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Human Anatomy and Physiology Honors

The Human Brain
From the time a person enters the world, his brain is working full time to enable the person to breathe, blink, and process his surroundings. The brain is one of the most important and vital organs in the human body. Without it, a person is incapable of storing memory, moving around, breathing, sleeping, and performing other necessary functions for survival. Although the makeup of the brain is highly complex, every region and hemisphere is significant and plays a key role in the human body.

The development of the human brain starts when the baby is still in his mother’s womb at three weeks old (Marieb, 2004). Once the brain is fully formed inside the skull, the main three regions are finally prevalent and consist of the brain stem, cerebellum, and the cerebrum (Rughani, 2011). The outermost layer of the cerebrum is the cortex, which has a gray appearance and is also where the conscious mind is found (Marieb, 2004). When one imagines the brain, they most likely visualize the cerebrum since it is the outermost layer and takes the shape of a walnut. The size of the brain is relatively the same as two fists put together (Marieb, 2004). The brain mass for the average male is 1600 g, while the brain mass for the average female is 1450 g (Marieb, 2004). Since the brain is easily subjected to injuries, it is encased inside of the skull, and is further protected by a membrane called Meninges and a watery cushion called cerebrospinal fluid (Marieb, 2004). The cerebrospinal fluid is especially important because it prevents the brain from crushing under its own weight, protects the brain from blows and other trauma, and also helps nourish the brain.

The brain, along with the spinal cord, is a part of the central nervous system (Marieb, 2004). This system is the “command center” of the body and interprets sensory inputs and response to a person’s current surroundings (Marieb, 2004). This system consists of mostly nervous tissue, which is made up of two different cells: supporting cells and neurons (Marieb, 2004). When a person touches a hot surface, the person’s hands instinctively retract because it knows that it is a danger to the body (Mayo Clinic, 2011). The neurons are most important during this kind of situation because they create nerve impulses from one area of the body to another (Marieb, 2004). When a neuron is stimulated, it causes the release of neurotransmitters, and soon, a communication network is created between the brain and the nerve cells, which enables one to think, move, feel, and communicate (Mayo Clinic, 2011). This results in the brain making the connection between the hot surface and the hand, and in a split second, the peripheral nervous system communicates with the brain and sends signals of the pain caused by the hot surface (Mayo Clinic, 2011). Because the neurons are associated with the brain, the human brain is able to receive important signals from the nerve cells and enables sensory and motor responses from the body.

The cerebrum makes up 83% of the total brain mass, and is divided into two hemispheres, which are then further divided into four lobes: the frontal, parietal, temporal, and occipital lobe (Rughani, 2011). It contains three kinds of functional areas: motor areas, sensory areas, and association areas (Marieb, 2004). The frontal lobe controls thinking, short-term memory, and movement, the parietal lobe interprets sensory information, the temporal lobe processes information from your senses and also stores memory, and the occipital lobe processes images perceived from the eyes and connects it with the memory already stored inside the brain (Mayo Clinic, 2011). The cerebellum is a band of tissue that is located under the brain. It collects sensory information from the eyes, ears, and muscles to coordinate movement (Mayo Clinic, 2011). The brain stem is located under the brain and cerebellum and is connected to the spinal cord...
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