2-Minute Neuroscience: Corticospinal Tract Video Lecture | A-Z Guide to Neuroscience - Personal Learning

Welcome to 2 minute neuroscience, where I
simplistically explain neuroscience topics
in 2 minutes or less.
In this installment I will discuss the corticospinal
tract.
The corticospinal tract is a major tract that
carries movement-related information from
the motor cortex to the spinal cord.
The neurons that travel in the corticospinal
tract are called upper motor neurons; they
form connections with neurons called lower
motor neurons, which carry movement-related
impulses to muscle itself, causing it to contract.
The upper motor neurons of the corticospinal
tract leave the motor cortex and descend to
the brainstem, entering the midbrain in large
fiber bundles called the cerebral peduncles.
The tract continues down into the medulla
where the fibers form two bundles, known as
the pyramids, which create visible ridges
on the exterior surface of the brainstem.
At the base of the pyramids, about 90% of
the fibers in the corticospinal tract decussate,
or cross to the other side of the brainstem
in a bundle called the pyramidal decussation.
The decussating fibers will then enter the
spinal cord on the opposite side of the body
from where they originated as part of the
lateral corticospinal tract.
The other 10% of the fibers will continue
into the spinal cord on the same side of the
body where they originated as part of the
ventral or anterior corticospinal tract and
only cross over when they reach the level
of the spinal cord where they will synapse
on a lower motor neuron.
It is thought that the lateral and anterior
corticospinal tract fibers have slightly different
specializations, with the lateral corticospinal
tract controlling the movement of more distal
muscles like those of the hands, and the anterior
corticospinal tract controlling the movement
of more proximal muscles like those of the
trunk.
Damage to the corticospinal tract can lead
to a collection of symptoms known as upper
motor neuron syndrome, which involves symptoms
like weakness or paralysis, hyperactive reflexes,
decreased motor control, and either increased
or decreased muscle tone.
Over time patients may regain the ability
to make crude movements but fine finger movements
like writing or typing may remain impaired,
suggesting the corticospinal tract is especially
important for these types of movements.