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Renal Objectives: Lecture VIII
Terms in this set (34)
Give the names of the two main body fluid compartments, and the percentage total body water in each.
Intracellular fluid (ICF), 66%
Extracellular fluid (ECF) 34%
What are the subdivisions, and percentages of them, of the ECF?
Interstitial fluid- 75%
Plasma volume - 25%
How does the composition of the ICF vary with the ECF?
ICF has high protein, potassium, HCO3 and phosphate.
ECF: Plasma: has Na, Cl, less proteins than ICF.
ECF: Interstitial fluid: Similar to plasma, but less protein concentration
What is an effective osmole?
When a solute in the ICF raises osmotic pressure, pulling fluid out of osmoreceptors, causing the release of ADH, and increasing thirst.
What is an example of effective osmole?
What does "ineffective osmole" mean?
A solute that can diffuse freely across a membrane and it doesn't cause osmoreceptors to shrink.
Why does an "ineffective osmole" not cause a net movement of water?
The solute diffuses into the osmoreceptors, lowering the ECF pressure.
What is an example of an ineffective osmole?
Will a raised urea concentration elicit ADH release?
Why does an elevated plasma urea concentration not elicit ADH release?
The cell membrane is permeable to urea, so it readily diffuses across the membrane and will not influence the movement of water, therefore osmoreceptros will not strech, and therefore the cells will not release ADH.
How does plasma osmolality control the release of ADH?
When posterior pituitary cells shrink due to increase of osmolality, ADH is released.
How do baroreceptors cause the release of ADH?
ECV sensors sense intravascular pressure by assessing streches in areas with varying pressure.
Where do baroreceptors asses strech in low pressure areas?
Where do baroreceptors asses stretch in high pressure areas?
Carotid sinus, aortic arch
When do low pressure baroreceptors have the greatest influence on ADH secretion?
until blood losses reach about 10% of total blood.
How does osmolality influence thirst?
Increased osmolality of ECF will cause a shrinkage of thirst osmoreceptors, causing thirst.
What hormone influences thirst?
How does the action of the Na/K ATPase affect ECF osmolality?
It increases the ECF Na, which raises osmolality.
How does an increase in ECF affect renal sympathetic nerves?
Increase ECF will raise blood pressure, decreasing activity of renal sympathetic nerves.
What are the results of renal sympathetic nerves?
Decrease in renin secretion
Decrease in proximal tubule reabosrption
What is the effect of a decrease in renin secretion?
Less angiotensin I, therefore less angiotensin II (which comes from I).
What are the effects of a decrease in angiotensin II?
less aldosterone, less systemic vasoconstriction, less sodium reabsorption by proximal tubules, less thirst.
What is the effects on atrial natriuretic peptides (ANP) due to high salt consumption?
You might get a little swollen, but your not gonna die. Steches in atria release ANP.
What is the effect of high ANP levels?
Inhibits release of renin, which results in less aldosterone (which reabsorbs ions and water).
ANP inhibits angiotensin II.
ANP inhibits sodium reabosrption in the collecting duct.
High salt level will cause person to feel more or less thirsty?
With high salt, will braiin osmoreceptors shrink or grow?
With increase salt, will ADH increase or decrease? Why?
Increase, so more water is reabsorbed from collecting ducts
What will the effects of ADH and drinking water cause?
Concentrated urine, resulting in the EXPANSION of ECF.
What will the expansion of ECF cause? How will this affect ADH?
It will increase blood pressure, decreasing ADH.
Overall, what is the temporary effect of salt ingestion?
Expansion of ECF.
How does the body react to drop in plasma/blood volume as the result of a hemorrhage?
A drop in arterial pressure will cause an increase in renin secretion, which increases plasma renin, increasing angiotensin II.
How does an increase in angiotensin II help in recovering from hemorrhage?
Constricts renal arteries which lowers GFR and RBF (renal blood flow). It also increases tubular salt and water reabsorption.
How does a decrease in arterial pressure due to hemorrhage influence the activity of renal sympathetics?
They are increased, causing a constriction of renal aarterioles, and an increase in renin secretion.
Three effects of ADH on the kidney:
1. Inserts aquaporins into the luminal membrane, increasing membrane permeability to water.
2. Vasoconstricts pericytes that surround descending vasa recta, preserving the medullary gradient which produces concentrated urine.
3. increases the permeability of the medullary collecting ducts to urea, which causes urea to leave the cell, and add to the concentration gradient of the medulla.
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