The hindbrain or rhombencephalon or lower brain is a
developmental categorization of portions of the
central nervous system in
vertebrates. It includes the
medulla,
pons, and
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
. Together they support vital bodily processes.
Metencephalon
Rhombomere
In the vertebrate embryo, a rhombomere is a transiently divided segment of the developing neural tube, within the hindbrain region (a neuromere) in the area that will eventually become the rhombencephalon. The rhombomeres appear as a series of s ...
s Rh3-Rh1 form the
metencephalon.
The metencephalon is composed of the
pons and the
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
; it contains:
* a portion of the fourth (IV) ventricle,
* the
trigeminal nerve (CN V),
*
abducens nerve (CN VI),
*
facial nerve (CN VII),
* and a portion of the
vestibulocochlear nerve (CN VIII).
Myelencephalon
Rhombomeres Rh8-Rh4 form the
myelencephalon.
The myelencephalon forms the
medulla oblongata
The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...
in the adult brain; it contains:
* a portion of the
fourth ventricle,
* the
glossopharyngeal nerve (CN IX),
*
vagus nerve (CN X),
*
accessory nerve (CN XI),
*
hypoglossal nerve (CN XII),
* and a portion of the
vestibulocochlear nerve (CN VIII).
Evolution
The hindbrain is homologous to a part of the
arthropod brain known as the sub-oesophageal ganglion, in terms of the genes that it expresses and its position in between the brain and the nerve cord.
It has been suggested that the hindbrain first evolved in the
Urbilaterian—the last common ancestor of chordates and arthropods—between 570 and 555 million years ago.
Hindbrain diseases
A rare brain disease of the
cerebellum
The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebel ...
is
rhombencephalosynapsis characterized by an absent or partially formed
vermis. Symptoms can include
truncal ataxia. The disorder is a main feature of
Gomez-Lopez-Hernandez syndrome.
References
Further reading
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Brainstem
Embryology of nervous system