Trans - Cellular Responses to Stress: Adaptation and Injury Flashcards
stages in the cellular response
- normal cell
- cellular adaptation
- cellular injury
homeostasis - define
process by which cells control the composition of their immediate environment and internal milieu within a narrow range of physiological parameters
adaptation - define
process by which cells reach a new steady state compatible with their new environment
cells adapt by:
altering their pattern of growth
cellular damage occurs when:
adaptive mechanisms can no longer compensate for changing environment
2 outcomes of cellular injury
- reversible
2. irreversible
reversible injury
return to normal when stress is removed
irreversible injury
severe injury leading to cell death (apoptosis and necrosis)
cellular response to injurious stimuli depends on these four factors
- type of injury
- duration of injury
- severity / intensity of injury
- vulnerability of cell
[T/F] relatively nonspecialized cells are more vulnerable to injury because they are more exposed to the environment
F, more specialized cells have high vulnerability (ex. brain)
which is lost first - symptoms of injury, or cell function?
cell function
generally, cell injury is caused by:
abnormalities on the biochemical and molecular level caused by stress
consequence of interdependence of biochemical systems in the context of injury
injury at one site typically causes secondary or tertiary injuries to other cellular processes
4 major molecular targets of cellular injury
- cell membrane
- mitochondrial function
- functional and structural proteins
- genetic integrity
5 general mechanisms of cellular injury
- ATP depletion
- loss of plasma membrane integrity
- loss of Ca2+ homeostasis
- mitochondrial damage
- oxygen deficiency
ATP depletion and decreased ATP synthesis are frequently associated with:
hypoxic and chemical injury
[T/F] cells with greater glycolytic capability are first injured in prolonged ischemia
F, cells with greater glycolytic capacity have greater capacity for anaerobic respiration
possible consequence of acidosis within the cell
damage to DNA
consequence of damage to plasma membranes
lysis due to disrupted ion balance
consequences of potassium leaking from plasma membrane
decreased ability to maintain resting membrane potential
consequences of injury to mitochondrial membrane
- impairment of energy metabolism
2. initiation of apoptosis due to release of cytochrome c
consequences of injury to lysosomal membrane
autophagy due to release of hydrolytic enzymes
consequences of injury to golgi-ER complex
impaired protein synthesis and protein transport
effect of ischemia in concentration of Ca and O2 within the cell
increase Ca
decrease O2
4 effects of increased cytosolic Ca
- phospholipid degradation due to activation of phospholipases by Ca
- degradation of the membrane due to activation of proteases by Ca
- activation of ATPase by Ca –> less ATP
- activation of endonucleases by Ca –> DNA damage
cytosolic Ca activates which two types of enzymes
- phospholipases
2. proteases
how does a decrease in ATP affect the membrane stability of a cell
a decrease in ATP causes a decrease in reacylation/synthesis of new phospholipids, which in turn allows the degradation of the membrane
high conductance channel in mitochondria that appears when the mitochondria are damaged
mitochondrial permeability transition
where in the mitochondria is the mitochondrial permeability transition located
inner mitochondrial membrane
2 main effects of mitochondrial membrane damage
- decrease in ATP
2. release of cytochrome C into the cytosol
effect of cytochrome C
facilitates apoptosis pathway
how does a cell maintain Ca homeostasis
through energy dependent pumps that keep cytosolic Ca low
free radical - define
highly reactive, unstable species with one unpaired electron, may facilitate damaging chain reactions that create other free radicals
how are free radicals generated
- from cellular metabolism (redox)
2, from enzymatic metabolism of exogenous enzymes - through ionizing radiation
- divalent metals
how are free radicals physiologically utilized in the body?
used by leukocytes in antimicrobial processes
how are free radicals neutralized
- spontaneous decay
- superoxide dismutase (for superoxide)
- glutathione (for OH)
- catalase (for H2O2)
- vitamin E, A, C, beta carotene, other antioxidants
examples of O2 determined free radicals
- superoxide O2-
- H2O2
- OH-
how do free radicals damage membranes
through lipid peroxidation –> attack on double bonds of unsaturated phospholipids
how do free radicals damage proteins
chain reactions
how do free radicals damage DNA
react with thymine in mitochondrial DNA, creating single strand breaks and abnormal cross linking
reaction wherein O2- is converted to H2O2 and then to OH
Fenton reaction
Fenton reaction is catalyzed by:
Cu 2+, Fe 2+
superoxide dismutase is used against
superoxide
catalase is used against
H2O2
glutathione is used against
OH
in general, damage to enzymes results to
very slow reactions and impaired transport mechanisms
hypoxia - define
oxygen deprivation
ischemia - define
blood deprivation
differentiate hypoxia and ischemia
hypoxia - only oxygen is gone
ischemia - oxygen and other metabolic substances gone
which is more serious? hypoxia or ischemia?
ischemia
causes of hypoxia
- cardiopulmonary failure
- hypoperfusion
- decrease in O2 carrying capacity of blood
- toxins
- low inspired O2
how does anemia and CO2 poisoning cause hypoxia
both interfere with the O2 carrying capacity of blood
effects of hypoxia
decrease in ATP, accumulation of cytosolic Ca
phenomena wherein restoration of blood flow to an ischemic area causes acceleration of injury
reperfusion damage
mechanism of reperfusion damage
- exposure of damaged cells to Ca
2. increase in free radicals due to damaged cell structures attempting to execute functional biochemical reactions
mechanical trauma - 2 types
acute and chronic
mechanisms of heat damage
- increased metabolic activity leading to inadequate O2
2. direct heat damage
mechanisms of cold damage
- crystal formation leading to puncture
2. slowing down and stopping of metabolism
3 types of radiation that may damage
- ionizing
- nonionizing
- ultraviolet
radiation above ultraviolet wavelength
ionizing radiation
mechanism of ionizing radiation damage
contact causes electron imbalance –> free radical formation
radiation below ultraviolet wavelength
nonionizing
mechanism of nonionizing radiation damage
prolonged contact causing misalignment of atoms
mechanism of UV damage
DNA damage –> formation of thymine dimers
which type of radiation is least dangerous?
nonionizing radiation
which type of radiation has the greatest chance of causing direct damage?
ionizing radiation
which type of radiation has the greatest chance of causing cancer?
UV
mechanism of electric damage
direct electrical damage, may be converted to direct heat damage and necrosis
2 types of chemical agent that may cause damage
- direct
2. indirect
differentiate direct and indirect chemical damage
direct –> chemical itself causes the damage
indirect –> metabolism of the chemical is toxic
cyanide - type of chemical damage and mechanism
direct damage through inhibition of cytochrome oxidase in aerobic respiration
mercury - type of chemical damage and mechanism
direct damage through inhibition of Na-K pump
example of indirect chemical damage
drug overdoses
damage through biological activity - mechanisms
- direct cytopathic activity
- toxins
- trigger harmful immune/inflammatory response
examples of direct cytopathic damage by biological agents
virus
examples of toxin damage by biological agents
diptheria and clostridium bacteria
damage from immunologic reactions - mechanisms
- hypersensitivity
- autoimmunity
- abnormal suppression of response
cellular changes in adaptation
change in
- size
- number
- type
- organelles
atrophy - definition
acquired decrease in cell size leading to decrease in organ/tissue size
physiological atrophy - examples
- involution of thymus in adult
2. cease of ova maturation in menopause
causes of pathological atrophy
- decreased workload
- no innervation
- decreased blood supply
- inadequate nutrition
causes of physiological atrophy
- loss of endocrine stimulation
2. aging
cell/tissue changes in atrophy
- smaller cell size
- organ stroma more prominent than parenchyma (support framework more prominent than functional component)
- lipofucsin present
lipofucsin - origin
remnants of autophagy from lysosomes
hypertrophy - define
increase in cell size causing increase in tissue/organ size
hypertrophy - found in which cells
cells that cannot divide (muscle, neuron)
mechanism of hypertrophy
accelerated protein synthesis
physiological hypertrophy - example
cardiac muscle hypertrophy during stenosis of aorta
hypertrophy - causes
- increased functional demand
2. hormonal stimulation
aplasia - define
no growth at all, resulting in rudimentary or absent organ
hypoplasia - define
incomplete growth
hyperplasia - define
increase in cell number, resulting in increase of tissue/organ size
hyperplasia is often accompanied by
hypertrophy
hyperplasia - found in which cells
cells that are capable of mitosis
2 types of physiological hyperplasia
- hormonal
2. compensatory
2 types of pathological hyperplasia
- hormonal (overstimulation)
2. due to noxious stimuli
example of hyperplasia due to noxious stimuli
formation of callus
metaplasia - define
adaptive conversion between cell types in adults
metaplasia is a response to:
chronic irritation/inflammation
example of metaplasia
replacement of PCCE to SSE in respiratory tract of smokers
dysplasia - define
abnormal cell growth of disproportionate cell types
displasia - cause
always pathologic
differentiate displasia and cancer
displasia is reversible, and displacia cells are nonautonomous / not mutated
[T/F] when dealing with cell injury, it is possible to identify the point of no return (from reversible to irreversible damage)
F
result of reversible damage
degradation
result of irreversible damage
necrosis
what cells are more vulnerable to degradation, parenchymal or stromal?
parenchymal
what is the cause of degradation?
minor, reversible damage caused by low-intensity injury
cloudy swelling - cause
inability to maintain fluid homeostasis (failure of pumps)
term for accumulation of water in cells affected by cloudy swelling
hydropic change
fat accumulation - where can this occur
liver
fat accumulation - appearance under microscope
“signet ring” cells
2 types of pathologic calcification
- dystrophic
2. metastatic
deposition of Ca in injured tissue
dystrophic pathologic calcification
deposition of Ca in tissues when in hypercalcemic states
metastatic pathologic calcification
necrosis - define
antemortem pathologic cell death
apoptosis - define
antemortem physiologic cell death
autolysis - define
postmotem cell death
autolysis - cause
cease of function
pyknosis - characteristics
dark shrunken nuclei
karyolysis - characteristics
faint, indistinct nuclei
karyorrhexis - characteristics
fragmented nuclei
characteristics of apoptotic cell death
- cell shrinkage
- chromatin condensation
- formation of cytoplasmic blebs and apoptotic bodies