Toothpaste tube experiment
cut nerves out of squid, put on rubber platform, squeezed all axons from nerve process (fundamental to learning how nervous system works)
Ion concentration across axonal membrane
sodium much higher in ECF, potassium much higher in ICF
Why do all animal cells have similar ICF and ECF salt contrations
#NAME?
What is the cellular basis of a membrane's separation of charge?
-lipid core allows for charge separation (capacitance)
-ion channel allows the charge to flow through membrane (conductance)
-Membranes have a negative charge on inside, positive charge on outside, separation of charges is a voltage -> voltage is membrane
Passive transport
diffusion across a biological membrane is driven by concentration
Chemical driving force
when diffusible solutes are unequally distributed, a chemical driving force will move them down their gradient
Equilibrium potential
When chemical driving forces are exactly balanced by electrical driving forces, an equilibrium is reached
How are unequal ion concentrations maintained?
#NAME?
What does the Nernst equation calculate?
The equilibrium potential for an ion
Nernst Potential
The equilibrium potential for any ion, where the separation of charge across a cell membrane, the electrical driving force is opposite to the chemical driving force produced by the ion gradient
Why is the Nernst equation not applicable to real neurons?
Real neurons have more than one type of ion, which have some permeability
Which ion species contributes most to Em of a real neuron? Why?
Potassium--it is the most permeable ion
Why are neuronal membrane potentials ~80mV?
Potassium dominates the resting membrane potential of neuronal membrane, and this is close to potassium's resting membrane potential
Goldman (Hodgkin-Katz) equation
#NAME?
What two major factors contribute to the membrane potential?
#NAME?
Why are membrane potentials important for neurons?
Transient alternations in membrane potential, called electrical signals, are used to encode and communicated information in an animals nervous system