Week 4 ELM 8: Transmission within Neurons

Vocabulary flashcards based on lecture notes about electrical and chemical signals in neurons.

Transmission

Ability to relay signals within or between neurons. Signals are electrical within neurons and chemical between neurons.

Attenuation

The loss of signal strength over a distance.

Length Constant (λ)

The distance over which the voltage drops to 37% of its original value.

Rm (Membrane Resistance)

The resistance of the neuron's membrane to current flow. Increase → better insulation

Ri (Internal Resistance)

The resistance inside the neuron to current flow. Decrease → better conduction cores

Myelination

The process of insulating axons with myelin sheaths to increase the speed of signal transmission.

Node of Ranvier

Gaps in the myelin sheath where action potentials are regenerated. High density of channels in node decreases rise time of AP

Saltatory Conduction

The process of action potentials jumping from one Node of Ranvier to the next, speeding up transmission. A “wave” of action potentials interspersed by segments of rapid cable conduction

Dendrites

Branched extensions of a neuron that receive signals from other neurons. When current is injected into it, the current decreases over time and distance

Axon

The long, slender projection of a neuron that conducts electrical impulses away from the cell body. When current is injected in it, it remains relatively constant over time and distance.

Cable theory

A model that describes how electrical signals propagate through the neuron's processes based on their resistance and capacitance.

Reason for big length constants and 3 components of LC

To get efficient transmission you want cables with big length constants. It depends on Rm, Ri, and diamter

Why is attenuation not a big problem in dendrites

Short distances are involved and there are many inputs

What is the key to non-attenuated transmission in axons

an AP wave, axons have a far higher density of sodium channels than dendrites

What is the mechanism of myelination

It increases conduction velocity. It decreases the current leaks (taping a leaky hose)