The nervous system is made up of all the nerve tissue in one’s human body. This nervous tissue is composed of two classes of cells: neurons and neuroglia. Neurons consist of a cell body, dendrites and an axon. Within the cell body is located the nucleus, most of the cellular organelles, as well as the mitochondria. The dendrites, branch-like structures attached to the cell body, are what recieve any stimuli from the environment, as well as sensory receptors and other neurons. Axons are extensions from the cell body that send signals to other neurons. Of course, these neurons need protection and support and that is where neuroglia comes in. About six to sixty neuroglia surround a single neuron to protect it and feed it. The nervous system is considered the center of communication for all parts of the body. It is the system that helps us perform everyday activities such as walking around, breathing and even blinking. The nervous system has to be well taken care of in order for one’s body to function properly. There are two anatomical divisions to this major system: the central nervous system and the peripheral nervous system.
The central nervous system consists of two major structures: the brain and the spinal cord. The brain is soft and wrinkled organ that weighs about three pounds and is located inside of the cranial cavity, where the skull protects it from being damaged. The brain alone contains about 100 billion neurons. It is responsible for things such as consciousness and the ability to remember things. The spinal cord is a long and thin accumulation of grouped-up neurons that transmits information through what is called the vertebral cavity of the spine. Moving on, the peripheral nervous system consists of everything other part within the nervous system outside of the brain and spinal cord. Some of these parts include different kinds of nerves and ganglia. Nerves are groups of axons that function as a pathway in which information is carried from the brain to spinal cord and back. Ganglia are oval shaped structures that serve as a station in which one nerve enters and another exits. The peripheral nervous system has its own division of systems: the somatic nervous system, autonomic nervous system and enteric nervous system. The somatic nervous system is made up of all voluntary efferent neurons which means that the SNS is the only part that is controlled in a conscious state. It is responsible for raising the levels of nervous activity in the skeletal muscles in the body. In contrast with this system, the autonomic nervous system is made up of all involuntary efferent neurons and is further divided into sympathetic and parasympathetic. The sympathetic division is what deals with the “fight or flight” response. It causes someone’s breathing to increase as well as their heart rate. On the other hand, the parasympathetic division deals with the “rest and digest” response and is responsible for undoing what the sympathetic system did. In that case, your heart rate and breathing decrease. The third and last division is the enteric nervous system which is in charge of controlling digestion and what your digestive organs do. At times, this system receives signals from both divisions of the autonomic nervous system in order to help it control its functions. Nevertheless, the enteric system mostly functions alone very well. It is quite an immense system in that it contains almost as many neurons as the spinal cord.
The nervous system’s physiology consists of three main functions: sensory, integrative, and motor. Within the sensory function, information is collected from sensory receptors that observe the internal and external conditions in the body. Following that, these signals travel to the central nervous system where afferent neurons process them further. Within the integrative function, which occurs in the gray matter of the brain and spinal cord, sensory signals in the central nervous system are processed and then analyzed by interneurons to decide whether they should be discarded or kept. As for the motor function, these interneurons, after deciding on the fate of these signals, stimulate efferent neurons. Signals from the central nervous system’s grey matter are carried from the peripheral nervous system nerves to effector cells by these efferent neurons. Following that, a hormone is released in order to react to the stimulus.
As with any other system in the body, the nervous system has some common diseases and two of these include Alzheimer’s disease and Parkinson’s disease. Alzheimer’s disease falls under the category of Dementia. Dementia is not specifically a disease, but rather a general term for a decrease in mental ability harmful enough to intervene with one’s daily life. With that in mind, Alzheimer’s disease is a type of Dementia in which the individual has trouble remembering, and struggles with behavior and thinking. In fact, Alzheimer’s disease is the “most common form of Dementia” (MacGill, 2016). From all Dementia cases, 60 to 80% of them are Alzheimer’s disease. Although the causes for this disease have not yet been fully understood, it is believed that it is caused by a mix of “genetic, lifestyle and environmental factors that affect the brain over time” (2017). Alzheimer’s gets worse over time; in its early stages, the individual’s memory loss isn’t as severe, but in the later stages is when one has trouble with conversations as well as their reactions to different environments. The second of these two diseases is Parkinson’s disease. Parkinson’s is a type of neurodegenerative disease in which an individual experiences progressive loss of muscle control. This then leads to trembling of the legs, arms, and head. If things worsen, it becomes more of a hassle to walk around and even complete simple tasks. This disease is caused by a loss of dopamine, which is a substance that acts as a messenger to the brain in order to produce movement. The progression of this disease varies from person to person. Some individuals can live a long life and get what they want done while others become disabled rapidly. The majority of individuals with Parkinson’s are over the age of 60.
For some diseases out there, there are treatments, or possibly even cures. As Alzheimer’s disease, there is currently no known cure. This is because it is impossible to stop or reverse the death of the brain cells in Dementia. However, there are a couple of treatments that can ease the symptoms and slow down the progress of the disease. For example, the FDA or Food and Drug Administration has approved two types of medicine: cholinesterase inhibitors and memantine. Cholinesterase inhibitors are prescribed as a treatment for symptoms that involve memory, language, and other thought processes. They halt the breakdown of acetylcholine as well as delay the intensity of the symptoms. Whereas cholinesterase inhibitors serves as a treatment for the early stages of Alzheimer’s, Memantine serves as a treatment for the later and more severe stages of Alzheimer’s. They are prescribed for similar symptoms to Alzheimer’s with the addition of the ability to perform basic tasks. They regulate the activity of glutamate as well as boosts mental function. Similar to Alzheimer’s there is no cure for Parkinson’s disease. Despite that fact, there are several therapies available to slow down the beginning of motor symptoms and improve them as well. The purpose of all of these therapies is to either replace dopamine or imitate it. One of the most effective therapies out there is Levodopa. In this case, Levodopa is transformed into dopamine in the brain. It is more often used during later stages of Parkinson’s disease due to its discomforting side effects. Another form of treatment available is surgery. This would be an option for those individuals with severe motor symptoms. This type of surgery is called DBS or deep brain stimulation, in which electrodes are implanted into the brain to stimulate sections having to do with motion. There is also another type of surgery available in which whatever areas in an individual’s brain cause the disease symptoms are completely destroyed.