potential difference

a measure of the potential energy that must be used to move a positive charge from one location to another.

current

the rate at which positive charges move between two locations that have a potential difference.

conductance & resistance

conductor is a material that permits movement of electric charge. resistance is how strongly a material opposes current flow.

capacitance

the ability of a structure to store electrical charge.

mechanisms for maintaining the concentration gradient for ions between the inside and outside of a cell

ion transporters and pumps

pores/openings in the cell membrane

ion channels.

three ways that ion channels open and close

1. conformation change in one region. 2. general structural change. 3. a blocking particle.

four types of gating mechanisms in ion channels

1. voltage gating. 2. ligand gating. 3. stretch or pressure gating. phosphorylation gating.

difference between ion channels & ion transporters

transporters use a source of energy to actively transport ions against the gradient. transporters move ions at lower rates than channels, too low for fast neural signalling.

action potential definition

a rapid, transient change in membrane potential. they occur in editable membranes and enable long distance signalling.

four properties of of an action potential important for neuronal signalling.

1. they can be initiated only when the cell membrane voltage reaches a threshold. 2. an all or nothing event. 3. conducted without decrement. 4. followed by a refractory period.

typical membrane voltage threshold

-50 mV.

myelinated and unmyelinated axons speed

unmyelinated signals are slower. myelinated signals are faster due to the node of ranvier.

the two refractory periods.

absolute & relative periods.

synapse

joint between a presynaptic neuron and postsynaptic cell.

components of a synapse

1. terminals of the presynaptic axon. 2. a target on the postsynaptic cell. 3. a zone of apposition.

two types of synapses

electrical, no delay, bidirectional. chemical, 0.3-1.5ms of delay, unidirectional.

electrical synapses are found

in the brain for attention, memory & perception. brainstem & spinal cord for reflexes and motor coordination. retina for spatial integration.

Gap junctions

ions travel through gap junctions channels called connexons.

four neurotransmitter types

amino acids, amines, acetylcholine, neuropeptides.