Lecture 2, Chapter 4&7 Flashcards
What is diffusion?
Random movement of molecules from high energy state to lower total energy
Find some reading on membrane potentials is highly recommended!
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What are the driving forces acting on solutes that determine net diffusion?
- Chemical (concentration gradient high to low)
- Electrical (charge attraction) opposite ions attract. Only important for charge particles like ions (K+, Na+, Cl-)
Ions can move in or out regardless of the chemical or electrical gradients but must think of ______ diffusion
Net
Does glucose have a charge?
No not charge but polar just like water, so glucose is only affected by chemical gradients
Charged molecules are affected by what type of gradients?
Both chemical and electrical gradients
* electrochemical gradient
Can a electrical gradient overpower a strong chemical gradient?
Yes
Separation of charge across a cell membrane. Difference between outside and inside the cell
Membrane potential. Produces a voltage measured in millivolts
A difference in voltage between two points?
Potential difference = E
Difference in voltage across the plasma membrane, always given in terms of voltage inside the cell relative to voltage outside the cell.
Membrane potential***
Difference in voltage across the plasma membrane when I saw is at rest, not receiving or sending signals
Resting Vm
A relatively small change in membrane potential produce by some type of stimulus that triggers the opening or closing of ion channels, strength is relative to strength of stimulus
-dif. Levles
Graded potential
Graded potentials produced in the post synaptic cell in response to neurotransmitters binding to receptors
Synaptic potential
Graded potentials produced in response to a stimulus acting on a sensory receptor.
(Hands, touch receptors, sensory neuron)
Receptor potential
A large, rapid change in membrane potential produced by depolarization of an excitable cells plasma membrane to the threshold.
(Pain- three for small pain, 50 for intense pain, how many and how often…)
Action potential
The membrane potential that counters the chemical force acting to move an ion across the membrane, thereby putting the ion at equilibrium
Equilibrium potential
The millivolts at which an action potential is initiated.
Threshold potential***
Potential that will generate an action potential
Threshold potential?
A cell is in equilibrium and has equal concentrations of sodium and potassium and chloride between inside and outside in what case?
Only when the cell is dead
The cell membrane is completely impermeable to sodium potassium and chloride but the membrane contains….
Na+,K+ pumps (uses ATP to pump)
2 K+ in and 3 Na+ out**
What is the primary active transport on the cell membrane?
What charge does it create on the inside and outside of the cell?
Sodium potassium pump
This will cause more negative inside the cell and positive on the outside of the cell
What if a typical cell is only permeable to potassium (K+)?
The electrical and chemical gradient will eventually reach equilibrium
Hypothetical membrane potential where the chemical an electrical gradients for the ions are equel opposite
Equilibrium potential
What is the Nernst equation?
E(ion) = (61mV/z) log [I]o/[I]i
E= equilibrium potential of ion I
Z= valence of ion I
[I]o=ECF Concentration of ion I
[I]i=ICF concentration of ion I 
If the particular ion equals that calculated concentration then it is in equilibrium
