COGNITIVE SCIENCE 17

The Electric Brain

Part 2 Jaime A. Pineda, Ph.D.

Phases of the Action Potential

Firing threshold is the point at which the number ofactivated Na+ channels > inactivated Na+ channels

Absolute refractory period

Relative refractory period

Nodes of Ranvier

Initialsegment

Advantages of myelination

• Reduces number of ion channels

• Reduces number of Na+ / K+ pump

• Increases speed of conduction

• Reduces energy needs

Saltatory Conduction

Exocytosis

RECEPTORS

Ionotropic Metabotropic

Ionotropic

Metabotropic

Form a channel

Ionotropic Receptor

agonist

antagonist

Metabotropic Receptor

(leads to openingof channel)

Upregulation

Downregulation

Changes to Postsynaptic Receptor Density as a Function of the Amount of Neurotransmitter Released