Biology of radiation

Question 1

Sources of radiation?

Answer 1

1-Background (natural)
2-Manmade (artificial)

Question 2

Dental radiation makes how much % of all manmade radiation?

Answer 2

0.26%

Question 3

what is radiation biology?

Answer 3

a branch of biology that is concerned with the effects of ionizing radiation on living tissues and organisms.

Question 4

who are the irradiated study populations?

Answer 4

1-atomic bomb survivors
2-workers exposed to radioactive materials (radium watch dial painters)
3-nuclear power plants accidents (Chernobyl)
4-patient undergoing radiation therapy (they are less because the radiation is area specific and not whole body)

Question 5

recent studies show that radiation workers in nuclear industries who have suffered low doses of radiation approximated to that of CT scan, and atomic bomb survivors who received low doses approximate to those from CT scans

Question 6

interaction of radiation with atoms?

Answer 6

9%= no interaction
7% coherent scattering (nowadays it is filtered)
27%=photoelectric effect
57%= Compton scattering

Question 7

mechanism of radiation injury are?

Answer 7

1-direct action
2-indirect action

Question 8

what happens to atom in direct action of radiation?

Answer 8

the ionized atom has a positive charge and it is chemically active trying to replace the missing electron..

Question 9

what happens if the ionized atom is a part of a larger molecule?

Answer 9

it will cause braking of the molecular bonds

Question 10

what will happen if enough molecules are damaged in direct action of radiation?

Answer 10

1-loss of cell function
2-didruption of cell organelles
3-death of cell

Question 11

what is the (critical biomolecular target) for radiation?

Answer 11

the DNA

Question 12

So by breaking molecular bonds, radiation has a DIRECT EFFECT on the cell

Question 13

what is the percentage of direct action of radiation?

Answer 13

20%

Question 14

what is the chemical effect of indirect radition?

Answer 14

radiolysis of water
-mechanism is mostly via chemical effect

Question 15

in the indirect action, which by product of the chemical reaction is the most dangerous?

Answer 15

H2O2 caused by free radicals
hydrogen peroxide.

Question 16

what are free radicals?

Answer 16

atoms, molecules or ions which is not combined to anything and carries unpaired electron

Question 17

why are free radicals dangerous?

Answer 17

they are highly reactive and become stable through breaking part or joining of molecules

Question 18

what is the effect of free radicals on DNA

Answer 18

they join with DNA molecule to producec damage

Question 19

so, in Indirect action, produced chemical reaction that indirectly harms the cell by leading to formation of the chemical that cause the damage.

Question 20

which part of the cell is the most radiosensitive?

Answer 20

the nucleus (it contains the DNA)

Question 21

what is the effect of radiation on the nucleus?

Answer 21

1-chromosomal aberrations (damage)
2-mitotic delay
3-cell death

Question 22

a dead cell is better than one with a chromosomal aberration, which may lead to?

Answer 22

cancer or genetic defect

Question 23

sequence of radiation injury?

Answer 23

exposure->injury->repair

Question 24

what is the latent period?

Answer 24

time period between exposure to radiation and appearance of observable clinical signs

Question 25

range of latent period

Answer 25

from few days to years

Question 26

repair is inversely proportional to ?

Answer 26

1-degree of exposure
2-rate of exposure

Question 27

what is the cumulative effect?

Answer 27

each radiation exposure adds to this residual damage

Question 28

critical organs

Answer 28

1-lens of the eyes
2-gonads
3-fetus
4-bone marrow
5-thyroid glans
6-skin

Question 29

difference between somatic and genetic damage?

Answer 29

somatic (all cells)
-damage if to the exposed individual only

genetic (occytes and spermatogonia?)
-damage in inherited from one generation to the next

Question 30

what are the types of dose response?

Answer 30

1-deterministic
2-stochastic

Question 31

what is deterministic dose effect?

Answer 31

increase in dose ->increase in severity

-there is a threshold that must be crossed.
examples?
1-epilation
2-erythema
3-cataract
4-sterility

Question 32

difference between deterministic and stochastic?

Answer 32

deterministic requires a large dose to produce serious damage.

Question 33

stochastic meaning?

Answer 33

increase in dose -> increase CHANCE only
the severity is unrelated to magnitude of dose

examples
1-genetic mutation
2-tumor induction

Question 34

what are the determinants of radiation injury? the radiation factors

Answer 34

1-type of radiation (alpha, beta…etc)
2-total dose (dental less than medical
3-quality of beam (superfacial vs deep tissue)
4-acute vs chronic (chronic has less efect because the tissue has time to repair themselves= similar to dental radiographic exposure
5-local vs whole body
6-dose rate

Question 35

what are the determinants of radiation injury? the host factors

Answer 35

1-species (mammals are more sensitive)
2-intrinsic resistance (cannot be predicted)
3-type of tissue (is it radiosensitive or not?)
4-rate of cell division

Question 36

what is hormesis?

Answer 36

low doses of radiation may have beneficial effect on tissue, through
1-stimulation of cellular repair
2-and immune system

Question 37

radioresistant tissue?

Answer 37

1-mature bone
2-muscle
2-nerves

Question 38

deterministic effect on oral cavity, include?

Answer 38

1-mucositis
2-taste loss
3-xerostomia
4-radiation caries
5-osteoradionecrosis
6-muscle trismus