The Nervous System

The functioning of the human body homogeneously as a unit is hinged on timely communication between various cells to ensure proper operational execution. Two systems are involved in this cellular interaction meant to aid in information exchange through input and output and are the endocrine as well as the nervous system. The former uses chemical messengers to initiate and sustain cellular interactions while the latter relies on a network of interconnected cells called neurons. The nervous system culminates in the maintenance of bodily functions as well as adaptation to different environmental scenarios.

Physiology of the Nervous System.

The nervous system is vast and complex, both in terms of its constitution as well as in terms of the array of functions it can execute. It comfortably passes as the fastest and most efficient modality of long-distance information transmission in the body (Nicholl & Appleton, 2015). At the basic level, it consists of neurons (the principle action cells) as well as a supportive network of cells whose function is to create and maintain a proper environment for the neurons to operate in.

            The nervous system is categorized into central (CNS) and peripheral nervous systems (PNS).  The peripheral nervous system consists of an extensive network of nerves running from the spine (spinal nerves) or the brain (cranial nerves) to all other parts of the body (Barrett, Barman, Boitano & Brooks, 2016). They provide input and output functions to the sections they are attached to, to ensure that a particular organ is operating as required. Essentially, therefore, the PNS forms the final port of interaction of the nervous system with the effector organs (Barret et al., 2018). The CNS, conversely, is made up of the brain and spinal cord. The two major in the integration and processing of information by assessing the input and output stream of the peripheral nerves to achieve functional homeostasis (Barret et al., 2018).

Additionally, the spinal cord is a collection of nerve tracts moving up and down either towards or from the brain to relay input/output information. Functionally, the nervous system activity is hinged on three basic processes, sensation, integration, and motor effect. The sensory bit is perhaps the most critical as it acts as the input mechanism of the whole system. It consists of receptors all over the body whose function is to detect specific stimuli and transmit them via peripheral nerves to the CNS for processing and perceiving (Clarke & Lemon, 2016). These receptors include those for touch, pain, pressure, temperature or even special receptors for smell, vision, and hearing. The motor system is just as vital since eventually, all information gathered has to be used to modulate specific body functions. The motor system is thus an output system that relays final processed decisions from the CNS to effector organs. Effector organs, the eventual anatomic entities that execute the signals from the CNS, include the skeletal muscles, smooth muscles, and secretory organs.

Processing of information, which occurs in the CNS, relies on matching input and output signals to achieve functional balance in the body for optimum functioning, which is usually a subconscious process. Another role of the nervous system is information storage. Clark & Lemon (2016) opine that information from the input wing is that is used to affect bodily functions are just a fraction of the processed content, and that most of it is usually sorted to inform processes in the future. This forms the basis of memory, which is critical for thinking. Thinking is thus thought of as a process of comparing on going sensory experiences with the stored ones to inform decision-making.

            Indeed, the exploration of the neuron, the fundamental cell in these processes is crucial to understanding all these. The body is estimated to have up to 1 billion neurons (Hall, 2015).  A neuron consists of a cell body made up of a nucleus, from which multiple projections called dendrites to emanate. Additionally, it has a long fibrous stalk projecting from the cell body (axon) which functions as the site for the transmission of the action potential. The terminal end of the axon has boutons that interconnect with other neurons through a process termed synapsis. Axons are lined by specialized cells that produce a myelin coating onto it. Myelin enhances speed or transmission of an action potential (Hall, 2015). The signals can be inhibitory or excitatory, and speed of transmission depends on myelination as well as the diameter of nerve fibres. Multiple neurons thus constitute a nerve.

Subjective Questions on the Nervous System

Assuming a patient came in with lower-limb paralysis and visual deficits;

            What is your name, age, residence, race, and occupation? Biodata forms the initial part of subjective data and is critical in many respects. Some diseases are common in specific environments and age groups and hence the basis for knowing residence and age, respectively. The role of racial disparities in various illnesses has never been more precise, and as such, its import in availing a diagnosis. Occupation has a role in predisposition to certain conditions such as lower back pain in heavy manual labourers.

When and how did your symptoms start? This is critical in establishing the severity of the possible condition as well as thinking out possible etiologies. Longstanding symptomatology commonly points to a sinister and possibly progressive pathology, while acute presentation usually results from infections or injuries (Boswell, 2019). Additionally, whether the onset is insidious or acute is critical is enabling the identification of etiology.

Is there pain? Pain is probably one of the most debilitating symptoms patients have and is a single most crucial cause of discomfort. In neurological cases, pain is essential in not only assessing the severity of the condition but also acts as a pointer to the possible pathology. Boswell (2019) argues that infectious and inflammatory processes almost invariably present with the pain while degenerative conditions commonly do not. Thus, asking whether the patient has pain in the paralyzed areas is critical. If pain is present, its characterization is vital.

Are you having a feeling of pins and needles in your extremities? This is also a significant symptom in neurology and comes across as an indicator of peripheral nerve issues. Aminoff, Greenberg & Simon (2015) state that in patients with paralysis causes can be central or peripheral, and paresthesias provide a diagnostic guide as to the possible pathology. However, it can also arise due to some medication.

Are you having any associated symptoms, such as bowel dysfunction or bladder issues? Again, the nervous system is an intricate network of connections and thus attempting to find out which organs are affected aids in establishing possible etiology (Aminoff, Greenberg & Simon, 2015). For a patient with bladder issues alongside paraplegia, the cause is likely in the PNS.

Have you had any trauma and infection in the recent past? This is now to accurately identify possible causes and or predisposing factors to the patient’s condition. Moreover, one would have to explore the patients past medical history, drug history, allergies, and family social history. The information therein may be necessary for diagnosis as well as have management implications for the patient.

Objective Data and Expected Normal Findings for the Nervous System

Objective data

Objective data includes the taking and recording of vital signs as well as performing a physical examination. Vital signs assessed are blood pressure, heart rate, temperature, respiratory rate, and oxygen saturation. Anthropometric measures, such as height and weight, are also taken and recorded. Concerning the physical exam, a general examination is first performed, before the nervous system examination gets underway.

Expected normal findings

Higher functions are intact that is, the patient speaks coherently and appropriately, is intelligible, can abstract, has good judgment, and has a good memory. Cranial nerve functions intact that is, sense of smell is present and appropriate, visual fields are, and acuity is normal, facial sensation and mastication is intact, as are facial expression and sense of taste, hearing, swallowing shoulder shrugging and tongue movements are all present and appropriate. Reflexes and tone are present and normal in all major muscle groups. In the sensory exam, cutaneous sensation to touch, pressure, and pain present all over the body, without sensory level. Cerebellar functions are normal, and gait is also appropriate.

Special Physical Examination Techniques or Procedures for the Nervous System

Corneal reflex

            They are modalities used to assess the functionality of trigeminal. In corneal reflex, soft cotton is rolled into a fine line and used to attempt to touch the cornea. Normal results involve shutting of the eyelids as a protective mechanism (Peterson & Hamel., 2018). Trigeminal is the afferent nerve in that reflex pathway.

Kernig’s sign

            It is a physical examination technique used to assess for signs of meningism. In Kernig’s, the patient lies supine, and one knee is then flexed both at the hip and the knee, and then extended at the knee (Karl et al., 2019). A positive test involves the patient wincing in pain during the extension. Brudzinski test is also a variant that can be used.

Rhine and Weber tests

            These are tests used to assess the etiology of hearing loss. They use a vibratory tuning fork placed either at the glabella (weber) or adjacent to the mastoid and external auditory canal for rhine (Davies, 2016). A rhine test is negative when bone conduction betters air conduction in the affected ear, and a weber test lateralizes to affected ear in conductive hearing loss and normal ear in sensorineural hearing loss.

Rhomberg sign

            This is used to assess proprioception sense. An individual is made to stand and then close their eyes for a while. Due to the lack of visual input, in individuals with significant nervous pathology, they end up falling (Counihan, 2016). It underpins the role of vision in balance.

Tinel’s test

It refers to a tingling sensation distally when a nerve is percussed. It is usually a pointer of entrapment or nerve degeneration. It is common in the upper limb.

Adaptation of Assessment and Interview to Specific Age-groups

Pediatrics

            In the pediatric population, some specific tests have to be performed. These include assessing the primitive reflexes such as startle, blink, palmer grasp, and Moro reflex. Additionally, Glynn & Drake (2017) outline that a thorough assessment of the development milestones is also an important diagnostic step. For the newborn, spinal examination are essential.

Pregnancy

            Pregnancy is a period of physiologic upheaval. One of the standard neurologic complications is eclampsia, and as such, expectant women need to have regular ANC visits for checks on blood pressure, urinalysis, complete blood count, and ultrasound examination. Moreover, it being a prothrombotic state hence predisposition for stroke, thorough evaluation needs to be done for those having neurological deficits.

Geriatric

            In geriatrics, one needs to take note that due to the decline in the physiologic capacity of tissues, the reduced function may be misconstrued as a pathologic process. Additionally, they commonly present atypically, hence proving a diagnostic nightmare. The implication is, therefore, that one needs to exhibit a lot more patience to nick the required information (Glynn & Drake, 2017). The patient should be made comfortable and ensured that distractions are minimal. It is usually multidimensional as the focus is more on quality of life and functioning (Glynn & Drake, 2017). The role of comorbidities in the presentation, as well as eventual management, cannot be understated.

Disease Process in the Nervous System

Cerebrovascular accident

It refers to the cessation of the blood flow to a specific area of the brain, leading to ischemia and even death of the cells, with attendant functional impairment. It is commonly an emergency since neuronal death is irreversible, and is common in older individuals. Presentation depends on the specific part of the brain deprived of blood supply as far as the functional mapping of the brain is concerned. On physical examination, patients tend to have an altered level of consciousness, visual field defects. In cardioembolic strokes, patients have heart murmurs, palpitations, and signs of heart failure such as breathlessness and oedema.

References

Aminoff, M., Greenberg, D., & Simon, R. (2015). Clinical Neurology. McGraw-Hill Education. Retrieved from https://lib.hpu.edu.vn/handle/123456789/32420

Brooks, H., Barrett, E. K., Boitano, S., & Barman, M. S. (2015). Ganong’s Review of Medical Physiology.

Boswell, G. M. (2019). Examination of the Nervous System. Pocket Guide to Physical Assessment, 185. Retrieved from https://books.google.co.ke/books?hl=en&lr=&id=IayWDwAAQBAJ&oi=fnd&pg=PA185&dq=Boswell,+G.+M.+(2019).+Examination+of+the+Nervous+System.+Pocket+Guide+to+Physical+Assessment,+185.&ots=BZUe_ib7eI&sig=IuHII1GyGQSpGEqtHmcMeApScW8&redir_esc=y#v=onepage&q&f=false

Clarke, C., & Lemon, R. (2016). Nervous system structure and function. Neurology: A Queen Square Textbook, 11-67. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1002/9781118486160.ch2

Counihan, T. J. (2016). Romberg Sign and neuromythology. Practical Neurology, 16(5), 421-421. Retrieved from https://pn.bmj.com/content/16/5/421.1

Davies, R. A. (2016). Audiometry and other hearing tests. In Handbook of Clinical Neurology (Vol. 137, pp. 157-176). Elsevier. Retrieved from https://www.sciencedirect.com/science/article/pii/B978044463437500011X

Glynn, M., & Drake, W. M. (2017). Hutchison's Clinical Methods E-Book: An Integrated Approach to Clinical Practice. Elsevier Health Sciences.

Hall, J. E. (2015). Guyton and Hall textbook of medical physiology e-Book. Elsevier Health Sciences.

Karl, A., Brandis, D., Auth, P., Clancy, R., & Rusgo, A. (2019). Kernig sign. StatPearls. Retrieved from http://knowledge.statpearls.com/chapter/pa-pance/23875/ 

Nicholl, D. J., & Appleton, J. P. (2015). Clinical neurology: why this still matters in the 21st century. J Neurol Neurosurg Psychiatry, 86(2), 229-233. Retrieved from https://jnnp.bmj.com/content/86/2/229.short