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Neural Communication. Action Potential Lesson 11. Action Potentials. Large and rapid change in membrane potential electrically-gated channels EPSPs threshold potential Occurs in axon triggered at axon hillock ~. axon hillock. AP Characteristics. Voltage-gated channels

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neural communication

NeuralCommunication

Action Potential

Lesson 11

action potentials
Action Potentials
  • Large and rapid change in membrane potential
  • electrically-gated channels
  • EPSPs
    • threshold potential
  • Occurs in axon
    • triggered at axon hillock ~
ap characteristics
AP Characteristics
  • Voltage-gated channels
  • All or none
  • Slow
  • Non-decremental
  • Self Propagated
    • regenerated ~
slide5

+40

0

-55

-65

-75

Time

Vm

slide6

+40

0

-55

-65

-75

Time

Vm

slide7

+40

0

-55

-65

-75

Time

Vm

slide8

+40

0

-55

-65

75

Time

Vm

slide9

+40

C & E gradients

drive Na+ into cell

Depolarization

Na+ influx

0

Vm

-55

-65

-75

Time

slide10

+40

= 105 mV

Amplitude

Depolarization

Na+ influx

0

- 65 mV to +40 mV

Vm

-55

-65

-75

Time

slide11

+40

Repolarization

K+ efflux

0

Vm

-55

-65

-75

Time

slide12

After-

hyperpolarization

+40

0

Vm

-55

-65

-75

Time

refractory period
Refractory Period
  • after AP
    • won’t fire again
    • relative & absolute
  • Relative
    • during after hyperpolarization
    • requires greater depolarization ~
absolute refractory period
Absolute refractory period
  • Na+ channels deactivate
    • will not trigger AP
    • must reset
  • Ball & Chain Model ~
frequency code
Frequency Code
  • Pattern = Intensity of stimulus
    • frequency of APs
  • Place = type of stimulus
    • Visual, auditory, pain, etc.
    • Brain area that receives signal
    • Doctrine of Specific Nerve Energies ~
slide19

1.

2.

3.

FREQUENCY CODE

Weak stimulus

Moderate stimulus

Strong stimulus

saltatory conduction
Saltatory Conduction
  • Myelinated neurons
    • oligodendroglia & Schwann cells
  • Transmit long distances
    • APs relatively slow, regenerates
    • EPSPs - fast, decremental
  • Saltatory: combines both types of current
    • speed without loss of signal ~
saltatory conduction21
Saltatory Conduction
  • Nodes of Ranvier
    • action potentials
  • Myelinated
    • like electricity through wire
    • decremental but triggers AP at next node
  • Safety factor - trigger AP across 5 nodes
    • .2 - 2 mm apart
      • larger neurons  farther apart ~
slide22

Saltatory Conduction

Nodes of Ranvier

psps vs aps
Graded

Summation

longer duration

*10-100 msec

chemical-gated

passive spread

instantaneous

decremental

All-or-none

short

1-2 msec

voltage-gated

propagated

slow

nondecremental

PSPs vs APs