The Brain: Interesting Facts and More

The human brain is an organ that consists of five major structures. These structures consist of the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon. The telencephalon consists of the right and left cerebral hemispheres (Axia College Week 1 reading Chapter 2, 2009). The diencephalon, mesencephalon, metencephalon, and myelencephalon make up the brain stem (Axia College Week 1 reading Chapter 2, 2009). Each structure plays an important part in the functions of the human body.

First, the telencephalon is the largest part of the brain. According to the Axia College Week 1 reading Chapter 2 (2009), "It initiates voluntary movement, interprets sensory input, and mediates complex cognitive processes such as learning, speaking, and problem solving" (p. 54). The telencephalon contains the cerebral cortex, which is convoluted tissue that covers the cerebral hemispheres (Axia College Week 1 reading Chapter 2, 2009). The tissue is convoluted, or furrowed, to make the brain fit the skull. According to the Axia College Week 1 reading Chapter 2 (2009), "The large furrows in a convoluted cortex are called fissures, and the small ones are called sulci" (p. 54). Fissures, namely the central fissure and lateral fissure, are responsible for separating each hemisphere into four lobes. These lobes are called the frontal lobe, parietal lobe, the temperal lobe, and the occipital lobe (Axia College Week 1 reading Chapter 2, 2009). Between fissures and sulci are structures, or ridges, called gyri (Axia College Week 1 reading Chapter 2, 2009). These also serve many purposes. According to the Axia College Week 1 reading Chapter 2 (2009), "Among the largest gyri are the precentral gyri, which contain motor cortex; the postcentral gyri, which contain somatosensory cortex; and the superior temporal gyri, which contain auditory cortex" (p. 55). Most of the cerebral cortex is a six layered cortex called the neocortex, which contains pyramidal (multipolar neurons) and stellate (interneurons) cells (Axia College Week 1 reading Chapter 2, 2009).

In addition, the rest of the cerebral cortex is thought to be primitive in nature and contains the hippocampus, dealing with memory, and the cingulate cortex (Axia College Week 1 reading Chapter 2, 2009). These are part of the limbic system, as are the mammillary bodies, the amygdala, the fornix, and the septum (Axia College Week 1 reading Chapter 2, 2009). According to the Axia College Week 1 reading Chapter 2 (2009), "The limbic system is involved in the regulation of motivated behaviors-including the four Fs of motivation: fleeing, feeding, fighting, and sexual behavior" (p. 56). The limbic system circles the thalamus in the midline brain region (Axia College Week 1 reading Chapter 2, 2009). The amygdala is a nucleus located in the anterior temporal lobe (Axia College Week 1 reading Chapter 2, 2009). In the back of this structure is the hippocampus that is located beneath the thalamus. Next is the cingulate cortex and fornix which encircle the dorsal thalamus (Axia College Week 1 reading Chapter 2, 2009). The fornix ends in the mamillary bodies and septum. According to the Axia College Week 1 reading Chapter 2 (2009), "The septumis a midline nucleus that is located at the anterior tip of the cingulate cortex" (p. 56).

Also in the cerebral cortex are the basal ganglia. The basal ganglia are a group of structures that deal with voluntary movement (Axia College Week 1 reading Chapter 2, 2009). If this is damaged, movement is affected. The amygdala is also a part of the basal ganglia. Also a part of the basal ganglia, the striatum is made of the caudate and the putamen. The globus pallidus is situated between the putamen and thalamus (Axia College Week 1 reading Chapter 2, 2009).

Secondly, the diencephalon contains the thalamus and hypothalamus. The thalamus is made up of two lobes, joined by the massa intermedia, which sit on top of the brain stem. The thalamus contains sensory relay nuclei that receive, process, and transmit signals from sensory receptors (Axia College Week 1 reading Chapter 2, 2009). The hypothalamus regulates hormones that are released from the pituitary gland. Along with the hypothalamus is the optic chiasm, which is where the optic nerves from the eyes come together (Axia College Week 1 reading Chapter 2, 2009). According to the Axia College Week 1 reading Chapter 2 (2009), "The mammillarybodies, which are often considered to be part of the hypothalamus, are a pair of spherical nuclei located on the inferior surface of the hypothalamus, just behind the pituitary" (p. 54).

Next, the mesencephalon has two divisions in the brain, known as the tectum and the tegmentum. The tectum has colliculi, or two pairs of bumps. According to the Axia College Week 1 reading Chapter 2 (2009), "The posterior pair, called the inferiorcolliculi, have an auditory function; the anterior pair, called the superiorcolliculi, have a visual function" (p. 53). The tegmentum contains the periaqueductal gray, the substantia nigra, and the red nucleus (Axia College Week 1 reading Chapter 2, 2009). The periaqueductal gray is significant in that it plays a role in mediating pain reducing effects of drugs like morphine and heroin (Axia College Week 1 reading Chapter 2, 2009).

Furthermore, the metencephalon holds the pons and cerebellum. The pons is a bulge made up of tracts and a part of the reticular formation (Axia College Week 1 reading Chapter 2, 2009). The cerebellum, also known as the little brain, is a large structure on the brain stem's surface. According to the Axia College Week 1 reading Chapter 2 (2009), "It is an important sensorimotor structure; cerebellar damage eliminates the ability to precisely control one's movements and to adapt them to changing conditions" (p. 52).

Also a part of the brain is the myelencephalon, or medulla. It is located towards the back of the brain and is made of tracts that carry signals between the brain and the body (Axia College Week 1 reading Chapter 2, 2009). The reticular formation is also a part of the myelencephalon. According to the Axia College Week 1 reading Chapter 2 (2009), "It is a complex network of about 100 tiny nuclei that occupies the central core of the brain stem from the posterior boundary of the myelencephalon to the anterior boundary of the midbrain" (p. 51). The reticular formation plays a part in sleeping and attention. It is also plays a part in cardiac, respiratory and circulatory reflexes (Axia College Week 1 reading Chapter 2, 2009).

In conclusion, the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon are five important structures of the brain. They all have intricate parts and control specific functions in the body. The brain would not function properly without them and the body would not be able to live.

Axia College of University of Phoenix. Chapter 2. The Brain, the Body, and the Mind Course.