intro to cellular regulation

Question 0

physiologic atrophy vs. pathologic atrophy

Answer 0

• physiologic atrophy- occurs with early development (ex. thymus gland undergoes physiologic atrophy during childhood)
• pathologic atrophy-occurs as a result of decreases in workload, pressure, use, blood supply, nutrition, hormonal stimulation, and nervous stimulation (ex. individual immobilized in bed for prolonged time)

Question 1

atrophy

Answer 1

• decrease or shrinkage in cellular size

- most common in skeletal muscle, heart, secondary sex organs, and the brain

Question 2

specific adaptations during atrophy

Answer 2

• atrophic muscle cell contains less endoplasmic reticulum and fewer mitochondria and myofilaments
• muscle atrophy caused by nerve loss- O2 consumption and amino acid uptake are reduced
• decreased protein synthesis, increased protein catabolism occur

Question 3

primary pathway of protein catabolism (during atrophy)

Answer 3

• ubiquitin-proteosome pathway
• this pathway involves proteosomes (protein degrading complexes)
• proteins are conjugated to ubiquitin (a small protein) and then degraded by proteosomes

-muscle atrophy occurs because of this pathway
(cancer can be a result of degredation of this pathway because of abnormal cell growth)

Question 4

What occurs in atrophy as a result of chronic malnutrition?

Answer 4

• “self-eating” process called autophagy that creates AUTOPHAGIC VACUOLES
• these vacuoles contain cellular debris and hydrolytic enzymes that break down substances to their simplest units of fat, carbs, or proteins
• in atrophy, the hydrolytic enzyme RISES rapidly
• LIPOFUSCIN- a yellow-brown age pigment that is in some granules that are able to resist destruction by lysosomal enzymes
• lipofuscin accumulates primarily in liver cells, myocardial cells, and atrophic cells

Question 5

hypertrophy

Answer 5

• increase in size of cells and consequently in the size of the affected organ
• cells of HEART and KIDNEYS are particularly prone to enlargement
• increase accumulation of protein occurs, but NOT an increase in cellular fluid

Question 6

two types of signals that trigger hypertrophy

Answer 6

1. mechanical signals (ex. stretch)

2. trophic signals (ex. growth factors, hormones, and vasoactive agents)

Question 7

physiologic and pathologic example of hypertrophy

Answer 7

1. physiologic example- increased growth of uterus and mammary glands in response to pregnancy, increase in skeletal muscles from heavy work, kidney enlargement when one kidney is removed from body
2. pathologic example- hypertrophy in the heart secondary to hypertension of diseased heart valves

Question 8

hyperplasia

Answer 8

• increase in number of CELLS resulting from increased rate of cellular division
• hyperplasia can occur in response to injury when there has been cell death
• loss of cells triggers DNA synthesis and mitotic division
• hypertrophy and hyperplasia often occur together except in NONDIVIDING cells (myocardial fibers), only hypertrophy occurs

Question 9

two types of physiologic hyperplasia

Answer 9

1. compensatory- adaptive mechanism that enables certain organs to regenerate (ex. removal of parts of liver leads to hyperplasia of remaining liver cells or thickening of skin, callus, is hyperplasia of epidermal cells)
   - some cells (nerve, skeletal muscle, myocardial cells, and lens cells of eyes) do NOT regenerate
   - cells in the epidermal and intestinal epithelia, hepatocytes, bone marrow cells, and fibroblasts, bone, cartilage, and smooth muscle cells, ARE ABLE to regenerate
2. hormonal hyperplasia- occurs chiefly in estrogen-dependent organs (uterus and breast)
   - examples are thickening and growing of endometrium to receive fertilized ovum and enlargement of uterus during pregnancy

Question 10

pathologic hyperplasia

Answer 10

• abnormal proliferation of normal cells, usually in response to excessive hormonal stimulation or growth factors on target cells
• example- pathologic endometrial hyperplasia- causes excessive menstrual bleeding

Question 11

dysplasia

Answer 11

• not a true adaptive change
• refers to abnormal changes in the size, shape, and organization of mature cells
• dysplasia is often called atypical hyperplasia
• dysplasia is classified as “low grade” or “high grade”
• if inciting stimulus is removed, dysplastic changes are often reversible

Question 12

metaplasia

Answer 12

• the reversible replacement of one mature cell type by another
• it develops from a reprogramming of stem cells that exist on most epithelia or of undifferentiated mesenchymal (tissue from embryonic mesoderm) cells present in connective tissue
• example of metaplasia- replacement of normal columnar ciliated epithelial cells of the bronchial lining by stratified squamous epithelial cells (these new cells do not secrete mucus or have cilia) most commonly caused by SMOKING
• can be reversed if stimulus (smoking) is removed

Question 13

three common forms of cellular injury

Answer 13

1. hypoxic injury
2. free radicals and reactive oxygen species injury
3. chemical injury

Question 14

hypoxic injury

Answer 14

• lack of sufficient oxygen
• most common cause of cellular injury
• can result from reduced amount of oxygen in the air, loss of hemoglobin or decreased efficacy of hemoglobin, decreased production of red blood cells, diseases of respiratory and cardiovascular systems, and poisoning of the oxidative enzymes within the cells

Question 15

most common cause of hypoxia

Answer 15

• ischemia (reduced blood supply)
• often caused by gradual narrowing of arteries (arteriosclerosis) and complete blockage by blood clots (thrombosis)

-ex. heart muscle (EXAMPLE PG. 64 purple diagram)

Question 16

injury by free radicals

Answer 16

• injury caused by free radicals, especially reactive oxygen species, is called oxidative stress
• free radical- electrically uncharged atom or group of atoms that has an unpaired electron (making it unstable)

Question 17

free radicals may be initiated within cells by 3 things….

Answer 17

1. absorption of extreme energy sources (ex. ultraviolet light, radiation)
2. activation of endogenous reactions by systems involved in electron and oxygen transport (ex. reduction oxygen to water)
3. enzymatic metabolism of exogenous chemicals or drugs

Question 18

free radicals cause several damaging effects by…

Answer 18

1. lipid peroxidation- destruction of polyunsaturated lipids, leading to membrane damage and increased permeability
2. protein alterations- causing fragmentation of polypeptide chains
3. DNA fragmentation- causing decreased protein synthesis
4. mitochondrial damage- causing liberation of calcium into the cytosol

Question 19

what is necrosis characterized by?

Answer 19

1. rapid loss of plasma membrane
2. organelle swelling
3. mitochondrial dysfunction
4. lack of typical features of apoptosis

*necrosis is the main outcome in several common injuries including ischemia, exposure to toxins, certain infections, and trauma

Question 20

definition of necrosis

Answer 20

necrosis is the sum of cellular changes after local cell death and the process of cellular self-digestion, known as AUTOLYSIS

Question 21

what are the structural signs of irreversible injury and progression to necrosis…

Answer 21

• dense clumping
• progressive disruption of both genetic material and of plasma and organelle membranes
• in later stages of necrosis, karyolysis (nuclear dissolution and lysis of chromatin from the action of hydrolytic enzymes) is under way
• sometimes, nucleus shrinks and becomes a small, dense mass of genetic material called a pyknosis (which eventually dissolves)

Question 22

coagulative necrosis

Answer 22

• occurs primarily in the kidneys, heart, and adrenal glands
• results from hypoxia caused by severe ischemia of hypoxia caused by chemical injury
• proteins turn from a gelatinous to a firm state (coagulation)

Question 23

liquefactive necrosis

Answer 23

• commonly results from ischemic injury to neurons and glial cells in the brain
• cells are digested by their own hydrolases and tissue becomes soft, liquefies, and segregates from healthy tissue, forming cysts

Question 24

caseous necrosis

Answer 24

• results from tuberculous pulmonary infection (esp. by mycobacterium tuberculosis)
• combination of coagulative and liquefactive necroses
• dead cells disintegrate, but debris is not completely digested
• tissues resemble CLUMPED CHEESE (soft and granular) and granulomatous inflammatory wall encloses areas of caseous necrosis

Question 25

fat necrosis

Answer 25

• cellular dissolution caused by enzymes called LIPASES
• occurs in breast, pancreas, and other abdominal structures
• necrotic tissue appears OPAQUE AND CHALK-WHITE

Question 26

gangrenous necrosis

Answer 26

• results from hypoxic injury, commonly occuring because of arteriosclerosis, or blockage, of major arteries (mainly in lower legs)
• dry gangrene- skin becomes very dry and shrinks, wrinkles, color turns to dark brown or black
• wet gangrene- usually occurs in internal organs; foul odor

Question 27

gas gangrene

Answer 27

• special type of gangrene caused by infection of injured tissue by one of many species of CLOSTRIDIUM
• tissue is destroyed and bubbles of gas form in muscle cells

Question 28

apoptosis

Answer 28

• “dropping off”
• active process of cellular self-destruction
• programmed cell death
• it can be physiologic or pathologic

Question 29

examples of pathologic apoptosis

Answer 29

1. severe cell injury
2. accumulation of misfolded proteins
3. infections
4. obstruction in tissue ducts