Ch.2 Electrical Signals of Nerve Cells

what is current?

flow of electric charge that is carried by ions

what is the potential difference?

electrical charge between the inside and outside of a neuron

what is the resting potential of a membrane?

-70mV, the neuron’s difference in electrical potential when the cell is not firing a signal, the inside is more negative than the outside

how is an electrical signal measured?

salt saturated pipette is inserted into a neuron, interior voltage is compared to the outside

what is the concentratoin gradient?

gradient of ion distribution between two sides, high to low

what is selective membrane permeability

only a certain amount of ions or types of ions can cross the membrane

what is an action potential?

all-or-none response, a certain membrane voltage is needed for a neuron to fire a signal

what is electrochemical equilibrium?

no ion movement and no change in voltage, KCl concentration is the same on both sides of the membrane,

what is diffusion?

produced from a concentration gradient, high to low

what are some concepts for ion movement?

• ions move through open state ion channels

• positive charge attracts a negative charge and repels other positive charges and vice versa (opposites attract)

• equilibrium can be reached in a variety of net movements of charge and concentration

• conc gradient is opposed by the voltage gradient created by ion movement

what is the Nernst equation?

calculates the electrical equilibrium potential of a cell across a membrane

what is the Goldman/Goldman-Hodgkin-Katz Equation

calculates the electrical equilibrium potential of a cell across the cell membrane when more than one ion is present

what does resting potential depend on?

concentration of all ions where the membrane is permeable

what does relative concentration depend on?

concentration gradient, its permeability (K+ serves as a base line)

what are some typical concentration gradients?

• higher K+ inside

• higher Na+, Cl-, and Ca2+ outside

what is the Hodgkin-Huxley model?

explains the ionic mechanisms for giant squid action potentials

how does potassium (K+) affect resting membrane potential?

increasing K+ concentration, increases membrane potential