Chapter 5 Flashcards
Which of the following statements regarding the biological effect mechanisms of the direct theory is false?
A) Most dental x-ray photons pass through the cell, causing no damage.
B) X-ray photons may collide with important cell chemicals and break them apart.
C) Ionization can cause critical damage to large molecules.
D) Irradiated cells cannot be repaired.
D) Irradiated cells cannot be repaired.
They can be repaired
Which of the following statements regarding the biological effect mechanisms of the indirect effect is false?
A) Ionization dissociates water into hydrogen and hydroxyl radicals.
B) Ions have a strong tendency to seek out new combinations.
C) New chemicals, such as hydrogen peroxide, can form from hydrogen and hydroxyl radicals.
D) Radiation must be massive to destroy entire body tissues that result in death.
B) Ions have a strong tendency to seek out new combinations.
Indirect effect is interaction of radiation with water molecules
Which of the following is most sensitive to damage from radiation?
A) Bone cells
B) Epithelial cells
C) Lymphocytes
D) Muscle cells
C) Lymphocytes
Which of the following statements about radiation repair is false?
A) Somatic cells cannot repair radiation damage.
B) Scientists believe that some radiation effects are cumulative.
C) Ions have a strong tendency to recombine immediately to form water again.
D) The quantity, duration, and body area irradiated determine the amount of damage inflicted by the radiation.
A) Somatic cells cannot repair radiation damage.
Somatic cells can repair radiation damage
Which of the following statements regarding the theory established by a threshold dose-response curve is true?
A) There is a dose below which no biological response would be expected.
B) It predicts the effects of very low levels of radiation exposure.
C) It indicates that any amount of radiation has the potential to cause a biological response.
D) It has been adopted by the radiation protection community as the conservative approach to radiation exposure.
A) There is a dose below which no biological response would be expected.
Each of the following is a potential effect of a low dose of radiation except one. Which one is the exception?
A) No cell response
B) Cell repairs itself and functions at preexposure levels
C) Cell repairs itself abnormally
D) Cell becomes radioactive
D) Cell becomes radioactive
Which of the following statements regarding radiation injury is false?
A) The smaller the area of tissue exposure, the greater damage to the individual.
B) The greater the dose, the more severe the probable biological event.
C) The rate at which the radiation is absorbed may determine which biological effects occur.
D) A given dose may produce fewer biological effects if the cells have a chance to recover.
A) The smaller the area of tissue exposure, the greater damage to the individual.
Which of the following statements regarding radiation injury is false?
A) The amount of injury to an individual depends on the volume of tissue radiated.
B) The lethal dose (LD 50/30) for humans is 1.5 grays.
C) Younger, more rapidly dividing cells are more likely to incur damage.
D) Individuals vary in radiation sensitivity within the same species.
B) The lethal dose (LD 50/30) for humans is 1.5 grays.
(The LD 50/30 for humans is 4.5 grays, not 1.5 grays.)
The lethal dose (LD 50/30) of radiation for humans is estimated to be:
A) 4,500 grays
B) 450 grays
C) 45 grays
D) 4.5 grays
D) 4.5 grays
Which of these is not a symptom of acute radiation syndrome?
A) Constipation
B) Nausea
C) Hemorrhage
D) Hair loss
A) Constipation
Which of the following is not a component of factors determining radiation injury?
A) Actively dividing cells with high mitotic activity are less sensitive.
B) Immature cells are more sensitive.
C) More specialized cells are more radioresistant.
D) Cells are most susceptible to injury during cell division.
A) Actively dividing cells with high mitotic activity are less sensitive.
Which of the following groups of cells are correctly ranked in order of radiosensitivity beginning with the most sensitive?
A) Muscle, brain, red blood, white blood
B) Reproductive, bone, nerve, muscle
C) Brain, bone, connective tissue, white blood
D) Red blood, bone, muscle, epithelial
B) Reproductive, bone, nerve, muscle
Continued exposure to radiation over prolonged periods may result in each of the following except one. Which one is the exception?
A) May alter the ability of genetic cells to reproduce normally.
B) May affect the ability of genetic cells to repair damage.
C) May produce offspring with increased resistance to radiation exposure.
D) May result in cumulative chromosome damage.
C) May produce offspring with increased resistance to radiation exposure.
What is the approximate surface (skin) dose of radiation from a full mouth series?
A) 12.6 mSv
B) 8 mSv
C) 0.4 mSv
D) 0.0005 mSv
A) 12.6 mSv
Which of these periods immediately follows radiation exposure?
A) The period of injury
B) The latent period
C) The reparable damage period
D) The recovery period
B) The latent period
When the severity of change is dependent on the radiation dose, the effect is called a(n):
A) stochastic effect
B) deterministic effect
C) acute radiation effect
D) lethal dose effect
B) deterministic effect
At what dose of whole-body radiation would an observable short-term effect of acute radiation syndrome result?
A) 0.01 Gy
B) 0.25 Gy
C) 1.0 Gy
D) 1.5 Gy
D) 1.5 Gy
Tissues have the capacity to repair radiation damage to a certain degree. However, some damage cannot be repaired and tissues remain weakened, especially with repeated exposures. This is called:
A) a long-term effect
B) radioresistant tissue
C) a cumulative effect
D) a stochastic effect
C) a cumulative effect
What theory of radiation damage to cells results from free radicals combining to form toxins such as hydrogen peroxide?
A) Primary
B) Secondary
C) Indirect
D) Direct
C) Indirect
A threshold dose-response relationship indicates that any dose, regardless of amount, can be expected to produce a biological response. A linear dose-response relationship indicates that the biological response is directly proportional to the dose.
A) The first statement is true. The second statement is false.
B) The first statement is false. The second statement is true.
C) Both statements are true.
D) Both statements are false.
B) The first statement is false. The second statement is true.
Scientists do not know whether low levels of radiation exposure carry health risks.
True
A less specialized cell is more radioresistant.
False
A nonthreshold dose-response curve indicates that there is a certain level of radiation below which no biological response should be anticipated.
False
The ALARA concept means “as low as reasonably achievable.”
True
The effects of irradiation depend on the type of energy and duration of the exposure.
True
All humans have the same sensitivity to radiation.
False
All cells in the human body have the same sensitivity to radiation.
False
X-rays have been shown to have carcinogenic effects.
True
The structures of the oral and facial regions are relatively radioresistant.
True
Cells are most sensitive to radiation injury during mitosis (cell division).
True
The biological effects of very low levels of radiation cannot be predicted.
True
Radioresistant refers to those tissues that are protected by the lead apron and thyroid collar during a dental x-ray exposure.
False
The latent period refers to the time between exposure to radiation and the ionization of molecules.
False
When radiation affects any cells of the body except the reproductive cells, the effect is called “indirect.”
False
A stochastic effect is when a biological response is based on the probability of occurrence rather than the severity of the change.
False
Stochastic effects are probabilistic effects that occur by chance. An extremely rare stochastic effect is the development of cancer in an irradiated organ or tissue. The probability of occurrence is typically proportional to the dose received.
Cancer is a stochastic effect of exposure to radiation.
True
Erythema is a stochastic effect of exposure to radiation.
False
Because they do not divide and are very specialized, reproductive cells are radioresistant.
False
White blood cells (lymphocytes) and reproductive cells (oocytes) are more radioresistant because they do not divide and are very specialized.
False
The average effective dose equivalent from naturally occurring background radiation to the population of the United States is approximately 8 µSv (microsieverts) per day.
True
What is the difference between the effects of irradiation to somatic cells compared to reproductive cells?
Somatic effects affect the individual, while reproductive effects can be passed to offspring.
What do scientists believe about radiation damage to somatic cells from repetitive exposures?
Repetitive exposures can lead to cumulative damage that the body may not repair.
Do scientists believe that radiation damage to reproductive cells is cumulative?
Yes, it is cumulative and may affect offspring due to mutations in reproductive cells.
What is the LD 50/30 for humans?
The LD 50/30 is 4.5 grays, the lethal dose for 50% of humans within 30 days.
Why are children more susceptible to radiation than adults?
Children’s cells divide more rapidly, making them more sensitive to radiation.
When do the effects of irradiation occur?
Effects can occur after the latent period, which can range from minutes to years depending on the exposure.
When the dose of radiation is increased, does the severity of a stochastic effect increase?
No, the probability of the effect increases, but the severity remains the same.
Who is more sensitive to equal doses of radiation exposure—adults or children, and why?
Children are more sensitive because their cells divide more rapidly.
Can dental x-rays cause cataracts in the lens of the eye?
No, dental x-rays do not cause cataracts, as much higher doses are required to induce cataract formation.
In addition to x-radiation, list other causes of changes to the genetic material of cells.
Drugs, chemicals, elevated body temperature, and x-irradiation can all cause genetic mutations.
