Nervous System: Structure, Function & Disorders | Comprehensive Guide
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Introduction : Comprehensive Nervous System Overview
Question 1 : What are the different levels of organization in the nervous system and their specific functions?
The contribution of knowledge about different levels of organization in the nervous system has been explained with a proper understanding of the functions (Sousa et al., 2017). An individual's nervous system is composed of various components with proper identification of specific functions, which leads to a better understanding of body activities with complete knowledge acquisition about different parts of the nervous system. It consists of two distinct parts, which then subdivided into many structural components with specific functions.
The Central Nervous System or CNS, which typically comprises the brain and the spinal cord
The Peripheral Nervous System or PNS, which comprises of the part external to CNS
The PNS is then subclassified into three individual components. The first part involves the nerves, which are mainly connected to the brain (Goldberger et al., 2019). The cranial nerves typically originate from and terminate in the brain, while the spinal nerves originate and terminate in the spinal cord.
Secondly, the classification of nerve fibers is based on their direction of propagation. The sensory nerve propagates impulse from the skin and from other sensory organs in the body to the components of the CNS. Next, the motor nerves propagate impulse from CNS components to the effectors.
Third, the motor nerves are further classified into the somatic nervous system, directing the skeletal muscle contraction and autonomous nervous system, which controls the organs and involuntary actions of the body.
The subdivision of the autonomic nervous system involves the sympathetic nerve, which stimulates the activities and hence prepares the body for specific action (Reiner and Levitz, 2018). On the other hand, the parasympathetic nerves reverse the stimulated action and induce tranquil functions.
Question 2 : How do motor and sympathetic nerves contribute to a man's sudden response to seeing a child in the road?
In the following case, where a response has been generated in the man due to the sudden action indicates the generation of an impulse by the different neurons or typically the motor nerves (Cekanaviciute et al., 20187). The main specification of these nerves is already illustrated in the previous discussion and summarized in the following diagram where the motor neurons induce an impulse transmitted from the central nervous system to the effectors, which significantly includes the muscles or glands. However, in this case, the main action has been transmitted to his body, especially hand movements and body posture. Further, sympathetic nerves have a significant role, which has induced a stimulation with activities that deliberately prepares the body for sudden action (Ziemssen and Siepmann, 2019). So when the driver (the man) saw the child in front of the road, his body was prepared with a stimulated response that resulted in a significant increase in heart rate and the breathing pattern.
Question 3 : How does the nervous system control the body's response and what role does the brain play in this process?
Different components of the nervous system typically control the effective response of the body. It is quite complicated to understand if not being observed minutely (Dresselhaus and Meffert, 2019). The central nervous system comprises two parts which are the brain and spinal cord. At many intervals, it has been accustomed that the brain is the epic centre for briefing the functions that the body normally performs and hence surmounts the specific voluntary and involuntary actions in a controlled manner. In certain case, as mentioned in the following question, it is the coordinate function of the brain that has memorized the number and identifies the person before directing the response ( Carpanini et al., 2019). Thus, the case specifies the voluntary action of the brain that the cerebrum has induced. The external layer of the cerebrum, also known as the cortex (the grey matter), directs the information to other components of the nervous system to draw a specific response based on the matter. Moreover, the thalamus's role indecisively directs the information from sensory organs to the cortex while promoting sensory response to the organ.
Question 4 : What is the structure of a nerve, and what are the functions of its different components?
A nerve can be defined as an enclosed structure with a configuration that forms the bundle-like projection of axons within the exterior region of the CNS and in the main region of the peripheral nervous system (Toral et al., 2019). The structure of a nerve typically provides a pathway that generally supports the electrochemical series of nerve fibres along the line of each axon fibres.
Based on the knowledge and information about the above-represented structure, the basic illustration of different parts of a nerve fibre and the functions they usually serve has been viewed thoroughly. The entire nerve configuration is composed of a layer of connective tissues known as epineurium, which further contains the glycocalyx (inner sleeves) and collagen fibres (Wagstyl et al., 2020). The main function of endoneurium is specific to the properties of the blood-brain barrier. It acts as a semipermeable membrane which allows certain molecules to cross the blood vessels and enter into the endoneurial fluid.
Further understanding about the structure of a nerve can be explained based on the categorization and function of each neuron fibre which includes-
Sensory Neuron essentially conducts sensory information from the receptors to CNS and then further processing of the information.
Motor Neuron essentially conducts signal transfer from CNS to muscle fibres.
Question 5 : How is a nerve impulse generated and transmitted between systems in living organisms?
The generation of nerve impulse and transmission of the same is a common and influential mechanism among living organisms that comprise different nerve cells, which typically helps in proper controlling and coordination processes with an effective outcome between two particular systems (Hooks et al., 2018). It mainly specifies the impulses that are generated by the nervous system and endocrine system. A series of events significantly occurs during the generation and transmission process of an impulse and generally prefers the following components in achieving single saltatory conduction.
During the resting state, there is no conduction of impulse by the Neuron. At this specific time, the nerve fibers are impermeable to sodium ions. The negatively charged proteins are found within the axoplasm, thereby enhancing potassium ions' permeability (Drukarch et al., 2018). This time the specific contribution of protein elements and potassium ions in the channels become more viable within the axon. However, the sodium ions remain at a lower concentration. The fluid present in the peripheral part of the axon is low in potassium ion concentration while high with sodium ions. Hence, establishing a concentration gradient.
The active transportation for both the ions generally takes place within the sodium-potassium pump. An event of specific transmission of 3 potassium ions within the channel and the outward movement of 2 sodium ions effectively occurs. Consequent to the action, the negatively charged inner surface and positively charged outer surface are established. This is called the polarisation of the cell.
Thus, the specific induction of a stimulus reverses the action and turns the freely permeable sodium ions to enter the cell. The reverse back action then turns the inner membrane to be positively charged, and the outer membrane becomes negatively charged (Cooper et al., 2017). This particular state of the cell is now termed depolarisation. Hence, a difference in electric potential is being established.
Question 6 : How does multiple sclerosis affect the brain and spinal cord?
The specification for multiple sclerosis explains the disabled condition where the brain is affected along with the spinal cord. The condition may deteriorate over a specific period. The nerve cells are typically surrounded by an insulating sheath known as the myelin sheath. It helps in the transmission of nerve impulse. In the case of multiple sclerosis, it certainly affects the myelin sheath, resulting in inflammation and severe damage.
Additionally, it affects the nerve cell fibres and typically damages them. It is responsive as an immunogenic specific disorder which creates resentment for the immune system to simultaneously affect the central nervous system (both the brain and spinal cord). It thereby causes a disruption in neuron signals across the body. Thus, the consequent disruption in nerve impulse propagation also takes place, which causes a total imbalance in body function and disjunction in the overall process.
Question 7 : What is multiple sclerosis and how does it affect the nervous system?
Dopamine has been considered a catecholamine neurotransmitter generally found in the central nervous system's neurons and the peripheral nervous system. This specific neurotransmitter is usually stored in the vesicles within the axon terminals and hence released at nerve depolarization (Caggiu et al., 2019). The dopamine interacts with the significant membrane receptor molecules to produce the effect. The effects are then terminated with re-uptake within the presynaptic Neuron. This specific action is influenced by the dopamine transporter or through metabolic inactivation through "monoamine oxidase (MAO-B)".
Parkinson's disease, also known as paralysis agitans, specifies a neurological disorder that generally affects the movement and its controlling action. With the onset of this disease, the nerve cells from the substantia nigra gradually degenerate, resulting in the overall content of dopamine neurotransmitter being lowered for the neurotransmission process within the corpus striatum.
Question 8 : What are the primary symptoms and brain regions affected by dyspraxia?
The condition with dyspraxia explains the significant indications of impairment or typical immaturity in proper muscle coordination. This can be recognized as a substantial issue which gradually increases with time and becomes convenient at a certain age (preferably in adulthood). With the conditions of dyspraxia, the main effect has been determined in the external region of the brain, i.e. in the cortex (van Leeuwen et al., 2018). The cortex generally divides into two specific hemispheres, typically named the left and right hemispheres of the brain. In usual conditions, both the parts function in coordination and hence promote an influential result. However, the person with dyspraxia seems to have improper coordination of both hemispheres, thus creating a mess in responsively doing proper activities.
Question 9 : What is tuberculosis, and how does it affect the central nervous system?
The condition tuberculosis defines a contagious and airborne disorder that generally affects the lungs and impacts a series of underlying symptoms. The microbe that significantly influences the disease has been recognized as a bacterial stain commonly known as Mycobacterium tuberculosis. The gradual increase of the conditions and lack of treatment can cause the significant flow of the bacteria within the bloodstream, thus infecting the organs and the tissues.
The region that is mainly affected by this bacteria during tuberculosis is the meninges. The external membrane covers the components of the central nervous system, i.e. the brain and the spinal cord. The infection in this membrane can cause fatal consequences resulting in meningeal tuberculosis.
Question 10 : What is the role of the medulla oblongata in the nervous system, and how can physical activity impact it?
The brainstem or middle part of the brain is considered to be the main interlink between main region (cerebrum) of brain and the spinal cord. This particular section is composed of three specific regions which significantly include the midbrain, pons and the medulla oblongata
(Wittbrodt et al, 2018). The contribution of medulla in the nervous system produces a specific knowledge about its location and the role it plays in proper functioning and maintaining body balance in a proper way. It typically lies in the lower section of the mid brain where it promotes a connection between cerebrum and the spinal cord. The essential role of medulla involves controlling of heart rate, body balance, and survival rate, proper blood circulation and maintaining the breathing rate. So after exercise it is necessary to maintain the heart rate and control the same during the recovery period otherwise the mid section of the brain, specially the medulla will affected which thereby can cause significant imbalance in body activities. Further, the excessive physical activities can damage the brain cells and reduces the abilities to make proper decisions.
Question 11 : How does a stroke affect the brain and body, and what are the consequences of damage to one hemisphere of the brain?
The effect of stoke is always one sided. This means that it only affects on part of the brain. The two sides of the brain usually control the alternate part, i.e. the left part of the control the right hemisphere while the right part controls the left hemisphere (Donkor, 2018). This can be illustrated with the fact that if there is severe damage on the right hemisphere of the brain then an individual may experience the effect of paralysis in the left side of the body. The general information of stroke explains that when there is insufficient or interruptive level of blood supply in various parts of brain then the consequence occurs which thereby reduces the ability of the person to do activities like earlier. The ultimate effect may lead to severe damage of brain cells and even complete death.
Reference list
Journals
Caggiu, E., Arru, G., Hosseini, S., Niegowska, M., Sechi, G., Zarbo, I.R. and Sechi, L.A., 2019. Inflammation, infectious triggers, and Parkinson's disease. Frontiers in neurology, 10, p.122.
Carpanini, S.M., Torvell, M. and Morgan, B.P., 2019. Therapeutic inhibition of the complement system in diseases of the central nervous system. Frontiers in immunology, 10, p.362.
Cekanaviciute, E., Rosi, S. and Costes, S.V., 2018. Central nervous system responses to simulated galactic cosmic rays. International journal of molecular sciences, 19(11), p.3669.
Cooper, J.F., Machiela, E., Dues, D.J., Spielbauer, K.K., Senchuk, M.M. and Van Raamsdonk, J.M., 2017. Activation of the mitochondrial unfolded protein response promotes longevity and dopamine neuron survival in Parkinson’s disease models. Scientific reports, 7(1), pp.1-16.
Donkor, E.S., 2018. Stroke in the century: a snapshot of the burden, epidemiology, and quality of life. Stroke research and treatment, 2018.
Dresselhaus, E.C. and Meffert, M.K., 2019. Cellular specificity of NF-κB function in the nervous system. Frontiers in immunology, 10, p.1043.
Drukarch, B., Holland, H.A., Velichkov, M., Geurts, J.J., Voorn, P., Glas, G. and de Regt, H.W., 2018. Thinking about the nerve impulse: a critical analysis of the electricity-centered conception of nerve excitability. Progress in neurobiology, 169, pp.172-185.
Goldberger, J.J., Arora, R., Buckley, U. and Shivkumar, K., 2019. Autonomic nervous system dysfunction: JACC focus seminar. Journal of the American College of Cardiology, 73(10), pp.1189-1206.
Hooks, B.M., Papale, A.E., Paletzki, R.F., Feroze, M.W., Eastwood, B.S., Couey, J.J., Winnubst, J., Chandrashekar, J. and Gerfen, C.R., 2018. Topographic precision in sensory and motor corticostriatal projections varies across cell type and cortical area. Nature communications, 9(1), pp.1-16.
Reiner, A. and Levitz, J., 2018. Glutamatergic signaling in the central nervous system: ionotropic and metabotropic receptors in concert. Neuron, 98(6), pp.1080-1098.
Sousa, A.M., Meyer, K.A., Santpere, G., Gulden, F.O. and Sestan, N., 2017. Evolution of the human nervous system function, structure, and development. Cell, 170(2), pp.226-247.
Toral, M., Robles-Vera, I., De la Visitación, N., Romero, M., Yang, T., Sánchez, M., Gómez-Guzmán, M., Jiménez, R., Raizada, M.K. and Duarte, J., 2019. Critical role of the interaction gut microbiota–sympathetic nervous system in the regulation of blood pressure. Frontiers in physiology, 10, p.231.
van Leeuwen, L.M., Boot, M., Kuijl, C., Picavet, D.I., van Stempvoort, G., van der Pol, S.M., de Vries, H.E., van der Wel, N.N., van der Kuip, M., van Furth, A.M. and van der Sar, A.M., 2018. Mycobacteria employ two different mechanisms to cross the blood–brain barrier. Cellular microbiology, 20(9), p.e12858.
Wagstyl, K., Larocque, S., Cucurull, G., Lepage, C., Cohen, J.P., Bludau, S., Palomero-Gallagher, N., Lewis, L.B., Funck, T., Spitzer, H. and Dickscheid, T., 2020. BigBrain 3D atlas of cortical layers: Cortical and laminar thickness gradients diverge in sensory and motor cortices. PLoS biology, 18(4), p.e3000678.
Wittbrodt, M.T., Sawka, M.N., Mizelle, J.C., Wheaton, L.A. and Millard?Stafford, M.L., 2018. Exercise?heat stress with and without water replacement alters brain structures and impairs visuomotor performance. Physiological reports, 6(16), p.e13805.
Ziemssen, T. and Siepmann, T., 2019. The investigation of the cardiovascular and sudomotor autonomic nervous system—a review. Frontiers in neurology, 10, p.53.
