Major Divisions of the Vertebrate Brain

Tutorial 16: Major Divisions of the Vertebrate Brain

Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test: 16a | 16b
Part 3: Multiple-Choice Self-Test

Return to main tutorial page

The vertebrate brain is divided into three major divisions, the hindbrain, midbrain, and forebrain. The structure and function of the hindbrain and midbrain in humans is very similar to those in lower animals. The forebrain, which is more highly developed in the human, is the division that distinguishes humans from other mammals.

Figure 16a illustrates the main location of each major division of the brain, and provides a description of the primary functions associated with each. Figure 16b provides additional illustrative and detail of the core structures of the brain.

Advanced

The major anatomical divisions of the central nervous system have their roots in embryology, the study of the development of organisms during gestation or pregnancy (Parent, 1996). In early stages of development, the ectoderm region along the middorsal line of the embryo develops into the neural plate. This precursor to the central nervous system is transformed into the neural tube by invagination. The neural tube then detaches from the ectoderm and thickens to form the spinal cord and brain. The rostral end of this neural tube differentiates into 3 primary brain regions called vesicles. The prosencephalon or forebrain lies closest to the rostrum. The mesencephalon or midbrain lies behind the prosencephalon. Finally, the rhombencephalon or hindbrain lies most caudal along the neural tube.

These three divisions are easily distinguished during development by both their gross appearance and extent of cellular differentiation. The more evolved a brain region is, the more differentiated or specialized its cells become during the development process. The most primitive regions of the brain are more similar across species and, therefore, the cells of these regions show little differentiation across species. This scheme of brain divisions is an example of ontogeny recapitulating phylogeny; during its complete course of development, an organism goes through the same successive steps (in gross form), as did the species during its evolutionary development. In essence, this classification scheme is based both on the grossly visible characteristics of the neural tube during various stages of embryonic development and the associated continuum of cellular differentiation that occurs to varied extent based on phylogenetic status.

Reference

Parent, A. (1996). Carpenter's human neuroanatomy (9th ed.). London: Williams & Wilkins.

Suggestions for further study

Tutorial 16: Major Divisions of the Vertebrate Brain

SUGGESTED READINGS:

RELATED LINKS:

Figure 16a:	Forebrain \| Hindbrain \| Midbrain
Figure 16b:	Cerebellum \| Medulla \| Pons \| Reticular Formation \| Thalamus