Five Main Structures of Human Brain - Coursework Example

The Brain The brain is considered as the most complex organ in the human body and the centerpiece of the human nervous system. Although the human brain functions has a unified whole, neurologists have identified three major divisions of the brain namely forebrain/prosencephalon, midbrain and hindbrain/rhombencephalon. These are further subdivided into five major sub-divisions or structures each of which is composed of smaller structures responsible for specific life regulating functions. These five major structures are telencephalon, diencephalon, mesencephalon, metencephalon and myencephalon. Myelencephalon The Myelencephalon is situated in the most inferior section of the brainstem. In terms of structure, it is mainly composed of tracts conducting signals between the other parts of the brain and the body (Pinel, 2009). This section of the brain is the origin of the reticular formation and has nuclei which control vital functions in the body. The myelencephalon consists of only one structure, medulla oblongata/oblong marrow thus its functions are wholly reflected in the functions of this structure. The medulla oblongata looks like an enlarged pyramid-shape of the spinal cord. The medulla oblongata is the control centre for three most autonomic body functions like respiration/breathing, vasoconstrictor/heart and blood vessel function and cardiac functions/heart rate thus its damage results to immediate death. It also controls reflex actions like swallowing, digestion, vomiting, and sneezing. It acts as a conduction path for motor and sensory neurons travelling from the fore and midbrains to the hindbrain. As part of the brainstem, it helps in transferring messages between the spinal cord and various parts of the brain. Metencephalon Metencephalon is situated below the posterior section of the medulla oblongata and the cerebrum. Just like the myelencephalon, the metencephalon is composed of numerous ascending and descending tracks. Its main functions are balance, arousal, fine muscle movement, sleep, circulation, maintenance of fine muscle tone, and cardiac reflexes. It is also part of the reticular formation. The metencephalon consists of two structures namely pons and cerebellum (Pinel, 2009). The cerebellum or little brain a large convoluted structure located on the dorsal surface of the brainstem. Jacobson and Marcus (2008) points out the chief function of cerebellum as the control of body movements. It accomplishes this through the coordination and precise maintenance of balance, control of voluntary and involuntary body movements, reception of somatosensory, vestibular, visual and auditory information, and that of individual muscle movement. In addition, it processes this information and because of this, it is able to guide body movements in a coordinated and smooth fashion. Pons appears like a large protrusion or bulge of the brainstem between the medulla oblongata and the mesencephalon. This structure contains part of the reticular formation and nuclei that is important for sleep and arousal. Mesencephalon Mesencephalon is the portion of the brain stem that connects the forebrain and the hindbrain because it is located between these two parts of the brain. Its functions include pupil dilation, eye and body movement, hearing and controlling responses to sight. The mesencephalon consists of the tegmentum and the tectum. The tectum is the upper surface of the midbrain. This is structure is composed of two parts which appear like small bumps namely inferior colliculi and superior colliculi. The superior colliculi is part of the visual system and thus is has a visual function while the inferior colliculi is part of the auditory system and thus it has an auditory function. The function of the tectum in man therefore relates to reaction to moving stimuli and visual reflexes (Pinel, 2009). The tegmentum is located below the tectum and it has tracks of passage, reticular formation and three colorful structures namely the substantia nigra, the periaqueductal gray and the red nucleus. The function of the tegmentun is to receive sensory information. It is also involved in arousal, sleep, attention, maintenance of muscle tone, movement and vital reflexes like respiratory, cardiac and circulatory reflexes. Diencephalon The diencephalon is located between the cerebral hemispheres and is the second biggest division or structure of the brain. Its two main structures are thalamus and the hypothalamus. According to Jacobson and Marcus (2008), the diencephalon is involved in many functions of the body like homeostasis, control of motor, endocrine and autonomic functions, hearing, vision, smell and taste, perception of touch and directing sense impulses all over the body. The main structures of the diencephalon are the thalamus and hypothalamus. The thalamus is the large, two-lobed component that constitutes the upper most part of the brain stem. The thalamus is composed of many and varied pairs of nuclei and majority of these project to the cortex. This description gives the thalamus a sensory function because the protruding nuclei receives signals from various sensory receptors, process the signals and transmit them to the correct areas of the sensory cortex. Examples of such nuclei are ventral posterior nuclei, medial geniculate nuclei and lateral geniculate nuclei which function as important relay stations for somatosensory, auditory, and visual systems respectively. Generally, the thalamus acts as a relay station for outgoing and incoming motor signals being received or sent from the cerebral cortex. The hypothalamus is located below the thalamus and is composed of distinct nuclei and areas that control important survival behaviors and activities in man like drinking, eating, homeostasis, sleep, sexual activity, and emotions. It controls the endocrine system and the autonomic nervous system directly, and regulates the release of hormones by the pituitary gland indirectly. This in turn controls other endocrine glands. Telencephalon The telencephalon is the largest portion of the human brain and performs the most complex functions of the brain. Main functions of the telencephalon include determining personality and intelligence, controlling sense of smell, planning and organization, touch sensation and interpretation of sensory impulses or input, mediating cognitive processes that are complex in nature like speaking, learning and problem solving, and initiating voluntary movement. The main structures of telencephalon are basal ganglia, cerebral cortex and limbic system. The cerebral cortex is largely convoluted structure divided into right and left hemispheres. The right hemisphere controls talking, writing, talking, reading, spelling, verbal intelligence and memories, speech communication, and information processing in areas like math, grammar, analytical reasoning. The left hemisphere controls creativity and insight, comprehension of body language, perception of faces and patterns, visual-spatial processing, comprehension of social cues and holistic comprehension (Pinel and Edwards, 2010). The basal ganglia are involved in the control of movement while the limbic system is involved in memory storage and recall, motivation, emotion and multifaceted behavior. Conclusion The human brain is composed of various structures that perform important functions that are required for human survival. Some of these are reflex or autonomic actions while others are non-reflex. Basically, the brain is composed of five major structures namely the telencephalon, diencephalon, mesencephalon, metencephalon and myencephalon. These structures are in turn composed of other structures that function differently to achieve the overall functions of the five major structures of the human brain. References Jacobson, S. and Marcus, E. (2008). Neuroanatomy for the Neuroscientist. New York. Springer. Pinel, J. (2009) Biopsychology. Boston, MA. Pearson. Pinel, J. and Edwards, M. (2010). A colourful introduction to the Anatomy of the Human Brain: A Brain and Psychology Coloring Book. New York. 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