Cell Injury & Adaptation Flashcards
(49 cards)
What is the difference between reversible and irreversible cell injury?
Reversible: Cell can recover if stress is removed
Irreversible: Leads to cell death
What causes hydropic swelling?
Increased water inside the cell due to failure of the Na⁺/K⁺ ATPase pump → Na⁺ builds up → water follows.
What are the cellular effects of hydropic swelling on organelles?
ER: Swelling, ribosomes detach → ↓ protein synthesis
Mitochondria: Swelling → ↓ ATP production
Plasma membrane: Blebbing (still reversible)
Nucleus: Nucleolar segregation → disrupted rRNA processing
What is ischemia?
A condition where blood flow (and thus oxygen) is restricted or reduced, causing hypoxia and ATP depletion.
What is oxidative stress?
Imbalance between reactive oxygen species (ROS) production and antioxidant defenses.
What are 3 major ROS molecules?
Superoxide (O₂⁻)
Hydrogen peroxide (H₂O₂)
Hydroxyl radical (OH∙)
Which ROS is most reactive and damaging?
Hydroxyl radical (OH∙)
What does lipid peroxidation result in?
Membrane damage due to ROS attacking unsaturated fatty acids.
How do ROS damage proteins?
By oxidizing sulfur and nitrogen-containing amino acids → fragmentation, cross-linking, and degradation.
How do ROS affect DNA?
They cause strand breaks, base modifications, and cross-links → mutations and cell death.
What enzymes protect against ROS damage?
SOD (Superoxide dismutase) – converts O₂⁻ → H₂O₂
Catalase – converts H₂O₂ → H₂O + O₂
Glutathione peroxidase (GPX) – detoxifies H₂O₂ and lipid peroxides
What vitamins act as ROS scavengers?
Vitamin C, Vitamin E, Retinoids (Vitamin A derivatives)
What role does nitric oxide (NO) play in oxidative stress?
Can be protective or damaging; reacts with O₂⁻ to form peroxynitrite (ONOO⁻), a harmful compound.
What is the role of p53 in oxidative stress?
Repairs DNA or promotes cell survival
If stress is severe, promotes cell death by impairing oxidant defenses
What are the main cellular adaptations to stress?
Atrophy
Hypertrophy
Hyperplasia
Metaplasia
Dysplasia
What is atrophy and what causes it?
A decrease in cell size or function caused by:
Disuse
Ischemia
Nutrient deficiency
Hormone loss
Aging
Chronic inflammation
Pressure (e.g., bed sores)
What is the cellular mechanism behind atrophy?
↓ Protein synthesis
↑ Protein degradation (via ubiquitin-proteasome pathway)
Differentiate between reversible cell shrinkage and irreversible cell loss in atrophy.
Reversible: cells reduce in size but can recover
Irreversible: excessive cell death (e.g., Alzheimer’s) leads to permanent tissue atrophy
What is hypertrophy?
An increase in cell size (and organ size) in response to increased demand or trophic signals.
Give examples of physiological vs pathological hypertrophy.
Physiological: Exercise, pregnancy
Pathological: Hypertension, valve disease → cardiac hypertrophy
What signaling pathway promotes muscle hypertrophy?
The Akt pathway, which promotes protein synthesis and inhibits apoptosis.
What is hyperplasia and when does it occur?
Increase in cell number due to:
Hormonal stimulation (e.g., endometrium)
Increased demand (e.g., bone marrow at high altitude)
Chronic injury/inflammation
Immune response (e.g., lymphoid hyperplasia)
What is metaplasia?
A reversible change from one differentiated cell type to another better suited to stress (e.g., bronchial columnar → squamous in smokers)
What is the clinical concern with metaplasia?
It’s protective but functionally inferior and can become preneoplastic if the stress persists.
