Fluid Compartments (1) Flashcards
Total body water
60% of body weight
= 42 L
ECF
20% of body weight
= 14 L
ICF
40% of body weight
= 28 L
Interstitial fluid
3/4 of ECF
= 10.5 L
Plasma
1/4 of ECF
= 3.5 L
Measurement of volume of fluid compartments
Dilution method
Adding tracer, allow mixing, measure concentration
Volume = Mass / Conc.
Dye for Total fluid compartment
Deuterium
(Hydrogen isotope)
Dye for ECF
Inulin
Dye for Blood plasma
Evans-blue
(binds albumin)
Na+ E/ICF
ECF: 135 - 147 mM
ICF: 10 - 15 mM
K+ E/ICF
ECF: 3.5 - 5.0 mM
ICF: 120 - 150 mM
Ca2+ E/ICF
(Total)
ECF: 2.1 - 2.8 mM
ICF: 100nM
Ca2+ E/ICF
(Free)
ECF: 1.1 - 1.4 mM
ICF: 100 nM
Cl- E/ICF
ECF: 95 - 105 mM
ICF: 20 - 30 mM
HCO3- E/ICF
ECF: 22 - 28 mM
ICF: 12 - 16 mM
Oncotic Pressure
Osmotic pressure of proteins
- Proteins are superosmols
Hyposmotic / Hypotonic
Cell volume increases
Hyperosmotic / Hypertonic
Cell shrinks
Isosmotic urea solution
Eventually Hypotonic due to movement of Urea into cell (permeable) causing hypotonicity and cell to swell
Osmolarity of most human body fluids
290 mOsm/L
2 Types of Protein mediated transport
- Carriers
- Channels
Carriers
- Slow
- Can saturate
- Active
Channels
- Fast
- Can’t saturate
- Passive
Primary vs Secondary active T
- Prim: Pump
- Sec: Coupled Active + Passive
Electrogenic vs Electroneutral T
Electrogenic T creates net charge across membrane
Facilitated diffusion
- Faster than free diffusion
- Passive
- Specific
- Integral pm protein
Aquaporins
Water transport across membrane
- 11 isoforms
- Passive
Special about GLUT4
Insulin dependent
(activates it)
GLUT 5
Transport of Fructose along with glucose
GLUT2 mech
Regulates glucose levels based on plasma glucose concentration, unlike GLUT1 which works constantly
Anion exchanger
Cl- / HCO3-
- RBCs fro CO2 transport
- Passive
- Electroneutral
- Antiporter
Na+ / K+ ATPase
- 3Na out, 2K in
- Electrogenic
- Inh: Ouabain
- In all cells
3 Ways to regulate Transporters
(in order of speed)
1) Activity (phosphorylation)
2) Trafficking (vesicle storage)
3) Expression (gene exp.)
Calcium ATPase
(SERCA)
Responsible for low cytoplasmic Ca levels
- Electrogenic
- SR & SER
- 2 Ca2+
ABC Transporter
Active transport of Hydrophobic compounds (Cholesterol, Bile,…)
- Responsible for multi-drug resistance of cells
- CFTR
2 Types of Exocytosis
- Constitutive: Non-regulated continuous
- Regulated secretory pathway (intracellular signalling)
Second messenger-gated channels
Controlled by changes of intracellular signaling molecules (cAMP, IP3)
- Sensors on IC membrane
VG Ca channels a1 subunit
a1 subunit forms ion pore
5 Types of VG Ca channels
- L-Type (long-lasting)
- T-Type (transient)
- N-Type (neuronal)
- P-Type (purkinje)
- R-Type (residual)
N-type VG Ca channel
For Synaptic NT release in Brain and PNS
- High activation voltage
T-type VG Ca channel
- SA node
- Pacemaker activity
- Low activation Voltage
L-type VG Ca channel
- Skeletal, SM, Myocytes Contraction
- High activation Voltage
Neurons Em
-70 mV
Skeletal muscle Em
-90 mV
RBC Em
-10 mV
Diffusion potential
Potential difference generated across a membrane when an ion diffuses down its conc. gradient
- Magnitude depends on size of con. gradient
Equilibrium potential (Eion)
Membrane potential when the net ion flow through an open channel is 0
What can we use to calc Eion
If we know ion conc. on both sides of a membrane and there is no net flow of the ions across the membrane,
= Nernst Equation
Relative permeability of Na, K, Cl
K: 1.0
Na: 0.01
Cl: 0.1
What happens if the permeability of an ion changes
The membrane potential will change in the direction of the equilibrium potential of that ion
Eion of ions K, Na, Cl, Ca
K: -94 mV
Na: +65 mV
Cl: -88 mV
Ca: +130 mV
Donnan Potential
Electric potential when impermeable ions (large molecules) create charge imbalance bw 2 compartments leading to unequal distribution of permeable ions
Action Potential
A spreading wave of VG Na+ Channel activation (all-or-none)
Spreads without Decrement
Rapid, Transient, Self-propagating.
Electrotonic potential
+ Examples
A localized change in the membrane potential in response to a stimulus.
Spreads with Decrement
- EPSP
- IPSP
- Receptor pot.
(size and duration proportional to the stimulus)
Receptor Potential
Change in Voltage across a receptor membrane proportional to the Stimulus Strength resulting in Inward current flow
- Sensory receptor
Length/Space constant
The distance over which the change in potential decreases to a factor 1/e of its maximal value
Higher S.C = Faster conduction
What type of signal is an AP
Digital signal
(all-or-none)
What type of signal is a Graded Electrotonic Potential
Analog
(electric pulses of varying amplitude)
How does AP form in relation to Electrotonic potential
AP is a result of Electrotonic potential which reaches the threshold voltage and stimulates VG ion channels
What is normal threshold potential of a cell for AP
-50 mV
Absolute refractory period
- Inactivation of VG Na channels
- No AP can form no matter the strength of the stimulus
Relative refractory period
- Hyperpolarization due to K+ channels
- Very strong stimulus needed to overcome the negative charge