Chapter 5 Flashcards

1
Q
A
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2
Q

At what dose of whole-body radiation would an observable short-term effect of acute radiation syndrome result?

A

1.5 Gy

If the dose of radiation is large enough (generally over 1.0 Gy or 100 rads, whole body), the resultant signs and symptoms that comprise these short-term effects are collectively known as acute radiation syndrome (ARS).

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3
Q

What is the term for the damage that cannot be repaired and tissues remain weakened, especially with repeated exposures?

A

Cumulative effect

A cumulative effect refers to the theory that radiation-exposed tissues accrue damage and may function at a diminished capacity with each repeated exposure.

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4
Q

What theory of radiation damage to cells results from free radicals combining to form toxins such as hydrogen peroxide?

A

Indirect theory

Indirect theory is based on the assumption that radiation can cause chemical damage to the cell by ionizing the water within it.

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5
Q

What does a threshold dose-response relationship indicate?

A

The first statement is false. The second statement is true.

A nonthreshold dose-response relationship indicates that any dose, regardless of amount, can be expected to produce a biologic response.

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6
Q

Do scientists know whether low levels of radiation exposure carry health risks?

A

TRUE

Scientists do not know whether a threshold level exists, below which radiation would be safe.

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7
Q

Is a less specialized cell more radioresistant?

A

FALSE

According to the law of Bergonié and Tribondeau, the more specialized a cell is, the more radioresistant the cell.

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8
Q

Does a nonthreshold dose-response curve indicate a certain level of radiation below which no biological response should be anticipated?

A

FALSE

A threshold dose-response curve indicates that there is a threshold amount of radiation below which no biological effects would be expected.

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9
Q

What does the ALARA concept mean?

A

As low as reasonably achievable.

Radiation protection guidelines assume that every dose of radiation produces damage and should be kept to the minimum necessary.

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10
Q

Do all humans have the same sensitivity to radiation?

A

FALSE

Individuals vary in sensitivity within the same species.

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11
Q

Do all cells in the human body have the same sensitivity to radiation?

A

FALSE

There is a wide variation in sensitivity to radiation among different types of cells and tissues.

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12
Q

Have X-rays been shown to have carcinogenic effects?

A

TRUE

X-rays can cause cancer by a variety of mechanisms.

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13
Q

Are the structures of the oral and facial regions relatively radioresistant?

A

TRUE

The maxillofacial structures are composed largely of specialized tissues such as bone, nerve, and muscle.

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14
Q

When are cells most sensitive to radiation injury?

A

During mitosis (cell division).

Actively dividing cells are more sensitive than slowly dividing cells.

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15
Q

Can the biological effects of very low levels of radiation be predicted?

A

TRUE

Radiobiologists have been unable to determine what effects result from exposure to very low levels of radiation.

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16
Q

What does radioresistant refer to?

A

Tissues that are not easily injured by ionizing radiation.

Radioresistant refers to a substance or tissue that is not easily injured by ionizing radiation.

17
Q

What is the latent period?

A

The time between exposure to radiation and the first clinically observable symptoms.

It does not refer to the ionization of molecules.

18
Q

What is a somatic effect?

A

Damage occurs to the affected individual but is not passed along to offspring.

This occurs when somatic cells are irradiated.

19
Q

What is the LD 50/30 for humans?

A

4.5 grays.

This is the average whole-body lethal dose to kill 50 percent of exposed humans in 30 days.

20
Q

Why are children more susceptible to radiation than adults?

A

Young cells divide more rapidly than mature cells.

More rapidly dividing cells are more sensitive to the effects of radiation.

21
Q

When do the effects of irradiation occur?

A

Following the latent period.

Effects can occur within a short or long latent period depending on the type of cell.

22
Q

Does the severity of a stochastic effect increase with increased radiation dose?

A

No.

The probability of a stochastic effect increases but not its severity.

23
Q

Who is more sensitive to equal doses of radiation exposure—adults or children?

A

Children.

Their cells are generally primitive and rapidly dividing.

24
Q

Can dental x-rays cause cataracts in the lens of the eye?

A

No.

At least 5,000 millisieverts (mSv) of radiation exposure is required to cause cataract formation.

25
Q

What are other causes of changes to the genetic material of cells?

A

Drugs, chemicals, elevated body temperature, and x-irradiation.

These can cause genetic mutations in cells.