Fluid, Electrolyte, and acid base balance Flashcards
What is the percentage of water in infants?
73% or more
(they have a low body fat and low bone mass)
What percentage of water do adult males hold?
60%
What percentage of water do adult females hold?
50%
(more fat and less skeletal muscle (that holds water)
What is the total body water volume?
40 Liters
What are the two main fluid compartments in the body?
Intracellular fluid
Extracellular fluid
What are the two parts of the extracellular fluid compartment?
Plasma (3L of water)
Interstitial fluid (12 L of water)
Water is a ____ solvent?
Universal
What are solutes?
What is dissolved in water
TF: Non electrolytes are mostly organic?
True (not soluble has many C’s)
Do not dissociate into water well
TF: Non electrolytes have a greater osmotic power than electrolytes
False
Electrolytes have the greatest ability to cause fluid shifts
What are the most abundant solutes in body fluids?
Electrolytes
What determines most chemical and physical reactions in the body?
Electrolytes
What two pressures regulate continuous exchange and mixing of fluids?
Osmotic
Hydrostatic
What causes net water flow?
Change in solute concentration of any compartment
Water intake must equal water _____
Output
How can the body intake water?
Beverages
Foods
Metabolic water
How can the body output water?
Urine
Insensible water loss (lost through skin and lungs)
Perspiration
Feces
What is osmolality usually maintained at in the body?
Around 280-300 mOsm
What happens when osmolality increases?
Stimulation of thirst
ADH release
(increase in osmolality means water is leaving)
What happens due to a decrease in osmolality?
Thirst inhibition
ADH inhibition
What is the main driving force for water intake?
Thirst mechanism
What is the thirst mechanism governed by?
Hypothalamic thirst center
What do hypothalamic osmoreceptors detect?
ECF osmolality
What is obligatory water loss?
Insensible water loss from lungs and skin
Feces
What is the daily minimum of sensible water loss volume?
500 mL in urine to excrete wastes
What is water reabsorption in collecting ducts proportional to?
ADH release
What senses ECF solute concentration?
Hypothalamic osmoreceptors
What factors may triggers ADH release?
Decrease in blood pressure
Large changes in blood volume
Factors lowering blood volume
What does dehydration cause?
Negative fluid balance
ECF water loss
What are the signs and symptoms of dehydration?
Cottony oral mucosa
Thirst
Dry flushed skin
Oliguria
What happens during hypotonic hydration?
Cellular over-hydration
water intoxication
What causes hypotonic hydration?
Renal insufficiency or rapid excess of water intake
How is hypotonic hydration treated?
With hypertonic saline
What is edema?`
Atypical accumulation of IF that causes tissue swelling (not cell swelling)
What causes edema?
Increase of fluid out of the blood or
Decrease of fluid in the blood
What causes an increase in fluid out of blood?
Increased capillary hydrostatic pressure or permeability
(incompetent venous valves, localized blood vessel blockage, congestive heart failure, increase in blood volume
What causes a decrease in fluid returning to blood?
Imbalance in colloid osmotic pressures
Fluid failes to return at venous ends of capillary beds
What is imbalanced colloid osmotic pressures a result of?
Protein malnutrition
Liver disease
Glomerulonephritis
What causes leaked proteins to accumulate in the interstitial fluid?
Blocked or surgically removed lymphatic vessel
Having more proteins (colloids) in the IF pulls fluids from the blood
What increases diffusion distance for nutrients and oxygen?
Edema
TF: Edema causes low blood pressure and severely impaired circulation
True
What does electrolyte balance usually refer to?
Salt balance
What do salts control?
Fluid movements
What do salts provide?
Minerals for excitability, secretory activity, and membrane permeability
What is the most abundant cation in the ECF?
Na+
What is the only cation that exerts significant osmotic pressure?
Na+
What determines osmolality of ECF?
Concentration of Na+
TF: there are many receptors that monitor Na+ levels in body fluids?
False
There are no known receptors `
What two control mechanisms are linked to Na+ water balance?
Blood pressure
Blood volume
What does aldosterone do?
Decrease urinary output
Increase blood volume
How does aldosterone increase blood volume and decrease urinary output?
Active reabsorption of remaining Na+ in distal convoluted tubule and collecting duct
(causes increased K+ secretion- remember if Na is going into blood K+ usually replaces it to keep the charge in the urinary system)
What percent of Na+ is reabsorbed in proximal tubules
65%
What percent of Na+ is reclaimed in the nephron loop?
25%
TF: Na is never secreted into the filtrate
True
What follows Na+ if ADH is present?
Water in the filtrate
What mechanism is the main trigger for aldosterone release?
Renin-angiotensin- aldosterone mechanism
What secretes renin in the kidneys?
Granular cells
What activates granular cells to secrete renin in the juxtaglomerular caps?
Sympathetic nervous system stimulation
Decrease filtrate NaCl concentration
Decrease in stretch due to decreased blood pressure of granular cells
What does renin catalyze?
production of angiotensin II
What does renin cause Na+ to do?
Become more reabsorbed by kidney tubules
What releases ANP?
Atrial cells in response to stretch (increase in blood pressure)
What does ANP cause?
Increase of excretion of Na+ and water
Promotes vasodilation
Decrease in angiotensin II
What female sex hormone increases salt reabsorption?
Estrogens
(H20 retention -bloating - during menstrual cycles and pregnancy
What female sex hormone decreases Na+ reabsorption?
Progesterone
Promotes Na+ and H2O loss
What do glucocorticoids do?
Increase sodium reabsorption and promote edema
What do baroreceptors do?
Alert the brain of increases in blood volume and pressure
(Baro=pressure)
What does potassium do for neurons and muscle cells?
Affect the resting membrane potential
What happens when there is not enough potassium?
Hyperpolarization and nonresponsiveness
What is hyperkalemia?
Too much K+
What is hypokalemia?
Too little K+
___ shifts in and out of cells in opposite direction of K+ to maintain cation balance?
H+
TF: Kidneys have low ability to retain K+
True
What is the most important factor affecting K+ secretion?
Its concentration in ECF
What reduces K+ secretion?
Low K+ diet
Accelerated loss of K+
What influence does aldosterone play for K+ secretion?
It stimulates K+ secretion and Na+ reabsorption
Through principal cells
Where is 99% of the body’s calcium?
In the bones as calcium phosphate salts
What is Ca2+ in the ECF important for?
Blood clotting
Cell membrane permeability
Secretory activities
Neuromuscular excitability
What does hypocalcemia cause
Increased excitability and muscle tetany
What does hypercalcemia cause?
Inhibition of neurons and muscle cells
Heart arrhythmias
What controls calcium balance?
Parathyroid hormone
What is the major anion in the ECF?
Cl-
How much calcium in percent is reabsorbed under normal pH conditions?
99%
What does pH affect?
All functional proteins and biochemical reactions
How is most H+ produced?
Through metabolism
H+ is liberated when CO2 is converted to _____ in the blood
HCO3-
What regulates concentration of hydrogen ions in order?
- Chemical buffers (rapid and first line of defense)
- Brain stem respiratory centers (act within 1-3 minutes)
- Renal mechanisms (most potent but requires hours to days)
What are three types of chemical buffer systems?
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system
What is contained in the bicarbonate buffer system?
Mixture of a weak acid (H2CO3) and salts of HCO3- (weak bases like NaHCO3)
What does the bicarbonate buffer system actually buffer?
ICF and ECF
What is the only important ECF buffer?
Bicarb buffer system
What are the components of the phosphate buffer system?
Sodium salts of Dihydrogen phosphate which is a weak acid
and Monohydrogen phosphate which is a weak base
TF: The phosphate buffer system is unimportant in buffering plasma
True
What is an effective buffer in urine and ICF?
Phosphate buffer systems
(Where PO4 concentration is high)
What are the components of a protein buffer system?
Intracellular proteins
Plasma proteins
_____ molecules are amphoteric
Protein
What does amphoteric mean?
Can function as both a weak acid and a weak base
What releases H+ ions when pH rises (in the protein buffer system?
Organic acid
Carboxyl groups
What binds to H+ when pH falls?
NH2
What do respiratory and renal systems do as buffer systems?
Regulate amount of acid or base in the body
Act more slowly
Have more capacity than chemical buffers
What do the lungs do for the Respiratory buffer system?
Eliminate volatile carbonic acid by eliminating CO2 (exhale)
What do the kidneys do as a buffer system?
Eliminate nonvolatile (fixed) acids produced by cellular metabolism to prevent metabolic acidosis
Regulate levels of alkaline substances
What are the most important renal mechanisms?
Conserving or generating new HCO3-
Excreting HCO3-
TF: Generating or reabsorbing one HCO3- is the same as loosing one H+
True
To reabsorb bicarbonate the kidneys must ____ H+
Secrete
Where in the kidney does H+ secretion occur?
In the PCT
In the collecting duct Type A intercalated cells
Secretion means it is going INTO the filtrate
Rate of H+ secretion changes with ECF _____ levels
CO2`
What happens to the rate of H+ secretion when CO2 increases in the peritubular capillary blood
H+ secretion rate is increased
What must the kidneys do the maintain the alkaline reserve?
Replenish bicarbonate
Two mechanisms in the ___ and ______ generate new bicarb to be added to alkaline reserve
PCT and Type A intercalated cells
Dietary __ must be balanced by generating new _____
H+
Bicarb
What is the most important urine buffer?
Phosphate buffer
H+ is secreted in the filtrate by what?
H+ ATPase pump
In what form is H+ secreted and excreted in the urine?
H2PO4-
What is the more important mechanism for excreting acid?
Ammonium ion excretion
What does ammonium ion excretion involve?
Metabolism of glutamine in the PCT cells
Each glutamine produces 2 ___and 2 new ____
NH4+
HCO3-
____ moves to the blood and ___ is excreted in the urine (from glutamine use)
HCO3-
NH4+
What replenishes alkaline reserve of blood?
Ammonium ion excretion
What do type B intercalated cells do?
Secrete HCO3-
Reclaim H+ to acidify the blood
What is the most important indicator for respiratory acidosis and alkalosis
Blood PCO2
What is the key indicator of Metabolic acidosis and alkalosis?
HCO3- levels
PCO2 above __mmHg represents respiratory acidosis
45
PCO2 below ___ mmHg represents respiratory alkalosis?
35
What is respiratory compensation?
Changes in respiratory rate and depth
