1. Depend on passive properties of membrane

2. Spread electronically over short distances

3. Initiated by local current flow and decay with distance from their site of initiation

1. An electrical signal that propagates over a long distance and without a change in amplitude

2. Depend on regenerative wave of channel openings and closings in the membrane

3. A transient change in membrane potential characterized by rapid depolarization followed by rapid repolarization

4. Depolarization due to rapid activation of voltage-gated sodium channels

1. Are always open

2. Responsible for the influx of Na+ and K+ when neuron is in resting state

3. Found throughout the neuron

1. Directly or indirectly activated by binding of chemical NTs to membrane receptors

2. When NTs bind to their receptors, the associated ion channels can either open or close to permit or block the movement of specific ions across the cell membrane

3. Found on dendritic spines, dendrites, and somata

1. Open when force (stretch) is applied across a membrane and close when the stretch is removed

2. Found in specialized sensory cells or peripheral branches of pseudounipolar sensory neurons

1. Sensitive to voltage difference across the membrane

2. In initial resting state, these channels are typically closed adn open when a critical voltage level is reached

3. Found on axons and axon terminals

1. Approximately -60mV relative to ECF

2. Reflects steady-state situation (which develops when more than one ion is permeable)

When membrane potential becomes more negative

When membrane potential moves from Em at rest towards zero (or above)

1. The ease with which ions flow across the membrane through their channels

2. The greater the conductance, the greater the flow of ions

3. Conductance is the inverse of resistance

4. Conductance is a constant value, determined in part by relative size of ion with respect to that of the channel and the charge distribution within the channel

The greater the resistance, the lesser the flow of ions

1. The membrane's ability to store an electrical charge

2. Consists of 2 conductors separated by an insulator

3. Positive charge accumulates on one of the conductive plates, while negative charge accumulates on the other plate

4. The biological capacitor is the lipid bilayer of the plasma  membrane, which separates 2 conductive regions, the extracellular and intracellular fluid

5. Positive charge accumulates on extracellular side, while negative charge accumulates on intracellular side

6. As capacitance increases, the pull that holds the charges together is stronger

7. As capacitance decreases, less pull, and thus charges are more easily displaced

Transmembrane currents derived from ions moving through leakage channels in the membrane along concentration and voltage gradients

Accumulation or repulsion of charges (ions) from the membrane without crossing the membrane

1. The distance at which the initial transmembrane voltage change has fallen to 37% of its peak value

2. Depends on the internal axoplasmic resistance and on transmembrane resistance

Decreases with increasing diameter of the axon or dendrite, thus more current will flow farther along inside of the cell, and the length constant is larger for smaller dendrites or axons

The greater the transmembrane resistance, the less current leaks out and the length constant is larger, and the larger the length constant, the farther along the membrane a voltage change is observed after a local stimulus (ionic current) is applied

1. The time required for the membrane potential to change after a stimulus is applied

2. Charge is delivered more rapidly when resistance is low

1. Also called axon hillock

2. High density of voltage-gated ion channels

3. Initiation site for AP

A critical membrane potential to cause AP

When the membrane potential reverses, with the inside becoming more positive (due to influx of sodium ions)

Inactivates voltage-gated channels (at the peak of an AP, sodium conductance begins to fall as an inactivation gate closes)

Alterations in voltage-gated sodium and potassium channels, as well as in voltage-gated calcium channels adn chloride channels that are the basis of disease of nerve and muscle

The speed at which action potentials are conducted, and increases as a function of increasing axon diameter and concomitant increase in the length (space) constant

1. Axons larger than 1 micrometer are myelinated, and the thickness of the myelin increases as a function of axon diameter

2. Myelin increases resistance of axonal membrane

3. Increased resistance of axonal membrane increases the length constant

4. Layers of  myelin decrease the effective capacitance of the axonal membrane because the distance between the extracellular and intracellular conducting fluid compartments is increased

5. Voltage-gated Na+ channels are highly concentrated in Nodes of Ranvier

Action potential in a myelinated axon appears to jump at neighboring nodes of Ranvier, resulting in faster conduction velocity

1. When the initiationof additional action potentials requires a greater degree of depolarization

2. Inactivation gate of a portion of the voltage-gated Na+ channel is open

1. When the initiation of additional action potentials cannot be initiated at all (due to the state of the voltage-gated Na+ channel-inactivation gate)

2. Limits the rate of firing of action potentials

3. Prevents action potentials from traveling in wrong direction along the axon

1. Open with depolarization from AP, causing rapid influx of Ca++ into presynaptic terminal

2. The influx of calcium causes NT-filled vesicles to fuse with the synaptic membrane and release contents into extracellular space, where it binds to ligand-gated receptors on the post-synaptic cell

Channels that open in response to NT from pre-synaptic cell, and alter the membrane potential of the post-synaptic cell