Basic Concepts in Physiology Flashcards
what are excitable tissues?
- tissues composed of cells that are capable of producing action potentials
definition of homeostasis
- a relatively stable condition of the internal environment that results from regulatory system actions
the average adult male weighs how much
- 70 kg
- 154 lb
total body water is
- 42 L
water is what percent of body weight
- 55-60%
total body water divided into what compartments?
- intracellular
- extracellular
volume of intracellular compartment compared to extracellular compartment
- about 2x
blood fills which compartment
- blood spans both intracellular and extracellular fluid
plasma exchanges with
- interstitial fluid
interstitial fluid exchanges with
- intracellular fluid
osmolarity
- the total solute concentration of a solution regardless of the chemical composition of the solutes
osmolarity is measured in
- osmoles/L
1 osmole =
- 1 mole of solute
1 osmole/L =
- 1 Osm
Osmolarity of NaCl
- 2
osmolarity of CaCL2
- 3
the osmolarity of a human cell is
- 275-295
less than 275 mOsm
- hypoosmotic
275-295 mOsm
- isoosmotic
more than 295 mOsm
- hyper osmotic
how is osmotic concentration expressed clinically
- osmolality = osmoles/kg
effective osmolarity =
- tonicity
water concentration in regard to osmolarity
- higher osmolarity has lower water concentration
water versus solute permeability in a cell
- water is permeable
- solutes are not
what happens in a hypertonic solution?
- cell shrinks
what happens in an isotonic solution?
- no change in cell volume
what happens in a hypotonic solution?
- cell swells
one of the most powerful features of the cell
- separation of charges across a semipermeable membrane
intracellular anions are mostly
- protein
extracellular anions are mostly
- Cl-
which cation is mostly prevalent inside the cell
- K+
which cation is mostly prevalent outside of the cell?
- Na+
concentration gradient of K+
- from inside of cell to outside
electrical gradient of K+
- develop inside negative membrane potential
result of negativity inside membrane
- begins to oppose further diffusion of K out of the cell
result of buildup of positive charge on outside of membrane
- begins to oppose further diffusion of K out of the cell
Nernst equation helps us determine
- equilibrium potential for a given ion
Nernst equation
- Ex=(60/z) * log(X out/X in)
x = is ion
z = charge of ion
X out = concentration of x in ECF
X in = concentration of X in cytoplasm
when does the Nernst equation apply
- when a membrane is permeable to only one ion
equilibrium potential for K+
-85.6 mV
equilibrium potential for Na+
+59 mV
equilibrium potential for Ca2+
+122 mV
equilibrium potential for Cl-
-82 -> -46 mV
biological membranes are permeable to
- not typically permeable to only one ion
2 major factors for determinants of membrane potential at any given time
- ion gradients
- relative permeability of membrane to those ions
Goldman-Hodgkin-Katz equation applies to
- multiple ions and their permeabilities
resting Em Na+ and K+ channels
- some Na+ and some K+ channels are open
Em in resting Em
- is between E_Na and E_K
- closer to E_K
- generally -40 -> and -85 mV
which ion has greater permeability at rest
- permeability of K
where does Na move in regard to the cell
- moves into the cell
where does K move in regard to the cell
- moves out of the cell
what happens in ATP formation is impaired
- gradients decrease which changes Em
changes in Em are signals used by
- excitable cells
where does Ca2+ move in regard to the cell?
- moves into the cell
