Ch. 27: Fluid, Electrolytes, Acid Homeostasis Flashcards
What are osmoreceptors and their function?
-osmoreceptors are specialised cells in the hypothalamus
-respond to changes in extracellular tonicity (ECF [Na+])
-effectively controls the distribution of water between ICF and ECF
What do baroreceptors do?
Where are high pressure baroreceptors located and inputs info via what pathway?
What do they respond to?
-provide input to the hypothalamus, mediate change by ADH secretion
-high pressure baroreceptors (located in the carotid sinus) input to the hypothalamus via adrenergic pathways
-respond to changes in mean arterial blood pressure.
What mechanisms maintain fluid balance?
Osmorecptors and baroreceptors
What is the range of normal vs dehydrated plasma osmolality?
260-280 hydrated
>290 dehydrated
Why does dehydration develop? What does water do to reach osmotic equilibrium? What happens when fluid imbalance continues?
Develops when water losses outpace water gains
Water loss from ECF increases osmotic concentration in ECF
Water moves from ICF to ECF to reach osmotic equilibrium
If fluid imbalance continues, loss of water from ICF produces severe thirst, dryness, wrinkling of skin
What disorder can dehydration lead to and describe what the disorder is
Hypovolemia: a state of low extracellular fluid volume, generally secondary to combined sodium and water loss
What is hypovolemia shock? What are symptoms?
The most severe form of hypovolemia, characterized by tachycardia, cold, clammy extremities, cyanosis, low urine output (less than 15 ml/hr)
What treatment does hypovolemia shock need?
Rapid treatment with isotonic fluid boluses and assessment and treatment
What are symptoms of different percentages of lost body weight of dehydration? (3)
1-2%: dry and sticky mouth, thirst, fatigue
3-4%: dry mouth, impaired physical performance, reduction in urine
5-6%: difficulty in concentrating, headache
What are the pounds needed to be lost to determine whether someone is severely, moderately, or mildly dehydrated?
mild: A woman who weighs 120 lost 5 lbs
moderate: A man who weighs 90 lost 15 lbs
severe: A woman who weighs 140 lost 20 lbs
What is hypervolemia vs hypovolemia?
Hypervolemia: excess fluid volume
Hypovolemia: decreased fluid volume
Does hypervolemia and hypovolemia inhibit or stimulate?
Hypervolemia: inhibits
Hypovolemia: stimulates
What does hypervolemia inhibit or stimulate ? What does it contribute to?
Inhibits
ADH release
Aldosterone
Thirst
Contributes to: increased urination of dilute urine
What does hypovolemia stimulate or inhibit? What does it contribute to?
Stimulates
Thirst
ADH release
Aldosterone
Contributes to: decreased urination of concentrated urine
What causes the cells of the body to shrink or swell and what does not cause it to shrink or swell.
-Changes in osmolarity of the ECF (as with dehydration/over hydration) can cause the cells of the body to shrink
-When ECF is isotonic to cells of the body, they do not shrink or swell.
What is osmolarity? Which type of solutions have low osmolarity or high osmolarity?
Osmolarity describes the total solute concentration of a solution
-Solutions with a low solute concentration have a low osmolarity
-Those with a high osmolarity have a high solute concentration.
What is intracellular fluid, extracellular fluid, and interstitial fluid? What do they include?
Intracellular fluid: The liquid found inside cells (ICF is 2/3 of fluid, cytosol)
Interstitial fluid: A solution that surrounds the cells also called tissue fluid (lymph plasma, CSF, aqueous humor)
Extracellular fluid: all body fluid outside of cells (ISF, blood plasma, CSF, lymph, aqueous humor)
Is water percentage higher in females or males and their percentage?
Water is higher in males (60%) and female are (50%)
What are some examples of electrolytes that are cations and anions and non electrolytes?
Cations (+): sodium, potassium, calcium, magnesium
Anions (-): chloride, bicarbonate , phosphate, sulfate
Non-electrolyte: glucose, urea, dextrose
Water moves from which osmolarity to which?
Water moves from the side of the membrane with lower osmolarity (more water) to the side with higher osmolarity (less water).
What is hypotonic solution?
ECF has a lower osmolarity than the fluid inside the cell; water enters the cell.
What is hypertonic solution?
ECF has a higher osmolarity than the fluid inside the cell; water leaves the cell.
What is isotonic solution?
ECF has the same osmolarity as the cell; there will be no net movement of water into or out of the cell.
What is osmosis?
The movement of water molecules from high water concentration to a lower water concentration through a cell’s partially permeable membrane.
What is diffusion?
Tendency of solutes to move freely from areas of high to low concentration (down hill)
What is active transport?
Requires energy to move ions or molecules across cell membrane into a region of higher concentration
What is filtration?
Passage of fluid through a permeable membrane. Movement is from high to low pressure
What stimulates the desire to drink fluids? What is the effect?
-Thirst center in hypothalamus
-Effect: water is gained if thirst is quenced