🛴 Nerve impulses and the motor neurone
The Myelin Sheath
Let’s delve into the basics of nervous transmission by looking at a motor neurone. Here is the structure of a myelinated motor neurone:
Labelled “insulating sheath”, the myelin sheath is responsible for protecting the electrical impulses that run across the neurone.
But first, what happens in a resting state where no impulses are being sent?
This is the resting potential where the membrane permeability differentiates between sodium (Na+) and potassium (K+) ions so that at any given time there are more Na+ ions outside than inside and more K+ ions inside than outside.
According to these electrochemical gradients, Na+ ions should move back inside to balance out their concentration (equilibrate) while K+ ions should move back outside the membrane until the concentrations are equal inside and out. This clearly isn’t the case, so what gives?
Found on the membrane there are Na+/K+ pumps which carry out active transport against the electrochemical gradient of these ions. The resting potential of the membrane is negative on the..