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Investigate the functions and dysfunctions of the nervous system.

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Introduction

Unit 16 AO6 Investigate the functions and dysfunctions of the nervous system. The nervous system contains a network of neurons that send signals to each other so that actions can be coordinated. The nervous system has two main divisions, the central nervous system (CNS) and the peripheral nervous system (PNS). The brain and spinal cord make up the CNS and the nerve fibers that branch from it make up the PNS. "These peripheral nerves constantly send information to the CNS which process it and sends signals back to the PNS" (Human body, Ted Smart, Darling Kinderley Limited, London). This information is transmitted as electrical impulses via nerve cells called neurons. The CNS then sends the instructions to the effectors (muscles and/or glands) which respond accordingly; muscles contract or relax whereas glands secrete hormones. The nerve fibers in the PNS sometimes form into groups in important areas so that they can maintain fine control. The PNS makes up the sensory nerves which send information from senses and motor nerves which send information to the muscles. There are two types of nerves in the PNS somatic (voluntary) and autonomic (involuntary). The involuntary nerves can also be divided into two further groups, sympathetic and parasympatic. The difference between the parasympathetic system and the sympathetic nervous system is that although they are both involuntary "the parasympathetic system is responsible for stimulation of "rest-and-digest" activities that occur when the body is at rest while the sympathetic nervous system is responsible for stimulating activities associated with the fight-or-flight response." ...read more.

Middle

The second function constructs a spatial coordinate system to represent the world around us" (Kandel, Schwartz & Jessel, 1991). The occipital lobe is associated with visual processing and involved in visual perception, such as recognizing objects and colors and the temporal lobe deals with perception, memory, speech and recognition of auditory stimuli. The cerebrum is also split into two halves, the right and left hemispheres; generally the right hemisphere coordinates the left of the body and vice a versa. The two hemispheres are connected by the corpus callosum. The bulk of the cerebrum is the neocortex, a six layered structure only found in mammals. "It is thought that the neocortex is a recently evolved structure, and is associated with "higher" information processing by more fully evolved animals (such as humans, primates, dolphins, etc)" (serendip.brynmawr.edu/bb/kinser/Structure1.html, 18/01/12). The cerebellum also has two hemispheres and is associated with regulating the body's movement, balance and posture. Inside of it is the limbic system which contains the hypothalamus, hippocampus, amygldala and thalamus. The brain stem is underneath this limbic system and is made up of the midbrain, pons and medulla and is responsible for basic vital life functions such as, blood pressure, heartbeat and breathing There can be dysfunctions of the nervous system, three of these are motor neuron disease, multiple sclerosis and Parkinson's disease. Motor neuron disease (MND) affects the motor neurons and there are different kinds of this neurological disorder, some can affect many things on an individual where as some kind's effect mainly one pacific thing. ...read more.

Conclusion

"In PD, brain cells deteriorate (or degenerate) in an area of the brain called the substantia nigra. From the substantia nigra, specific nerve cell tracts connect to another part of the brain called the corpus striatum, where the neurotransmitter called dopamine is released." (emedicinehealth.com/parkinson_disease/page2_em.htm, 18/1/12) the alterations in dopamine can lead to medical problems, however the mechanism for the brain cell loss is not known. In Parkinson's disease the nerves that produce dopamine break down causing, stooping of posture, muscle rigidity, involuntary tremor, shuffling walk, slowness of movements, and perhaps an affected intelligence later on in the disease. Although it is not known why this happens it is thought to be because of a number of reasons, and it is thought that there can be some risk factors to Parkinson's disease, such as contracting a viral infection in later life or having a head trauma. It is also thought that a number of things cause it to happen such as medication and drug's, but it is not known why this is, it is thought that it may be because of the way the medication or drugs work that they interfere with the brain's natural dopamine. "Due to feedback inhibition, L-dopa can eventually cause the symptoms of Parkinson's Disease that it initially relieves. Dopamine receptors can also eventually contribute to Parkinson's disease symptoms by decreasing the sensitivity of dopamine receptors." (viartis.net/parkinsons.disease/causes.htm, 18/1/12) Genetic mutations of the Parkinson's disease can also be inherited; this can make a person more prone to getting the disease rather than directly causing it. ...read more.

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