased GFR

26
Q

What will happen to glomerular filtration rate when there is a higher blood flow?

A

Higher blood flow; Less water is filtered through so osmotic pressure increases less so increased GFR

27
Q

How are we able to alter afferent and efferent arteriole resistance?
What effect does alteration of arteriole have

A

Afferent and efferent arteriolar are smooth muscle so we can either relax or constrict this muscle
Alteration affects flow of hydrostatic pressure/blood flow and therefore GFR

28
Q

What would happen to GFR if afferent arterioles were constricted?

A
  1. -Less blood would be coming in as passage is constricted, therefore decreased blood flow
    -decreased blood flow causes a decreased GFR
  2. -there would be a decreased hydrostatic pressure as there’s less blood so less fluid movement out of capillaries, therefore decreased GFR

Overall both changes cause a DECREASE in GFR

29
Q

What would happen to GFR if efferent arterioles were constricted?

A
  1. -less blood is able to leave so decreased blood flow
    -causes decreased GFR once again
  2. -there is increased hydrostatic pressure there is more blood within capillaries due to constricted exit
    -causes increase in GFR

Overall opposing effects mean there is NO CHANGE in GFR

30
Q

Since GFR can be regulated by blood pressure, this means any easy task requiring a change in BP would cause effect on GFR. How then do we regulate GFR if there is an ACUTE or MODERATE blood pressure change?

A

By autoregulation; changes the resistance of the afferent arterioles which will ultimately maintain GFR

31
Q

What are the 2 types of autoregulation—>

A

-myogenic reflex
-tubuloglomerular feedback

32
Q

Response to acute moderate changes in BP:
Myogenic Reflex
-how does it work when there is an increased BP

A

Increase BP:
Stretch receptors are stimulated which brings about a reflex contraction of afferent arteriole
Contraction decreases blood flow back to normal and therefore GFR is maintained

33
Q

Response to acute moderate changes in BP:
Myogenic Reflex
-how does it work when there is an increased BP

A

Decreased BP:
-Detected by stretch receptors
-Reflex dilation of afferent arteriole= more blood flow
-GFR stabilised

34
Q

Response to acute moderate changes in BP:
Tubuloglomerular feedback
-how does it work

A

Stimulus is the amount of filtrate being produced
-recognises amount at Macula densa (makes close connection with afferent arteriole)
-for example decrease in GFR causes decreased flow past macula densa
-results in decreased NaCl concentration
-this stimulates release of paracrine factors from macula densa
-these act on afferent arteriole
-afferent arteriole is dilated-> more blood flow—> more filtrate and therefore ^GFR to normal

35
Q

How do we regulate GFR if there is an CHRONIC (longer term) blood pressure change?

A

Use of Renin Angiotensin Aldosterone system

36
Q

How does the Renin Angiotensin Aldosterone system in regulating GFR

A

Release of renin causes angiotensin I to change forms to angiotensin II which causes arteriole vaconstriction (causing ^ BP) and ^ in sympathetic NS activity

Overall there is a constriction of efferent arterioles to combat low BP. There is also increased water Reabsorption. Ultimately maintains GFR back to normal.

37
Q

Why should we assess estimation of GFR in body?

A

Can be a clinical indicator of progress of renal disease

38
Q

How do we estimate GFR

A

GFR = urinary excretion of a substance/minute —————————————————————-plasma concentration of substance

(Substance must be freely filtered and neither reabsorbed nor secreted)

39
Q

Which plasma conc substance can be used to estimate GFR

A

Inulin (a fructose polymer)

40
Q

What is clearance?

A

volume of plasma, that contains the amount of the substance excreted in the urine per minute (i.e. what’s filtered and secreted)

Module 6 Week 2 (10 decks)

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