PSL301: Water 1 Flashcards
Functions of the kidney (3)
- Maintain normal volume & composition in the body
- Excrete waste from body
- Maintain BP, hemoglobin, Ca++ levels through hormone secretion
What is the main waste secreted by the kidneys?
Products of protein metabolism
How does the kidney maintain normal volume & composition in the body?
filter large volumes of plasma, water, solutes at the glomerulus
The kidney clears ___x the total plasma volume every day
40
How does the kidney Excrete waste from body?
filtered fluid goes through tubules: add or remove water & solutes to form final urine product
How does the kidney Maintain BP, hemoglobin, Ca++ levels?
Secretes hormones in response to changes in BP, hemoglobin, Ca++
Case: slow marathon runner with headache, nausea, vomit, grand mal seizure, hyponatremia
What’s wrong?
Cells in brain swell due to hyponatremia:
- increase intracranial pressure; parts of brain get compressed
- seizure, coma, death
Case: slow marathon runner with headache, nausea, vomit, grand mal seizure, hyponatremia
How to treat?
Give IV (hypertonic saline solution)
- raise Na+ in ECF
- water move out of brain cells
define: solutes
particles dissolved in a water solution
define: electrolytes
charged solutes
define: osmolarity
concentration of solutes in water which generates an osmotic force
define: osmosis
movement of water across semi-permeable membrane in response to an osmotic gradient
Water moves from __ osmolality to __ osmolality
low
high
define: osmotic gradient
a difference in the osmolality in the compartments separated by the membrane
Humans are __ % water
50 - 60
Body water is split into…
- intracellular space (2/3)
2. extracellular space (1/3)
ECF is split into…
Plasma (25%) Interstitial fluid (75%)
What is ISF?
Fluid outside both the cell and the blood stream
Plasma is bordered by…
Cells are bordered by…
Capillary walls (endothelial cells) Cell membrane
What factor determines body water as a fraction of weight?
Ratio of fat : muscle
__ contains most of the water in the body, while ___ has very little water.
Muscle
Fat
On average, the fat:muscle ratio is higher in…
- women
- older people
- sick people
Males are __% water, while females are __%
60
50
Why do males have more water than females?
They have more muscle
What solutes are present in body fluids?
- ions/electrolytes
- fuels
- proteins
- waste products
cations in body fluids include…
- Na
- K
- Ca
- Mg
anions in body fluids include…
- Cl
- bicarb
- phosphate
- protein
Which 2 ions balance?
Na and Cl
fuels in the body fluid include..
- glucose
- lactate
- AA
- ketones
proteins in body fluids include…
- albumin
- globulins
- hormones
waste products in body fluids include…
- urea
- creatinine
- uric acid
…
Na is more abundant in the…
plasma
K is more abundant in the…
ICF
Ca is more abundant in the…
plasma
Cl is more abundant in the…
plasma
bicarb is more abundant in the…
plasma (slightly)
proteins & phosphates are more abundant in the…
ICF
What maintains the neg charge inside cells?
- proteins & phosphates
- cell more permeable to K than Na (RMP closer to K equilibrium potential)
proteins & phosphates are not found..
ISF
ICF has a ___ charge compared to ECF
neg
___ is the same between the ECF and ICF because…
Osmolality
water cross membrane through water channels when there is an osmotic gradient
Define: osmolality
particles per volume
How is the difference between ICF and ECF generated?
- Na/K ATPase
- Neg proteins that can’t leave the cell
- Ion channels
The Na/K ATPase pumps…
2 K into cell
3 Na out of cell
the RMP is…
-70 mV
When ATP is hydrolyzed at the Na/K ATPase, what happens?
Brings 3 Na from inside cell to ECF
Why are ionic gradients across cell membrane important?
- nerve conduction
- muscle contraction
- pacemaker activity
- transport in the body
- cell signalling
Which ion is responsible for cell signalling?
calcium
Example of cell signalling?
secretion of insulin
why are ionic gradients important for transport?
water follows Na+, so Na/K ATPase important for building Na+ gradient
Mechanism of insulin secretion
- Glucose starts cell respiration
- More ATP inside cell
- High ATP closes K+ channels
- Inside of cell becomes positive (depolarize)
- Ca++ channels open, Ca++ comes into cell
- Ca++ triggers exocytosis of insulin vesicles
3 rules of ECF/ICF volume
- Sodium is always in the ECF
- WATER is the one that moves across cell membrane
- Regulate body osmolality by drinking/excreting WATER
What hormone is used to make us secrete water?
inhibit ADH (vasopressin)
ECF volume depends on…
amount of Na+ in body
ICF volume depends on…
ECF Na+ concentration
Effect on ICF: hyponatremia
increased volume (big things are hyp(obese))
Effect on ICF: hypernatremia
decreased volume (small things are hyper)
Relationship between ICF volume and [Na+]
negative
Water flux at capillaries is determined by…
Starling forces
- hydrostatic pressure
- osmotic pressure
There is ___ g/L of albumin in plasma
40
Albumin provides…
oncotic pressure
Formula: fluid flux
permeability x (hydrostatic pressure gradient - oncotic pressure gradient)
Jv = Kf (hydrostatic - oncotic)
Hydrostatic pressure is generated by…
pumping action of the heart
___ > ___, and the lymphatic system is used to bring excess ISF back to circulation
filtration
absorption
What is net ex-flux?
3L/day
causes of edema
- increased hydrostatic pressure (heart failure)
- decreased albumin in plasma (liver failure)
- increased capillary permeability (allergy, trauma)
- lymphatic obstruction
Ways to determine ECF
Plasma volume:
- jugular venous pressure
- BP
ISF volume:
- edema
Where is the jugular venous pressure measured?
At external jugular vein
What is a cause of distension at the jugular venous pressure?
coronary bypass operation
ECF volume can be determined by ___, but ICF can’t.
clinical / physical test
How is ICF volume determined?
Looking at serum Na+ and osmolality
Case: slow marathon runner with headache, nausea, vomit, grand mal seizure, hyponatremia
What did the runner do to cause this?
- Excessive water intake
- Stimulate ADH release (??)