The brain is the control point of the nervous system in all vertebrates and most invertebrate animals (Bailey & Newlands, 2006). Vertebrates have complex brains as compared to invertebrates. As such, the brain is situated in the head adjacent to the primary sensory organs. These sensory organs are linked to the brain by the nerves. The sensory organs include; the eye, the ear, the tongue and the nostrils. The brain of a fully developed vertebrate is separated into hemispheres that are differentiated on longitudinal gap. Equally, these hemispheres are made up of four lobes that are separated from the lateral plane, the central gap, and the lateral cleft. Inside the brain, over 30 billion neurons are linked together by synapses to form a complex structure known as the cerebral cortex (Bailey & Newlands, 2006). Neurons communicate information of signals via axon to the recipient cells within the body organs. On the other hand, the spinal cord mediates the reflexes within the brain. Muscle movements and secretion of hormones enhance the functioning of the brain.
Vertebrates’ brains are comprised of several divisions and subdivisions. The main parts of the brain include; telencephalon, myelencephalon, diencephalon, mesencephalon, and metencephalon (Kandel, 1991). The telencephalon is the conspicuous division of the brain which is located in the forebrain and therefore enhances the interpretation of sensory output and the voluntary output in the brain cells. It also mediates major cognitive processes such as learning, ability to speak, and enabling solutions to problems. Another part of the brain is the diencephalon (Bailey & Newlands, 2006). The thalamus and the hypothalamus are the main components of the Diencephalon. Similarly, the thalamus contains many pairs of nuclei. The hypothalamus controls the release of hormones.
The other major division of the brain is the mesencephalon. The Mentencephalon’s ascending and descending band of fibers generates Pons. The Mentencephalon is situated in the mid-brain. This region is subdivided into two major parts the tectum and the tegmentum and is situated on the stems ventral plane. In this part, the inferior colliculi are responsible for auditory function, and the superior colliculi are responsible for visual function. The periaqueductal gray, red nucleus, and the substantia nigra are the main components of the tegmentum (Bailey & Newlands, 2006). Periaqueductal is a gray matter adjacent to the cerebral aqueduct. It is responsible for pain reduction. The other two components of the tegmentum ; the substantial nigra and the red nucleus perform the same role as a sensory-motor structure.
Myelencephalon and the cerebellum are also major divisions of the brain. The cerebellum is situated on the brain stem’s dorsal surface and enhances movements and the adaptations to the changing environmental conditions. The transmission of signals between the brain cells and the body tissues is enhanced by the myelencephalon that is made of several tracts (Bailey & Newlands, 2006). As such, the myelencephalon is a delicate region of the brain. The reticular arrangement of this region results in the building up of several connections of nuclei that occupies the central core of the brain. Diencephalon reticular activating structure plays a significant role in the arousal phase. The reticular arrangement of the myelencephalon enhances the physical and psychological activities of the body. For instance, sleep, movements, contraction, and relaxation of the muscles, cardiac functioning, circulatory and even the respiratory reflexes.
Bailey, B. J. & Newlands, S. D. (2006). Head & neck surgeryotolaryngology (4th Ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
Kandel, E. R. (1991). Principles of neural science (3rd Ed.). New York: Elsevier Science.