Water & Electrolytes Flashcards
Water’s functions
Carrier
Maintains molecular structure
Participates in chemical rxns
Solvnet
Lubricant
Thermoregulation
Blood volume maintenance
Intracellular fluid
⅓ of volume, 20% of weight
Inside all cells
Extracellular fluid
⅔ of volume, 40% of weight
Intravascular
Interstitial
Intravascular fluid
Within vessels
Blood plasma
Interstitial fluid
75% of ECF
Around cells
Osmosis
Movement of water across a semipermeable membrane
Dependent on osmotic particles
Osmotic particles
Solutes that can’t cross membrane
Salts, sugar, protein
Osmotic pressure
Pressure necessary to stop the movement of water across semi permeable membrane
Membrane separates 2 solutions that have different particle concentration
Isotonic
Particle concentration outside = inside
Hypotonic
Particle concentration higher on inside
Water comes into cell
Cells expand
Hypertonic
Particle concentration higher on outside
Water leaves the cell
Cells shrink
Electrolytes
Salts that dissolve in water and dissociate into ions
Electrolyte equilibrium
Body regulates amount of water in each compartment
Control the amount of electrolytes in each
Water follows movement of electrolytes via diffusion
Extracellular electrolytes
Na
Cl
Intracellular electrolytes
K
HPO4 (phosphate)
Ion exchange
Body maintains gradients of electrolytes
Use energy to exchange sodium and potassium
Fluid pH
Bicarbonate and some proteins = pH buffers
Maintain pH in a very narrow range
Cardiovascular system
Closed
Hydrostatic pressure
Capillaries
Site of fluid and solute exchange
Huge surface area (capillary beds)
Pressure gradients drive
Movement of blood
How absorption and filtration occur
Capillary hydrostatic pressure
Forces fluid out of the capillary
Force generated by pressure of fluid on capillary walls
Plasma oncotic pressure
Draws fluid back in the capillaries
Exerted by proteins in blood plasma or fluid
Arterial side
Hydrostatic > oncotic
Deliver nutrients to tissue
Stuff in blood is filtered out
Venous side
Hydrostatic < oncotic
Tissues drop things into blood
Dispose of waste
Edmea
Accumulation of fluid within interstitial space
Water intake requirements vary on
Diet
Activity
Environment
Insensible water loss
Skin (not sweating)
Respiration
Only the kidneys can compensate for these losses
Water loss
Must excrete urine to remove metabolic waste
Regulated by kidneys
Temperature regulation
Evaporated perspiration
Sweating
Dehydration 1-2%
Thirst
Fatigue
Weakness
Discomfort
Loss of appetite
Dehydration 3-4%
Impaired physical performance
Dry mouth
Reduction in urine
Flushed skin
Impatience
Apathy
Dehydration 5-6%
Difficulty concentrating
Headache
Irritability
Sleepiness
Impaired temp regulation
Increased respiratory rate
Dehydration 7-10%
Dizziness
Spastic muscles
Loss of balance
Delirium
Exhaustion
Collapse
GI tract
Handles 9 L of water per day
Ingerst 2000 mL per day
Other 7000 mL recycled
Sense of thirst
Excessive loss of body water
Increase in osmolarity sensed by the body
Increase in osmolarity of 2-3% → strong desire to drink
Hypo-osmolality
Water intoxication
Rapid fall in osmolality
Water from ECF moves into cells
Kidneys regulate
Bodily fluid osmolality + volume
Electrolyte balance
Acid base balance
Nephron
Functional unit of the kidney
Tubular system involved in urine production
Glomerulus
Part of the nephron
Rich in capillaries
Site of plasma filtration into renal tubes
Tubules
Site of processing of plasma filtrate to create urine
Filtration
Initial removal of water and solutes from the blood
Not large proteins or blood cells
Reabsorption
Selective removal of water and solutes from glomerular filtrate into blood
Secretion
Selective removal of some solutes from the plasma into the tubules
Excretion
Removal of final urine to the bladder
PTH and Calcium
Induces kidney to activate more vitamin D
Increases calcium reabsorption
Decreases calcium excretion
Antidiuretic hormone (ADH)
Arginine vasopressin
Released by pituitary
Response to increased osmolarity / decreased blood pressure
Increase water absorption (kidneys)
Renin
Released from kidneys
Response to low bp
Acts on angiotensinogen to produce angiotensin I
Angiotensin I
Coveted to angiotensin II in the lungs
Angiotensin II
Vasoconstrictor
Constricts blood vessels
Increase blood pressure
Release of aldosterone from adrenal glands
Aldosterone
Acts on renal tubes
Increase Na reabsorption and K excretion
Water follows Na
Blood volume increased
ACE inhibitors
Hypertension drug
Prevent angiotensin I → II conversion (ACE enzymes)
Inhibit hydrolysis of vasodilator
Lower blood pressure
Sodium function
ECF cation
Important for regulating body water and electrolyte balance
Neural and muscular function
Sodium requirement
No RDA
Depend on physical activity and climate
Intake more than we need
Sodium sources
Processed foods
Sodium bicarbonate, NaCl, sodium saccharin
Fruits and veggies contain the least
Sodium sensitivity
Chronic renal disease, diabetes, hypertension
Lower bp with restricted sodium intake
Sodium deficiency
Occurs with vomiting, diarrhea, heavy sweating
Muscle cramps, mental apathy
Sodium toxicity
Edmea
Hypertension
Potassium function
Main cation inside cells
Role in fluid and electrolyte balance
Nerve and muscle function
Potassium sources
Fresh, unprocessed foods
Fruit and veg
Coffee
Tea
Milk
Potatoes
Animal products
Potassium deficiency
Hypokalemia
Occurs b/c of diarrhea, vomiting
Associated with use of diuretics, steroids, laxatives
Potassium deficiency symtoms
Muscle weakness
Paralysis
Confusion
Arrhythmia
Hypertension
Potassium toxicity
Hyperkalemia
Overuse of supplements
Hard to induce from diet
Muscle weakness, vomiting, heart failure