Neurological System the Nervous System Is Composed

Neurological System

The nervous system is composed of an interlocked system of neurons. The neurons conduct impulses to and from the periphery. They also interconnect with each other to deliver impulses to the various parts of the brain. Neurons generate and conduct electrical impulses by selectively changing the electrical gradient of their membrane and releasing neurotransmitters. Neurotransmitters may be inhibitory or excitatory. Through time, as new skills are adapted or new information is learned, new circuits are formed. With the repetition of learned information, the new circuits undergo myelination. This enables the neurons to conduct impulses faster. The ability of the nervous system to make or break new circuits is responsible for functions of the mind. (McCance & Huether, 2010)

Visual problems can be either congenital or acquired. The most common visual disorders are errors of refraction, strabismus, cataract and retinopathies. Patients with errors of refraction can either be hypermetropic, myopic or astigmatic. Hypermetropia and myopia occur because of an alteration in the axial length of the eyeball, change in the lens or cornea curvatures or due to a displacement of the lens. Hypermetropia is treated with a convex lens whereas a concave lens is used to treat myopia. Astigmatism occurs due a change in the curvature meridian of the cornea or lens, for example in keratoconus, cataract or lenticonus. . This condition is treated with a hard contact lens, or cylindrical or spherocylindrical lenses. All refractive errors can lead to strabismus, which is treated by correcting the underlying error or through surgery. Symptoms of refractive errors and strabismus are similar; they include: eyeaches, headaches, difficulty concentrating and blurred vision. Strabismus may also present with an intermittent squint, that may not be immediately apparent. (Riordan-Eva & Cunningham, 2011)

Cataracts are most commonly because of age related degenerative changes in the lens. It can however also occur due to trauma, drugs, metabolic disorders, or as a part of other congenital syndromes, such as Down's. In the initial phase of the disease, patients usually experience an improvement of near vision, and only present to the doctor later on in the disease course with blurred vision. They also complain of glare, diplopia and colored halos. Treatment of cataract essentially consists of surgical removal. However, non-surgical measures are used until surgery, such as use of spectacles, dark glasses to reduce glare, and use of mydriatics to improve vision. (Riordan-Eva & Cunningham, 2011)

Retinopathies occur as a complication of prematurity, diabetes and hypertension. Symptoms are related to impairment of vision which may be either sudden or gradual. Premature infants exposed to oxygen therapy need to be screened. The definitive treatment is only with the appropriate management of the underlying cause. (Riordan-Eva & Cunningham, 2011)

3) Chronic pain is generally described to last for greater than 3 months. The exact cause of chronic pain is unknown but an imbalance between neuromodulatory controls is hypothesized. Examples include, back pain, myofascial pain syndromes, chronic post-operative pain, and cancer pain. (McCance & Huether, 2010)

Acute pain, on the other hand, is more sudden and severe in onset, therefore alerting an individual to something more serious. Symptoms of acute pain include those of sympathetic stimulation, for example, tachycardia, hypertension and dilated pupils. Acute pain maybe either somatic or visceral in origin, or maybe referred from another site. Examples of acute pain include aortic dissection and acute pancreatitis. (McCance & Huether, 2010)

4) Genetic epidemiological studies reveal that schizophrenia might be a heritable disorder. There is a higher prevalence of this disease in monozygotic twins and siblings. However, the genetic inheritance differs from mendelian disorders. Schiziophrenia exhibits reduced penetrance. Another hypothesis of its etiology is environmental interference during prenatal neural development, such as infections, nutritional deficiencies. Perinatal complications of birth asphyxia have also shown to be important risk factors. (McCance & Huether, 2010)

5) The development of depression involves both environmental and hormonal factors. Depression of certain neurotransmitters, namely, dopamine, serotonin, norepinephrine, and monoamines have shown to cause depressive symptoms. Also a polymorphic variant of the serotonin receptor has also shown to play a role in depression. Individuals homozygous with the s variant of the allele, encoding for this receptor, have shown to have a two fold risk of developing major depression in response to a stressor. (McCance & Huether, 2010)

Typical symptoms of Major depressive disorder include: depressed or irritable mood, loss of interest, significant weight loss or gain (> 5%), sleep disturbances, psychomotor agitation, fatigue, feelings of worthlessness or excessive guilt, poor concentration and recurrent thoughts of death and suicide. (McCance & Huether, 2010)

MODULE 5:

1) Traumatic injuries to the brain can be either direct (coup) or indirect (countercoup). The clinical manifestation differs with the type, site and severity of injury. Focal injuries of the brain are because of direct damage, or hematomas (epidural, subdural and subarachnoid) that produce pressure symptoms. In cases of direct damage, for example in gun shot wounds, there will be motor, sensory and cranial nerve impairment of functions that correlate with the site of injury. Pressure symptoms include nausea, vomiting, loss of consciousness, papilledema and focal impairment of function. Manifestations of diffuse brain injury can range from mild impairment, confusion and momentary amnesia to loss of consciousness and severe neurologic impairment. Subarachnoid hemorrhage also produces signs and symptoms that mimic meningitis. (McCance & Huether, 2010)

2) Multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) are both hereditary and autoimmune in nature. MS, however, is a disorder of the myelin sheath, whereas ALS affects the motor neurons. Lesions of MS are mostly in the white matter of the brain, whereas in ALS, it is in the motor neurons of the brain and in the anterior horn cells of the spinal cord. The mean age of onset of disease in MS is at 20-40 years whereas the onset of ALS is usually after the age of 50. In MS, almost any neurologic dysfunction can occur, whereas ALS only affects the motor component. Progression to death is faster in ALS as compared to MS. (McCance & Huether, 2010)