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Lecture 35
Fluid Balance
Term | Definition |
---|---|
Balance Concept | The ECF is proof of available material for cells.input comes from ingestion or metabolic production.output occurs from excretion or consumption.balance must occur over the ling run,w/input=output |
Negative Balance | output is greater than input. net reduction in pool concentration |
Positive Balance | input is greater than output.net inc in pool concentration |
Fluid Balance | balance of h2o in the body.60% of the body is h2o w/ adipose tissue causing variation.plasma 90% water,soft tissues 70-90%,bone 22%,adipose 10% |
Intracellular Fluid | 2/3 of total body water. k+ dominated,w/protein |
Extracellular Fluid | 1/3 total body water,na+ dominated |
Plasma | 20% ECF,w/ protein |
Interstitial Fluid | 80% of ECF,no protein |
Minor ECF Components | Relatively small volumes:lymph,CSF,saliva etc |
ECF Volume Regulation | regulation of volume needed for long-term BP control.changes in BP cause shifts of fluid btw plasma and IF |
Blood Pressure Control | short term,a drop in pressure causes:auto-transfusion:movement of fluid from IF to plasma to maintain BP. changes in baroreceptor activity.long term control of vol is balance of thirst/intake and kidney fluid excretion |
Salt Intake | the kidneys need 0.5g nacl/day for fluid loss in sweat,feces,intake is 10.5 nacl/day excess excreted in urine.cl- follows na+ |
Salt Excretion | kidneys good at eliminating na+, but inc retention inc BP.must balance 10.5g/day input.fitness reduces na+ content in sweat. |
Renin-Angiotensin-Aldosterone System | long term control of na+ excretion controls BP.everyone has their own set pt. for BP. |
ECF Osmolarity Control | needed to prevent swelling or shrinking of cells.total amount of material in a vol,regardless of composition,produces its osmolarity |
Ions | na+ and k+ dominate the osmolarity of ICF and IF.other non-penetrating substances like proteins,also contribute to osmolarity.water moves by osmosis if there are diff in ICF and IF osmolarity. Normal ICF and IF osmolarity is 300 mOsm |
Tonicity | the standard for tonicity isis not the # of dissolved particles but the behavior of cells in the solution. cells saved in hypotonic solutions-ECF is rarely hypotonic. |
Hypertonicity | Cells shrink in hypertonic solution (> than 300 mOsm). dehydration-low intake,excess loss,diabetes |
Vasopressin | controls osmolarity of urine. vp adds aquaporins to collecting duct to inc water reab. |
Water Intake | fluid drinking,food intake,metabolism,add water.balance water loss from lungs,skin,sweat,feces,urine. |
Osmoreceptors | receptors in hypothalamus that control VP release inc osmolarity,inc VP release,inc h2o retention. dec osmolarity,dec VP relese,inc h2o excretion |