Ch 26: Electrolytes Part 1 Flashcards
What is the body water content of infants?
73%
What is the body water content of adult males?
60%
What is the body water content of females?
50%
What is the total body water amount?
40L
How much does water does the ICF take?
2/3
How much does water does the ECF take?
1/3
Plasma: 3L
IF: 12 L
What is the universal solvent?
Water
What dissolves in water?
Solute
What is a non electrolyte?
- Organic
- Doesn’t dissociate in water
What is electrolyte?
- Dissociate into ions in water
- Greater osmotic power than non
What are the major ions in the ECF?
- Na+
- Cl-
Except: higher protein, lower Cl- content of plasma
What are the major ions in the ICF?
- Low in Na+ and Cl-
- K+
- HPO4 2-
More soluble proteins than in plasma
What are the bulk of dissolved solutes in ECF and ICF?
- Proteins
- Phospholipids
3 Cholesterol - TAGs
What is the purpose of osmotic and hydrostatic pressures?
Regulate continuous exchange and mixing of fluids
What occurs if ECF osmolality increases?
Water leaves cell
What occurs if ECF osmolality decreases?
Water enters cell
What occurs between plasma and IF across capillary walls?
Fluid leaks from arteriolar end of capillary, reabsorbed at venule end; lymphatics pick up remaining and return to blood
What occurs between IF and ICF across membrane?
Two-way osmotic flow of water
Ions move selectively; nutrients, wastes, gases unidirectional
What is water intake?
Beverages, food, metabolic water
What is water output?
Urine, insensible water loss, perspiration, feces
What is equal to water intake?
Water output
What is the normal body Osmolality?
280-300mOsm
What occurs when osmolality rises?
- Stimulates thirst
- ADH release
What occurs when osmolality decreases?
- Thirst inhibition
- ADH inhibition
What is the driving force for water intake?
Thirst mechanism
What governs the thirst mechanism?
Hypothalamic thirst center
What does the hypothalamus do in regards to thirst?
Hypothalamic osmoreceptors detects osmolality and activated by Increased plasma osmolality, dry mouth, decreased blood volume, and angiotensin
What is the inhibitory feedback signals for thirst?
- Relief of dry mouth
- Activation of stomach and intestinal stretch receptors
What is obligatory water losses?
- Insensible water loss from lungs and skin
- Minimum daily sensible water loss of 500 ml in urine to excrete wastes
What occurs when ADH is low?
Dilute urine and lowers volume of body fluids
What occurs when ADH is high?
Concentrated urine; reabsorption of water causing and increase in volume of body fluids
What regulates ADH accordingly?
Hypothalamic osmoreceptors sense ECF solute concentration
What factors other than the hypothalamus can trigger ADH release?
Blood volume and pressure
What is dehydration?
Negative fluid balance
What are the effects of dehydration?
- Excessive loss of H2O from ECF
- ECF osmotic pressure rises
- Cells lose H2O to ECF by osmosis, cell shrink
What are symptoms of dehydration?
“Cottony” oral mucosa, thirst, dry flushed skin, oliguria
What are some of the causes of dehydration?
Hemorrhage, burns, vomiting, diarrhea
What is hypotonic hydration?
Cellular over hydration or water intoxication
When would hypotonic hydration occur?
- Ecessive H2O enters the ECF
- ECF osmotic pressure falls
- H2O moves into cells by osmosis, cell swells
How is hypotonic hydration treated?
Hypertonic saline
What is an edema?
Atypical accumulation of IF causing tissue to swell (not cell)
What happens during an edema?
- Fluid increase out of blood causes and increase in capillary hydrostatic pressure or permeability
- Decrease fluid returning to blood cause an imbalance in colloid osmotic pressures (hypoproteinemia)
What causes an edema?
- Blocked lymphatic vessels
- Increases diffusion distance for nutrients and oxygen
- Results in low blood pressure and severely impaired circulation
What is the purpose for salt in electrolyte balance?
Salts control fluid movements, provide minerals for excitability, secretory activity, and membrane premeability
What is the most abundant cation in ECF?
Na+
How does Na+ effect osmotic pressure?
- Controls ECF volume and water distribution
- Changes in Na+ levels affects plasma volume, blood pressure, and ECF and IF volumes
What is the purpose of Na+ concentration?
- Osmolality of ECF
- Excitability
- Remains stables due to water shifting in and out into ICF
What is the purpose of Na+ content?
Total body content determines ECF volume and blood pressure
What regulates Na+ balance?
- No known receptors
- Na+-water balance is linked to BP and blood volume control mechanisms
- Hormonal and neural controls
How does aldosterone regulate Na+ balance?
- Decreased urinary output increasing blood volume
- Increase K+ secretion
- Na+ is reabsorbed
What is never secreted in filtrate?
Na+
What catalyzes production of angiotensin II?
Renin
What triggers aldosterone release?
Elevated K+ levels in ECF
What does the RAAS mechanism achieve?
- Granular cells of JGC secrete renin due to:
- Sympathetic NS
- Decrease in filtrate NaCl concentration
- Decrease in stretch of granular cells (low BP)
What does ANP do to regulate Na+ balance?
Released by atrial cells in response to stretch and increase in BP
What are the effects of ANP?
- Decrease BP and volume
- Decrease RAAS production
- Increase excretion of Na+ and water
- Promotes vasodilation
How does estrogen affect Na+ balance?
Increases NaCl reabsorption (like aldosterone)
How does progesterone affect Na+ balance?
Decreases Na+ reabsorption by blocking aldosterone
How does glucocorticoids affect Na+ balance?
Increase Na+ reabsorption and promote edema
What are the effects of baroreceptors?
Sympathetic nervous system impulses to kidneys decline → afferent arterioles dilate → GFR increases → Na+ and water output increase → Reduced blood volume and pressure