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Renal Physiology Flashcards

0
Q

Fluid compartments of the body

A
  1. Blood plasma: fluid component of the blood
  2. Interstitial fluid: fluid surrounding cells
  3. Intracellular fluid: fluid within cells

1&2 separated by endothelium
2&3 separated by cell membrane

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1
Q

Why is it necessary to have control over water and electrolyte balance?

A

No known species has a completely passive relationship between their internal and external environment. Water and ion regulation is important to prevent unwanted loss or gain of those substances.

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2
Q

Osmolarity

A

Solute concentration (number of osmoles of solute per litre) based on both penetrating and non penetrating solutes

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3
Q

Tonicity

A

Refers to solute concentration based only on penetrating solutes (particles that pass through membrane)

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4
Q

How does osmotic pressure affect water movement?

A

Water moves from low to high osmotic pressure (areas of low solute to high solute)

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5
Q

Which fluid compartments have similar ion concentrations and which do not?

A

Blood plasma and interstitial fluid have same concentration. Intracellular fluid has different concentration.

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6
Q

Osmotic regulators

A

Show constant blood osmotic pressure (maintains constant fluid composition regardless of the external environment)

Ex. Shrimp

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7
Q

Osmotic conformers

A

Show blood osmotic pressure that mimics the external environment (changes fluid composition to equal that of the environment)

Ex. Mussel

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8
Q

Challenges to freshwater regulators

A

Environment is hypo-osmotic

Therefore, water is constantly being brought in to the internal environment due to osmosis

Solution: Get rid of excess water to prevent ion loss

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9
Q

Challenges to marine regulators

A

External environment is hyper-osmotic

Therefore, water is constantly being drawn out to the external environment

Solution: Retain more water to prevent ion loading

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10
Q

Special case: Elasmobranchs and osmoregulation

A

Elasmobranchs produce high levels of inorganic solute to meet the same osmotic pressure as the external environment. These solutes are not identical to the ones in the external environment but they create a similar solute concentration.

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11
Q

Special case: Salmon

A

Salmon are born in fresh water and migrate to sea water. To return to fresh water for the breeding season salmon spend time in brackish water which is an intermediate between fresh and sea water.

In the transition process:

  1. Kidney function change to make more dilute urine in freshwater
  2. Gills take up ions in fresh and lose them in sea
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12
Q

How do gills help osmoregulation in freshwater environments?

A

Gills have a high surface area and permeability which benefits gas exchange. This is counter productive for water-salt balance.

High surface area = increase water uptake through osmosis
High permeability = increase ion loss or loading

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13
Q

Solution to gills

A

Active transport of ions into the gills coupled with copious amount of dilute urine

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14
Q

Osmoregulatory gill cells

A

Pavement cells: occupy 90% of the gill epithelium and is responsible for oxygen uptake

Mitochondria rich cells: uptake Na, Cl, Ca; partial under hormonal control; density and type depends on conditions

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15
Q

How do marine birds and reptiles deal with a hyper osmotic environment ?

A

Thick and less permeable integument (skin)

Salt glands

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16
Q

Salt glands in birds

A

Nasal

Ducts transfer ions to the nostrils located in the beak (replaces function of gills)

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17
Q

Salt glands in reptiles

A

Lingual or tongue
Nasal
Optical

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18
Q

How salt glands work?

A

When osmoreceptors near the heart and brain detect high blood osmotic pressure, the parasympathetic system releases AcH. This induces Cl and K gated channels in the mitochondria rich cells. The build up of negative charge inside the mitochondria rich cells attract Na to the apical membrane for excretion.

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19
Q

Humidic Animals

A

Restricted to humid and water rich environments
(Ie. earthworms, slugs, etc.)

Highest integument permeability

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20
Q

Xeric animals

A

Animals that live in dry, water poor places
(Ie. mammals, birds, etc.)

Lower integument permeability via thin lipid layers

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21
Q

Temperature and water loss through respiration

A
  1. Air entering body increases in temperature
  2. Warmer moist air travels down tubes until matched to the temperature of the body
  3. During exhale, air moves back out the same tube where it’s temperature is cooled to reduce the water content of the leaving air.
22
Q

Evaporative water loss

A

Depends on body size and phylogenetic group.

Water loss decreases with increasing body size.

23
Q

Excretory Water Loss

A

2nd most abundant source of water loss

Required to remove waste from body

Composition of urine can be modified to reduce water loss or ion loss.

24
When is urine concentration modified?
During times of drought During times of water loading Represented by U/P ratio
25
U/P ratio
Osmotic pressure of urine (divide) osmotic pressure of plasma. U/P = 1: urine is isosmotic to plasma U/P > 1: urine is hyper osmotic to plasma U/P < 1: urine is hypo osmotic to plasma
26
Podocytes
Specialized endothelial cells contain end feet that cross over each other and contact the basement membrane of the glomerulus. The crossovers form fenestrations that allow water, waste, and glucose to pass but prevent the permeability of large proteins.
27
Hydrostatic pressure of blood outside Bowman's Capsule
Created by systole, it is the driving force that directs content of blood towards the lumen of the Bowman's Capsule. This force exceeds the colloid pressure and hydrostatic pressure of the lumen. Also known as filtration pressure
28
Primary urine
The aqueous solution that is first introduced into the kidney tubules. That is the filtrate entering the Bowman's capsule.
29
Colloid osmotic pressure
The pressure generated due to impermeability of blood proteins. This makes blood hyper osmotic compared to the filtrate which causes some water to be drawn back to the blood from the capsular fluid.
30
Glomerular filtration rate
The rate of production of primary urine About 120mL/min Full blood volume is filtered every 30 mins
31
How does glomerular filtration rate alter?
Disease Chronic hypertension or diabetes mellitus Increased thickness of basement membrane Damaged capillaries in glomerulus Normal conditions: Change blood pressure or vary number of filtrating nephrons
32
Loops of Henle
Long in mammals Short in non mammals Composed of a descending and ascending limb (longer limb = greater urine concentration; associated with thicker medulla)
33
Loop of Henle: Descending thin segment
Highly permeable to water Moderately permeable to most solutes
34
Loop of Henle: Ascending thin segment
Impermeable to water Moderately permeable to most solutes
35
Loop of Henle: Ascending thick segment
Impermeable to water Active transport of Na/Cl
36
Osmotic pressures in the Loop of Henle
Single effect: initial change in pressure due to active transport Countercurrent multiplication: osmotic pressure multiplied due to fluid moving in opposite directions
37
Osmotic pressure gradient
Osmotic pressure increases towards the inner medulla
38
Antidiuresis
The process of concentrating urine as it moves through the collecting duct. The concentration gradient generated from the loop of Henle allows water to move out of the collecting duct as urine travels through it.
39
Diuresis
The process of maintain dilute urine by decreasing the permeability of the collecting duct to water.
40
Hormonal control of the collecting duct
1. ADH or vasopressin
41
ADH
Antidiuretic hormone Released when blood plasma is low (dehydration) to alter permeability of collecting duct Change in blood pressure is detected by osmoreceptors and baroreceptors
42
Baroreceptors
Located in pulmonary venous system, cardiac atria, aortic arch, carotid sinus
43
Osmoreceptors
Located in hypothalamus
44
Aquaporin 2 release
Aquaporin channels inserted into the wall of collecting duct in the presence of ADH. ADH stimulates the release of the channels from aquaporin water channel containing vesicles.
45
Aquaporin 2 retracted
Decrease in ADH levels cause the retraction of aquaporin 2 channels from the membrane back into free floating vesicles.
46
Aquaporin 2 structure
6 transmembrane domains 5 inter helical loops Pore is found between 2 and 5 loop
47
Urea
Produced by oxidation of amino acids not used in protein synthesis Or Produced by conversion of ammonia from nitrogenous metabolism
48
Permeability of urea
Freely passes into Bowman's capsule but is only permeable in the thin segment of loop of Henle and the collecting duct of the inner renal medulla
49
Urea transporter protein
Facilities diffusion of urea from collecting duct into interstitial fluid which contributes to osmotic gradient. Upregulated by ADH
50
How does urea leave the body?
Urea that enters the interstitial space is facilitated back into the loop of Henle until it is excreted out.
51
The vasa recta
Parallels the nephron but has slow blood flow Does not impede osmotic pressure gradients Descending limb absorb solute and release water Ascending limb absorb water and release solute
52
Methods of water Retention
1. Large body size (less surface area to mass) 2. Modulate body temp with greater range (large in camels, limited in humans) 3. Allow body temp to rise to decrease absorption of heat 4. Keep brain cool via cool blood to brain via nasal passage 5. Reduce water lost in waste 6. Special physical attributes (ie. camel fur acts as shield) 7. Behavioural adaptation (ie. create shade)
53
Camels
Extreme temperature adapted High dehydration tolerance Can tolerate 30-40% loss of body weight Drink copious amount of water

Animal Physiology (5 decks)

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