Renal - Fluid Balance Flashcards by Mary Kate Heard

Define

Internal Pool

The quantity of a substance in the ECF

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Define

Balance Concept

Inputs and outputs must be equal to main balance of the renal system

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Types of input to the internal pool

Ingestion
Metabolic produced

Input from external environment

Inhalation, absorption through body surface, or artificial injection

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Types of outputs from the internal pool

Excretion
Metabolic Consumption (O2 to CO2)

Excretion to external environment

Through kidneys, lungs, digestive tract, or body surface, e.g. sweat, tears, sloughed skin

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Types of reversible incorporation to internal pool

Reversible incorporation into more complex molecular structures

Fulfills a specific function

Iron incorporated into hemoglobin in RBC -> RBC breaks down and iron is released

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Balance Concept

Total body input =

Total body output

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What type of balance exists when

Input > output

positive balance exists

in Children - Growth Phase - positive Nitrogen Balance

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What type of balance exists when

Input < output

Negative Balance

In older people - negative Nitrogen Balance

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Control of:

Input

Input of substances is poorly/not controlled

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Why is the input of substances poorly controlled?

Eating and drinking is variable
H+ is uncontrollably generated internally

Eating and drinking is based on want not need

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Control of:

Output

H20, salt, and H+

H20, salt, and H+ can be lost to external environment uncontrolably

Through vomiting, sweating, dead skin, etc.

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How do the kidneys maintain the outputs of the internal pool?

Kidney used urinary excretion to balance output with input

very controlled

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Define

Fluid Balance

Maintenance of H2O and salt balance

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Fluid Balance

How does sex effect % of H2O in individuals?

Estrogen promotes fat deposition, which decreases water

Fat - tissue without water
Increases fat content, decreases water

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Fluid Balance

How does age effect % of water in individuals?

H20% decreases with age

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Fluid Balance

A low body water content is associated with

Obesity

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Fluid Balance

A high water body content is associated with…

leanness

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Which of the following individuals would have the lowest percentage of body H20?
A. A chubby baby
B. A well-proportioned female college student
C. A well-proportioned male college student
D. An obese, elderly woman
E. A lean, elderly man

D. An obese, elderly woman

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How is water distributed between the 2 major fluid compartments?

ICF - 2/3
ECF - 1/3

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What are the two major fluid compartments in the body?

Intracellular Fluid (ICF)
Extracellular Fluid (ECF)

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Define

Intracellular Fluid (ICF)

Fluid inside the cell

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Define:

Extracellar Fluid (ECF)

Fluid outside the cell

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What barrier lives between the ICF and ECF?

Cell membrane

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What barrier exists between the two major components of the ECF?

Capillary Wall

Endothelial Cells of the capillary wall

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What are the 2 major components of ECF?

Plasma Interstitial Fluid

# Characteristics of barrier between plasma and interstitial fluid: Capillary Wall Barrier

Thin, pore-lined Free exchange, except plasma membranes Nearly identical composition

# Characteristics of barrier between ECF and ICF: Cell Membrane Barrier

Highly selective Unequal distribution of Na+ and K+ due to Na+-K+ pump | ICF has presence of proteins that cannot leave the cell unless lysed

K+ concentration is higher _ cell

inside

Na+ concentration is higher _ cell

Outside

# Ion composition of ECF compartments What are the major cations found in the plasma/interstitial fluid of the ECF?

Na+

# Ion composition of ECF compartments What are the major anions found in the Plasma/Interstitial of the ECF?

Cl-, HCO3-

# Ion composition of ICF compartment What are the major cations found in the ICF?

K+

# Ion composition of ICF compartment What are the major anions found in the ICF?

PO4^3- Proteins and anions

What governs water movement vs capillary wall?

Starling Forces | Hydrostatic Pressure (BP), Oncotic Pressure (Plasma Proteins) ## Footnote Starling Forces influence filtration or reabsorption

What governs water movement vs plasma membrane?

Osmotic Effects alone

The only fluid that can be directly acted on to control volume and composition

Plasma

How does altering plasma control volume and composition?

Alter plasma -> alter intersitial fluid -> ICF is influences as membrane allows

What two factors regulate Fluid Balance?

ECF Volume ECF Osmolarity

# Importance ECF Volume

Important in long term regulation of blood pressure

How does ECF regulate BP in the long term?

By maintaining salt balance in plasma

# Salt Balance What causes input of salt?

Ingestion | Not well controlled - based on want

# Salt Balance What causes salt output?

Sweat Feces Urine | urine is altered to match input

# Salt Balance What controls sweat output of salt?

Aldosterone can decrease Na+ loss

# Salt Balance What controls feces output of salt?

Nothing | not under control

# Salt Balance What controls urine output of salt?

The kidneys alter it to match input to maintain balance

# Salt Balance How do the kidneys adjust sodium output?

Kidneys adjust Na+ via adjusting GFR and tubular reabsorption

# Regulating Fluid balance ECF Osmolarity prevents

Prevents swelling or shrinking of cells

# Regulating Fluid Balance What controlls ECF Osmolarity?

Controlled by water balance in plasma

# ECF Osomolarity Losing H2O in ECF

Cell becomes hypertonic | >300 mosm/l ## Footnote Concentration is higher outside cell (in ECF), water leaves cell

# ECF Osmolarity Gain water in ECF

Cell becomes hypotonic | <300 mosm/l ## Footnote Concentration is greater inside cell (ICF), water moves into cell

# Define Hypertonic

Cell shrinkage

# Define Hypotonic

Cell swells | Hypo Hippo Cell Swells

# Changes in ECF Osmolarity What is the result of water loss in the ECF?

Dehydration Cell shrinkage | increase ECF osmolarity, cell loses water

# Changes in ECF Osmolarity How does water loss in the ECF cause dehydration?

Insufficient water intake Excessive water loss Diabetes insipidus

# Changes in ECF Osmolarity Symptoms and effects of water loss in ECF:

Shrinking of brian neurons Circulatory distrubances Dry skin, sunken eyeballs, dry tongue ## Footnote Shrinkage of brain neurons -> confusion , irritablity delirium, convulsions, coma Circulatory distrubances -> lowering of BP, circulatory shock

# Changes in ECF Osmolarity What is the result of gaining water in the ECF?

Overhydration Cells tend to swell | Can't excrete water ## Footnote water enters cell higher concentration in cell

# Changes in ECF Osmolarity What are the causes of overhydration in a cell?

Patients with renal failure H2O is rapidly ingested inappropriate secretion of ADH

# Changes in ECF Osmolarity What are symptoms and effects of gaining water in ECF?

Swelling of brain cells Circulatory distrubances Weakness ## Footnote Swelling of brain cells - confusion, irritability, headache, dizziness, vomiting, drowsiness, convulsions, coma, death Circulatory Distrubances - hypertension and edema Weakness - swelling of muscle cells

Why is H2O balance crucial?

Cells do not function properly when shrunken or swollen

What causes water input?

Drinking Water in food Metabolically produced ## Footnote Fruits/veggies = most Grains = least

What causes water output?

Expired air contains water vapor Urine

# Maintaining water balance Thirst

Increases water input

# Maintaining water output Urine Formation

Decreases water output | ADH

# ADH and Thirst What controlls ADH and thirst?

Hypothalamic osmoreceptors ## Footnote Located near ADH-secreting cells and thirst center

# ADH and Thirst How does increasing osmolarity effect ADH secretion and thirst?

Increase osmolarity -> neuron shrinkage -> opens cation channels -> depolarization -> increase AP firing rate -> increase ADH secretion and thirst | Na+ leaves cell for ECF, ECF is hypertonic, rapid depolarization

# ADH and Thirst How does decreasing osmolarity effect ADH secretion and thirst?

Decrease osmolarity -> neuron swelling -> close cation channels -> less depolarization -> decrease AP firing rate -> decrease ADH secretion and thirst | ECF is hypotonic

What stimulates production of ADH?

Increasing ECF Osmolarity Decreasing ECF Volume

# General What happens if we need to save water?

Increase renin -> increase Angiotensin II -> increases ADH and Aldosterone ## Footnote Renin (enzyme) - triggers cascade to save water Ang II - triggers thirst, and production of ADH/Aldosterone ADH - vasopressin Aldosterone - triggers Na+ retention

# Fluid Balance Normal Body

ICF - 2/3 ECF - 1/3 input and output are equal

# Fluid Balance What happens to ECF and ICF when 2L of pure water is added to the ECF?

Fluid moves from ECF to ICF until balance is regained Volume increases and Osmolarity decreases in both

# Fluid Balance What happens to ECF and ICF when 2L of isotonic saline is added to the ECF? ## Footnote Like gatorade

Osmolarity stays the same in ICF and ECF Volume decreases in ECF Fluid exchange is maintained

What happens to the body when 1.0L of 5% NaCl is added to the ECF? | 0.9% saline solution would be isotonic

Fluid moves from ICF to ECF ECF volume decreases Osmolarity decreases in both