Cellular Adaptation:
• Cells adapt to changes in the internal environment when confronted with stress that endanger normal structure and function. These cells adapt to increase work demands by changing in:
1. Size (Atrophy and Hypertrophy)
2. Number (Hyperplasia)
3. Form (Metaplasia)
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NUR 3032 Pathophysiology Exam 1 Study Guide
Pathophysiology Exam 1 Study Guide
CHAPTER 5:
Cellular Adaptation:
• Cells adapt to changes in the internal environment when confronted with stress that
endanger normal structure and function. These cells adapt to increase work demands by
changing in:
1. Size (Atrophy and Hypertrophy)
2. Number (Hyperplasia)
3. Form (Metaplasia)
• These mechanisms depend largely on signals transmitted by chemical messengers that
exert their affects by altering gene function. In general, the genes are expressed in
two categories:
1. Operating genes that are necessary for normal function of a cell
2. Genes that determine the differentiating characteristics of a particular
cell type
• In many adaptive cellular responses, the expression of the differentiation genes is
altered but that of the operating genes remains unaffected. Thus, a cell is able to change
size or form without compromising its normal function. Once the stimulus for
adaptation is removed, the effect on expression of the differentiating genes is removed
and the cell resumes its previous state of specialized function.
• Whether the adaptive cellular changes are normal or abnormal depends on whether the
response was mediated by an appropriate stimulus
• Some adaptive changes include:
1. Intracellular accumulations
2. Storage of products in abnormal amounts
Lecture Notes:
• Anything that’s genetic can change the cell. Radiation as well. Any external factor. Cell
injury can occur from genetic, chemical, immunoglobin or x-rays, etc. As a result you
can have several different changes.
• Free Radicals: when the cells do not have an enough amount of electrons and protons
therefore free ions are migrating because they don’t have a pair so it makes the cell at
risk for more injury to occur.
, o EX: if you have a negative and a positive and they are unpaired they are
going to cause free radicals.
o These free radicals can also happen with radiation.
• Cells adapt with changes in their size, number and form.
Atrophy:
• Atrophy is a decrease in cell size
• EX: When you go regularly to the gym, and then all of a sudden you stop your
muscles are going to atrophy, meaning they are going to decrease in size.
• When confronted with a decrease in word demands or adverse environmental conditions,
most cells cam decrease in size in order to have a lower yet more efficient level of
functioning that is compatible with their survival
• Causes of atrophy include:
1. Disuse: reduction in skeletal muscle use. EX: muscles of extremities that have
been encased in plaster cast. Since atrophy is adaptive and reversible, the muscle
size can be restored when cast is removed.
2. Denervation: a type of muscle atrophy that occurs in the muscles of
paralyzed limbs.
3. Loss of endocrine stimulation: loss of estrogen stimulation during menopause
results in atrophic changes in the reproductive organs.
4. Inadequate nutrition
5. Ischemia or decrease blood flow
• With Malnutrition and decreased blood flow, cells decrease their size and
energy requirements as a means of survival.
• Cells that are atrophies reduce their oxygen consumption and other cellular functions by
decreasing the number and size of their organelles and other structures.
• EX: cell size in muscle tissue is related to work load. As the work load of a cell
declines, oxygen consumption and protein synthesis will both decrease
• Insulin levels and insulin growth factor-1 is what maintains proper muscle mass. If these
levels are low or catabolic signals are present, the muscle atrophy occurs by mechanisms
,that reduce synthetic processes, increased proteolysis by the ubiquitin proteasome system and
apoptosis or cell death.
Lecture Notes:
• Ischemia: anything that causes hypoxia or decreased oxygenation to an organ.
o EX: ischemia to the brain will cause a stroke
• Atrophy can be both pathological (disease causing) and physiological (something
normal).
• Physiological atrophy:
o EX: the thymus. As we get older, our thymus shrinks naturally. It doesn’t
mean there is something wrong, its just normal a normal physiological
response.
o EX: the adenoids. You can remove them and be completely okay
without them.
• Pathological atrophy:
o EX: a spinal cord injury and its cause from a trauma
o EX: paralytic, extremities will become smaller, you wont use
your muscles as much, no blood flow
Hypertrophy:
• Hypertrophy is an increase in cell size and also with it an increase in the amount
of functioning use of tissue mass.
• IMP: Left ventricular hypertrophy is caused by uncontrolled long term hypertension.
• Results from an increased workload imposed on an organ or body part and is
commonly seen in cardiac and skeletal muscle tissue, which CANNOT adapt to an
increase in workload through mitotic division and formation of cells.
• Hypertrophy can result from a normal physiologic condition or an abnormal
physiologic condition.
1. Physiologic hypertrophy: increases in muscle mass associated with exercise.
2. Pathologic hypertrophy: occurs as a result of disease conditions that can
be either adaptive or compensatory.
• Hypertrophy can occur as a result of disease conditions and can either be:
, 1. Adaptive: an example is the thickening of the urinary bladder from long
continued obstruction of the urinary outflow and the myocardial hypertrophy that
results from vascular heart disease or hypertension.
2. Compensatory: an example would be the enlargement of a remaining organ or
tissue after a portion has been surgically removed or rendered inactive. An
example of this is one of the kidneys are removed; the other becomes enlarged
to compensate for the other kidney.
• Signals of hypertrophy appear to be complex and related to ATP depletion, mechanical
forces such as stretching of the muscle fibers, activation of cell degradation products and
hormonal factors.
Hyperplasia:
• Hyperplasia refers to an increase in the number of cells in an organ or tissue. Occurs
in tissues with cells that are capable of mitotic division.
o EX: Epidermis, interstitial epithelium, and glandular tissue
• Evidence suggests that hyperplasia involves activation of genes controlling cell
proliferation and the presence of intracellular messengers that control cell replication and
growth.
• Normal response: hyperplasia is controlled in response to an appropriate stimulus and
ceases after the stimulus has been removed.
• The stimulus that induce hyperplasia may be physiologic or non-physiologic:
1. Physiologic: hormonal and compensatory.
o EX: hormonal would be the breast and uterine enlargements
during pregnancy are examples of physiologic hyperplasia that
result from estrogen stimulation.
o EX: compensatory would be when the liver regenerates after having a part
removed.
• Although hypertrophy and hyperplasia are two distinct processes, they may
occur together and are often triggered by the same mechanism.
• Non-physiologic: due to excessive hormonal stimulation or the effects of growth
factors on target tissues.
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