Local/passive Potentials Vs. Action Potentials (ap)
What "causes" a local/passive potential?
Stimulation at "input" sites disturbs resting state causing LP.
input can be from sensory receptors or chemical receptors, on dendrites or soma
size of LP is graded with intensity of input
As LP moves across membrane, it decays with time and distance.
What "causes" an action potential?
Define the role of "threshold"
Define the roll of the axon hillock in this process
If the LP reaches the AXON HILLOCK with enough intensity to increase the membrane potential to threshold AP is initiated. The threshold is the "magic number" that allows the message to move across. The role is to determine whether or not to initiate the AP
The AXON HILLOCK- is an integration point where it connects. If the Local Potential reaches the Axon Hillock with enough intensity to activate the threshold an AP is conducted. When it is conducted it doesn't lose strength as it moves down the axon.
What part(s) of the cell do local potentials travel along?
The dendrites and soma
What part(s) of the cell do AP's travel along?
Axon to the axon terminal
Compare and contrast the Local Potential and Action Potential with regard to their:
Typical duration and amplitude
Where they occur on the cell
Whether they are graded or all-or-none
Whether they decay with time and distance or not
LP-signaled to axon hillock, occurs on dendrites to soma, graded with intensity of input, decays with time and distance
AP- signaled from hillock to next neuron for Synaptic transmission, occurs on axon to terminals, all-or-none, conducted with no loss of strength
How does the PP convey information about the intensity of the stimulus? How does the AP convey information about intensity of the stimulus?
The PP conveys information about the intensity of the stimulus by grading the size of the PP(The amplitude). Size of LP is graded with intensity of input.
The AP conveys information about the intensity of the stimulus by frequency