deck_2682836 Flashcards
What are the four principle adaptive responses of cells?
hypertrophy, hyperplasia, atrophy, and metaplasia
What characteristics of stress result in irreversible damage and cell death?
stress is severe, persistent and rapid in onset
What are physiologic adaptations?
represent responses of cells to normal stimulation by hormones orendogenous chemical mediators (e.g., the hormoneinducedenlargement of the breast and uterus during pregnancy)
What are pathologic adaptations?
responses to stress that allow cells to modulate their structure and function and thus escape injury
What are trophic triggers?
soluble mediators that stimulate cell growth such as growth factors and adrenergic hormones
Does metaplasia occur to mature cells?
No, metaplasia is thought to arise due to a change in gene expression in the stem cells
Compare and Contrast Apoptosis and Necrosis
Necrosis: Enlarged cell size, disrupted plasma membrane, enzymatic digestion, accompanies inflammation, always pathologicApoptosis: Reduced cell size, intact membrane, no inflammation, can be physiologic or pathologic
Differentiate hypoxia from ischemia
Ischemia is the inadequate supply of oxygen to a tissue due to a physical obstruction, hypoxia is inadequate supply of oxygen because of a lowered concentration of oxygen in the blood
What are the common causes of cell injury?
Oxygen Deprivation, Chemical Agents, Infectious Agents, Immunologic Reactions, Genetic factors, Nutritional Imbalances, Physical agents, and Aging
Can we immediately see cell death?
No, cell death occurs before any accompanying ultrastructural changes that can be seen by light microscopy and even longer before any gross morphological changes
Which two characteristics are consistent signs that cell damage has become irreversible?
The inability to correct mitochondrial dysfunction and profound disturbances in membrane function
What are themajor morpholigical correlates of reversible cell injury?
Cellular swellin due to failure of energy dependent ion pumps and Fatty change resulting in the appearance of lipid vacuoles in the cytoplasm. Dilation of the ER with detachment of ribosomes, and nuclear alterations with clumping of chromatin
What type of necrosis is characteristic of infarcts?
Coagulative necrosis (everywhere but the CNS)
What are the four principal targets and biomechanical mechanisms of cell injury?
Mitochondria and their ability to generate ATP and ROS Disturbance of Ca2+ homeostasis Damage to cellular membranes Damage to DNA and protein misfolding
What are the effects of Mitochondrial damage?
Decrease in ATP production leading to multiple downstream effects and an increase in ROS leading to lipid, protein, and DNA damage
What are the effects of increased Ca2+ permeability?
Entry of calcium leads to increased mitochondrial permeability and activation of multiple cellular enzymes
What are the effect of membrane damage?
Plasma membrane damage leads to the loss of cellular components, lysosomal membrane damage leads to the digestion of cellular components
What are the effects of protein misfolding and DNA damage?
Activation of pro-apoptotic proteins leading to eventual apoptosis
What are the effects of mitochondrial damage?
Increased influx of Ca2+, H20, and Na+ leading to cellular swelling and loss of microvilli Increased efflux of K+ Decreased ATP production Increased glycolysis leading to increased lactic acid production and decreased pH Detachment of ribosomes leading to decrease production of proteins
What changes cause mitochondria to undergo necrotic changes? Apoptotic Changes?
Necrosis: Decreased O2 supply, Toxins, Radiation lead to decreased ATP and increase in reactive oxygen species Apoptosis: Decreased survival signals, DNA or Protien damage results in leakage of mitochondrial proteins and apoptosis
How do cells get rid of free radicals?
The rate of decay of superoxide is increased by Superoxide Dismutases Glutathione peroxidase in teh cytoplasm of cells catalyzes the breakdown of H2O2 into H2O GS-SG + H2O2 = 2GSH + 2H20 Catalase is peroxisomes breaks down H2O2 extremely quickly Endogenous antioxidants prevent formation of free radicals or quickly bind them
How do ROS cause cell injury?
Lipid peroxidation of membranes resulting in an autocatalytic radical chain Promotion of sulfhydryl protein cross-linking leading to enhanced degredation or loss of activity DNA damage via reaction with thymine in nuclear and mitochondrial DNA
What are the mechanisms of membrane damage in cell injury?
Decreased phospholipid synthesis due to decrease in concentration of ATP Increased phospholipid breakdown by endogenous phospholipases activated by increased cytosolic Ca2+ levels Lipid peroxidation by free radicals Activation of proteases leading to cytoskeletal damage and eventually membrane damage Presence of lipid breakdown products act as a detergent to cell membranes
Describe the mitochondrial pathway of apoptosis
Cell injury leads to Bcl-2 family sensors activating Bax and Bak which cause increased mitochondrial permeability allowing cytochrome C to enter the cytosol and activate caspases that cleave proteins at aspartic residues leading to nuclear degredation and membrane blebbing and eventual apoptosis
Describe the death receptor pathway of apoptosis
Fas or TNF receptors are activated by ligand, they in turn activate adapter proteins which activate caspases resulting in nuclear fragmentation and membrane blebbing leading to eventual apoptosis
How do Bax and Bak increase mitochondrial membrane permeability?
They dimerize and enter the mitochondrial membrane to form channels through which cytochrome C and other pro-apoptotic proteins can travel
What are the five external manifestations of inflammation and their latin names?
Heat (Calor) Redness (Rubor) Swelling (Tumor) Pain (Dolor) Loss of function (functio laesa)
What vascular change occurs during inflammation?
Vasodilation and increased vascular permeability, additionally endothelial cells are activated leading to increased adhesion to leukocytes
What cellular events occur during inflammation?
Emigration of leukocytes from the circulation (Margination, Rolling, Adhesion, Diapedesis) as well as activation of leukoctyes allowing them to remove the offending agent
What stimuli can trigger acute inflammation?
Infections, Trauma, Tissue necrosis, foreign bodies, and immune reactions.All have characteristics that are distinctive but share the same basic features.
What are the two most important families of Pattern Recognition Receptors?
Toll-like receptors and the Inflammasome
What are toll-like receptors (TLRs)?
Microbial sensors present on the cell membrane and in the endosomes so they can recognize both internal and external pathogens.They recognize products from different types of microbes and are able to provide defense against all classes of infectious pathogens.Activate transcription factors for a number of secreted and membrane proteins
What is “The Inflammasome”?
A multiprotein cytoplasmic complex that recognizes the products of cellular death.Triggering the inflammasome activates caspase 1 which activates IL-1B which is an important mediator of leukocyte recruitment.
Describe how vasodilation leads to margination
Following transient vasoconstriction the smooth muscle walls of the blood vessels relax allowing more blood flow. Additionally exudate flows from the blood vessel into the tissues increasing the concentration of RBCs which increases viscosity and slows blood flow. The slowed blood flow results in leukocytes moving toward the vessels walls and “rolling” due to interaction with selectins.
What factors account for rapid and prolonged endothelial cell contraction?
Rapid: Histamines, bradykinins, leukotrienes, and specific mediators Prolonged: Changes in the cytoskeleton caused by cytokines like TNF and IL-1
What cytokines influence the expression of P and E selectin and the ligand for L selectin on the surface of endothelial cells?
IL-1 and TNF secreted by macrophages which have phagocytized infecting microbes
Following activation of leukocytes by chemokines, which integrins are expressed and what do they bind which allows for adhesion to the endothelium.
LFA-1 and VLA-4 are expressed in their high affinity form on leukocytes. These bind to ICAM-1 and VCAM-1 respectively which are expressed on endothelial cells after activation by IL-1 and TNF
What cellular adhesion molecule is responsible for diapedesis?
CD31 also called PECAM-1 (Platelet endothelial cell adhesion molecule 1)
What exogenous and endogenous substances are chemotaxic for leukocytes following diapedesis?
Bacterial products, chemokines, complement C5a, and LTB4 (a product of the lipoxygenase pathway of arachidonic acid metabolism)
What factors account for the early abundance of neutrophils during the first 6-24 hours of infection?
Neutrophils are the most numerous leukocyte in the blood They respond more rapidly to chemokines and may attach more firmly to adhesion molecules expressed on activated endothelial cells
Which functions of leukocytes are enhanced by activation?
Phagocytosis of particles Intracellular destruction of phagoctosed microbes and dead cells Liberation of substances that destroy extracellular microbes and dead tissues Production of mediators including arachadonic acid metabolits and cytokines which produce a positive feedback recruitment of leukocytes
What receptors present on Leukocytes recognize opsonins resulting in increased phagocytosis?
FcyRi recognizes IgGs CR1 and CR3 recognize complement fragments C1q recognizes the collectins
What are the three steps of phagocytosis?
Attachment and binding Englufment and fusion of phagosome with lysosomes to form phagolysosome Destruction of ingested particles by iNOS, NO, and ROS
What are the lysosomes of neutrophils called?
Azurophilic granules
Following oxidative burst what occurs to breadown and kill bacteria in the phagolysosome?
Superoxides are created which spontaneously dismute to form H2O2. Myeloperosidase (MPO) in the presence of a halide converts H2O2 into hypochlourous radical (bleach) which kills bacteria by halogenation or by protein and lipid peroxidation.
Which other constituents of leukocytes granuoles are capable of killing pathogens?
Bactericidal permeability-increasing protein lysozyme major basic protein defensins
How are the contents of microbicidal granules secreted into the extracellular space?
The phagocytic granule may remain transiently open before complete closure of the phagolysosome Attempts to phagocytise materials that are not easily ingested triggers release of lysosomal enzymes The membrane of the phagolysosome may be partially damaged leading to the expulsion of its contents
Which cells in the tissue producecell derived mediators?
Tissue macrophages, mast cells, and endothelial cells at the site of inflammation
What two vasoactive amines are among the first mediators to be released in acute inflammatory reactions and how are they stored?
Histamine and Serotonin are stored in preformed secretory granules
What stimuli cause the release of histamine from mast cell granules?
Physical injury Immune reactions involving binding of IgE to Fc receptors on mast cells C3a and C5a fragments (anaphylatoxins) Leukocyte derived histamine releasing proteins Neuropeptides (substance P) Certain cytokines (IL-1, IL-8)
How does Serotonin function when released?
Serotonin functions in vasoconstriction. It is stored in secretory granules of platelets and is released during platelet aggregation. It is produced mainly in neurons and entereochromaffin cells.