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Year 1 NME > Regulation of Homeostasis by the Kidney: Fluid Balance > Flashcards

Regulation of Homeostasis by the Kidney: Fluid Balance Flashcards

1
Q

In an average 70kg patient, 60% of the patients weight is H2O. What is the largest proportion of where the H2O is stored/used in the body?

A
  • intracellular compartments = 28L
  • essentially within cells
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2
Q

In an average 70kg patient, 60% of the patients weight is H2O. Rhe majority of this is made up by the intracellular fluid compartment, which is 28L (inside cells). What are the other 2 area where fluid can be?

A

1 - intravascular fluid (plasam) = 3L

2 - extravascular fluid (interstial - not in vascular or cells) = 11L

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3
Q

What does transcellular fluid mean?

A
  • fluid between cells
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4
Q

The renal system is able to regulate bodily fluids. But of all of the bodily fluids in the image below, which specifically can the renal system influence?

A
  • intravascular fluid (plasma) perfusing tissue
  • also referred to as Effective Circulating Volume (ECF)
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5
Q

What is effective circulating volume?

A
  • the proportion of extracellular (not contained within cells) fluid that is actively perfusing tissue
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6
Q

Effective circulating volume is the proportion of extracellular fluid that is able to activley perfuse tissue. What are a few basic things that can affect this?

A
  • blood pressure (vasodilation)
  • cardiac output
  • osmotic ressure
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7
Q

If there is a drop in blood flow to te kidneys, what do they do to try and increase blood flow?

A
  • GFR will be reduced
  • low Na+ detected by macula densea cells in proximal tubules
  • juxtaglomerular cells release renin into plasma
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8
Q

If there is a drop in blood flow or blood pressure to organs including the heart, lungs or liver, these organs are able to relay a message to the brain and activate 2 different mechanisms in an attempt to increase blood flow. What 2 mechanisms does the body use to increase blood flow and blood pressure that are located in the brain?

A
  • signal the brain for 2 things:

1 - sympathetic activity (causes vasoconstriction of blood vessels)

2 - release of anti-diuretic hormone (ADH), which retains H2O, increasing blood volume and blood pressure

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9
Q

Renin Angiotensin Aldosterone System, Sympathetic nervous system and Antidiuretic Hormone (ADH) release all aim to increase blood volume and increase blood pressure. However, what does Atrial Natriuretic Peptide (ANP) do?

A
  • released from atrial myocytes when over stretched
  • signals kidneys to reduce Na+ reabsorbtion
  • reduces blood volume and BP
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10
Q

What is the basic principle of how the kidneys are able to regulate effective circulating volume?

A
  • control of how much H2O and electrolytes are retained or excreted
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11
Q

What are the main components that contribute to counter current multiplication?

A
  • Na+ and Cl- secretion from tubules into interstitial space
  • Urea secretion into interstitial space
  • H2O secretion into interstitial space
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12
Q

What is the main site where counter current multiplication is effective in the nepherons?

A
  • loop of henle
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13
Q

What does anti-diuretic hormone (ADH) also known as vasopressin contribute to H2O retention?

A
  • binds to ADH receptors and increase aquaporins
  • increases permeability in the collecting ducts
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14
Q

Anti-diuretic hormone (ADH) also known as vasopressin is released from the pituitary gland in response to low plasma levels, which reduced effective circulating volume (ECV). ADH is able to increase ECV by telling the kidneys to retain H2O and increase the permeability in the collecting ducts. What receptors do ADH bind with?

A
  • ADH binds with V2 receptors which are GPCR Gs
  • Gs activates adenlyly clyclase (AC) converts ATP into cyclic adenosine monophosphate (cAMP)
  • cAMP then activates protein kinase A (pKA)
  • pKA activates synthesis of new aquaporins on collecting ducts on the tubule lumen
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15
Q

Anti-diuretic hormone (ADH) also known as vasopressin is released from the pituitary gland in response to low plasma levels, which reduced effective circulating volume (ECV). ADH is able to increase ECV by telling the kidneys to retain H2O and increase the permeability in the collecting ducts. ADH binds with a GPCR Gs which activates intracellular pathways in the principle cells resulting in the synthesis of new aquaportins in the collecting ducts. What does this do to the urine that we excrete?

A
  • low volumes of concentrated urine
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16
Q

Angiotensin II (ANG-II) is an established component of the RAAS system. There are 2 typesd of ANG-II receptors, what do they both do?

A
  • type 1 ANG-II receptor = vasoconstriction, cell proliferation, inflammatory responses, blood coagulation and extracellular matrix remodelling
  • type 12 ANG-II receptor = opposite of type 1 ANG-II receptors
17
Q

What is the main purpose of angiotensin-II?

A
  • increase effective circulating volume
18
Q

In addition to causing vasoconstriction by increasing systemic vascular resistance and arterial pressure, how does angiotensin II affect the heart?

A
  • stimulate cell proliferation and extracellular matrix remodelling
  • causes cardiac hypertrophy and vascular hypertrophy
  • can become chronic and pathological
19
Q

In addition to causing vasoconstriction by increasing systemic vascular resistance and arterial pressure, angiotensin II stimulates cell proliferation and extracellular matrix remodelling, causing cardiac hypertrophy and vascular hypertrophy, which can ultimately become chronic and pathological. Angiotensin II can also trigger inflammatory pathways, what are the 3 most common?

A

1 - blood coagulation

2 - increased protein synthesis

3 - extracellular matrix remodelling

20
Q

Why is angiotensin II classified as a stress hormone?

A
  • it prepares us for stress
  • fight or flight response
21
Q

Angiotensin II stiumulates the release of aldosterone from the suprerenal (adrenal) glands. What does aldosterone then do to the kidneys?

A
  • increases Na+ reabsorbtion and K+ excretion
  • H2O follows Na+
22
Q

Angiotensin II stiumulates the release of aldosterone from the suprerenal (adrenal) glands. Aldosterone triggers increased Na+ and H2O reabsorbtion and K+ excretion. Where in the kidneys are the aldosterone sensitive cells?

A
  • distal tubules
23
Q

Angiotensin II stiumulates the release of aldosterone from the suprerenal (adrenal) glands. Aldosterone triggers increased Na+ and H2O reabsorbtion and K+ excretion. In addition aldosterone is involved in a negative feedback loop, why is this?

A
  • increase effective circulating volume and lowers K+
24
Q

Angiotensin II stiumulates the release of aldosterone from the suprerenal (adrenal) glands. Aldosterone triggers increased Na+ and H2O reabsorbtion and K+ excretion. In addition aldosterone is involved in a negative feedback loop by increasing effective circulating volume and lowering K+. Why is this control of K+ important?

A
  • K+ is mainly an intracellular electrolyte
  • we do not want too much in plasma
25
Q

What are osmoreceptors and where are they found in the brain?

A
  • generally found in hypothalamus
  • detects changes in osmotic pressure, important for maintaining body fluids
26
Q

Antidiurectic hormone (ADH) is produced in the hypothalamus and secreted into the pituitary gland. If osmoreceptors in the hypothalamus detect hyperosmolarity (high electrolyte concentrations and low H2O) ADH is released. What does this then do to thirst and kidney function?

A
  • increases thirst to increase H2O levels
  • increases H2O reabsorbtion in collecting ducts
27
Q

Baroreceptors are able to detect changes in arterial pressure, specifically at the carotid sinus and aortic arch. What do these baroreceptors tirgger?

A
  • RAAS system
  • sympathetic nervous sytem
  • anti-diuretic hormone release
  • atrial natriuretic peptide (anp)
28
Q

Baroreceptors are able to detect changes in arterial pressure, specifically at the carotid sinus and aortic arch. These baroreceptors tirgger the RAAS system, sympathetic nervous sytem, anti-diuretic hormone release and atrial natriuretic peptide (anp) release. What are the long and short term effects of these pathways?

A
  • short term = heart and blood vessels influencing BP
  • long term = kidneys influencing Na+ levels
29
Q

There are central vascular baroreceprtors which are very important. What are they able to detect and where are they located?

A
  • low pressure blood volume receptors
  • located in large systemic veins, atria and pulmonary vasculature
30
Q

There are high pressure arterial stretch baroreceprtors which are important. What are they able to detect and where are they located?

A
  • detect high pressures
  • carotid sinus, aortic arch and renal afferent arteriole
31
Q

We have both central vascular and arterial stretch baroreceptors. Which detect low and high pressures?

A
  • central vascular baroreceptors = LOW pressure
  • arterial stretch baroreceptors = HIGH pressure

Year 1 NME (61 decks)

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