Welcome to 2 minute neuroscience, where I simplistically explain neuroscience topics
in 2 minutes or less.
In this installment I will discuss the medulla oblongata.
The medulla oblongata, or the medulla, is the lowest part of the brainstem, found below
the pons and above the spinal cord.
There is no clear separation between the medulla and the spinal cord; instead the spinal cord
gradually transitions into the medulla.
Perhaps the most important action linked to the medulla is the regulation of cardiovascular
and respiratory functions.
The medulla gets information about changes in blood pressure from baroreceptors, which
are found inside blood vessels.
This information is sent the nucleus of the solitary tract in the medulla, which initiates
reflexive actions to return blood pressure to a desired range.
The medulla is also responsible for generating breathing movements and for regulating respiration
to ensure there is enough oxygen in the blood.
To accomplish this, chemoreceptors, which are found inside blood vessels, detect changes
in oxygen and carbon dioxide levels in the blood.
When oxygen levels fall, neurons in and around the nucleus of the solitary tract and the
nucleus ambiguus respond by increasing respiration.
The medulla also controls a number of other reflexive actions like swallowing, coughing,
sneezing, and vomiting.
It is home to the inferior olivary nuclei, which are connected to the cerebellum and
involved in movement.
It also contains the nucleus gracilis and nucleus cuneatus, important nuclei of the
dorsal-columns medial lemniscus sensory pathway.
A number of cranial nerve nuclei are also found in the medulla.
The medulla contains a number of tracts that pass from the brainstem to the spinal cord
and vice versa.
The corticospinal tract and corticobulbar tracts, important tracts for movement, form
triangular bundles of fibers in the medulla that create ridges on the outside of the brainstem.
The bundles and ridges have been termed the medullary pyramids, and because of this the
corticospinal and corticobulbar tracts are often referred to as the pyramidal tracts.