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HAP 2 > week 11 > Flashcards

week 11 Flashcards

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?

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
Q

what are the disorders of water balance?

A

dehydration, hypotonic hydration, oedema

26
Q

what is Dehydration ?

A

ECF water loss due to: hemorrhage, severe burns,
prolonged vomiting or diarrhea, profuse sweating, water
deprivation, diuretic abuse, endocrine disturbances

27
Q

signs and symptoms of dehydration

A

Signs and symptoms: “cottony” oral mucosa, thirst, dry
flushed skin, the production of abnormally small amounts
of urine

28
Q

what may dehydration lead to:

A

May lead to:
– weight loss
– fever
– mental confusion
– hypovolemic shock
– loss of electrolytes

29
Q

what is Hypotonic Hydration?

A
  • 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
Q

when does Hypotonic Hydration occur?

A

Occurs with renal insufficiency or rapid excess water
ingestion

31
Q

what is Hypotonic Hydration treated with?

A

Treated with
hypertonic saline
(high NaCl ~ extra
salty)

32
Q

what is Oedema?

A
  • Atypical accumulation of IF –> tissue swelling (not cell swelling)
  • Result of ^ fluid out of blood or v fluid into blood
33
Q

increase and decrease fluid in/out blood in oedema:

A
  • ^ 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
Q

what is oedema also caused by?

A

Also caused by blocked lymph vessels
– Cause leaked proteins to accumulate in IF
– ^ Colloid osmotic pressure of IF draws fluid from blood

35
Q

what does oedema increase?

A

Increases diffusion distance for nutrients and oxygen

36
Q

what does oedema result in?

A

Results in low blood pressure and severely impaired circulation

37
Q

what are electrolytes?

A

Electrolytes are salts, acids, bases, some
proteins

38
Q

what is electrolyte balance?

A

Electrolyte balance usually refers only to salt balance

39
Q

Salts control fluid movements by …

A

provide
minerals for excitability, secretory activity and
membrane permeability

40
Q

how does salt enter body?

A

Salts enter body by ingestion and
metabolism; lost via perspiration, faeces,
urine and vomit

41
Q

what is the Central Role of Sodium?

A

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
Q

Regulation of Sodium Balance

A

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
Q

what is Aldosterone?

A

a steroid
hormone produced by the adrenal
gland (aka suprarenal gland)

44
Q

what does Aldosterone result in?

A

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
Q

Regardless of aldosterone presence

A

– 65% Na+ reabsorbed in proximal tubules;
25% reclaimed in nephron loops
– Na + never secreted into filtrate

46
Q

Water in filtrate follows ….

A

Na+ if ADH is
present

47
Q

what is the main trigger for aldosterone release?

A

Renin-angiotensin aldosterone
mechanism main trigger for
aldosterone release

48
Q

what does Angiotensin II do?

A

– Prompts aldosterone release from
adrenal cortex
– ^ Na+ reabsorption by kidney tubules

49
Q

what is Aldosterone release also triggered by?

A

Aldosterone release also triggered
by elevated K+ levels in ECF

50
Q

when does Aldosterone bring about its effects?

A

Aldosterone brings about its effects
slowly (hours to days)

51
Q

what is Atrial Natriuretic Peptide (ANP)?

A

Protein hormone

52
Q

what is Atrial Natriuretic Peptide (ANP) released by?

A
  • Released by atrial myocytes of the heart
    in response to stretch (^ blood pressure)
53
Q

Effects of Atrial Natriuretic Peptide (ANP)

A
  • 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
Q

Influence of Female sex hormones

A
  • 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
Q

what is Glucocorticoids?

A

^ Na+ reabsorption and promote
oedema

56
Q

what do baroreceptors do?

A

Baroreceptors alert brain of increases in
blood volume and pressure

57
Q

what are the cardiovascular baroreceptors in kidney?

A

– Sympathetic nervous system impulses to
kidneys decline –>
* Afferent arterioles dilate –>
* GFR increases –>
* Na+ and water output increase –>
* Reduced blood volume and pressure

58
Q
A

HAP 2 (11 decks)

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