Pathophysiology Key questions Ch 1-10
How does allostatic overload contribute to the development of disease?
Allostatic overload reflects maladaptation or damage that occurs to the body's tissues and organs due to an allostatic response that is excessive or ineffectively regulated. When homeostasis can no longer be attained and protective mechanisms are weakened, dysregulation of the mechanisms and mediators involved in the stress response can increase the risks of developing certain diseases
Why is an immune response usually more effective on subsequent exposure to an antigen than after the first exposure?
An immune response is usually more effective on subsequent exposure because the T-cell receptors on T lymphocytes and memory B cells are able to recognize the antigen and quickly produce the appropriate antibodies, resulting in a much faster and larger lymphocyte response. The immune response to primary exposure is usually slow and often insufficient to prevent illness
How do noncellular immune system components, including antibodies, complement, and clotting factors, aid the immune response?
Antibodies bind to particular antigens and function in precipitation, agglutination, neutralization, opsonization, and complement activation. Complement activation results in inflammation and formation of membrane attack complexes that directly lyse cellular antigens. Tissue injury from the infectious process activates the coagulation cascade which forms a fibrin meshwork to help entrap and localize the agent. The kinin system is also activated, which promotes vasodilation to increase blood flow to the area
How do immune cells communicate through cell-to-cell interactions and through secreted cytokines?
Antigen-presenting cells bind to T cells which stimulate intracellular signaling pathways in the B cell and helper T cell that promote clonal expansion and differentiation. Activation of the helper T cell causes release of cytokines, which is required for B cells to proliferate and begin antibody synthesis
What is the role of the environment in the development of congenital disorders?
Certain chemicals, radiation, and viral infections can cause adverse influences during fetal development resulting in congenital malformations. Susceptibility to a teratogen depends on the amount of exposure, developmental stage of the fetus when exposed, the prior condition of the mother, and the genetic predisposition of the fetus
How are substances transported across the cell membrane?
Large, lipid-insoluble molecules are transported across the plasma membrane by endocytosis and exocytosis. Small, lipid-insoluble molecules are transported across the plasma membrane by three kinds of membrane proteins: ATP-driven pumps, carriers, and channels
How might lifestyle and carcinogen exposure contribute to cancer risk?
Lifestyle choices may lead to a greater amount of carcinogen exposure, which increases cancer risk. Lifestyle factors of particular importance are tobacco use, nutrition, and obesity. Sun exposure is a particular risk factor for skin cancer, and sexual exposure to certain strains of human papillomavirus predisposes to cervical cancer
How do macrophages, granulocytes, and lymphocytes work together to locate, recognize, and eliminate pathogens?
Macrophages and dendritic cells are commonly the first immune cells to encounter the antigen; they engulf and display the antigen on their cell surface; macrophages secrete cytokines that stimulate white blood cell (WBC) production and help WBCs locate the area. T helper cells are activated by these antigen-presenting cells and secrete cytokines that stimulate the production of WBCs in the marrow, initiate proliferation of mature B and T cells, and stimulate the phagocytic potential of macrophages and neutrophils. T cells also assist in B cell proliferation and antibody secretion
What conditions compromise host defenses against microorganisms?
Malnutrition and immunosuppressive agents can depress immune function; chronic illnesses such as diabetes and cardiovascular disease impair circulation of immune components, trauma, burns, and invasive instrumentation/procedures disrupt epithelial barriers allowing greater exposure to microorganisms; the very young have immature immune function while the very old may have degenerating immune function; and stress may the increase secretion of corticosteroids which depresses immune function
What are the common features of autoimmune disorders and certain types of hypersensitivity disorders?
Most autoimmune reactions toward self tissues are mediated through type II (cytotoxic) and type III (immune-complex) hypersensitivity mechanisms
How does the simple four-base structure of DNA serve as a template for synthesis of proteins that may contain 20 varieties of amino acids?
A series of three nucleotides (triplet) is needed to code for each of the 20 amino acids. Since there are four different bases (cytosine, guanine, adenine, and thymine), there are 64 different possible triplet combinations. Three of the nucleotide triplets, or codons, signal the end of the protein code and do not code for amino acids, while some of the amino acids are specified by more than one codon (
What general factors affect the expression of disease in a particular person?
Age, gender, genetic and ethnic background, socioeconomic factors and lifestyle considerations, and geographic location may affect the expression of disease in a particular individual
Why is it that some cells can produce action potentials and others cannot?
Action potentials are triggered by membrane depolarization. Thus, cells that are capable of rapid changes in the membrane potential, such as nerve and muscle cells, are able to produce action potentials. These cells are electrically "excitable" and can generate and propagate action potentials. The usual trigger for depolarization in nerve and muscle cells is binding of a neurotransmitter to cell surface receptors, which causes channels in the membrane to open and allow sodium ions to enter the cell
What are the major cellular structures and their functions?
A. The plasma membrane protects internal cell contents from the external environment, transports nutrients and waste products, generates membrane potentials, and provides cell recognition, communication, and growth regulation. B. The cytoskeleton, made up of actin, microtubules and intermediate filaments, regulates the cell shape, movement, and the trafficking of intracellular molecules. C. The nucleus contains the genomic DNA, which contain nuclear genes that code for the synthesis of proteins. D. Endoplasmic reticulum and Golgi apparatus function together to synthesize proteins and lipids for transport to lysosomes or the plasma membrane. E. Lysosomes and peroxisomes are membrane-bound bags of digestive enzymes that degrade intracellular debris. F. The mitochondria contain enzymes necessary for oxidative phosphorylation to produce ATP
What are the inheritance patterns and general clinical features of some common genetic disorders?
Autosomal Dominant Disorders (pgs. 113-114) Marfan syndrome, in which there is a disorder of the connective tissue of the body resulting in a tall and slender build with long, thin arms and legs. Huntington disease, which primarily affects neurologic function, results in mental deterioration and uncontrollable movements of the limbs. Autosomal Recessive Disorders (pgs. 116-117) Albinism refers to a lack of pigmentation of the hair, skin and eyes resulting in blonde hair, pale skin, and light-colored eyes. Phenylketonuria results from an inability to metabolize the amino acid phenylalanine due to a lack of the enzyme phenylalanine hydroxylase. Affected children tend to be overly irritable and tremulous with slowly developing mental retardation. Cystic fibrosis, in which there is a defect in a membrane transporter for chloride ions in epithelial cells, resulting in abnormally thick secretion in glandular tissues. It primarily affects the lung bronchioles and pancreatic ducts. Sex-Linked Disorders (pgs. 117-118) Hemophilia is associated with a deficiency of factor VIII and results in a bleeding disorder in which the individual bleeds easily and profusely from minor injuries.
To what kind of injuries are cells susceptible?
Cellular injury and death can result from a variety of cellular assaults, including ischemia and hypoxic injury, reperfusion injury, nutritional deficits, infectious and immunologic injury, and chemical, physical, and mechanical factors
What are the usual cellular responses to reversible injury?
Cellular responses to reversible injury, regardless of the cause, often result in cellular swelling and the accumulation of excess substances within the cell. These changes reflect the cell's inability to perform normal metabolic functions owing to insufficient cellular energy in the form of adenosine triphosphate (ATP) or dysfunction of associated metabolic enzymes
How do infectious microorganisms, including bacteria, viruses, fungi, and parasites, differ in structure, life cycle, and infectious processes?
Bacteria are characterized according to shape (cocci, rods, spirals), reaction to stains (Gram negative, Gram positive, acid fast), and oxygen requirements (aerobic, anaerobic). Once they have penetrated the initial defense mechanisms, the bacteria multiply and create a colony, which stimulates an acute inflammatory reaction from the host. If the responses are insufficient to contain the infection, the bacteria move throughout the body through the natural currents of fluid. They can invade any organ of the body (pg. 168-170). Viruses are bits of genetic material (DNA or RNA) with associated proteins and lipids. They are intracellular pathogens that use the host's energy sources and enzymes to replicate. DNA viruses first produce messenger RNA in the host cell's nucleus with the host cell's enzymes, which produces proteins from the messenger RNA that allow the DNA of the virus to replicate. RNA viruses replicate depending on their type: Retroviruses can create messenger RNA and DNA from their own genome. Viral DNA is incorporated into the host cell's DNA, thus when the host cell replicates, the viral DNA also replicates (pg. 171). Viruses in which the RNA is a single positive copy use the strand as a direct template to make viral proteins and a complementary RNA strand. The complementary strand then serves as a template for making more positive strands that can be packaged into new viruses. The RNA viruses that posses a negative copy replicate in the same manner except that the RNA must be transcribed to a positive complementary copy before it can produce proteins or viral RNA (pgs. 174-175). Fungi are nonphotosynthetic, eukaryotic protists that are disseminated through the environment. They can reproduce by simply dividing or by combining their genetic information before dividing. Fungi cause infection first by colonizing the area (adherence and proliferation), and then invading the epithelium. Fungal infections can be superficial, subcutaneous, or systemic (pgs. 175-176). Parasites include protozoa, helminthes, and arthropods. These parasites live on or in their host during some part of their life cycle, which includes a larval and adult stage. Manifestations of parasitic infection vary depending on the organism and site of infection, with the skin and gastrointestinal tract being the most common sites
In what ways to benign and malignant tumors differ?
Benign cells more closely resemble their tissue type of origin, grow slowly, have little vascularity, rarely have necrotic areas, and often retain functions similar to those of the tissue of origin. Malignant cells often grow rapidly and spread to distant sites, frequently have necrotic tissue, initiate vessel growth in the tumor, and are dysfunctional
What is the role of major histocompatibility complex (MHC) class I and II proteins in cell-mediated immunity?
Cytotoxic T cells can only recognize an antigen if it is physically bound to an MHC class I molecule, in which it is stimulated to release enzymes and pore-forming proteins that lyse the target cell. MHC class II proteins are used to present antigens obtained from extracellular sources, which are engulfed by the antigen-presenting cell. The MHC II-antigen complexes are then displayed at the cell surface where T helper cells can detect them
By what mechanisms can the cells of an organism, which all contain identical genes, become differentiated into divergent cell types?
It is the expression of a relatively few tissue-specific genes that results in differences among cell types. Differences in DNA packaging and the combination of gene regulatory proteins passed on during cell division are important mechanisms that lead to the stable expression of tissue-specific genes in particular cell types
What properties are gained during tumor progression that contribute to malignant behavior and metastasis?
During tumor progression, cancer cells proliferate despite the lack of growth-initiating signals from the environment; they escape signals to die and are capable of unlimited replication; they are genetically unstable and evolve by accumulating new mutations at a much faster rate than normal cells; they invade local tissue and migrate from their site of origin to colonize in distant sites
What is the relationship between homeostasis and allostasis?
Homeostasis is a state of equilibrium, of balance within the organism, whereas allostasis is the overall process of adaptive change necessary to maintain survival and well-being. Thus, allostasis is a process that supports homeostasis; the organism's overall stability is accomplished through change
How do cells acquire and use energy?
Energy-requiring reactions within cells are driven by coupling to ATP hydrolysis. Cells acquire energy through catabolism, the energy-releasing breakdown of nutrient sources to provide ATP to the cell. Cells use energy in the form of ATP. Each cell must continuously synthesize its own ATP to meet its energy needs. ATP is synthesized primarily from the breakdown of glycogen and fat through glycolysis, the citric acid cycle, and oxidative phosphorylation
What are the general structures and functions of the four main tissue types: epithelial, connective, muscle, and nerve?
Epithelial cells adopt a variety of shapes and functions depending on their locations. Stratified epithelium makes up the epidermis of the skin and is primarily protective in function. Simple epithelium, consisting of a single layer of cells, lines the blood vessels and intestines, and forms the kidney tubules, where absorption is its primary function. Classifications of connective tissue include loose connective tissue, dense or supportive connective tissue, and hematopoietic tissue. Connective tissue commonly functions as a scaffold on which other cells cluster to form organs, holds tissues together, forms an elaborate extracellular matrix which is important in the maintenance of cell differentiation, and plays an important part in the support and repair of tissues and organs. Muscle tissues include skeletal, cardiac, smooth and myoepithelial tissues, and are specialized for contraction. Nervous tissue generates and transmits electrical impulses throughout the body, which provides a rapid communication network between the central nervous system and various body parts
How are etiology and pathogenesis used to predict clinical manifestations and response to therapy?
Etiology is the study of the causal factors that provoke a particular disease or injury. Pathogenesis is a description of how etiologic factors are thought to alter physiologic function and lead to the development of clinical manifestations that are observed in a particular disorder or disease. An understanding of the etiology, pathogenesis and clinical manifestations of a particular disorder may suggest that certain treatments could be helpful
What factors influence the transmission of infectious agents?
Factors that influence the transmission of infectious agents include the reservoir of the infectious agent, the portal of exit and entry, the mode of transmission (direct or indirect), and the victim's susceptibility
How is gene expression regulated?
Gene expression is regulated at each of the steps in the pathway from DNA to RNA to protein synthesis by regulating the rate and timing of gene transcription. Cells contain DNA-binding proteins that are able to enhance or inhibit gene expression. These gene regulatory proteins recognize and bind only particular DNA sequences, and thus are specific to the genes they regulate
How is genetic information stored in the cell and transmitted to progeny during replication?
Genes are the basic units of genetic information and are composed of DNA located on chromosomes. The DNA double helix separates into single strands to provide a template for synthesizing new, identical DNA strands that can be passed on to daughter cells during cell division
How are hypersensitivity disorders detected, prevented, and treated?
Hypersensitivity disorders are detected based on presenting symptoms and organ involvement, which can range from an acute systemic allergic reaction with anaphylaxis, to a more localized response, such as with immune complex glomerulonephritis, causing hematuria, proteinuria, oliguria, and red cell casts in the urine.Since hypersensitivity reactions are specific to a particular antigen, these disorders are prevented by avoiding the antigen if identified (if possible) or desensitization therapy. Treatment depends on the type of hypersensitivity reaction but may include immunosuppressive agents, such as corticosteroids or cytotoxins, or plasmapheresis
How are genes transmitted from parent to offspring?
In humans, genes are organized into 46 different chromosome units (23 pairs). One member of each pair is inherited from the mother, and the other is inherited from the father
How do innate and adaptive immune mechanisms differ?
Innate immune mechanisms do not require any previous exposure to mount an effective response against an antigen, and a wide variety of different antigens are recognized. Adaptive, or specific, immune mechanisms respond more effectively on second exposure to an antigen, and are highly restricted in the ability to recognize antigens
How do cells in a multicellular organism communicate with one another?
Intercellular communication is accomplished by three means: (1) gap junctions, which directly connect the cytoplasm of adjoining cells; (2) direct cell-to-cell surface contact; (3) secretion of chemical mediators, or ligands
How do necrosis and apoptosis differ?
Necrosis is usually a consequence of disrupted blood supply and can result in local and systemic symptoms, including pain, inflammation and loss of function. Apoptosis results from activation of intracellular signaling cascades that cause cell suicide and is not usually associated with systemic manifestations of inflammation
How do neoplastic cells differ from normal cells?
Neoplastic cells have an altered expression of cellular genes that normally regulate cell proliferation and differentiation that leads to uncontrolled cellular growth
What are the key features of Selye's General Adaptation Syndrome?
Nonspecific physiologic responses to stress incorporate three systemic stages: alarm, resistance, and exhaustion. The alarm stage (fight-or-flight response) begins when the hypothalamus senses a need to activate the general adaptation syndrome (GAS) in response to a stimulus, a stressor placing the balance of homeostasis at risk. The hypothalamus then mediates the activation of the sympathetic nervous system, which in turn stimulates the adrenal medulla to release catecholamines into the system. The release of corticotropic-releasing hormone (CRH) from the hypothalamus stimulates the anterior pituitary to release ACTH. ACTH subsequently causes the adrenal cortex to release glucocorticoids, specifically cortisol. In the resistance stage, the sympathetic nervous system and adrenal medulla and cortex are working at full force. If the stressor is adequately addressed or resolved, the organism returns to its steady-state with all of the mechanisms activated by the alarm stage returning to their baseline level of functioning. Exhaustion occurs when the body is no longer able to bring about a return to homeostasis, which can lead to maladaptation, development of pathology, and death
How are normal and abnormal physiologic parameters defined?
Normal physiologic parameters are defined by measuring a particular variable in the general population, and determining the standard deviation. A normal range is suggested as the mean +/- 2 standard deviations. Measurements outside of the normal range are considered to be abnormal
How might abnormal meiosis lead to alterations in chromosome number or structure?
Normally, meiosis results in four daughter cells, each having one-half the normal number of chromosomes (23). Nondisjunction and anaphase lag, which can occur during meiosis, can lead to an abnormal number of chromosomes, termed aneuploidy. Alterations in chromosomal structure are usually due to breakage and loss or rearrangement of pieces of the chromosomes during meiosis. The process of crossing results in abnormal meiosis, resulting in portions of chromosomes that are lost, attached upside down, or attached to the wrong chromosome. Abnormal chromosomal structures result from translocations, inversions, deletions, or duplications
What are opportunistic infections, and when do they develop?
Opportunistic infections are caused by normal flora or microorganisms that do not normally cause infection, which become pathogenic when the immune system is compromised
How might overexpression of proto-oncogenes lead to abnormal cellular proliferation?
Overexpression of proto-oncogenes can lead to abnormal cellular proliferation through increased coding for components of the cellular growth-activating pathways: growth factors, receptors, cytoplasmic signaling molecules and nuclear transcription factors
What is pathophysiology?
Pathophysiology is the study of abnormalities in physiologic functioning of living beings and seeks to reveal physiologic responses of organisms to disruptions in its internal or external environment
How is pedigree analysis used to determine if a trait is inherited as autosomal dominant, autosomal recessive, or X-linked?
Pedigree analysis is used to trace the transmission of a single-gene trait through the history of a family. A pedigree chart demonstrates family relationships and members that have a certain trait. Autosomal dominant traits are expressed in the heterozygous condition, thus affected individuals will have at least one affected parent, the trait will generally appear in every generation, two affected parents may have unaffected offspring, and two unaffected parents only have unaffected offspring. Autosomal recessive traits are only expressed in the homozygous condition, thus unaffected parents can have affected male and female offspring, whereas two affected parents will result in all of the offspring being affected. If the trait is inherited as X-linked (typically recessive), generally only males will be affected
What methods of genetic testing are available?
Prenatal genetic testing can be performed on samples from amniocentesis, chorion tissue, or umbilical cord blood. Postnatal genetic analysis is usually done on peripheral blood samples of lymphocytes
How do the etiologic processes of primary and secondary immune deficiency disorders differ?
Primary deficiencies are congenital, genetic, or acquired defects that directly affect immune cell function. Secondary deficiencies are conditions that impair immune function as a result of other nonimmune system disorders
What factors affect the stress response?
Response to a stressor depends upon its magnitude and the meaning that the stressor has for an individual. Stressors may be perceived as more or less stressful. Perception depends on genetic constitution, past experiences and conditioning, and cultural influences. The type of stressor also affects the stress response; they may be physical, chemical, biological, sociocultural, or psychological. The developmental stage of life and effects of other previous or concurrent stressors all contribute to the stress response
How are reversible and irreversible cellular injuries differentiated?
Reversible and irreversible cellular injuries are differentiated by the cell's ability to adapt or repair. In reversible injuries, hydropic swelling and intracellular accumulation typically resolve when the causative factors are removed. As the cell adapts to persistent stress, atrophy, hypertrophy, hyperplasia, metaplasia, and dysplasia may occur, which are potentially reversible when the cellular stress is relieved. However, when the injury is too severe or prolonged to allow cellular adaptation or repair, irreversible cellular injuries cause pathologic cell death, necrosis and apoptosis
What are the normal mechanisms of cellular growth control?
Somatic cells divide by mitosis in which daughter cells each receive an identical and complete set of 46 chromosomes. Germ cells, such as eggs and sperm, divide by meiosis, where significant chromosomal rearrangement occurs. Cell replication normally requires specific extracellular mitogens that activate signaling systems within the cell. Cyclin proteins and cyclin-dependent kinases alter the function of the Rb protein, causing it to release transcription factors that begin the process of replication
What treatment options are available for benign and malignant tumors?
Surgery is used for benign and malignant solid tumors, and may be curative for localized benign tumors. Radiation therapy is used to kill tumor cells when surgery is not an option, and to kill tumor cells in the local area after tumor removal; it may be used for benign or malignant tumors. Chemotherapy, immunotherapy, gene and molecular therapy, and stem cell transplantation are typically reserved for malignant tumor types
What are the potential mechanisms whereby erroneous reaction of the immune system with self tissue leads to autoimmune diseases?
The antigenic mimicry theory proposes that small alterations in self tissue may lead to immunogenic attack; self antigens that do not come in direct contact with lymphocytes during fetal development may cause autoimmune reactions if they are subsequently released from sequestration. Abnormal production of subclasses of T lymphocytes, particularly T-suppressor cells, as well as the development of abnormal B cells that do not respond to suppressor T cell signals has also been proposed. Viruses may also be a factor as they can alter self cells. A genetic component is also probable in many presentations
What are the clinical features of the common immunodeficiency disorders?
The clinical features of the common immunodeficiency disorders are severe recurrent, unusual, or unmanageable infections
What is the role of epidemiology in the identification, definition, and prevention of infectious diseases?
The goals of epidemiology are to define the disease, identify outbreaks, assist in the development and evaluation of treatment protocols, and develop prevention strategies
What are the major organs and cellular components of the body's defense against foreign antigens?
The major organs and cellular components of the body's defense against foreign antigens include: Skin and mucous membranes—monocytes and macrophages Bone marrow—B lymphocytes and leukocytes Thymus—T lymphocytes Tonsils, spleen, and lymph nodes—B and T lymphocytes Peyer patches - primarily B lymphocytes
What kinds of information about disease can be gained through understanding concepts of epidemiology?
The occurrence, incidence, prevalence, transmission, and distribution of diseases in large groups of people or populations are established through epidemiology, which are essential for effective prevention strategies and treatment
What roles do genes play in determining cell structure and function?
The presence of structural proteins and enzymes, as well as their relative activity, produce the characteristics of the cell. Genes play a fundamental role in determining cell structure and function by directing the synthesis of proteins and coding for ribonucleic acid (RNA) molecules, which also direct the synthesis of proteins during translation. Many additional molecules are involved in the process of protein synthesis. However, it is the selective expression of genes in particular cells that ultimately determines cell structure and function
How do the sympathetic nervous system and neuroendocrine system respond to stress?
The primary role of the sympathetic nervous system is appraisal of a stressful stimulus and release of norepinephrine. Norepinephrine released from sympathetic nerve endings increases heart rate and contractility, constricts blood vessels, enhances blood flow to skeletal muscle, reduces gastrointestinal motility and secretion, and dilates the pupils. Stress simultaneously stimulates sympathetic activation of the adrenal medulla to release epinephrine. The actions of epinephrine are similar to those of norepinephrine and are particularly important for increasing cardiac performance and the release of glucose from the liver. Stimulation of the sympathetic nervous system activates the renin-angiotensin-aldosterone system, with aldosterone promoting volume expansion and increasing blood pressure. The actions of the HPA axis may synergize or antagonize the effects of the catecholamines. Catecholamines facilitate the release of adrenocorticotropic hormone (ACTH), which acts to maintain the function of the HPA axis and the release of cortisol. Cortisol, from the adrenal cortex, has widespread effects on numerous tissues that are both synergistic and antagonistic with catecholamines, and has an antiinflammatory role
How are tumor grading and staging used to guide the selection of cancer therapies?
Tumor grading, or identifying the histological characterization, is used to determine the malignancy potential. Generally, tumors with a higher malignancy potential are treated more aggressively. Staging the tumor, or identifying the location and pattern of spread of the tumor, is used to determine the treatment modality which may include surgical removal, radiation therapy, chemotherapy, or a combination of these. Localized tumors may be managed with surgery and radiation therapy, whereas evidence of metastasis generally necessitates the addition of chemotherapy
How might underexpression of tumor suppressor genes lead to abnormal cellular proliferation?
Tumor suppressor genes normally inhibit cell proliferation, thus underexpression of these genes would lead to less regulation of cellular proliferation, or uninhibited cellular proliferation
How do types I, II, III, and IV hypersensitivity reactions differ according to the immune cell types involved and the mechanism of tissue injury?
Type I hypersensitivity is an immediate allergic or anaphylactic type of reaction mediated primarily by sensitized mast cells. Mast cell degranulation releases chemicals that mediate the signs and symptoms of anaphylaxis, including vascular permeability, vasodilation, hypotension, urticaria, and bronchoconstriction. Type II hypersensitivity occurs when antibodies are formed against antigens on cell surfaces, usually resulting in lysis of target cells. Cell lysis may be mediated by activated complement fragments or by phagocytic cells that are attracted to target cells by the attached antibodies. Type III hypersensitivity reactions occur when antigen-antibody complexes are deposited in tissues and result in the activation of complement and subsequent tissue inflammation and destruction. Antigen-antibody complexes activate the complement cascade and subsequently attract phagocytic cells to the tissue. Type IV hypersensitivity reactions are T-cell mediated and do not require antibody production. Sensitized T cells react with altered or foreign cells and initiate inflammation
What are the usual physiologic changes of aging and how are these differentiated from disease?
Typical physiologic changes of aging include a decrease in functional reserve or inability to adapt to environmental demands. Age-related changes are differentiated from disease by their irreversible and universal nature