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
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Counihan, T. J. (2016). Romberg Sign and
neuromythology. Practical Neurology, 16(5), 421-421. Retrieved
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Davies, R. A. (2016). Audiometry and other hearing tests.
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