**General Overview of Body Function and Dysfunction**

1. Characteristics of Life

Life is a unique state of matter characterized by the following features:

a) Constant Renewal:

– Metabolism: This process involves a series of interconnected stages, from respiration and digestion to intracellular metabolism and excretion.

– Anabolism: The process of acquiring substances from the environment and transforming them into nutrients for the body’s survival and development.

– Catabolism: The process of breaking down substances, releasing energy for the body’s life processes and eliminating metabolic byproducts.

– Note: Anabolism and catabolism are always opposing, parallel, and mutually supportive processes. The cessation of metabolism signifies the end of life. Metabolic disturbances lead to dysfunction in the body’s operations.

b) Responsiveness:

– Ability to Respond to Stimuli: The body has the capacity to perceive and react to stimuli from both external and internal environments. These stimuli include:

– Physical Agents: Mechanical, electrical, light, heat

– Chemical Agents

– Psychological Agents

– Manifestations: Responsiveness is evident at the cellular, organ, and whole-body levels.

– Threshold of Stimulation: Each cell type and organ has a unique minimum threshold of stimulation, representing the intensity required to elicit a response.

c) Reproduction:

– Genetic Replication: Reproduction is achieved through genetic codes encoded in the DNA of cells, leading to the creation of daughter cells identical to the parent cell.

– Cell Regeneration: When cells die, the body can regenerate new cells to compensate, sustain life, and promote growth.

d) Homeostasis:

– Internal Environmental Balance: This refers to the body’s ability to maintain the stability of the internal environment (extracellular fluid), regardless of changes in the external environment.

– Role: Homeostasis is crucial for sustaining the body’s life functions, enabling adaptation to the environment and ensuring normal development.

2. Extracellular Fluid and Intracellular Fluid

a) Extracellular Fluid:

– Composition: Includes blood, interstitial fluid, cerebrospinal fluid, lymph, ocular fluid, synovial fluid, etc.

– Transport: Constantly transported by the circulatory system.

– Exchange: Blood and interstitial fluid exchange substances through the intercellular space.

– Role: Extracellular fluid provides a living environment for cells, supplying nutrients, oxygen, and removing metabolic byproducts.

– Chemical Composition: Extracellular fluid contains numerous nutrients like oxygen, glucose, amino acids, fatty acids, and high concentrations of Na+, Cl-, and HCO3-.

b) Intracellular Fluid:

– Composition: Contains K+, Mg++, PO3-, and other nutrients vital for cell survival.

3. Mechanisms of Homeostasis Regulation

The body employs three primary mechanisms to regulate homeostasis:

a) Neural Regulation:

– Nervous System: Encompasses subcortical structures, the cerebral cortex, brainstem, spinal cord, sensory nerves, cranial nerves, motor nerves, and autonomic nerves.

– Reflex Arc: This is the pathway for transmitting neural signals from sensory organs to effector organs, allowing the body to react quickly and precisely to environmental stimuli.

– Receptor: Skin, mucous membranes, joint surfaces, vessel walls, surfaces of internal organs.

– Afferent Pathway: Sensory nerves, autonomic nerves.

– Neural Center: Brainstem, spinal cord.

– Efferent Pathway: Motor nerves, autonomic nerves.

– Effector: Muscle, glands.

– Unconditional Reflexes:

– Innate, lifelong reflexes.

– Species-specific.

– Genetically determined.

– Dependent on the receptor and stimulating agent.

– Reflex centers located in the lower nervous system.

– Tendon-bone reflexes, muscle tone located in the spinal cord.

– Baroreflex, respiration located in the brainstem.

– Examples: withdrawal reflex upon needle pricking, salivation upon seeing food.

– Conditional Reflexes:

– Acquired during life, based on unconditional reflexes.

– Individual-specific.

– Independent of the stimulating agent and receptor.

– Examples: a dog salivating upon hearing a bell (after training), a child fearing the dark (due to experience).

b) Humoral Regulation:

– Factors: Solutes in blood and body fluids, such as gas concentrations (O2, CO2), ions (Na+, Mg++, Ca++, K+), and hormones.

– Mechanism: These substances act on target organs to regulate bodily functions and maintain internal equilibrium.

c) Autoregulation Mechanisms:

– Mechanism: The body’s self-regulation to maintain homeostasis, based on the principles of negative and positive feedback.

1) Negative Feedback:

– Mechanism: When a factor in the body exceeds its permissible level, the body automatically triggers a response to reduce that factor back to normal, and vice versa.

– Examples:

– High blood pressure → vasodilation, decreased heart rate → blood pressure returns to normal.

– High target gland hormone concentration → suppression of the control gland’s activity → target gland function returns to normal.

2) Positive Feedback:

– Mechanism: When a factor in the body exceeds its permissible level, the body automatically triggers a response to further increase that factor.

– Examples:

– Blood clotting: when blood flows, the body automatically generates a clot to stop the bleeding.

– Labor: when the uterus contracts, the body automatically releases hormones to intensify uterine contractions.

– Note: Positive feedback typically operates within a specific range, after which it transitions to negative feedback to maintain the body’s stability.

4. Organ Systems Involved in Homeostasis Regulation

a) Digestive System:

– Function: Ingesting, grinding, and digesting food into nutrients the body can absorb through digestive enzymes and secreted fluids.

– Nutrients Received by the Body: Fatty acids, amino acids, ions, vitamins, water.

– Excretion: Undigested substances (fiber, intestinal bacteria residue, digestive fluids, etc.) are expelled as feces.

b) Liver:

– Function:

– Altering the chemical composition of numerous substances, converting them into forms more suitable for the body.

– Storing essential substances and releasing them when the body requires them.

– Participating in detoxification processes.

c) Respiratory System:

– Function: Providing oxygen to the body and eliminating CO2.

– Mechanism: Air circulation from the external environment into the body, through the nose, trachea, bronchi, alveoli, gas diffusion membrane, lung membrane, respiratory muscles, and thoracic cavity.

– Excretion: The lungs expel CO2 into the environment.

d) Muscular System:

– Skeletal Muscle: Enables bodily movement, searching for and processing food.

– Smooth Muscle: Helps the body receive air and nutrients entering cells, and expel metabolic byproducts.

e) Nutrient Transport System (Extracellular Fluid System):

– Blood: Transports nutrients to tissues.

– Two Stages of Transport:

– Transporting substances to tissues.

– Exchange of substances between capillaries and cells.

– Exchange of Substances: Blood and interstitial fluid constantly exchange substances and fluids.

f) Circulatory System:

– Function: Ensuring continuous blood circulation through a pump system comprising the heart and vascular system.

g) System for Excreting Metabolic Byproducts:

– Includes: Respiratory, digestive, urinary, and integumentary systems.

h) Urinary System:

– Function: Filtering blood, eliminating unnecessary or surplus substances (urea, some other metabolic byproducts), and reabsorbing substances essential for the body.

i) Kidneys:

– Function: Filtering, eliminating substances unnecessary for the body, and participating in regulating blood solute concentrations.

j) Skin:

– Function: Protecting the body, regulating body temperature, excreting sweat, Na+, Pb+.

5. Dysfunction of Body Functions

a) Disease:

– Unstable New Balance: A change in the state of internal balance, rendering the body less efficient in its operations.

– Limited Adaptability: Decreased ability of the body to adapt to the environment, making it susceptible to injury.

– Limited Work Capacity: Impacts the body’s health and work capacity.

b) Etiology:

– Study: Investigating the causes of disease, the mechanisms of action, and the conditions for disease manifestation.

c) Ancient Concepts of Disease:

– Monocasal Theory: Attributed disease to bacteria.

– Condition Theory: Disease arises from a confluence of conditions, with the patient themselves being one condition.

– Constitution Theory: Disease develops spontaneously, with severity varying depending on the individual’s constitution.

d) Contemporary Concepts of Disease:

– Cause: The factor that triggers the disease.

– Condition: The objective factor that facilitates the cause’s action.

– Reality:

– Every disease has a cause.

– The cause precedes the condition.

– The presence of a cause without a condition and good health may not lead to disease.

– A single cause can trigger multiple diseases, depending on the condition.

– Different causes can lead to the same disease.

– The body’s response can also be a condition.

e) Causes of Disease:

– Internal: Genetic inheritance and constitution.

– External:

– Mechanical and Physical Factors: Tissue or organ injuries, hot and cold temperatures, electric currents.

– Chemical and Toxic Factors.

– Social Factors:

– Allergies, ulcers, hypertension.

– Mental health, stress.

– Deafness due to noise, radiation-induced diseases.

f) Pathogenesis:

– Process of Disease Progression: From onset to resolution.

g) Etiological Agent:

– Initiator of Pathogenesis: The etiological agent causes the disease and then ceases to play a role, allowing pathogenesis to progress and resolve on its own.

– Coexistent with Pathogenesis: Eliminating the etiological agent also halts pathogenesis.

h) Impact of the Etiological Agent on Pathogenesis:

– Duration, dose, intensity of action.

– Location of action.

i) Influence of the Body on Pathogenesis:

– Nervous system, mental state.

– Endocrine system.

– Gender and age.

– Environmental influences.

– Systemic and local effects.

j) Influence of Hormones on Pathogenesis:

– ACTH and Corticosteroids: Anti-inflammatory effects, suppression of phagocytosis, inhibition of antibody production, reduced vascular permeability, decreased scar formation.

– Thyroxine: Increased basal metabolism and heat production, triggering febrile responses, mobilizing energy to combat pathogens.

– Growth Hormone and Aldosterone: Enhance inflammation, connective tissue proliferation, resistance to necrosis.

k) Pathological Vicious Circle:

– Process of Pathological Progression: Through multiple stages, where stages are interconnected, with earlier stages setting the stage for later ones, and later stages influencing earlier ones, intensifying the progression of pathogenesis, forming a closed loop.

Note:

– This article provides basic knowledge about body function and dysfunction.

– This information is for informational purposes only and should not be substituted for professional medical advice.

– If you have any health concerns, please consult a doctor for advice and treatment.