Fluid & Electrolyte Balance (PART 1) Flashcards
Interrelationship of Fluid & Electrolyte Balance X 3
- Fluid and electrolyte balance implies _______
- ________ have chemical bonds that allow dissociation into ions, which carry an electrical charge; of critical importance in fluid balance.
- Fluid balance and electrolyte balance are
______________
homeostasis
Electrolytes
interdependent
Total Body Water
- Water content of the human body ranges from
_____ to ______ of its total weight - Water content varies according to ____, _______ & __________
50% TO 70%
age, gender, and weight
Body Fluid Compartments X 2
Two major fluid compartments:
- _____________ fluid compartment (ECF) constitutes the INTERNAL environment of the body – 40%
– Consists mainly of plasma and interstitial fluid
– Lymph, CSF, and specialized joint fluids are considered extracellular
– Functions of ECF provide a relatively constant
environment for cells and transport substances to and
from the cells. - Intracellular fluid (ICF) – 20%
– Functions to ________ intracellular chemical reactions
that maintain life
– By volume, ICF is the largest body fluid compartment
Extracellular
facilitate
Body Fluid Compartments
Extracellular vs. intracellular fluids:
- Plasma and interstitial fluid are almost identical in
chemical make-up, with intracellular fluid showing striking differences - Extracellular fluids
– Difference between blood and interstitial fluid; blood
contains a slightly larger total of _____than interstitial
fluid
– Functionally important difference between blood and
interstitial fluid is the number of ______ _____; blood
has an appreciable amount, whereas interstitial fluid
has hardly any
ions
protein anions
Shift of Water Between Compartments
• Volume of fluid compartment depends on the
amount of ________ it contains.
• ____________ is the concentration of osmotically
active particles, expressed as mOsm/L.
• In the steady state, IC osmolarity is equal to EC
osmolarity.
• Solutes such as NaCl and NaHCO3 and large
sugars such as mannitol are assumed to be
confined to the ECF compartment.
solute
Osmolarity
Movement of Water
- Water enters the body via the ______ ________; water is also added to the total fluid volume from each cell as it catabolizes food, and the resulting water enters the bloodstream
• Water leaves the body via four exits: – \_\_\_\_\_\_\_\_\_\_\_ – \_\_\_\_\_\_\_\_ – Skin – Intestines
digestive tract
Kidney
Lungs
General Principles of Fluid Balance (Osmoregulation)
- Cardinal principle of fluid balance is: fluid balance can be maintained only if _______ equals ________
- Mechanisms are available to adjust output and intake to maintain fluid balance, e.g., _________ mechanism,
renin-angiotensin mechanism - Most rapid fluid balance devices are mechanisms for
controlling _______ movement between fluid compartments of the body; will maintain normal blood volume at the expense of interstitial volume
intake
output
aldosterone
water
Mechanisms That Maintain Homeostasis of Total Fluid Volume X 4
- Under NORMAL conditions, homeostasis of total volume of water is maintained or restored primarily by adjusting ______ volume and secondarily by fluid intake
- Regulation of fluid intake – when _________ begins to develop, salivary secretion decreases, producing the sensation of thirst; individual increased fluid intake to offset increased output tends to restore fluid balance
urine
dehydration
Mechanisms That Maintain Homeostasis of Total Fluid Volume X 4
- Regulation of urine volume – two factors determine urine volume:
a – GFR remains fairly constant
b – Rate of tubular reabsorption of water fluctuates
considerably; normally adjusts urine volume to fluid intake; influenced by amount of _____ and aldosterone - Factors that alter fluid loss under abnormal conditions – rate of respiration and volume of sweat secreted may alter ______ output; vomiting diarrhea, or intestinal drainage can produce fluid and electrolyte ___________.
ADH
fluid
imbalance
REGULATION of Water and Electrolyte Levels in PLASMA and Interstitial Fluid X 3
- Starling’s Law of Capillaries – the control mechanism for water exchange between plasma and interstitial fluid consists of four pressures: ________ hydrostatic and colloid osmotic pressure on one side of the capillary membrane and __________ fluid hydrostatic and colloid osmotic pressures on the other side.
– Blood hydrostatic pressure (BHP)
– Blood colloid osmotic pressure (BCOP)
– Interstitial fluid hydrostatic pressure (IFHP)
– Interstitial fluid colloid osmotic pressure (IFCOP)
blood
interstitial
Regulation of Water and Electrolyte Levels in Plasma and Interstitial Fluid X 3
- The ____ and _______ of fluid exchange between capillaries and interstitial fluid are determined by the hydrostatic and colloid osmotic pressures of the two fluids.
- Some principles about transfer of water between
blood and interstitial fluid:
– No net transfer of water occurs as long as
(BHP+IFCOP)=IFHP+BCOP)
– Fluid shifts out of blood into interstitial fluid whenever
(BHP+IFCOP)>(IFHP+BCOP)
– Fluid shifts out of interstitial fluid into blood whenever
(BHP+IFCOP)
rate
direction
Control of Extracellular Osmolarity (NaCl Concentration)
Mechanism:
INCREASED extracellular osmolarity (NaCl) stimulates______release, which INCREASES H2O reabsorption, and stimulates thirst (intake of water)
ADH
Concentration and Dilution of the Urine
- MAXIMAL urine concentration
=______-________ mOsm / L
(specific gravity ~ 1.030) - MINIMAL urine concentration
= _____–________ mOsm / L
(specific gravity ~ 1.003)
1200 - 1400
50 - 70
Formation of a DILUTE urine
- Continue electrolyte reabsorption
- ____________ water reabsorption
Mechanism:
DECREASED ADH release and reduced
water permeability in ______ and collecting tubules
Decrease
distal
Formation of a CONCENTRATED Urine
- Continue electrolyte reabsorption
- ____________ water reabsorption
Mechanism :
INCREASED ADH release which INCREASES water permeability in distal and collecting tubules
a. High osmolarity of _______ medulla
b. Countercurrent flow of tubular fluid
Increase
renal
Formation of a Concentrated Urine occurs when antidiuretic hormone (ADH) is \_\_\_\_\_\_
high.
Obligatory Urine Volume
- The _________ urine volume in which the excreted
solute can be dissolved and excreted
Example:
If the max. urine osmolarity is 1200 mOsm/L,
and 600 mOsm of solute must be excreted each
day to maintain electrolyte balance, the
obligatory urine volume is:
600 mOsm/d divided by 1200 mOsm/L = 0.5 L/day - In renal disease the obligatory urine volume may be increased due to _______ urine concentrating ability
Example:
• If the max. urine osmolarity = 300 mOsm/L,
• If 600 mOsm of solute must be excreted each day to maintain electrolyte balance
• obligatory urine volume = ?
600 mOsm/d divided by 300 mOsm/L = 2.0 L/day
minimum
impaired
Corticopapillary Osmotic Gradient x 7
- It is the gradient of osmolarity in the interstitial fluid of the ___________ from the cortex to the papilla.
- Osmolarity of cortex is approximately 300
mOsm/L. - At the tip of papilla, the osmolarity can be as
high as 1200 mOsm/L.
kidney
Corticopapillary Osmotic Gradient
What solutes contribute to this gradient?
What mechanisms deposit these solutes in the IF?
- Countercurrent multiplication
* Urea recycling
Corticopapillary Osmotic Gradient x 7
- Active transport of Na+, Cl-, K+ and other ions from thick _________ loop of Henle into medullary interstitium
- Active transport of ions from _______ collecting ducts into interstitium
- Passive diffusion of ______ from medullary collecting ducts into interstitium
- Diffusion of only small amounts of _____ into medullary interstitium
ascending
medullary
urea
water
Urea Recycling x 4
- Urea is passively reabsorbed in ________ tubule
(~ 50% of filtered load is reabsorbed) - In the presence of ADH, water is reabsorbed in ____ and collecting tubules, concentrating urea in these parts of the nephron
- The ________ medullary collecting tubule is highly permeable to urea, which diffuses into the medullary interstitium
- ________ increases urea permeability of medullary
collecting tubule by activating urea
transporters (UT-1)
proximal
distal
inner
ADH
The Vasa Recta Preserve Hyperosmolarity of Renal Medulla
- The vasa recta serve as ____________ exchangers
- Vasa recta blood flow is low (only __-__ % of total renal blood flow)
countercurrent
1-2
Disorders of Urine Concentrating Ability
- Failure to produce ADH :
“______________” diabetes insipidus - Failure to respond to ADH:
“_________________” diabetes insipidus
a. -impaired loop NaCl reabs. (loop diuretics)
b. - drug induced renal damage: lithium, analgesics
c. - kidney disease: pyelonephritis, hydronephrosis,
chronic renal failure
d. - malnutrition (decreased urea concentration)
Central
nephrogenic
______________– antidiuretic hormone (ADH) feedback
mechanism for regulating extracellular fluid osmolarity
Osmoreceptor
ADH synthesis in the magnocellular neurons
of _____________, is released by the posterior
pituitary, and starts action on the kidneys
hypothalamus
Stimuli for ADH Secretion
- Increased osmolarity
- __________ blood volume (cardiopulmonary reflexes)
- __________ blood pressure (arterial baroreceptors)
- Other stimuli :
- input from cerebral cortex (e.g. fear)
- angiotensin II
- nausea
- nicotine
- morphine
Decreased
Decreased
Factors That DECREASES ADH Secretion
- _________ osmolarity
- _______ blood volume (cardiopulmonary reflexes)
- ________blood pressure (arterial baroreceptors)
- Other factors :
- alcohol
- clonidine (antihypertensive drug)
- haloperidol (antipsychotic, Tourette’s)
Decreased
Increased
Increased
Stimuli for INCREASE Thirst X 5
- ____________ osmolarity
- ____________ blood volume (cardiopulmonary reflexes)
- ____________ blood pressure (arterial baroreceptors)
- ___________ angiotensin II
- Other stimuli: - dryness of mouth
Increased
Decreased
Decreased
Increased
Factors That DECREASE Thirst
- ___________ osmolarity
- ___________ blood volume (cardiopulmonary reflexes)
- ___________ blood pressure (arterial baroreceptors)
- ____________ angiotensin II
- Other stimuli: -Gastric distention
Decreased
Increased
Increased
Decreased
Significance of CH2O
- ________ = no solute-free water is excreted; urine
is isosmotic with plasma (isosthenuric) - ___________ = urine is hyposmotic; ADH levels are
low or ADH is ineffective - ____________= urine hyperosmotic; all free water
is reabsorbed; ADH levels are high
Zero
Positive
Negative
