Renal - Fluid Balance Flashcards
Define
Internal Pool
The quantity of a substance in the ECF
Define
Balance Concept
Inputs and outputs must be equal to main balance of the renal system
Types of input to the internal pool
Ingestion
Metabolic produced
Input from external environment
Inhalation, absorption through body surface, or artificial injection
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
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
Balance Concept
Total body input =
Total body output
What type of balance exists when
Input > output
positive balance exists
in Children - Growth Phase - positive Nitrogen Balance
What type of balance exists when
Input < output
Negative Balance
In older people - negative Nitrogen Balance
Control of:
Input
Input of substances is poorly/not controlled
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
Control of:
Output
H20, salt, and H+
H20, salt, and H+ can be lost to external environment uncontrolably
Through vomiting, sweating, dead skin, etc.
How do the kidneys maintain the outputs of the internal pool?
Kidney used urinary excretion to balance output with input
very controlled
Define
Fluid Balance
Maintenance of H2O and salt balance
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
Fluid Balance
How does age effect % of water in individuals?
H20% decreases with age
Fluid Balance
A low body water content is associated with
Obesity
Fluid Balance
A high water body content is associated with…
leanness
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
How is water distributed between the 2 major fluid compartments?
ICF - 2/3
ECF - 1/3
What are the two major fluid compartments in the body?
Intracellular Fluid (ICF)
Extracellular Fluid (ECF)
Define
Intracellular Fluid (ICF)
Fluid inside the cell
Define:
Extracellar Fluid (ECF)
Fluid outside the cell
What barrier lives between the ICF and ECF?
Cell membrane
What barrier exists between the two major components of the ECF?
Capillary Wall
Endothelial Cells of the capillary wall
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)
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
Concentration is higher outside cell (in ECF), water leaves cell
ECF Osmolarity
Gain water in ECF
Cell becomes hypotonic
<300 mosm/l
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
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
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
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
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
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
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?
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
