Passive current flow in dendrites and cell bodies

- dendrites extend 0.5 to 1 mm in all directions from soma and receive signals from a large area
- 80-90% of all presynaptic terminals terminate on dendrites
- most can't produce action potentials (too few or no Na+ channels)
- transmit current by passive spread down dendrites to the soma
- therefore the membrane potential decreases as move along dendrite due to current loss thanks to our friends ri, rm and cm
- because dendrites have no voltage gated Na+ channels (few exceptions to this rule) and cell bodies have little or no voltage-gated Na+ channels current flow is solely dependent on the Cable Properties of the dendrites and soma - called cable because analogous to properties of long copper telecommunication cables