Global challenges Revision Notes

What is Cancer?

Cancer is a disease caused by uncontrolled cell growth and division. Healthy cells follow a regulated cycle of growth, division, and death. In cancer, cells undergo changes that cause them to lose this control, leading to rapid and continuous division. This disruption can occur due to damage to DNA or other cellular components responsible for regulating cell division.

Formation of Tumours

The uncontrolled division of abnormal cells results in the formation of a mass of cells called a tumour. Tumours are categorised as either benign or malignant. Benign tumours are non-cancerous; they typically grow slowly and remain in one location without spreading. Malignant tumours are cancerous; their cells can invade nearby tissues and spread to other parts of the body.

Metastasis: The Spread of Cancer

Malignant tumours have the ability to metastasise. This means that cancer cells can detach from the primary tumour, enter the bloodstream or lymphatic system, and travel to distant parts of the body. Once they settle in a new location, these migrating cells can begin to divide and form secondary tumours, which further disrupts body functions and makes the disease more severe.

Defining Health

Health is broadly defined as a state of complete physical, mental, and social well-being, not just the absence of illness. This definition highlights that true health goes beyond merely being free from identifiable diseases. A healthy individual functions optimally in all these aspects of life, allowing them to engage fully in daily activities and maintain a good quality of life. Various factors contribute to maintaining physical health, such as balanced diet, regular exercise, and adequate sleep.

Understanding Disease

Disease refers to a condition that negatively affects the normal functioning of the body or mind. Diseases can be categorised as communicable or non-communicable. Communicable diseases, such as tuberculosis or influenza, are caused by pathogens and can be spread from one person to another. Non-communicable diseases, like diabetes or cardiovascular disease, are not infectious and often result from a combination of genetic, lifestyle, and environmental factors. Both types of diseases disrupt the body's natural processes.

Interconnection of Health and Disease

Health and disease are not mutually exclusive; they are two points on a continuous spectrum. Being free from disease does not automatically mean perfect health, and living with a disease does not always equate to poor overall well-being. For instance, someone might not have a specific illness but still exhibit unhealthy behaviours that compromise their health over time. Conversely, individuals with chronic conditions can maintain good mental and social well-being through effective symptom management and support, which contributes to their overall health. This intricate relationship means that promoting health can often prevent disease, and managing disease can improve health.

Factors Influencing Health and Disease

Several factors interact to influence an individual's health status and susceptibility to disease. These include lifestyle choices (e.g., diet, exercise, smoking, alcohol consumption), genetic predispositions, environmental factors (e.g., air and water quality), socio-economic conditions (e.g., income, education, access to healthcare), and psychological well-being. For example, a poor diet can lead to obesity and increase the risk of heart disease, whereas a healthy lifestyle can enhance immunity and reduce the likelihood of contracting infections. Understanding these interconnected factors is crucial for effective health promotion and disease prevention strategies.

Benefits of Gene Technology in Agriculture

Gene technology, including genetic modification (GM), offers several advantages for modern agriculture. Crops can be engineered to be resistant to pests, reducing the reliance on chemical pesticides which can be harmful to beneficial insects and the environment. This also lowers production costs and makes food safer for consumption. GM crops can also be made more tolerant to environmental stresses such as drought, frost, or high salinity, allowing them to grow in challenging conditions and expanding cultivable land. Furthermore, genetic modification can increase crop yields, producing more food from the same amount of land, which is crucial for meeting the demands of a growing global population. Some GM crops are also enhanced with additional nutrients, such as 'golden rice' fortified with vitamin A, which can help combat nutritional deficiencies in certain regions. This can lead to improved human health outcomes.

Risks Associated with Gene Technology in Agriculture

Despite the benefits, there are several potential risks associated with the widespread use of gene technology in agriculture. One concern is the potential impact on biodiversity. For example, pest-resistant GM crops might reduce populations of certain insect species, disrupting food webs and ecological balance. Another significant risk is the possibility of gene transfer from GM crops to wild plants or non-GM crops through cross-pollination, leading to the creation of 'superweeds' that are resistant to herbicides, or contaminating conventional crop varieties. This makes weed management more challenging and could necessitate stronger chemical applications. There are also concerns about the long-term effects of consuming GM foods on human health, including potential allergic reactions or transfer of antibiotic resistance genes, although current scientific consensus generally indicates GM foods are safe. However, public perception and acceptance remain a barrier for some.

Ethical and Economic Implications

Beyond environmental and health considerations, gene technology in agriculture raises important ethical and economic questions. Ethically, some people object to the idea of manipulating the genetic makeup of living organisms, viewing it as 'playing God' or interfering with natural processes. This can lead to societal resistance against GM products. Economically, the development of GM crops is often controlled by a few large biotechnology corporations that hold patents on their genetically modified seeds. This can lead to increased seed costs for farmers, potential economic dependency on these companies, and reduced access to diverse, traditional seed varieties. It could also consolidate power within the food system, potentially disadvantaging small farmers and leading to monopolies. There are also concerns about intellectual property rights and the flow of genetic information.

Lifestyle Changes as a Primary Treatment for CVD

Many cardiovascular diseases are closely linked to lifestyle choices. Adopting healthier habits is often the initial and most fundamental step in both preventing and managing these conditions. A balanced diet, low in saturated fats, trans fats, cholesterol, salt, and added sugars, can significantly reduce blood pressure and cholesterol levels. Regular physical activity strengthens the heart, improves circulation, and helps maintain a healthy weight. Quitting smoking is crucial as smoking severely damages blood vessels and increases the risk of blood clots. Stress management techniques can also help lower blood pressure. The benefits of lifestyle changes include minimal side effects, improved overall health, and long-term sustainability. However, they require significant personal commitment and discipline, and their effects may take time to become apparent.

Medication-Based Treatments for CVD

Pharmacological interventions are common in treating cardiovascular diseases. Statins are prescribed to lower levels of 'bad' cholesterol (LDL) in the blood, reducing the risk of atherosclerosis. Anticoagulants, such as aspirin or warfarin, are used to prevent blood clots that can lead to heart attacks or strokes; however, they increase the risk of bleeding. Blood pressure medications, like beta-blockers or ACE inhibitors, help to control high blood pressure, reducing the strain on the heart and arteries. Diuretics help remove excess fluid and salt from the body, which can lower blood pressure. While these medications are highly effective, they often require long-term use and can have side effects, which vary depending on the specific drug. The benefits usually outweigh the risks when prescribed appropriately.

Surgical and Interventional Treatments for CVD

For more severe cases of cardiovascular disease, medical procedures or surgery may be necessary. Angioplasty is a procedure where a balloon is inflated inside a narrowed artery to widen it. Often, a stent (a small mesh tube) is then inserted to keep the artery open, preventing it from narrowing again. These procedures restore blood flow but carry risks such as artery damage, bleeding, and re-narrowing. Coronary artery bypass graft (CABG) surgery involves taking a healthy blood vessel from another part of the body and grafting it to create a new pathway around a blocked coronary artery, improving blood supply to the heart muscle. This is a major surgery with significant recovery time and risks, including infection and stroke. Artificial pacemakers can be implanted to regulate irregular heart rhythms. In cases of severe heart failure, a heart transplant may be the ultimate solution, though donor hearts are scarce and the patient requires lifelong immunosuppressants. Artificial hearts can be used as bridges to transplant or permanent solutions.