Fluid Balance Flashcards
Why is water important?
- Transport of nutrients, electrolytes, waste.
- Temp regulation.
- Lubrication.
- Chemical reagent.
- Blood pressure.
What percentage of the body weight is water?
40-80%.
What are the 2 fluid compartments in the body?
1) . Extracellular fluid (ECF).
2) . Intracellular fluid (ICF).
What are the 2 types of extracellular fluid?
1) . Interstitial fluid =
- found outside the cells.
2) . Intravascular fluid =
- in blood plasma.
What percentage of body fluid is ECF?
40%.
Where is intracellular fluid found?
Within the cell.
What percentage of body fluid is ICF?
60%.
What separates the 2 fluids?
Cell membrane.
How is blood volume determined?
- Amount of water + sodium ingested.
- Excreted by kidneys into the urine.
- And lost through GI tract, lungs and skin.
What happens to arteries when there is a higher volume of fluid?
Greater the pressure against arterial walls.
- rise in blood pressure.
What happens when there is lower arterial blood volume?
Lower arterial blood pressure.
Summarise the homesostatic response to a fall in blood volume?
ADH release from hypothalamus/posterior pituitary gland.
- water content in blood becomes normal.
What is the homesostatic response to a fall in blood volume?
- Detected by baroreceptors/osmoreceptors.
- Hypothalamus produces ADH.
- Posterior pituitary releases more ADH.
- ADH increases water reabsorption in DCT and collecting ducts in nephrons.
- Blood volume increases.
- Blood pressure increases.
What hormonal system regulates blood pressure/fluid balance?
Renin-Angiotensin-Aldosterone System (RAAS).
When does the RAAS kick in?
When blood volume is low.
Which specialist cells in the kidneys secretes renin?
Juxtaglomerular cells.
What is the effect of secreting renin?
Causes angiotensinogen to be converted to angiotensin I.
Where is angiotensinogen preoduced?
Liver.
Where does angiotensin I travel to in order to be converted?
Lungs.
What is angiotensin I converted to once it has reached the lungs?
Angiotensin II.
What enzymes causes angiotensin I to convert to angiotensin II?
Angiotensin converting enzyme (ACE).
How does angiotensin II increase blood pressure?
Vasoconstriction =
- increases peripheral resistance.
What gland does angiotensin II stimulate?
Adrenal glands =
- to secrete aldosterone.
What are the effects of aldosterone?
Decreases urine production in the kidneys.
How does aldosterone decrease urine production in the kidneys?
Exchanging potassium for sodium in distal renal tubule =
- sodium reabsorption.
- potassium secretion.
What are the effects of aldosterone on blood pressure?
Raises it.
What other hormone does angiotensin II stimulate?
ADH (acts of DCT + collecting ducts) =
- increases water reabsorption.
Summarise the process of RAAS?
1) . Renin –> angiotensin –> angiotensin I.
2) . Angiotensin –> angiotensin II (via ACE).
3) . Angiotensin II –> aldosterone (adrenal).
What are the actions of angiotensin II?
- Causes vasoconstriction.
- Stimulates aldosterone secretion.
- Stimulates thirst sensation.
- Stimulates ADH secretion to increase water reabsorption.
Where is the oscoreceptors located?
Hypothalamus.
Where are baroreceptors located?
- Carotid sinus.
- Aortic arch.
What are the receptors, controllers and effectors in the regulation of blood pressure by ADH?
1). Receptor =
- baroreceptor.
- osmoreceptor.
2) . Controller =
- ADH.
3) . Effectors =
- distal convoluted tubules (DCT).
- collecting ducts.
What way does ADH and RAAS regulate blood pressure?
Hormonally.
What is high blood pressure also known as?
Hypertension.
What is the pharmacological approach to blood pressure management (hypertension)?
Diuretics.
What are the different classes of diuretics that manage blood pressure?
- Loop diuretics.
- Thiazides.
- ACE inhibitors.
Name some loop diuretics?
- Furosemide.
- Bumetanide.
- Lasix.
What do loop diuretics do?
- Act on the loop of Henle.
- Inhibit the reabsorption of sodium.
- Sodium excreted through urine.
When are loop diuretics used?
More serious cases of hypertension.
Why are loop diuretics used sparingly?
- Toxicity.
- Potential to cause dehydration.
Name some thiazides?
- Bendroflumenthiazide.
- Indapamide.
- Xipamide.
What do thiazides do?
Inhibit sodium reabsorption at the beginning of the distal convoluted tubule.
Name some ACE inhibitors?
- Lisinpril.
- Perindopril.
- Captopril.
- Enalapril.
What do ACE inhibitors do?
- Produce vasoconstriction by inhibiting the formation of angiotensin II.
- Decrease blood pressure.
Summarise the different classes of antihypertensive drugs?
1) . Loop diuretics =
- inhibit sodium reabsorption.
2) . Thiazides =
- inhibits sodium reabsorption in DCT.
3) . ACE inhibitors =
- produce vasoconstriction –> inhibit angiotensin II.
