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week 11 Flashcards

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1
Q

Body Water Content in humans (amounts)

A
  • Infants: 70% or more
    water (high body fat,
    low bone mass)
  • Adult males: ~60%
    water
  • Adult females: ~55%
    water (less skeletal
    muscle mass)
  • Water content declines
    to ~45% in old age
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2
Q

what is the total body water percentage?

A
  • Total body water = 60% of body weight (42 L ~ 70kg)
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3
Q

what are the fluid compartments?

A

Two main fluid compartments:
– Intracellular fluid (ICF)
compartment: ~26L in cells
– Extracellular fluid (ECF)
compartment: ~16L outside
cells
* Plasma: ~3 L
* Interstitial fluid (IF):
~13 L in spaces between cells
– Usually considered part of IF:
lymph, CSF, humors of the
eye, synovial fluid, serous
fluid, and gastrointestinal
secretions

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4
Q

what is the universal solvent?

A

water

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5
Q

what are solutes?

A
  • Solutes: what is dissolved in water
    – Classified as non-electrolytes and electrolytes
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6
Q

what are non-electrolytes?

A

Non-electrolytes
– Do not dissociate in water: e.g., glucose, lipids, creatinine, and urea
» No charged particles created

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7
Q

what are electrolytes?

A
  • Electrolytes (~charged particles, e.g. Na+, Cl-
    )
    – Electrolytes are the most abundant solutes in body fluids;
    determine most chemical and physical reactions
    – Dissociate into ions in water; e.g., inorganic salts, all acids and
    bases, some proteins
    » Ions conduct electrical current
    – Greater osmotic power than non-electrolytes
    » Greatest ability to cause fluid shifts
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8
Q

Fluid Movement Among
Compartments

A
  • Osmotic and blood hydrostatic pressures regulate
    continuous exchange and mixing of fluids:
    – Water moves freely along osmotic gradients
    – All body fluid osmolality (measure of solute concentration)
    almost always equal (equilibrium)
    – Change in solute concentration of any compartment leads to
    net water flow
  • ^ ECF osmolality (measure of solute concentration) –> water leaves cell
  • v ECF osmolality (measure of solute concentration) –> water enters cell
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9
Q

fluid movement Between plasma and IF across capillary walls

A

Fluid leaks from arteriolar
end of capillary,
reabsorbed at venule
end; lymphatics pick up
remaining and return to
blood

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10
Q

fluid movement Between IF and ICF
across cell membrane

A

– Two-way osmotic flow of
water
– Ions move selectively;
nutrients, wastes, gases
unidirectional

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11
Q
  • Water intake must =
A

Water intake must = water output = ~ 2500 ml/day

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12
Q

what is water intake?

A

Water intake:
beverages, food,
and metabolic water

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13
Q

what is Water output?

A

urine
(60%), insensible
water loss (lost
through skin and
lungs), perspiration,
and faeces

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14
Q

what is osmolality?

A

Osmolality is a measure of the osmoles (Osm) of solute per
kilogram of solvent, Osmolarity is defined as the number of
osmoles of solute per litre of solvent

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15
Q

what is Measure of solute concentration?

A

~ how much solute in the fluid

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16
Q

what is Osmolality maintained within a small range

A

~ 280 – 300 mOsm

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17
Q

Rise in osmolality (↑solute concentration) –>

A

– Stimulates thirst
– Anti-Diuretic Hormone (ADH) released by pituitary gland

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18
Q

Decrease in osmolality (↓solute concentration) –>

A

– Thirst inhibition
– ADH inhibition

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19
Q

what is the Renin-Angiotensin Aldosterone
System?

A

The RAAS is a hormone system for regulating the
body’s blood volume and therefore blood pressure
– Granular cells of juxtaglomerular complex release renin (enzyme)
in response to:
* Sympathetic nervous system stimulation
* v filtrate NaCl concentration (detected by macula densa cells -
chemoreceptors)
* v stretch (due to ^ blood pressure) of granular cells (mechanoreceptors)
– Renin catalyses angiotensinogen (a protein made in the liver) into
Angiotensin I
– Angiotensin I is converted in Angiotensin II by another enzyme
– Angiotensin II:
* is a potent vasoconstrictor (which increases BP)
* stimulates the release of aldosterone (hormone) from the adrenal/suprarenal
gland –> leads to an ^ Na+ reabsorption by kidney tubules –> water follows

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20
Q

what is a driving force for water
intake?

A

thirst mechanism

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21
Q

what is the Regulation of Water
Intake governed by?

A

Governed by hypothalamic thirst centre
– Hypothalamic osmoreceptors detect ECF
osmolality; activated by:
*  Plasma osmolality of 1 – 2%
– Dry mouth detected from reduced saliva
– Decreased blood volume or pressure
– Angiotensin II or granular cell input
* Sensation of thirst
* Drinking of water inhibits the thirst centre
* Inhibitory feedback signals include:
– Relief of dry mouth
– Activation of stomach and intestinal stretch
receptors

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22
Q

what is Regulation of Water Output

A
  • Obligatory water losses
    – Insensible water loss from lungs and skin
    – Sensible water loss from faeces and urine
  • Minimum daily sensible water loss of 500 ml in
    urine to excrete wastes
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23
Q

what is Regulation of Water Output:
Influence of ADH?

A
  • Hormone from pituitary gland
  • Water reabsorption in collecting ducts
    proportional to ADH release
    – v ADH –> dilute urine (light in colour) and
    v volume of body fluids
    – ^ ADH –> concentrated urine (darker in
    colour); reabsorption of water –> ^
    volume of body fluids
  • Hypothalamic osmoreceptors sense
    ECF solute concentration and
    regulate ADH accordingly
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24
Q

what Other factors may trigger ADH
release?

Study These Flashcards
A

– Large changes in blood
volume or pressure
* E.g., v BP –> ^ ADH release due to
blood vessel baroreceptors and reninangiotensin-aldosterone mechanism
* Factors lowering blood volume:
intense sweating, vomiting, or
diarrhea; severe blood loss; traumatic
burns; and prolonged fever

25
what are the disorders of water balance?
dehydration, hypotonic hydration, oedema
26
what is Dehydration ?
ECF water loss due to: hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, diuretic abuse, endocrine disturbances
27
signs and symptoms of dehydration
Signs and symptoms: "cottony" oral mucosa, thirst, dry flushed skin, the production of abnormally small amounts of urine
28
what may dehydration lead to:
May lead to: – weight loss – fever – mental confusion – hypovolemic shock – loss of electrolytes
29
what is Hypotonic Hydration?
- Cellular over-hydration, or water intoxication - ECF osmolality v --> hyponatremia (low sodium levels) --> net osmosis into tissue cells --> swelling of cells --> severe metabolic disturbances (nausea, vomiting, muscular cramping, cerebral oedema) --> possible death
30
when does Hypotonic Hydration occur?
Occurs with renal insufficiency or rapid excess water ingestion
31
what is Hypotonic Hydration treated with?
Treated with hypertonic saline (high NaCl ~ extra salty)
32
what is Oedema?
* Atypical accumulation of IF --> tissue swelling (not cell swelling) * Result of ^ fluid out of blood or v fluid into blood
33
increase and decrease fluid in/out blood in oedema:
* ^ fluid out of blood caused by: – Increased capillary hydrostatic pressure or permeability * Capillary hydrostatic pressure increased by incompetent venous valves, localised blood vessel blockage, congestive heart failure,  blood volume * Capillary permeability increased by ongoing inflammatory response * v fluid returning to blood result of: – Imbalance in colloid osmotic pressures, * Fluids fail to return at venous ends of capillary beds * Results from protein malnutrition, liver disease, or glomerulonephritis
34
what is oedema also caused by?
Also caused by blocked lymph vessels – Cause leaked proteins to accumulate in IF – ^ Colloid osmotic pressure of IF draws fluid from blood
35
what does oedema increase?
Increases diffusion distance for nutrients and oxygen
36
what does oedema result in?
Results in low blood pressure and severely impaired circulation
37
what are electrolytes?
Electrolytes are salts, acids, bases, some proteins
38
what is electrolyte balance?
Electrolyte balance usually refers only to salt balance
39
Salts control fluid movements by ...
provide minerals for excitability, secretory activity and membrane permeability
40
how does salt enter body?
Salts enter body by ingestion and metabolism; lost via perspiration, faeces, urine and vomit
41
what is the Central Role of Sodium?
Most abundant cation in ECF * Only cation exerting significant osmotic pressure – Controls ECF volume and water distribution – Changes in Na+ levels affects plasma volume, blood pressure, and ECF and IF volumes * Na+ leaks into cells (into ICF); pumped out against its electrochemical gradient (~requires energy) * Na+ moves back and forth between ECF and body secretions (e.g., digestive secretions) * Renal acid-base control mechanisms are coupled to Na+ transport (Acid/Base Lecture)
42
Regulation of Sodium Balance
No known receptors that monitor Na+ levels in body fluids * Na+-water balance is linked to blood pressure and blood volume control mechanisms (baroreceptors and osmoreceptors) * Changes in blood pressure or volume trigger neural and hormonal controls to regulate Na+ content
43
what is Aldosterone?
a steroid hormone produced by the adrenal gland (aka suprarenal gland)
44
what does Aldosterone result in?
Aldosterone --> decreased urinary output; increased blood volume – By active reabsorption of remaining Na+ in distal convoluted tubule and collecting duct – Also causes increased K+ secretion
45
Regardless of aldosterone presence
– 65% Na+ reabsorbed in proximal tubules; 25% reclaimed in nephron loops – Na + never secreted into filtrate
46
Water in filtrate follows ....
Na+ if ADH is present
47
what is the main trigger for aldosterone release?
Renin-angiotensin aldosterone mechanism main trigger for aldosterone release
48
what does Angiotensin II do?
– Prompts aldosterone release from adrenal cortex – ^ Na+ reabsorption by kidney tubules
49
what is Aldosterone release also triggered by?
Aldosterone release also triggered by elevated K+ levels in ECF
50
when does Aldosterone bring about its effects?
Aldosterone brings about its effects slowly (hours to days)
51
what is Atrial Natriuretic Peptide (ANP)?
Protein hormone
52
what is Atrial Natriuretic Peptide (ANP) released by?
* Released by atrial myocytes of the heart in response to stretch (^ blood pressure)
53
Effects of Atrial Natriuretic Peptide (ANP)
* Effects: – Decreases blood pressure and blood volume * v ADH, renin and aldosterone production * ^ excretion of Na+ and water * Promotes vasodilation directly and also by decreasing production of angiotensin II (vasoconstrictor)
54
Influence of Female sex hormones
* Female sex hormones – Oestrogens: ^ NaCl reabsorption (like aldosterone) * --> H2O retention during menstrual cycles and pregnancy – Progesterone: v Na+ reabsorption (blocks aldosterone) * Promotes Na+ and H2O loss
55
what is Glucocorticoids?
^ Na+ reabsorption and promote oedema
56
what do baroreceptors do?
Baroreceptors alert brain of increases in blood volume and pressure
57
what are the cardiovascular baroreceptors in kidney?
– Sympathetic nervous system impulses to kidneys decline --> * Afferent arterioles dilate --> * GFR increases --> * Na+ and water output increase --> * Reduced blood volume and pressure
58

HAP 2 (11 decks)

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