1. Chapter 2 Cellular Responses to Stress, Injury, and Aging

2. 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. F T

3. 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

4. Cellular Adaptation
Allows the stressed tissue to survive or maintain function
Atrophy
Hypertrophy
Hyperplasia
Metaplasia
Dysplasia

5. 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.

6. Answer
True Adaptive 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.

7. 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

8. Intracellular Accumulations
Stressed cells may fill up with:
Unused foods
Lipids
Glycogen
Abnormal proteins
Pigments
Calcium salts

9. Injurious Agents Hypoxia Heat and cold Electricity Chemical agents
Biologic agents
Radiation
Nutritional imbalances

10. Stresses Damage Cells By:
Direct damage to proteins, membranes, DNA
ATP depletion
Free radical formation
Increased intracellular calcium

11. Hypoxia Causes ATP Depletion or “Power Failure”
Aerobic metabolism stops  less ATP is produced
Na+/K+ ATPase cannot run fast enough
Cell swells up with water
Anaerobic metabolism used  lactic acid produced
Acid damages cell membranes, intracellular structures, and DNA

12. Question
How does hypoxia cause cell damage?
Directly damages DNA
Diminishes ATP production
Forms free radicals
Increases intracellular calcium

13. Answer
Diminishes ATP production
Oxygen 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.

14. 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?

15. Molecules with an unpaired electron in the outer electron shell
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

16. 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 membrane
Letting in more calcium
“Calcium cascade”

17. Scenario Mr. 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?

18. Result of Cell Injury

19. 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

20. 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

21. 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

22. Cell death and degradation Cells may undergo:
Necrosis
Cell death and degradation
Cells may undergo:
Liquefaction
Coagulation
Infarction
Caseous necrosis
Cell contents often released
Inflammation often results

23. Question
Tell whether the following statement is true or false: Necrotic tissue may be reversed using high concentrations of oxygen.

24. Answer
False Necrotic tissue is already dead, so it cannot be restored to functional tissue.

25. 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

26. Question
Which type of gangrene results in crepitus (bubbles that can be felt under the skin)?
Dry
Wet
Gas
All of the above

27. 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.

28. 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