02 Cell AdaptationCell AdaptationCell AdaptationCell AdaptationCell AdaptationCell AdaptationCell Adaptation

Cell Adaptation
Cell Adaptation
Cell Adaptation

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 Clostridiumbacteria.
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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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
ºLipids
ºGlycogen
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
ºCell 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?
a.Directly damages DNA
b.Diminishes ATP production
c.Forms free radicals
d.Increases intracellular calcium

13. ANSWER
b.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. 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. 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
membrane
Letting in more calcium

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. 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

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. 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: Clostridiuminfection
produces toxins and H
2S bubbles

26. QUESTION
Which type of gangrene results in crepitus
(bubbles that can be felt under the skin)?
a.Dry
b.Wet
c.Gas
d.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