graded potential vs action potential n.
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Graded potential vs action potential. graded potentials – current flow, amplitude - post-synaptic potentials Action potentials Trigger zone threshold voltage All-or-none Channel activity Refractory period Coding for stimulus intensity.

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graded potential vs action potential
Graded potential vs action potential
  • graded potentials – current flow, amplitude

- post-synaptic potentials

  • Action potentials
    • Trigger zone
    • threshold voltage
    • All-or-none
    • Channel activity
    • Refractory period
    • Coding for stimulus intensity
graded potential
Graded potential
  • Amplitude is directly proportional to the strength of the stimulating event
  • Depolarization wave known as local current flow
  • Strength depends on how much charge enters the cell
  • Decreases in strength as it travels through the cytoplasm
  • Can be depolarizing or hyperpolarizing
slide5

Action potential

  • Initiated if a threshold depolarization
  • is reached at the trigger zone
  • Also called a spike
  • Always the same amplitude
  • Amplitude does not diminish
  • “All or none”, essential for long
    • distance propogation
slide6

overshoot

After hyperpolarization

(undershoot)

the voltage gated na channels
The voltage gated Na+ channels
  • Has two gates: an activation gate and an inactivation gate (gate can be opened, gate can be locked)
refractory period
Refractory period
  • Another action potential cannot fire when the inactivation gate is latched.
  • Action potentials cannot overlap
  • The absolute refractory period
  • Limits the rate of spike frequency
  • Important for frequency coding
slide16

Resting membrane potential is not restored,

Na+ channel gates are unlatched (inactivation

Is removed)

no lecture on friday
NO lecture on Friday
  • Today
  • How are action potentials propagated?
  • Factors that affect conduction speed
  • The consequences of abnormal levels of extracellular K+
abnormally high levels of k will cause
Abnormally high levels of K+ will cause
  • Resting membrane potential will be shifted toward action potential threshold
  • Get too much excitation (too many action potentials)
abnormally low k
Abnormally low K+
  • Membrane resting potential hyperpolarizes
  • Cell is far away from threshold for action potential