Chapter 15 - Fluid Balance Flashcards
Internal Pool
-the quantity of any particular substance in the ECF
How to increase the internal pool (input)?
-transferring more in from the external environment (ingesting it)
-metabolically producing it
How to decrease the internal pool (output)?
-excreting it to the outside
-metabolic consumption
Input must be balanced by an equal _____.
-output (balance concept)
Positive Balance
-exists when input exceeds output
Negative Balance
-exists when output exceeds input
Input
-poorly controlled or not controlled
-eating habits are variable
-involves the input of substances into the plasma
Output
-compensatory adjustments
-occur by urinary excretion
Body fluid is __% extracellular
33 (1/3)
Body fluid is __% intracellular.
67 (2/3)
Extracellular fluid is __% interstitial fluid.
75
Extracellular fluid is __% plasma.
25
Water is __% of body weight.
60
Lymph
-a minor ECF component
-the fluid being returned from the interstitial fluid to the plasma
Transcellular Fluid
-CSF
-intraocular fluid
-synovial fluid
-pericardial, intrapleural, peritoneal fluids
-digestive juices
-don’t usually reflect changes in the body’s fluid balance
Cellular Plasma Membranes
-the barrier between the ECF and ICF
-ICF has proteins that cannot permeate cell membrane
-Na+K+ are unequally distributed
Blood Vessel Walls
-the barrier between plasma and interstitial fluid
-the fluid is near identical (minus plasma proteins in ISF)
Chemical Disequilibrium
-concept of having an unequal distribution of solutes in different fluid components
ECF Volume
-regulated to help maintain blood pressure
-maintaining salt balance (long term salt volume regulation)
ECF Osmolarity
-regulated to prevent swelling or shrinking of cells
-maintaining water balance
-cell volume/shape
Salt Balance
-long-term ECF volume regulation
-input by ingestion
-output by urine (+perspiration and feces)
Amount of salt excreted is regulated by:
- GFR
- Tubular reabsorption
Baroreceptor Reflex
-alters cardiac output and TPR
-extrinsic control; SNS on afferent arteriole
Isotonic
-fluid outside cell has same osmolarity as inside
Hypertonic
-fluid outside cell has a higher osmolarity than inside
Hypotonic
-fluid outside cell has lower osmolarity than inside
Which ions are responsible for ECF osmotic activity?
-sodium and its anions
Which ions are responsible for ICF osmotic activity?
-potassium and its anions
ECF Free water DEFICIT
-osmolarity becomes hypertonic
-associated with dehydration
-cells tend to shrink
Hypertonicity Causes
-insufficient water intake
-excessive water loss
-diabetes insipidus
Hypertonicity Symptoms and Effects
-shrinking of brain neurons (confusion, irritability, delirium, convulsions, coma)
-circulatory disturbances (low plasma volume, low BP, circulatory shock)
-dry skin
-shrunken eyeballs
-dry tongue
ECF Free water EXCESS
-osmolarity becomes hypotonic
-associated with over hydration
-cells tend to swell
Hypotonicity Causes
-renal failure patients who cannot excrete dilute urine when they consume more water than solutes
-when rapid water is ingested and kidneys don’t respond quick enough
-excess water is retained due to inappropriate vasopressin secretion
Hypotonicity Symptoms and Effects
-swelling of brain cells
-muscle weakness
-circulatory disturbances (hypertension and edema)
-water intoxication
Water Input
-drinking liquids
-eating solid foods
-metabolically produced water
Water Output
-insensible loss (lungs, non-sweating skin)
-sensible loss (sweating, feces, urine)
In order to maintain stable water balance water input must ________ water output.
equal
The majority of water output comes from_____.
Urine
Where is water excretion controlled?
-collecting ducts
-tubules of nephron
Vasopressin
-produced by hypothalamus
-stored and released from posterior pituitary (hypothalamus controls)
Hypothalamic Osmoreceptors
-located near vasopressin-secreting cells and thirst centre
Osmolarity Increase
-increased vasopressin secretion
-thirst stimulated
Osmolarity Decrease
-decreased vasopressin secretion
-thirst suppressed
Left Atrial Volume Receptors
-monitor BP
-upon detection of reduction: stimulate vasopressin and thirst
-upon detection of elevation: vasopressin and thirst inhibited
Angiotensin II
-stimulates vasopressin secretion and thirst when RAAS is activated
-used to conserve Na+
