WATER AND ELECTROLYTE BALANCE. 1 Flashcards
WATER BALANCE
What is the range of average water content in the human body?
The average water content in the human body varies from 40% to 75% of total body weight.
Where is this water located within the body?
The water is located in intra and extra cellular spaces.
How does age affect the average water content in humans?
Average water content tends to decline with age.
Is there a difference between men’s and women’s average water content? If so, what is it attributed to?
Yes, there is a difference. Women have lower average water content than men, primarily due to their higher fat content.
Why is water known as a solvent for all processes in the human body?
Water acts as a solvent for all processes because it:
1. Transports nutrients to cells
2. Removes waste products through urine
3. Determines cell volume
4. Serves as the body’s coolant through sweating
What percentage of body fluids does intracellular fluid account for
Intracellular fluid accounts for two-thirds of total body fluids.
What are the two subdivisions of extracellular fluid?
Extracellular fluid is subdivided into intravascular ECF (plasma) and interstitial cell fluid.
What is the approximate percentage of water in normal plasma?
Normal plasma contains approximately 93% water.
By what means is the distribution of body fluid controlled?
The distribution of body fluid is controlled by maintaining the concentration of electrolytes and proteins.
What is osmolality?
Osmolality is the physical property of a solution based on the concentration of solutes. It is expressed as millimoles per kilogram of solvent (w/w).
How is osmolality expressed
Osmolality is expressed in terms of millimoles per kilogram of solvent (w/w).
What effect does increased blood osmolality have on hormone release
Increased blood osmolality triggers the secretion of arginine vasopressin hormone (AVP) (also known as antidiuretic hormone (ADH)
Which hormones are involved in fluid reabsorption by the kidneys?
The hormones involved in fluid reabsorption by the kidneys are ADH (AVP), which promotes reabsorption of fluids.
What is the parameter to which the hypothalamus responds?
The hypothalamus responds to osmolarity in plasma.
How does Na+ concentration affect plasma
Na+ concentration and its associated anions account for approximately 90% of the osmotic activity in plasma.
What percentage of the osmotic activity in plasma is accounted for by Na+ and its associated anions?
Approximately 90% of the osmotic activity in plasma is attributed to Na+ and its associated anions.
How do osmoreceptors in the hypothalamus respond?
Osmoreceptors in the hypothalamus respond to the smallest change in osmolarity.
what is the clinical significance of osmolarity
- Osmoreceptors in the hypothalamus respond to smallest change in osmolarity
- It affects the Na+ concentration in plasma, Na+ and its associated anions account for approximately 90% of the osmotic activity in plasma.
- Osmolarity in plasma is the parameter to which the hypothalamus responds
- An increase or decrease of 1 – 2% in osmolarity causes a fourfold in AVP concentration and shuts off AVP production respectively
- Hypoosmolality and hyponatremia usually occur only in patients with impaired renal excretion of water
- Hypo-osmolality may occur in diabetes insipidus patient
When does hypoosmolarity and hyponatremia ussually occur
in patients with renal impaired renal excretion of water
in which patients does hypo-osmolarity occur
in diabetes insipidus patients
What is interconnected in controlling blood volume
The regulation of both sodium (Na+) and water is interconnected in controlling blood volume.
Which system responds primarily to a decreased blood volume?
The renin-angiotensin-aldosterone system responds primarily to a decreased blood volume.
What is secreted by renal glomeruli?
Renal glomeruli secrete renin.
What does renin convert angiotensinogen into
Renin converts angiotensinogen into angiotensin I and then into angiotensin II
What are the effects of vasoconstriction mentioned in the text?
Vasoconstriction causes an increase in blood pressure (BP) and secretion of aldosterone, which increases sodium and water retention.
what happens when blood volume decreases
renin-angiotensin-aldosterone system kicks in.
where is renin secreted from
Renal glomeruli
effects of angiotensin II
Angiotensin II causes blood vessels to narrow, increasing blood pressure (BP)
What detects increase in pressure and volume of blood water
stretch receptors located in cardiopulmonary circulation, carotid sinus, aortic arch, and glomerular arterioles
what role does blood/water receptors play
activate a series of responses that restore volume by varying vascular resistance, cardiac output, and renal Na+ and water retention
what factors affects blood volume
- Atrial natriuretic peptide
- Volume receptors independent of osmolality stimulating the release of AVP
- Glomerular filtration rate
- Increased plasma Na+ will increase urinary Na+ excretion and vice versa (see diagram on page 11 and 12)
Which substances provide the largest contribution to serum osmolality?
Sodium (Na+), chloride, and bicarbonate provide the largest contribution to the osmolality value of serum.
Why is plasma use not recommended for determining osmolality?
Plasma use is not recommended because osmotically active substances may be introduced into the specimen from the anticoagulant.
How do osmometers operate?
Osmometers operate by freezing point depression and are standardized using sodium chloride reference solutions.
test procedure forosmolarity
- Sample is pipetted into the required cuvette or sample cup and placed in the analyzer.
- The sample is supercooled below its freezing point (to about -7°C) till equilibrium is reached and measured,
- Osmolal gap is calculated (difference between the measured osmolality and the calculated osmolality)
- Results for serum and urine osmolality reported as milliosmoles per kg
