Types of Neurons
Myelination
Myelinated neurons are wrapped in a myelin sheath made of a fatty substance called
myelin
Individual cells in the myelin sheath are called Schwann cells
Each Schwann cell wraps around the neurone so there are several layers of membrane
and cytoplasm making up the sheath
The Schwann cells prevent the movement of ions across the neurone membranes and
insulate them from other neurones
Between Schwann cells are gaps called Nodes of Ranvier
Movement of ions can occur at nodes of Ranvier
Action potentials jump from one node of Ranvier to the next, increasing the speed of
transmission
Myelinated neurones conduct much faster than non-myelinated neurones
Saltatory Conduction
Action potentials travel along a neurone by localised depolarisation – the impulse
causes voltage gated sodium ion channels to open which allow sodium to diffuse in and
open the next voltage gated sodium ion channel
In myelinated neurones, the action potential jumps between nodes of Ranvier and only
has to polarise the channels at the nodes, not the entire length of the axon
This is saltatory conduction
Myelination
Myelinated neurons are wrapped in a myelin sheath made of a fatty substance called
myelin
Individual cells in the myelin sheath are called Schwann cells
Each Schwann cell wraps around the neurone so there are several layers of membrane
and cytoplasm making up the sheath
The Schwann cells prevent the movement of ions across the neurone membranes and
insulate them from other neurones
Between Schwann cells are gaps called Nodes of Ranvier
Movement of ions can occur at nodes of Ranvier
Action potentials jump from one node of Ranvier to the next, increasing the speed of
transmission
Myelinated neurones conduct much faster than non-myelinated neurones
Saltatory Conduction
Action potentials travel along a neurone by localised depolarisation – the impulse
causes voltage gated sodium ion channels to open which allow sodium to diffuse in and
open the next voltage gated sodium ion channel
In myelinated neurones, the action potential jumps between nodes of Ranvier and only
has to polarise the channels at the nodes, not the entire length of the axon
This is saltatory conduction
