BLOCK 7: IONIZING RADIATION - Unit 5: Biological Effects of Ionizing (complete)

Question 1

The basic unit of the human body is the _________. The smallest functioning unit of life that is capable of independent existence.

Answer 1

CELL

Question 2

Determines how the cell will function, as well as the basic structure of that cell.

Answer 2

NUCLEUS

Question 3

Within each nucleus are protein structures called _______________.

Answer 3

CHROMOSOMES

Nucleic acid in the chromosomes, called deoxyribonucleic acid (DNA), contains codes for hereditary characteristics and controls for cell functioning.

Question 4

With the exception of the nucleus, the _______________ contains all of the living substances of the cell. It is a clear, watery fluid that is alive with constant cellular activity.

Answer 4

CYTOPLASM

All the functions for cell expansion, growth, and replication are carried out in the cytoplasm of a cell.

Question 5

The outermost layer of the cell, and serves to separate and protect a cell from its surrounding environment. It is the skin of the cell and holds everything in.

Answer 5

CELL MEMBRANE (PLASMA MEMBRANE)

Question 6

The cyclical process involving the growth of a cell until it divides and becomes two new cells, which then undergo the same process.

Answer 6

CELL LIFE CYCLE

Question 7

The process by which new cells are formed for growth, repair, and replacement in the body. This process includes division of the nucleus material and division of the cytoplasm. Genes duplicate before cell reproduction, one set going to each daughter cell.

Answer 7

CELL DIVISION

Question 8

_______________ exposures occur when the body is irradiated directly from sources located outside the body, such as radiation from radionuclides on ground surfaces, dissolved in water, or dispersed in the air.

Answer 8

EXTERNAL EXPOSURES

In general, external exposures are from gamma-emitting radionuclides which readily penetrate clothing, skin, and internal organs. Beta radiation and alpha radiation from external sources are far less penetrating and deposit their energy primarily on the skin’s outer layer.

Question 9

_______________ exposures occur when radionuclides that have entered the body through inhalation, ingestion, or dermal pathways undergo radioactive decay, resulting in the deposition of energy to atoms and molecules of internal cells.

Answer 9

INTERNAL

This radioactive material may be eliminated from the body quickly (hours to days) or may take longer (weeks to years).

Question 10

If radiation interacts with the atoms of the DNA molecule, or some other cellular component critical to the survival of the cell, it is referred to as a _______________.

Answer 10

DIRECT ACTION

The DNA can be damaged enough to destroy the reproduction capacity in some cells and cause mutation in others.

Question 11

Damage to cells caused by free radicals is an __________ action of ionizing radiation.

Answer 11

INDIRECT ACTION

Question 12

Biological effects of radiation on living cells may result in three outcomes for the exposed cell:

Answer 12

• COMPLETE REPAIR
• DEFECTIVE REPAIR
• CELL DEATH

Question 13

Despite the similarities in cellular structure, not all living cells are equally sensitive to radiation.
Properties that make a cell radiosensitive include cells that:

Answer 13

• Are young and growing
• Reproduce quickly
• Are active
• Are undifferentiated

Question 14

As a general rule, the radiosensitivity of a cell type is _______________ to its rate of division and _______________ proportional to its degree of specialization.

Answer 14

PROPORTIONAL ; INVERSELY PROPORTIONAL

Cells that are young and growing are very sensitive to radiation, like blood. Cells that are active – cells that make something else – like bone marrow (bone marrow makes blood cells) are very sensitive. Cells that are undifferentiated – cells that do not have a job yet (stem cells) – are sensitive. Also, cells that have a high oxygen or water count are more sensitive.

Question 15

As a result, living cells can be classified according to their rate of _______________, which also indicates their relative sensitivity to radiation. This means that different cell systems have different sensitivities.

Answer 15

RATE OF REPRODUCTION

Lymphocytes (white blood cells) and cells that produce blood are constantly regenerating and, therefore, are the most sensitive. Gastrointestinal cells do not regenerate as quickly and are less sensitive. Nerve and muscle cells are the slowest to regenerate and are the least sensitive cells.

Question 16

Can be thought of as how much radiation energy is absorbed in relation to the total time of exposure; helps determine whether exposures and the effects of exposure will be chronic or acute.

Answer 16

DOSE RATE

Question 17

Continuous or intermittent exposure to low doses of radiation over a long period of time.

Answer 17

CHRONIC EXPOSURE

With chronic exposure, there is a delay between the exposure and the observed health effect.

Question 18

Dxposure to a large, single dose of radiation, or a series of moderate doses received during a short period of time. High doses tend to kill cells.

Answer 18

ACUTE EXPOSURE

In most cases, a large acute exposure to radiation causes both immediate and delayed effects.

Question 19

TRUE OR FALSE:

Equal doses of the various types of ionizing radiation are equally harmful.

Answer 19

FALSE

Linear energy transfer (LET) differs between the types of ionizing radiation. For example, alpha particles produce greater harm than beta particles, gamma rays, and x-rays for a given absorbed dose. Both high and low LET interactions can cause significant damage to the DNA and can result in a wide array of biological effects.

Question 20

TRUE OR FALSE:

The location of the radiation exposure can determine the outcome of the dose.

Answer 20

TRUE

Exposures can be to the whole body or localized to only part of the body.

Question 21

The _______________ are particularly susceptible to radiation exposure in industrial processes.

Answer 21

EXTREMITIES

Question 22

Sensitivity to radiation differs among cell types. Cells that are rapidly growing and dividing are __________ sensitive to the effects of ionizing radiation.

Answer 22

MORE SENSITIVE

Question 23

Low doses spread out over long periods of time do not cause an immediate problems to organs.
The effects of low doses of radiation occur at the _______________ level, and the results may not be observed for many years.

Answer 23

CELLULAR

These delayed effects can include cancer, benign tumors, temporary or permanent sterility, cataracts, and potentially harmful genetic effects in the children of exposed persons.

Question 24

Acute exposure to the whole body, if large enough, can cause what is called _______________.

Answer 24

ACUTE RADIATION SYNDROME (ARS)

Question 25

____________________ is seen only after whole-body exposures to relatively high doses of radiation, such as what might occur in a serious nuclear accident or being close to a nuclear weapon detonation.

Answer 25

ACUTE RADIATION SYNDROME (ARS)

Question 26

ACUTE RADIATION SYNDROME (ARS)

After a large exposure of radiation, biological effects manifest in general categories. As the dosage increases, three main areas of the body are affected:

Answer 26

the hematopoietic organs
the gastrointestinal tract
the central nervous system

Question 27

Refers to effects on blood-forming organs, mainly bone marrow.

Answer 27

HEMATOPOIETIC SYNDROME

Recall that blood-forming organs are the most radiosensitive. As such, hematopoietic syndrome occurs at lower doses than the others and would be the most common form of radiation sickness seen. It involves exposure of the whole body to radiation dose greater than 200 rad (2 Gy).

Question 28

This syndrome is caused by the death of the cells in the lining of the GI tract. It involves exposure to radiation above 600 rad (6 Gy). This causes intestinal dysfunction, leading to other complications.

Answer 28

GASTROINTESTINAL (GI) SYNDROME

GI syndrome usually goes along with hematopoietic syndrome.

Question 29

This syndrome is associated only with very high acute doses of radiation. It is caused by damage to the nerve cells in the body.

Answer 29

CENTRAL NERVOUS SYSTEM SYNDROME

Other systems in the body are affected as well. The full syndrome occurs with a dose of radiation greater than 1200 rad (12 Gy). Doses large enough to cause this syndrome are probably not survivable.

Question 30

PHASES OF ARS

Following recovery from the prodromal phase, there will be a latent phase during which the exposed individual will be relatively symptom free. The individual may look and feel healthy. This phase lasts for hours to a few weeks.

Answer 30

Latent Phase

Question 31

PHASES OF ARS

The initial phase of early symptoms is characterized by the relatively rapid onset of nausea, vomiting, and malaise. These effects are a common response to acute radiation exposure. This phase occurs within minutes to days after the exposure.

Answer 31

Prodromal Phase

Question 32

PHASES OF ARS

A person will either die or recover from exposure. Complete recovery will range from a week to years. Delayed effects may occur many years later.

Answer 32

Recovery or Death

Question 33

PHASES OF ARS

This phase presents with the clinical symptoms associated with the major organ system injured (marrow, intestine, central nervous system). This phase lasts for hours to months.

Answer 33

Manifest Illness Phase