chapter 2 cellular responses to stress, injury, and aging
TRANSCRIPT
CHAPTER 2
CELLULAR RESPONSES TO STRESS, INJURY, AND AGING
CHAPTER 2
CELLULAR RESPONSES TO STRESS, INJURY, AND AGING
PRE LECTURE QUIZ Cells are able to adapt to changes in work
demands or threats to survival by changing their size, number, type, and DNA composition.
Apoptotic cell death and necrotic cell death are both pathologic forms of cell death that are unregulated and invariably injurious to the organism.
Prolonged exposure to cold increases blood viscosity and induces vasoconstriction.
Gas gangrene is a special type of gangrene that results from infection of devitalized tissues by one of several species of Clostridium bacteria.
All mechanisms of cell injury (e.g., hypoxia, mechanical forces, extremes of temperature, electrical injuries) lead to irreversible cellular damage with cell destruction or death.
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PRE LECTURE QUIZ Atrophy is the ______________ in the size of
a tissue organ resulting from a decrease in the cell size of the individual cells or in the number of cells.
_________________ calcification involves the abnormal deposition of calcium salts, together with smaller amounts of iron, magnesium, and other minerals, in dead or dying tissue.
_________________ is the term used for programmed cell death or cell suicide.
The injurious effects of ionizing radiation vary with the __________________.
Electrical forces can affect the body through extensive tissue injury and disruption of neural and __________________ impulses.
Apoptosis
cardiac
decrease
Dose
Dystrophic
CELLULAR ADAPTATION
Allows the stressed tissue to survive or maintain function Atrophy Hypertrophy Hyperplasia Metaplasia Dysplasia
QUESTION
Tell whether the following statement is true or false:
If a cell does not make adaptive changes as a result of stress, it will die.
ANSWER
TrueAdaptive changes, like the ones
illustrated on slide 3, allow the cell to survive and maintain some degree of function. If the cell makes no changes or makes maladaptive changes as a result of stress, the cell will not survive.
WHAT KINDS OF CELL AND TISSUE ADAPTATIONS OCCURRED IN THIS CASE? A woman broke her left leg; 3 weeks later you
find:
The left leg is smaller than the right leg
The circumference of the right calf has increased by 2 cm
New calluses on the right foot
A nodule of skin tissue has formed a fluid-filled cyst near her incision
INTRACELLULAR ACCUMULATIONS
Stressed cells may fill up with: Unused foods
º Lipidsº Glycogen
Abnormal proteins Pigments Calcium salts
INJURIOUS AGENTS
Hypoxia Heat and cold Electricity Chemical agents Biologic agents Radiation Nutritional imbalances
STRESSES DAMAGE CELLS BY:
Direct damage to proteins, membranes, DNA
ATP depletion Free radical formation Increased intracellular
calcium
HYPOXIA CAUSES ATP DEPLETION OR “POWER FAILURE”
Aerobic metabolism stops less ATP is produced Na+/K+ ATPase cannot run fast enough
º Cell swells up with water Anaerobic metabolism used lactic acid
produced Acid damages cell membranes, intracellular
structures, and DNA
QUESTION
How does hypoxia cause cell damage?a. Directly damages DNAb. Diminishes ATP productionc. Forms free radicalsd. Increases intracellular calcium
ANSWER
b. Diminishes ATP productionOxygen is a key ingredient for the
majority of ATP production. With less oxygen, less ATP is produced, and the cell cannot function at the same level. If hypoxia is severe or prolonged, the cell will die.
SCENARIO
Two Boys Suffered Hypoxia One was at a normal body temperature. The other one was very cold. Questions: Which one will have a lower intracellular pH? Which one will have more cell swelling? Why?
FREE RADICALS Molecules with an unpaired electron in
the outer electron shell Extremely unstable and reactive Can react with normal cell components:
Damaging them Turning them into more free radicals
Normally removed from body by antioxidants
CALCIUM Cell usually maintains low intracellular
calcium When calcium is released into the cell, it:
Acts as a “second messenger” inside the cell Turns on intracellular enzymes, some of
which can damage the cell Can open more calcium “gates” in the cell
membraneº Letting in more calciumº “Calcium cascade”
SCENARIOMr. X Had a Stroke … Blood flow to part of his brain was cut off His wife can understand why they gave him an
anticoagulant, but she does not comprehend why he was also put on:
Oxygen A calcium channel blocker
Question: What is the explanation?
RESULT OF CELL INJURY
CELL DEATH
Programmed cell death: apoptosis or “cell suicide”
Removes cells that are being replaced or have “worn out”
Removes unwanted tissue Normal process in the body
Necrotic cell death Unregulated death caused by injuries
to cells Cells swell and rupture Inflammation results
APOPTOSIS OR PROGRAMMED CELL DEATH Damaged or worn-out
cells commit “suicide” Turn on their own
enzymes inside the cell, especially caspases
Digest their own cell proteins and DNA
Are then destroyed by white blood cells
APOPTOSIS CAN BE CAUSED BY:
Signaling factor attached to “death domains” of cell surface receptors
Mitochondrial damage inside the cell Protein p53 activated by DNA damage
NECROSIS
Cell death and degradation
Cells may undergo: Liquefaction Coagulation Infarction Caseous necrosis
Cell contents often released
Inflammation often results
QUESTION
Tell whether the following statement is true or false:
Necrotic tissue may be reversed using high concentrations of oxygen.
ANSWER
FalseNecrotic tissue is already dead, so it
cannot be restored to functional tissue.
GANGRENE A large area of necrotic tissue Dry gangrene: lack of arterial
blood supply but venous flow can carry fluid out of tissue Tissue tends to coagulate
Wet gangrene: lack of venous flow lets fluid accumulate in tissue Tissue tends to liquefy and
infection is likely Gas gangrene: Clostridium
infection produces toxins and H2S bubbles
QUESTION
Which type of gangrene results in crepitus (bubbles that can be felt under the skin)?
a. Dryb. Wetc. Gasd. All of the above
ANSWER
c. Gas The only type of gangrene that causes
crepitus is gas gangrene. The bubbles are the result of gas produced by the Clostridium infection.
CELL CHANGES WITH AGING—WHY?
Is it programmed into the cells? Telomeres become too short; cell can no
longer divide Is it the result of accumulated damage?
Older cells have more DNA damage Older cells have more free radicals Cells can lose the ability to repair their
telomeres