What is the role of the nervous system regarding sensation and movement?
Sensation- This is the crucial role of the nervous system. The sensation is the art of receiving information regarding an environment to gain inputs. The inputs pertain to whatever is occurring outside the body or at times in the body. In the nervous system, sensory roles record the existence of change as of homeostasis or certain events within an environment. A game is described as a stimulus (Carter, 2019). In most instances, when we talk about sense, what comes into mind is “big five”. These are hearing, touch, smell and taste. Ideally, taste and smell stimuli are chemical substances, which are in the form of compounds, molecules or ions. Feel is mechanical or rather physical, which interacts with skins. The stimulus for sight is light. Hearing is defined as sound perception. Sound is the stimulus of hearing which is the same as some touch aspects (Murray, Aquino & Nugent, 2019). There are more senses as compared to those available. However, the described list is a representation of the primary feelings. The above mentioned five senses receive stimuli from the exterior world where there exist conscious acuity. Further sensory stimuli can be attained from internal environments within the body). These might include organ wall otherwise concentration of particular ions within the blood.
The body has zillion sensory receptors-stimuli, which sense changes in an environment. These take place both within or outside the body. Stimuli monitor things like light, temperature as well as sound as of external environment (Murray, Aquino & Nugent, 2019). Within the body, that is to say, internal environment, receptors are tasked with detecting changes in the concentration of carbon dioxide, pH, pressure, different levels of electrolytes. The collected information is known as sensory input. After the sensory inputs have been collected, they are turned into electrical signals known as nerve impulses which transmitted towards the brain. Signals are then brought together to create sensations in producing thoughts which are added to memory. In most instances, decisions are made every moment anchored on sensory inputs.
Movement- the body movements are enabled through rhythmical contraction and relaxation of the muscles selected (Clauwaert, Schouppe, Van Oosterwijck, Danneels & Van Damme, 2019). Contraction takes if nerve impulses are transmitted across neuromuscular junctions towards the membrane which covers every fibre muscle. The muscles are never contracting incessantly but are kept in a contraction state. Slight movement results in widespread activities of muscles starting from the trunk up to the limps.
The movement might be intrinsic to the body and executed through muscles of body cavities and trunk. Examples can be seen on the muscles involved in swallowing, defecating, laughing, breathing and urinating. The movements are done through viscera smooth muscles like alimentary canals and bladders. These are innervated with parasympathetic and sympathetic nerves. Other movements associated with the body to the environments are either for signalling or moving to other persons. These are done through skeletal muscles which are located at the limbs and trunks. The skeletal muscles are attached to the bones thus are responsible for producing movements happening at the joints (Clauwaert, Schouppe, Van Oosterwijck, Danneels & Van Damme, 2019)). Again such moves are made possible by efferent motor nerves.
Each body movement has to have appropriate force, position and speed, and these movement aspects are incessantly reported to the central nervous systems by sensitive receptors to posture, stance, equilibrium the internal body conditions (Clauwaert, Schouppe, Van Oosterwijck, Danneels & Van Damme, 2019). The receptors are known as proprioceptors. They work towards keeping continuous reports in positions of a limb.
How do upper and lower motor neurons differ?
The upper and lower motor neurons are the two basic set of neurons which are present within the somatic motor pathway. By definition, upper motor neurons were initially discovered by William Gower. It was established within the brain stream and cerebral cortex. It transmits information down towards activating interneurons as well as lower neurons (Ravits, Paul & Jorg, 2007). On the other hand, a lower motor neuron is started within the spinal cord and ending into skeletal muscles. When lower motor neurons get lost, then the body will develop some weakness, muscle atrophy as well as muscle jerking (Ravits, Paul & Jorg, 2007). Both neurons are composed of the somatic nervous system meant to control voluntary movements of muscles. The table below outlines differences which can be witnessed in the lower and upper neuron as indicated by Mitsumoto et al. (2007).
| Upper Motor Neurons | Lower Motor Neurons |
| Are categorized concerning pathways which they move into | Are classified concerning the form of muscle fibre which they innervate |
| Are bound to form synapses with lower motor neurons | Are forming synapses with the body muscles |
| These are situated within Central Nervous Systems | Are located at either cranial nerve nuclei within brain stems or spinal cord within the grey matter |
| The lesions of a lower motor neuron might result in muscular atrophy, hyporeflexia, fasciculation and flaccid weakness of muscles | The lesions of upper motor neuron produce muscle weakness and spastic hyporeflexia. |
| These are meant to convey motor impulses as of the brain towards the synapses of the lower motor neurons. | Gather the already transmitted motor impulses as of upper motor neurons within the body |
| The cell bodies which are found on the upper side of the motor neuron are more significant as compared to those which are located on the lower side. | Most of the cell bodies for the lower motor neurons are smaller comparatively. |
The pathways, sensory tracts and motor tracts within the spinal cord are carrying motor and sensory nerves impulses from and to the brain. The paths of the somatic sensory and somatic motor are two forms of spinal tracts within the human nervous system. The pathways for somatic sensory is tasked with transmitting motor impulses towards the skeletal muscles as of the cerebral cortex (Winger et al., 2014). In summary, it is appropriate to conclude that the critical differences between lower and upper neurons are seen in the functionality and origin point.
Explain why you lose both motor and sensory function of a body part when a spinal nerve is numbed with anaesthetic agents.
Overall, anaesthetics often induce anaesthesia all through the body. These can be administered either via inhalation or rather direct injections into the bloodstream. The association between administered anaesthetic as well as depression which is seen in the sensory responsiveness of the brain is subdivided into the four phases. Stage one is where the patient gets to lose consciousness having diffident muscular relaxation. This is apt for minor procedures which are done shortly (Alkire, Hudetz & Tononi, 2008).
Additionally, anaesthetic often stimulates stage two, where augmented excitability as well as involuntary activities of making most of the surgery to be impossible. The rapid passages via stage two are sought with the physicians. Complete surgical anaesthesia is attained within stage two, which increases excitability as well as involuntary activities, making the surgery to be impossible. Anaesthesia of step four often marked by the loss of respiration as well as imminent collapsing of cardiovascular controls (Sloan & Heyer, 2002). General anaesthetics are provided to block neuromuscular impulse transmissions. Additional drugs are offered to make the muscles to relax to enable the process of surgical manipulations to be more comfortable for most of the physicians. Within these conditions, artificial respirations might be needed to maintain appropriate levels of carbon dioxide and oxygen within the blood.
Ideal anaesthetic agents permit rapid as well as pleasant induction to happen. It makes it possible to the anaesthetic levels to be controlled as well as rapid reversibility, appropriate relaxation of muscles as well as adverse or few toxic impacts on the patients. When these drugs reached the brain, they cut the link between the sensory and motor systems, making them appear inactive. In most cases, pain sentiments rely on the information transmissions from the region, which is traumatized to the brain centres. These anaesthetics are causing temporary blockage along the nerve fibres. This is generating a temporary loss in the pain sensations. For safer, rapid as well as anaesthesia which is well-controlled could be enabled through the administration of depressants via the central nervous system. This would lead to early anaesthesia onset when one gets a single dose. This is because most of the anaesthesia provided is highly soluble within lipids. Again, they have a higher rate of perfusion into the brain. Also, anaesthetics block nerve impulse conduction along with all forms of a nerve fibre (Sloan & Heyer, 2002). These incorporate sensory and motor nerve fibre, which are meant to carry impulses as of the brain towards the periphery. This is the collective experience which most of the dosages are having particularly leading to the list of pain. The function of the motor gets impaired. On most cases, thinner fibres are getting blocked first. The conduction can never occur when then the nerve fibres inactivated. Thus, it is the crucial reason as to why the motor and sensory function of a body part when a spinal nerve is numbed with anaesthetic agents (Alkire, Hudetz & Tononi, 2008).
References
Alkire, M. T., Hudetz, A. G., & Tononi, G. (2008). Consciousness and anaesthesia. Science, 322(5903), 876-880.
Carter, R. (2019). The human brain book: An illustrated guide to its structure, function, and disorders. Penguin.
Clauwaert, A., Schouppe, S., Van Oosterwijck, J., Danneels, L., & Van Damme, S. (2019). Hypervigilance for bodily sensations in the back during a movement task in people with chronic and recurrent low back pain.
Mitsumoto, H., Uluğ, A. M., Pullman, S. L., Gooch, C. L., Chan, S., Tang, M. X., … & Montes, J. (2007). Quantitative objective markers for upper and lower motor neuron dysfunction in ALS. Neurology, 68(17), 1402-1410.
Murray, K., Aquino, N., & Nugent, J. (2019). The Role of the Physical Therapist on the Neuro-Rehabilitation Team. In Acquired Brain Injury (pp. 163-199). Springer, Cham.
Ravits, J., Paul, P., & Jorg, C. (2007). Focality of upper and lower motor neuron degeneration at the clinical onset of ALS. Neurology, 68(19), 1571-1575.
Sloan, T. B., & Heyer, E. J. (2002). Anaesthesia for intraoperative neurophysiologic monitoring of the spinal cord. Journal of Clinical Neurophysiology, 19(5), 430-443.
Wainger, B. J., Kiskinis, E., Mellin, C., Wiskow, O., Han, S. S., Sandoe, J., … & Berry, J. D. (2014). Intrinsic membrane hyperexcitability of amyotrophic lateral sclerosis patient-derived motor neurons. Cell reports, 7(1), 1-11.