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Physiology > Exam 4 - Electrolytes 1 > Flashcards

Exam 4 - Electrolytes 1 Flashcards

1
Q

Total body water volume

A

40 L, 60% of body weight

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2
Q

Intracellular fluid volume (inside the cell)

A

25 L, 40% of body weight

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3
Q

Extracellular fluid volume

A

15 L, 20% of body weight

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4
Q

Interstitial fluid volume

outside of blood system and cell

A

12 L, 80% of ECF

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5
Q

Plasma volume (inside the blood system)

A

3 L, 20% of ECF

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6
Q

Water movement

A

water moves easily between COMPARTMENTS AND ACROSS MEMBRANES

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7
Q

Losing water through sweat and replacement

A
  1. water loss (sweating)
  2. sweat glands produce perspiration by capillary filtration
  3. blood volume and pressure drop: osmolarity rises
  4. blood absorbs tissue fluid to replace loss
  5. intracellular fluid diffuses out of cells to replace lost tissue fluid
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8
Q

How is water acquired in the body?

A

Preformed water and metabolic water

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9
Q

Preformed water

A

ingested in food and drink

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10
Q

Metabolic water

A

by-product of:

  • aerobic metabolism
  • dehydration synthesis
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11
Q

Dehydration

A

DECREASED blood volume and pressure

INCREASED blood osmolarity

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12
Q

Mechanisms of regulating water intake: osmoreceptors in hypothalamus are stimulated by:

A
  • Angiotensin II (produced in response to decreased BP)

- increased ECF osmolarity

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13
Q

Mechanisms of regulating water intake: responses

A
  • ADH produced
  • CEREBRAL CORTEX is notified of conditions to create SENSE OF THIRST
  • SALIVATION IS INHIBITED because sympathetic signals are sent to salivary glands (source of “dry mouth” when preparing to give a speech)
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14
Q

Long term inhibition of thirst

A

Rehydration of blood (decrease blood osmolarity)

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15
Q

Short term inhibition of thirst

A

Act quickly but only last for 30-45 minutes

  • cooling and moistening of mouth
  • distention of stomach and intestine
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16
Q

Routes of water loss

A
  • urine
  • feces
  • expired breath
  • sweat / cutaneous transpiration
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17
Q

Respiratory loss of water

A

increases w/ cold, dry air or heavy work

18
Q

Perspiration loss of water

A

increases w/ hot, humid air or heavy work

19
Q

Obligatory water loss

A
  • breath
  • sweat / cutaneous transpiration
  • feces
  • minimum urine output (400 mL/day)
20
Q

Mechanisms of regulating water output

A

Controlling Na reabsorption
- as Na is reabsorbed or excreted, water follows

Action of ADH
- AQUAPORINS (membrane proteins in renal collecting ducts to channel water back into renal medulla) are synthesized in response to ADH

21
Q

Mechanisms of ECF volume regulation

A

Increased blood pressure in right atrium > Increased ANH > increased Na excretion and increased water loss result in decreased BP

Decreased BP > kidney releases renin > Angiotensinogen > Angiotensin I > Angiotensin II > increased aldosterone secretion > increased Na and water reabsorption results in increased BP

22
Q

What do kidneys compensate well for?

A

they compensate well for EXCESSIVE fluid intake, but not for INADEQUATE intake

(no matter how much fluid you overly take in, your body can maintain the same amount of around 5L)

23
Q

Volume depletion (hypovolemia)

A
  • Decreased total body water

OSMOLARITY NORMAL because FLUIDS AND ELECTROLYTES ARE LOST IN ROUGHLY EQUAL PROPORTIONS

24
Q

How does hypovolemia occur?

A
  • hemorrhage
  • severe burns
  • chronic vomiting
  • diarrhea
25
Q

Dehydration

A
  • loss of RELATIVELY MORE WATER than solute
  • decreased total body water
    OSMOLARITY INCREASES
26
Q

Sources of dehydration

A
  • lack of drinking water
  • diabetes
  • profuse sweating
  • diuretics
27
Q

What are the most serious effects of hypovolemia and dehydration

A
  • circulatory shock
  • neurological dysfunction
  • death
28
Q

Volume excess

A
  • both Na and water retained, ECF is ISOTONIC

- source includes aldosterone hypersecretions

29
Q

Hypotonic over-hydration

A
  • MORE WATER THAN Na RETAINED or ingested, ECF is HYPOTONIC

EX: drinking water instead of Gatorade after exercise

30
Q

What are the most serious effects of volume excess and hypotonic over-hydration?

A

pulmonary and cerebral edema

31
Q

Sequestration problems

A

Overall body volume is ok but fluid is not properly distributed among the compartments

32
Q

most common form of sequestration problems

A

edema w/ fluid accumulation in the interstitial spaces

33
Q

Other examples of fluid sequestration problems

A

Hematomas

  • hemorrhage into tissues
  • blood is therefore lost to circulation

Pleural effusions
- several liters of fluid may accumulate in some lung infections

34
Q

Functions of Na

A
  • membrane potentials
  • accounts for 90-95% of OSMOLARITY of ECF
  • Na-K pump creates a gradient for COTRANSPORT of other solutes (e.g. glucose) and also generates heat
  • NaHCO3 has major role in buffering pH
35
Q

Primary concern of Na homeostasis

A

excretion of dietary excess

- 0.5 g/day needed, typical diet has 3 to 7 g/day

36
Q

Hormonal mechanisms that enhance dilution or excretion of Na

A

ADH
- released when Na level increases causing kidneys to reabsorb more water w/o retaining more Na

ANP (atrial natriuretic peptide)
- released when atria are stretched causing kidneys to excrete more Na and H20 thus decreasing Na and volume

37
Q

Hypernatremia

A

plasma volume > 145 mEq/L

38
Q

Frequent cause of hypernatremia

A

IV saline administrations

39
Q

Hypernatremia effects/results

A
  • water retention
  • hypertension
  • edema
40
Q

Hyponatremia

A

plasma volume < 130 mEq/L

41
Q

Hyponatremia effects/results

A

Excess body water (relative to sodium) as might occur in SIADH (syndrome of inappropriate antidiuretic hormone) - excessive release of ADH

Physiology (13 decks)

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