Lecture 2: Renal Physiology: Body Fluid Composition Flashcards Preview

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Flashcards in Lecture 2: Renal Physiology: Body Fluid Composition Deck (39)
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31

Hypotonic ECF osmolality

Decreased Na concentration outside of cells --> Relatively greater Na concentration of osmotically active particles inside of cells --> Water moves via osmosis into cell --> cells swell --> try to return to equilibrium --> (If swell excessively --> burst --> Death)
Note: swollen brain = painful
Remove water from ECF to dilute
e.g. Excessive water consumption --> body needs to remove the H2O in order to concentrate the NA --> maintains isotonic environment

32

What are concentration gradients referring to?

Relatively greater number of osmotically active particles
Water movement occurs to try and reach equilibrium again/ isotonic environment

33

Hypertonic ECF osmolality

Increased Na concentration outside of cells --> Relatively smaller Na concentration of osmotically active particles inside of cells --> Water moves via osmosis out of cell into ECF --> cells shrink --> try to return to equilibrium --> (If shrink excessively --> Death)
Note: shrunk brain = painful
Add water to ECF to dilute

34

Control of ECF Osmolality

ECF osmolality control is critical for cell survival --> tightly controlled --> varies 1-2%
ECF osmolality (salt concentration) is largely regulated by altering water levels --> more rapid response to water levels > salt levels

35

How is the Tight control of ECF osmolality regulated?

Altering water levels
--> as ECF volumes (H2O content) is primarily dependant on the amount of Na --> as Na is the most osmotically active solute in the ECF
--> results in ECF volume levels being less tightly controlled (more dynamic range of 15% regulation)

36

Maintenance of compartment sizes

1. Kidney: major regulator of water and salt homeostasis (i.e. ECF osmolality and volume)
2. Starling Forces:
- change in plasma protein levels --> change in oncotic pressure -- change in starling forces

37

Oedema

Causes: Inflammation, Obstruction (lymphatic or venous), sodium retention, Low serum albumin
--> Changes in charged/osmotically active plasma protein levels --> change in starling forces in plasma --> fluid movement into the interstitial space --> Abnormal expansion of the interstitial fluid compartment
Can be localised or general

38

Balance b/w daily intake and output for an adult at room temperature

What goes in (salt and water) = Has to come out
Water intake: Total: 2.5L
1. Drinking 1.2L
2. In Food 1L
3. Metabolism 300mL
Water Out-take: Total 2.5 L
1. Insensible 700mL
2. Sweat 100mL
3. Faeces 200mL
4. URINE 1.5L = MAJORITY URINE AND SALT OUTPUT of the body

39

Role of urine

Urine = largest components of the balanced 2.5L daily water outake = 1.5L = as urine contains the majority of urine and salt output of the body
Urine ouput and urine Osmolality VARIES --> in order to balance water and salt levels
--> allows water intake to be completely balanced by water output
Note: if water intake isnt balanced by water output --> expansion --> change in osmolality outside of 1-2% tightly regulated range --> need dialysis