Health is a state of physical, mental and social well-being, not just the absence of disease or infirmity.
Physical well-being refers to the normal structure, function and metabolism of the body, and no abnormality is found using today’s technology. Mental well-being refers to a normal state of emotion, psychology, learning, memory and thinking, which is characterized by fullness of spirit, optimism and happiness in work and study, and the ability to cope with emergency events and complex problems. The state of social adaptation intact means that a person’s behavior matches with social moral norms, can maintain good interpersonal relationships, and can assume appropriate roles in society. It emphasizes that health is not only the absence of physical illness, but must also be mentally and socially intact. At the same time, this definition also implies a shift in the medical paradigm from a purely “biomedical model” to a “biopsychosocial medical model”. The above definition of health by the World Health Organization is highly general and is now widely accepted.
Diseases
Disease is generally considered to be a process of abnormal life activity caused by the disturbance of homeostasis under the action of certain etiological factors. In this process, the intact state of physical, mental and social adaptation is destroyed, and the organism enters a state of imbalance of internal environmental homeostasis and incompatibility with the environment or society.
Etiology
Etiology is the study of the causes and conditions of disease.
I. The cause of disease (cause )
Etiology refers to the factors that are essential to cause a disease and determine its specificity. For example, the hepatitis B virus causes hepatitis B.
There are many causes of disease, which can be generally divided into the following seven categories.
1.Biological factors
Biological factors mainly refer to pathogenic microorganisms and parasites. About 1/3 of all deaths worldwide each year are due to infectious diseases. (Examples: SARS virus caused by SARS, 23 people in Beijing eat snails infected with Guangzhou tubeworm disease, etc.) These causes cause a variety of infectious diseases, the pathogenicity depends on the number of pathogens invasion, virulence and invasiveness (invasiveness), but also with the body’s own defense and resistance to the size.
Characteristics of pathogenicity.
(1) certain invasion portal and localization
(2) The pathogen interacts with the organism to cause disease
(3) Both can be altered
(4) conditions have a great influence on its pathogenesis
2.Physical and chemical factors)
High temperature (or cold), high pressure (or sudden decompression), electric current, radiation, mechanical force, noise, strong acid, strong alkali and toxic substances, etc. For example, carbon monoxide poisoning, alcoholic cirrhosis of the liver, etc. Currently there is an increasing number of potential poisonings, such as renovation and food additives.
Pathogenic characteristics.
(1) Most of them have no obvious organ selectivity.
(2) Generally only initiating action.
(3) Incubation period is generally short or absent.
3, nutritional factors (nutritional factors)
It refers to the lack or excess of various essential substances or nutrients.
The normal life activities of the body rely on many essential substances such as water, various nutrients, certain trace elements, etc. to maintain. Lack or excess of these substances can lead to disease and even death in serious cases.
4.Hereditary factors (genetic factors)
Genetic factors refer to chromosomal aberrations or genetic material defects such as gene mutations.
Gene mutation is a change in gene structure that causes changes in protein expression, structure, and function, resulting in disease. For example, mutation or deletion of clotting factor VIII causes hemophilia A.
Chromosomal aberration (chromosomal aberration) – The disease is caused by abnormal number or structural changes of chromosomes.
5.Congenital factors
These factors cause various malformations and developmental defects, such as cleft lip, cleft palate, anencephaly, etc. Some congenital factors are genetic mutations, which are also hereditary factors. However, most congenital factors are acquired, such as rubella virus infection, use of teratogenic drugs, etc.
6.Immunological factors
Immunological factors such as excessive immune response, immunodeficiency or autoimmune response can affect the body.
Allergic reaction (anaphylactic reaction): The immune system reacts abnormally strongly to the antigen, resulting in tissue cell damage and physiological dysfunction. For example, allergy to penicillin, etc.
Autoimmune disease (autoimmune disease): diseases caused by reactions to autoantigens that cause damage to one’s own tissues. For example, systemic lupus erythematosus, etc.
Immunodeficiency disease (immunodeficiencydisease): Diseases caused by defects in humoral or cellular immunity. Such as AIDS, the body’s immune function fully collapsed, often due to co-infection and death.
7.Social andpsychological factors
Refer to the stressful work, poor interpersonal relationship, fear, anxiety and anger and other adverse emotional reactions. They are important in the development and prevention of the disease.
The human being is not a purely biological concept. People have a rich spiritual life, complex social connections, and often encounter social and psychological problems. These problems are of great importance in the development of diseases and in their prevention and treatment.
Conditions for the occurrence of disease (condition)
A condition is a state of the body or natural environment that can influence (promote or slow down) the occurrence of a disease.
For example
① malnutrition and overwork → resistance ↓ → invasion of TB bacteria → TB disease
Here, malnutrition and overexertion are the conditions, and the tuberculosis bacillus is the cause.
②Infants and young children → respiratory defense insufficiency → pathogenic microbial infection → respiratory infectious disease
Here, poor respiratory defenses are the condition and pathogenic organisms are the etiology.
In addition, there are two terms related to conditions: causative factors and risk factors.
Precipitatingfactors – factors that enhance the action of the etiology and promote the development of the disease.
For example: infection, excessive and rapid infusion, emotional stress → induced heart failure
riskfactors – when it is not clear whether they are causes or conditions.
For example, hyperlipidemia, hypertension, smoking, etc. are risk factors for atherosclerosis.
General patterns of disease occurrence
(I) Imbalance andregulation of homeostasis
In a normal state, the organism coordinates the activities of various systems, organs, tissues and cells through the fine regulation of nerves and body fluids, and the organism maintains an adaptive relationship with the natural and social environment, which is called homeostasis. When a disease occurs, one aspect of homeostasis is disturbed first, and the original balance is disrupted, and the body establishes a new balance in the pathological state through feedback regulation (especially negative feedback regulation). The establishment of various new equilibrium to the development of disease play a certain compensatory role, but also formed a variety of different pathological characteristics of the disease.
(II) Damage and anti-damage
Damage and anti-damage is also the universal law of disease development. It runs throughout the disease, and the contrast between the two forces determines the development direction and prognosis of the disease.
Anti-damage response to various kinds of damage is an important characteristic of biological organism, and is also a necessary condition for the survival of biological organism. Primitive unicellular organisms have this characteristic, such as amoebae that can extend their pseudopods to escape when they encounter harmful stimuli. When organisms evolved to mammals and humans, the organism’s organ systems became finely differentiated and the neuroendocrine system coordinated the organism’s response to injury, so the anti-injury response became very complex. In the process of disease development, the body needs to mobilize various anti-injury mechanisms to help eliminate pathogens, inhibit various injury factors, promote wound repair, and enhance the body’s resistance to injury. The anti-injury response is specific to the injury factors, but sometimes there are crossover or non-specific anti-injury responses exist. For example, the body can activate detoxification, stress, antioxidant enzymes and other reactions at the same time when toxic substances act.
(C) alternation of causeand result
The alternation of cause and result refers to the continuous transformation of cause and effect, which drives the disease to develop continuously and forms a vicious circle.
(D) local-systemic relationship
The biological organism is an interconnected whole. Diseases can be manifested as local changes, systemic changes, or both. For example, in addition to local symptoms such as cough and hemoptysis, tuberculosis can also lead to systemic reactions such as fever, night sweats, wasting, weakness and accelerated blood sedimentation, and can even spread to other parts of the body to form new tuberculosis lesions. Another example is boils in the danger triangle (local infection) → extrusion → spread to the skull → intracranial infection and sepsis. This is a typical example of a local lesion causing systemic changes. On the other hand, systemic diseases can also manifest as local changes. For example, local boils may appear in diabetic patients, and pathological fractures may manifest in uremic patients. Medical workers should be good at recognizing the relationship between the local and the whole, revealing the causal connection between the complex manifestations of the disease, and seizing the main contradiction to deal with it correctly, instead of adopting the simple method of “treating the head when it hurts and treating the foot when it hurts”.
The basic mechanism of disease occurrence
1.Neural mechanism
As we all know, many vital activities of living organisms are regulated by the nervous system (especially neural reflexes), and many causes of diseases are also caused by affecting the structure and function of the nervous system, which is called neural mechanism. Examples: B encephalitis, rabies, organophosphorus pesticide poisoning, shock.
2.Humoral mechanism
Body fluids are an important factor in maintaining the stability of the internal environment. Many pathogenic factors cause disease by affecting the quality and quantity of body fluids or their regulation, which is called the humoral mechanism.
Humoral factors usually act on the receptors of target cells in three ways, see the diagram.
3.Cellular and molecularmechanism
Various causes of disease by affecting the structure, function and metabolism of cells and molecules to cause disease, called cellular and molecular mechanisms. In recent years, many scholars attach great importance to the research of cellular and molecular mechanisms of diseases (including gene level and protein level research). Some scholars even believe that all human diseases (including monogenic diseases, polygenic diseases, and even acute damaging diseases) are directly or indirectly related to the alteration of genes.
However, the information obtained from the cellular-molecular level must also be integrated back to the whole to obtain a holistic understanding of life phenomena or diseases. Therefore, the concept of integrative medicine has been proposed in recent years.
Fate of disease
I. Recovery
There are two types of recovery: complete recovery and incomplete recovery. Complete recovery means that the damage caused by the disease has completely disappeared, and the function, metabolism and morphology of the body have completely returned to normal. Some infectious diseases may also lead to the acquisition of specific immunity. Incomplete recovery means that the damage caused by the disease has been controlled, the main symptoms disappear, and the body maintains relatively normal life activities through compensatory mechanisms, but the basic pathological changes of the disease have not been completely restored, and some may have sequelae (such as the scar left after myocardial infarction).
Death
Death is the termination of an individual’s life activity, which is the inevitable law of life. According to the traditional view, death is a process, which is divided into near-death period, clinical death period and biological death period. This is not conducive to the accurate determination of the time of death. Nowadays, academics tend to consider death as an event, with brain death as the hallmark of the event.
Brain death ( 脑死亡)
(1) Concept.
The irreversible permanent loss of function of the whole brain and the permanent cessation of function of the organism as a whole.
(2) Judgment criteria of brain death:
① irreversible coma (coma), unresponsive to external stimuli.
(ii) disappearance of brain-stem reflexes (brain-stem reflexes).
③autonomous respiratory arrest (apnea), requiring continuous artificial respiration.
④ disappearance of brain wave.
(5) Complete cessation of cerebral blood circulation.
(3) The significance of using brain death as a marker of death is as follows.
(1) It is beneficial to accurately determine the time of death and save medical resources.
(2) To provide more and better donors for organ transplantation.
In addition, it is important to distinguish brain death from “vegetative state”.
Treatment
Most diseases are related to one’s own bad habits, so a good diet and proper exercise can prevent many diseases and lead to a happy life!
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