Basis Of Disease Flashcards
3 Cellular responses to stress
cellular adaptation, injury and death.
Cellular adaptations include:
atrophy, hypertrophy, hyperplasia, metaplasia, dysplasia.
ATP-MD
Which adaptations are reversible if the stress is removed?
ALL adaptations are completely reversible if the stress is removed.
Cellular Atrophy
- a dec in organ/tissue size (due to either dec in cell size or number)
- cells shrink to a more manageable metabolic state, cellular activities decrease.
causes of cellular atrophy including:
- disuse (being bedridden)
- loss of trophic stimuli (without innervation, no use of muscle, so they’ll shrink)
- decreased blood flow
- persistent cell injury and aging
Cellular Hypertophy
- an increase in cell size (but not number of cells) –> inc in functioning tissue mass allowing the cell to match the demands imposed on it.
- Hypertrophy results from increased workload on an organ or body part.
- hypertrophy can be compensatory. (if you donated your kidney or liver, remaining tissue will undergo hypertrophy to compensate for lost mass)
3 major Mechanisms of Cellular Injury
- Depletion of ATP (hypoxia)
- Free Radical Formation (ROS)
- Disruption of Intracellular Calcium Homeostasis (Lead poisoning)
What causes Free Radical Injury?
ROS– molecules with unpaired electrons, try to take an electron from other molecules. Typically, ROS will take from larger molecules that are unable to take the electron back, like lipids, proteins and DNA.
When a cell lacks oxygen and nutrients, it can lead to ____
depletion of ATP
Depletion of ATP cause 2 main problem:
1) without ATP, Na/K ATPase pumps on cell membrane fail –> depolarization of membrane–> opening of voltage gated channels allow sodium and calcium to rush into the cell–>Cell swells and eventually lyses.
2) without nutrients and oxygen, the cell will shift from aerobic to anaerobic metabolism, leading to buildup of Lactic acid–> decrease in cellular pH. If low enough lysosomes will lyse and its degrading enzymes can damage the cellular membrane and cause whole cell to lyse.
Ischemia Reperfusion Injury
ischemia = blockage of blood flow
- during ischemia, cells release various chemokines, cytokines and ROS into the blood.
- When blockage is removed and reperfusion occurs, blood filled with these factors causes a massive inflammatory response which damages the rest of the tissue
Hypoxia is a major cause of cellular injury, causes damage in 2 ways:
- Decreases available ATP which results in depolarization of cellular membranes
- Shifts metabolism from aerobic to anaerobic
difference between hypoxia and ischemia.
Hypoxia is a lack of oxygen to tissue.
Ischemia is a lack of blood flow to a tissue which can cause hypoxia.
Cellular Injury that can be caused by Temperature Extremes
- Heat: Accelerates cell metabolism, can inactivate sensitive enzymes, disrupts cell membranes, Coagulates blood vessels and tissue proteins
- Cold: Increases blood viscosity, induces vasoconstriction, ice crystal formation, capillary stasis, arteriolar and capillary thrombosis.
Damage from Lead exposure
- no safe threshold, bc lead can cross bbb, any amount exposure can affect cognitive and neuronal function.
- lead can go in between endothelial cells of capillaries and cross tight junctions.
- bc it is similar to Calcium, lead can use Ca+2 transporters to cross and damage BBB.
- can lead to mental retardation, reading impairment and other cognitive effects.
- also cause increase in reactive oxidative species (ROS), glomerular fibrosis and proximal tubule mitochondrial damage.
