Introduction
The human body is incredibly complex and contains many sophisticated mechanisms. The different reactions and disorders it possesses result from the performance, or lack of performance, of these processes. The two case studies for this assignment show examples of these features. Hence, the intricacies of these mechanisms must be thoroughly examined to properly diagnose and treat illnesses and gain a greater understanding of the human organism.
Pain Sensitivity Case
Role of the Brain and Spinal Cord in Reflex Responses
The first case study features Chen and his response to touching a hot burner. Chen instinctively takes his finger away after touching the burner because he feels pain. The brain and spinal cord play a significant role in this response.
Nearly all body tissues include free nerve endings acting as pain receptors. When a tissue is injured, cells release chemicals that notify the injury to the free nerve terminals. The brain interprets the signal from Chen’s nerve endings as pain when the activated sensory neurons carry it there via the spinal cord (Goodenough & McGuire, 2016). Hence, the pain receptors transmitted the signal to Chen’s brain through the spinal cord, thus causing him pain.
Neurons Involved and the Withdrawal Reflex
In the abovementioned example, three distinct types of neurons allow Chen to feel pain and react to it. Pain receptors were the first class of neurons to become active. These neurons responded to potentially harmful stimuli by sending nerve signals to the spinal cord and brain (Goodenough & McGuire, 2016). The second type is the reticular activating system (RAS) neurons, which filter out sensory input, leaving only the most infrequent or important stimuli to reach the brain (Goodenough & McGuire, 2016). RAS is why Chen’s body instantly reacts to the burner’s heat instead of, for example, feeling his clothes rubbing on his body.
The third type is the motor neurons responsible for reflexes (Goodenough & McGuire, 2016). That is why Chen immediately pulled his arm away from the hot burner. Hence, the three types of neurons responsible for Chen’s reaction were pain receptors, RAS, and motor neurons.
Evolutionary Significance of Reflexes
As shown in the example above, pain is an important evolutionary mechanism that keeps organisms safe. The body uses pain as a warning system and a defense against additional damage (Goodenough & McGuire, 2016). For instance, pain typically deters someone who has a broken arm from moving it, which could result in further injury. Thus, pain is a crucial feature of the human body that prevents further damage to the organism.
Congenital Insensitivity to Pain: Case Study of Amira
Definition of Congenital Insensitivity to Pain
However, a complete lack of pain can lead to several disadvantages for a person. Congenital insensitivity to pain is an autosomal recessive condition identified by the absence of a pain reaction against harmful stimuli. Biallelic loss-of-function mutations in SCN9A, a gene with 27 exons on chromosome 2 (2q24.3) that encodes the alpha subunit of the voltage-gated sodium channel 1.7 (NaV1.7), are the source of this disorder (Marchi et al., 2022).
The NaV1.7 channel is more abundantly expressed in the olfactory sensory neurons and the peripheral nervous system. The role of NaV1.7 in the range of human pain syndromes has been shown by genetic, structural, and functional research (Marchi et al., 2022). Hence, congenital insensitivity to pain results from an inability of the organism to create NaV1.7, resulting in the absence of pain-related defense mechanisms.
An example of a person with the abovementioned disorder is Amira, the wife of Chen from the case study. If she touched the hot burner, she would not react to the sensation that caused Chen to pull his hand away reflexively, as she would not feel any pain. This is why people, especially kids, with this disorder need to be aware of their surroundings.
For example, a child with congenital insensitivity interested in contact sports must inspect their body regularly and inform nearby medical workers of their condition. This is because they will not feel pain if they suffer a fracture or other injury. Hence, people with congenital insensitivity to pain are in constant danger of injuries, as they cannot immediately react to harmful stimuli.
Multiple Sclerosis Case
Understanding Multiple Sclerosis (MS)
The second case study is based on Monica, who, right after her 30th birthday, was diagnosed with multiple sclerosis. Multiple sclerosis (MS) is a chronic autoimmune condition that causes demyelination, gliosis, and neuronal death in the central nervous system (CNS) (Tafti et al., 2022). The symptoms may include incontinence of the bladder and intestines, cognitive decline, tingling and numbness, focal weakness, and vision impairment.
Primary Cell Structures Affected in MS
Hence, the primary cell structure of Monica’s body affected by MS, which causes her symptoms, is the CNS, by which all voluntary and unconscious nervous system functions are integrated and coordinated (Goodenough & McGuire, 2016).
Connection Between MS and Symptoms
Perivascular lymphocytic infiltrates and macrophages cause the pathological breakdown of the myelin sheaths that protect the neurons, leading to myelin loss, which produces failure of axonal action-potential conduction (Tafti et al., 2022). Thus, MS is a chronic autoimmune condition that affects the CNS and diminishes the action potential of neurons through the loss of myelin.
Treatment and Mechanism of Action
However, MS can be, and currently is, treated through disease-modifying medication. Some of the most common disease-modifying treatments include glatiramer acetate, dimethyl fumarate, interferon-beta preparations, natalizumab, mitoxantrone, and fingolimod. Glatiramer acetate is a mixture of synthetic polypeptides, helping MS treatment through binding to limit activation and inducing regulatory cells (Tafti et al., 2022). Interferon-beta preparations modulate T and B-cell function, possibly alter cytokine expression, play a role in blood-brain barrier recovery, and have a chance at decreasing the expression of matrix metalloproteinase (Tafti et al., 2022).
Natalizumab inhibits leukocyte migration into the CNS (Tafti et al., 2022). Mitoxantrone helps with MS treatment by interfering with DNA repair and RNA synthesis, possibly affecting cellular and humoral immunity (Tafti et al., 2022). Finally, fingolimod has immunomodulatory effects possibly related to the suppression of T-cell migration (Tafti et al., 2022). Hence, MS is treated through disease-modifying medications.
Etiology and Hypotheses
While the etiology of MS is unclear, possible causes include immune, environmental, and genetic factors. The most hypothesized cause for MS is dysimmunity with an autoimmune attack on the central nervous system. Theoretically, an unidentified antigen stimulates and activates both Th1 and Th17, causing them to adhere to the CNS endothelium, penetrate the blood-brain barrier, and then launch an immune onslaught through cross-reactivity (Tafti et al., 2022).
Environmental factors that can cause MS include a lack of vitamin D and infections such as Epstein-Barr virus (Tafti et al., 2022). Finally, patients who have biological relatives who have MS are at a higher risk of developing MS, with an estimated heritability of between 35% and 75% (Tafti et al., 2022). Hence, MS can be caused by immune, environmental, or genetic factors.
Conclusion
Thus, the human body has many hidden mechanisms and features that must be adequately understood. As in the example of Amira and her congenital insensitivity to pain, one must keep in mind their physical disorders to prevent accidents and injuries. Moreover, further research on illnesses and their causes can lead to increased ease of treatment, as shown with multiple sclerosis. To summarize, accumulating and properly utilizing knowledge on medical conditions can lead to a safer, healthier future.
References
Goodenough, J., & McGuire, B. (2016). Biology of Humans: Concepts, Applications, and Issues (6th ed.). Pearson.
Marchi, M., D’Amato, I., Andelic, M., Cartelli, D., Salvi, E., Lombardi, R., Gumus, E., Lauria, G. (2022). Congenital insensitivity to pain: a novel mutation affecting a U12-type intron causes multiple aberrant splicing of SCN9A. PAIN, 163(7), 882–887. Web.
Tafti, D., Ehsan, M., Xixis, K. L. (2022). Multiple Sclerosis. National Library of Medicine. Web.