Homeostatic Regulation of Body Fluids Flashcards

1
Q

Molarity definition

A

The amount of a substance dissolved in a solution relative to its molecular weight

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2
Q

Equivalence definition

A

The amount of a substance dissolved in a solution relative to its molecular weight and stoichiometry

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3
Q

Osmolality

A

Number of solute particles per kg of H2O
Concentration multiplied by number of dissociable particles
Determinant of the direction of water flow between the body compartments

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4
Q

Osmolality vs osmolarity

A

Osmolarity: number of solute particles per LITER of H2O
Osmolality: Number of solute particles per KG of H2O

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5
Q

What 3 ions are normally the most active solute particles?

A

Na
Cl
HCO3

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6
Q

Osmosis

A

Movement of water across membranes down its concentration gradient
Determined by the number of solute particles
Driven by osmotic pressure

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7
Q

Oncotic pressure

A

Osmotic pressure generated by large molecules and proteins

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8
Q

Tonicity

A

The effect of a solution on the volume of the adjacent cell

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9
Q

Body water

A

60% of body weight (for a 70 kg male)
Water content less in adipose tissue
Distributed across the 3 body compartments

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10
Q

What ‘third space’ is created in pathological conditions?

A

When there is extra fluid begin stored in the bowels

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11
Q

How is plasma osmolality measured?

A

2(plasma [Na]) + [glucose] + [urea]

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12
Q

3 body compartments

A

Plasma
Interstitial
Intracellular
No difference between plasma and interstitial

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13
Q

Capillary fluid exchange

A

Water moves freely between compartments
Determined by hydrostatic pressure and oncotic pressure
Sum of starling’s forces

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14
Q

3 factors that determine hydrostatic pressure

A

Arterial/venous pressure
Length of capillary
Pre and post capillary sphincters

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15
Q

3 characteristics of the membrane that influence the movement of fluid

A

Surface area
Permeability to water
Permeability to proteins

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16
Q

Cellular fluid exchange is affected by what 2 things

A

Osmotic differences between ECF and ICF

Aquaporin channels

17
Q

Effective circulating volume

A

Portion of the ECF in the vascular system that is “effectively” perfusing tissue
Not directly measurable
Not the same as plasma volume

18
Q

5 determinants of effective circulating volume

A
Volume of the ECF
Volume of the vascular space
Blood pressure
Cardiac output
Intact sensors (baroreceptors)*