ACTION POTENTIAL

1
ACTION POTENTIAL

• NEURONAL ACTION

2
ACTION POTENTIAL

• ACTION POTENTIALTHE FIRING OA NEURON WHEN
  DEPOLARIZATION CAUSES A CHANGE IN THE RATE OF
  ENTRY OF SODIUM (Na) TO INTERIOR OF A CELL
• DEPOLARIZATIONOPENING OF INSIDE TO OUTSIDE OF
  THE CELL MEMBARANE. OCCURS PRECEEDING ACTION
  POTENTIAL.
• ELECTRICAL GRADIENTDIFFERENCE BETWEEN
  ELECTRICAL CHARGE ACROSS CELL MEMBRANE. INSIDE
  IS NGATVELY CHARGED (-) OUTSIDE IS POSITIVELY
  CARGED (). POTASSIUM (K) IS INSIDE OF CELL AND
  SODIUM (Na) IS OUTSIDE. Na AND K WILL
  INTERCHANGE AS THE CELL MOVES FROM A POLARIZED
  RELAXED STATE, ALSO KNOWN AS THE RESTING
  POTENTIAL (MORE NEGATIVE CHARGE INSIDE) TO A
  DEPOLARIZED STATE AS THE CELL FIRES AND THE
  ACTION POTENTIAL STARTS.

3
ACTION POTENTIAL

• REFRACTORY PERIOD1 MILLISECOND ACTION POTENTIAL
  WHEN THE NEURON WILL NOT FIRE AND IS RESITANT TO
  EXCITATION.
• RELATIVE REFRACTORY PERIODSTIMULUS MUST BE
  POWERFUL ENOUGH TO PRODUCE THE ACTION POTENTIAL.
• RESTING POTENTIALPOLARIZED NEURON READY TO
  FIRE.
• ALL OR NONE PRINCIPLE OR LAWALL THE EXCITED
  CELLS WILL FIRE WITH EQUAL (OR APPROXIMATE) SIZE
  OF AMPLITUDE IN NORMAL CIRCUMSTANCES.
• ABSOLUTE REFRACTORY PERIODTHE CELL WILL NOT
  FIRE WITH ANY STIMULUS.

4
ACTION POTENTIAL

• STEP 1
• THE PRECEEDING NEURON SENDS NEURTRNSMITTERS TO
  RECEIVING SITES ON THE DENDRITES.
• STEP 2
• ENOUGH RECEPTOR SITES ARE FILLED WITH THE
  MATCHING NEUROTRANSMITTER TELLING THE NUCLEUS OF
  THE CELL TO FIRE
• STEP 3
• THE THE CELL FIRING STARTS AND FLOWS THROUGH THE
  AXON TO THE AXON TERMINALS. DONE BY ACTION OF
  SODIUM-POTASSIUM PUMP (2 Na let out and 3 K let
  in).
• STEP4
• THE AXON TERMINALS OPEN OR CLOSE DEPENDING ON THE
  STREHGTH OF THE IMPULSE AND MESSAGE AND SEND
  NEUROTRANSMITTERS TO THE NEXT RECEIVING SITES TO
  START THE PROCESS OVER AGAIN