What happens from the site of a local potential
It spreads passively away from initial site
How big are local potentials
Small - typically a few mVs
What does it mean “local potentials are graded”
Vary in size and duration in relation to strength and duration of stimulus
How are local potentials conducted
Passively through diffusion
Decremental
Decrease in size with distance from initiation site
where can local potentials arise
At any point on a cell membrane
Electrotonic spread
Exponentially over a distance determined by cell properties
Lambda
Distance over which response decays to ~37% of original size (V0)
Lambda determinants
- resistance to flow of charge across the membrane and within the neuron
Large lambda
Signals spread far
Small lambda
Signal dissipates quickly
Local potential summation
Different local potentials can add or cancel each other
Summation function
Used to integrate information and do computations
Types of summation
- temporal summation
- spatial summation
Temporal summation
Summation of local potentials from the same input that occur close together in time
Spatial summation
Summation of local potentials that occur close enough together in space from different inputs
Which kinds of signals can contribute to temporal summation
Either EPSPs or IPSPs
- can’t be a mix as it’s all from the same input
Which kinds of signals can contribute to spatial summation
Can be a mix of EPSP and IPSP
