Nurs 6501 Midterm Exam Review Guide (Weeks 1-6)

Cellular Processes and the Genetic Environment

1. Describe cellular processes and alterations within cellular processes.

Movement. Muscle cells can generate forces that produce motion. Muscles that are attached to

bones produce limb movements, whereas those that enclose hollow tubes or cavities move or

empty contents when they contract. For example, the contraction of smooth muscle cells

surrounding blood vessels changes the diameter of the vessels; the contraction of muscles in

walls of the urinary bladder expels urine.

Conductivity. Conduction as a response to a stimulus is manifested by a wave of excitation, an

electrical potential that passes along the surface of the cell to reach its other parts. Conductivity

is the chief function of nerve cells.

Metabolic absorption. All cells take in and use nutrients and other substances from their

surroundings. Cells of the intestine and the kidney are specialized to carry out absorption. Cells

of the kidney tubules reabsorb fluids and synthesize proteins. Intestinal epithelial cells reabsorb

fluids and synthesize protein enzymes.

Secretion. Certain cells, such as mucous gland cells, can synthesize new substances from

substances they absorb and then secrete the new substances to serve as needed elsewhere. Cells

of the adrenal gland, testis, and ovary can secrete hormonal steroids.

Excretion. All cells can rid themselves of waste products resulting from the metabolic breakdown

of nutrients. Membrane-bound sacs (lysosomes) within cells contain enzymes that break down,

or digest, large molecules, turning them into waste products that are released from the cell.

Respiration. Cells absorb oxygen, which is used to transform nutrients into energy in the form of

adenosine triphosphate (ATP). Cellular respiration, or oxidation, occurs in organelles called

mitochondria.

Reproduction. Tissue growth occurs as cells enlarge and reproduce themselves. Even without

growth, tissue maintenance requires that new cells be produced to replace cells that are lost

normally through cellular death. Not all cells are capable of continuous division.

Communication. Communication is vital for cells to survive as a society of cells. Pancreatic

cells, for instance, secrete and release insulin necessary to signal muscle cells to absorb sugar

from the blood for energy. Constant communication allows the maintenance of a dynamic steady

state.

2. What is the impact of the genetic environment on disease?

Genetic diseases caused by single genes usually follow autosomal dominant, autosomal

recessive, or X-linked recessive modes of inheritance. The recurrence risk for autosomal

dominant diseases is usually 50%. Germline mosaicism can alter recurrence risks for genetic

diseases because unaffected parents can produce multiple affected offspring. This situation

occurs because the germline of one parent is affected by a mutation but the parent's somatic cells

are unaffected. Skipped generations are not seen in classic autosomal dominant pedigrees. Males

and females are equally likely to exhibit autosomal dominant diseases and to pass them on to

their offspring. Penetrance may be age-dependent, as in Huntington disease and familial breast

cancer. Most commonly, parents of children with autosomal recessive diseases are both

heterozygous carriers of the disease gene. In this case, the recurrence risk for autosomal

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NURS 6501 MIDTERM EXAM REVIEW GUIDE (WEEK 1-6)

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recessive diseases is 25%. Males and females are equally likely to be affected by autosomal

recessive diseases. The frequency of genetic diseases approximately doubles in the offspring of

first-cousin matings. In each normal female somatic cell, one of the two X chromosomes is

inactivated early in embryogenesis. X inactivation is random, fixed, and incomplete (i.e., only

part of the chromosome is actually inactivated). It may involve methylation. Gender is

determined embryonically by the presence of the SRY gene on the Y chromosome. Embryos that

have a Y chromosome (and thus the SRY gene) become males, whereas those lacking the Y

chromosome become females. When the Y chromosome lacks the SRY gene, an XY female can

be produced. Similarly, an X chromosome that contains the SRY gene can produce an XX male.

X-linked genes are those that are located on the X chromosome. Nearly all known X-linked

diseases are caused by X-linked recessive genes. Males are hemizygous for genes on the X

chromosome. X-linked recessive diseases are seen much more often in males than in females

because males need only one copy of the gene to express the disease. Fathers cannot pass Xlinked genes to their sons. Skipped generations are often seen in X-linked recessive disease

pedigrees because the gene can be transmitted through carrier females. Recurrence risks for Xlinked recessive diseases depend on the carrier and affected status of the mother and father. A

sex-limited trait is one that occurs in only one of the sexes. A sex-influenced trait is one that

occurs more often in one sex than in the other. Congenital diseases are those present at birth.

Most of these diseases are multifactorial in etiology. Multifactorial diseases in adults include

coronary heart disease, hypertension, breast cancer, colon cancer, diabetes mellitus, obesity, AD,

alcoholism, schizophrenia, and bipolar affective disorder. It is incorrect to assume that the

presence of a genetic component means that the course of a disease cannot be altered—most

diseases have both genetic and environmental aspects.

3. Explain how healthy cell activity contributes to good health and how its

breakdown in cellular behavior and alterations to cells lead to health

issues.

Cells adapt to their environment to escape and protect themselves from injury. An adapted cell is

neither normal nor injured—its condition lies somewhere between these two states. Adaptations

are reversible changes in cell size, number, phenotype, metabolic activity, or functions of cells. 1

However, cellular adaptations are a common and central part of many disease states. In the early

stages of a successful adaptive response, cells may have enhanced function; thus, it is hard to

differentiate a pathologic response from an extreme adaptation to an excessive functional

demand. The most significant adaptive changes in cells include atrophy (decrease in cell size),

hypertrophy (increase in cell size), hyperplasia (increase in cell number), and metaplasia

(reversible replacement of one mature cell type by another less mature cell type or a change in

the phenotype). Dysplasia (deranged cellular growth) is not considered a true cellular adaptation

but rather an atypical hyperplasia.

Injury to cells and to extracellular matrix (ECM) leads to injury of tissues and organs ultimately

determining the structural patterns of disease. Loss of function derives from cell and ECM injury

and cell death. Cellular injury occurs if the cell is “stressed” or unable to maintain homeostasis in

the face of injurious stimuli or cell stress. Injured cells may recover (reversible injury) or die

(irreversible injury). Injurious stimuli include chemical agents, lack of sufficient oxygen

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(hypoxia), free radicals, infectious agents, physical and mechanical factors, immunologic

reactions, genetic factors, and nutritional imbalances. Cell injury and cell death often result from

exposure to toxic chemicals, infections, physical trauma, and hypoxia.

4. What are the roles genetics plays in disease processes?

See answer for question 2.

5. What is the relationship of how cells are involved in disease processes?

Common biochemical mechanisms are important to understanding cell injury and cell death

regardless of the injuring agent. These mechanisms include adenosine triphosphate (ATP)

depletion, mitochondrial damage, accumulation of oxygen and oxygen-derived free radicals,

membrane damage (depletion of ATP), protein folding defects, DNA damage defects, and

calcium level alterations. Examples of cell injury are (1) ischemic and hypoxic injury, (2)

ischemia-reperfusion injury, (3) oxidative stress or accumulation of oxygen-derived free

radicals–induced injury, and (4) chemical injury. Altered cellular and tissue biology can result

from adaptation, injury, neoplasia, accumulations, aging, or death. Knowledge of the structural

and functional reactions of cells and tissues to injurious agents, including genetic defects, is key

to understanding disease processes. Cellular injury can be caused by any factor that disrupts

cellular structures or deprives the cell of oxygen and nutrients required for survival. Injury may

be reversible (sublethal) or irreversible (lethal) and is classified broadly as chemical, hypoxic

(lack of sufficient oxygen), free radical, unintentional or intentional, and immunologic or

inflammatory. Cellular injuries from various causes have different clinical and pathophysiologic

manifestations. Stresses from metabolic derangements may be associated with intracellular

accumulations and include carbohydrates, proteins, and lipids. Sites of cellular death can cause

accumulations of calcium resulting in pathologic calcification. Cellular death is confirmed by

structural changes seen when cells are stained and examined with a microscope. The most

important changes are nuclear; clearly, without a healthy nucleus, the cell cannot survive. The

two main types of cell death are necrosis and apoptosis, and nutrient deprivation can initiate

autophagy that results in cell death.

Altered Physiology

6. Evaluate cellular processes and alterations within cellular processes.

Injury to cells and their surrounding environment, called the extracellular matrix, leads to tissue

and organ injury. Although the normal cell is restricted by a narrow range of structure and

function, it can adapt to physiologic demands or stress to maintain a steady state called

homeostasis. Adaptation is a reversible, structural, or functional response to both normal or

physiologic conditions and adverse or pathologic conditions. For example, the uterus adapts to

pregnancy— a normal physiologic state—by enlarging. Enlargement occurs because of an

increase in the size and number of uterine cells. In an adverse condition, such as high blood

pressure, myocardial cells are stimulated to enlarge by the increased work of pumping. Like most

of the body's adaptive mechanisms, however, cellular adaptations to adverse conditions are

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usually only temporarily successful. Severe or long-term stressors overwhelm adaptive processes

and cellular injury or death ensues. Altered cellular and tissue biology can result from adaptation,

injury, neoplasia, accumulations, aging, or death. Knowledge of the structural and functional

reactions of cells and tissues to injurious agents, including genetic defects, is key to

understanding disease processes. Cellular injury can be caused by any factor that disrupts cellular

structures or deprives the cell of oxygen and nutrients required for survival. Injury may be

reversible (sublethal) or irreversible (lethal) and is classified broadly as chemical, hypoxic (lack

of sufficient oxygen), free radical, unintentional or intentional, and immunologic or

inflammatory. Cellular injuries from various causes have different clinical and pathophysiologic

manifestations. Stresses from metabolic derangements may be associated with intracellular

accumulations and include carbohydrates, proteins, and lipids. Sites of cellular death can cause

accumulations of calcium resulting in pathologic calcification. Cellular death is confirmed by

structural changes seen when cells are stained and examined with a microscope. The most

important changes are nuclear; clearly, without a healthy nucleus, the cell cannot survive. The

two main types of cell death are necrosis and apoptosis, and nutrient deprivation can initiate

autophagy that results in cell death. Cellular aging causes structural and functional changes that

eventually lead to cellular death or a decreased capacity to recover from injury.

7. Analyze alterations in the immune system that result in disease processes.

Inappropriate immune responses are misdirected responses against the host's own tissues

(autoimmunity); directed responses against beneficial foreign tissues, such as transfusions or

transplants (alloimmunity); exaggerated responses against environmental antigens (allergy); or

insufficient responses to protect the host (immune deficiency). Allergy, autoimmunity, and

alloimmunity are collectively known as hypersensitivity reactions. Mechanisms of

hypersensitivity are classified as type I (IgEmediated) reactions, type II (tissue-specific)

reactions, type III (immune complex–mediated) reactions, and type IV (cell mediated) reactions.

Type I (IgE-mediated) hypersensitivity reactions are mediated through the binding of IgE to Fc

receptors on mast cells and cross-linking of IgE by antigens that bind to the Fab portions of IgE.

Cross-linking causes mast cell degranulation and the release of histamine (the most potent

mediator) and other inflammatory substances. Histamine, acting through the H1 receptor,

contracts bronchial smooth muscles, causing bronchial constriction; increases vascular

permeability, causing edema; and causes vasodilation, increasing blood flow into the affected

area. Histamine with H2 receptors results in increased gastric acid secretion and a decrease of

histamine released from mast cells and basophils. Histamine enhances the chemotaxis of

eosinophils into sites of type I allergic reactions. Atopic individuals tend to produce higher

quantities of IgE and to have more Fc receptors for IgE on their mast cells. Ex: seasonal allergic

rhinitis.

Type II (tissue-specific) hypersensitivity reactions are caused by five possible mechanisms:

complement-mediated lysis, opsonization and phagocytosis, neutrophil-mediated tissue damage,

antibody-dependent cell-mediated cytotoxicity, and modulation of cellular function. Ex: Graves

disease, autoimmune thrombocytopenic purpura, and autoimmune hemolytic anemia.

Type III (immune complex–mediated) hypersensitivity reactions are caused by the formation of

immune complexes that are deposited in target tissues, where they activate the complement

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