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Rad Bio unit 2

Law of Bergonie & Tribondeau- Radiosensitivity of living tissues varies with: maturation and metabolism
Radiosensitive cells Stem Cells, Younger tissues and organs, tissues with high metabolic activity, and High growth rate in tissues.
Radioresistant cells Mature cells, & as cells become specialized the sensitivity decreases.
Response of the radiated tissue is determined by: the amount of energy deposited per unit mass, (dose of rad (Gyt)
Linear Energy Transfer (LET) measure of the rate at which energy is transferred from ionizing radiation to soft tissue.
as LET increases, the ability of ionizing radiation to produce a biological response: increases
The highest LET heavy neutrons are alpha particles
low LET neutrons Gamma rays & x-rays
x-rays are _____ energy & _____ LET. high & low
High LET is of greatest concern when... implanted, ingested, injected, & inhaled.
alpha particles have the _____ LET and can do a great deal of damage from inside the body. HIGHEST
Relative Biologic Effectiveness Describes the capability of radiation with different LETs to produce a particular biologic response.
LET & RBE are _____ proportional directly
Diagnostic x-rays ____LET _____RBE 3.0 LET & 1.0 RBE
5 MeV alpha particles ____LET ____RBE 100 LET & 20 RBE
Protraction Dose is delivered continuously but at a lower dose rate (spread over time)
Fractionation same dose rate as protraction but in equal fractions (allows for recovery and repair).
oxygen effect tissue if more sensitive to radiation when irradiated in the oxygenated state.
OER highest for ____ LET radiation LOW
Hormesis Theory that small quantities of radiation may be good for you.
Stochastic radiation dose-response probabilistic- probability of seeing effect. results from low radiation exposure. Late radiation response.
Deterministic radiation dose-response Nonstochastic- severity of effects. results from high, acute dose of radiation. Early radiation response.
Threshold dose level below which there is no response
Nonthreshold dose Any dose is expected to produce a response.
Current radiation protection philosophy is based on... assumption of linear, nonthreshold relationship (no safe dose).
In Vitro Irradiation outside of the cell or body
In Vivo Irradiation in the body
Main-Chain Scission results in the reduction of a long, single molecule into many smaller molecules which still may be macromolecular. (reduces size and viscosity of solutions)
Cross-linking small, spur-like side structures that extend off the main chain attach to a neighboring macromolecule or to another segment of the same molecule.
Point lesions disruption of single chemical bonds. Not detectable but they can result in minor modification of the molecule which can cause a malfunction.
Catabolism Molecular nutrients are broken down into smaller molecules with an accompanying release of energy.
Transcription Occurs in the nucleus. DNA info transferred to mRNA..
Translation Occurs in cytoplasm @ ribosome. mRNA transfers info to tRNA. Polypeptide chain forms becoming a protein.
The most radiosensitive molecule. DNA
Proteins are ___ radiosensitive than nucleic acids (DNA) less
5 results of radiation & DNA interation; Single Strand break Double Strand Break Rung Breakage cross-linking Change or loss of base
Which radiation effects are reversible? single strand break double strand break rung breakage cross-linking
3 principle observable effects resulting from irradiation Cell Death Malignant Disease Genetic Damage
Free Radicals uncharged molecule w/o single unpaired electrons in the outer shell.
Direct Effect results when radiation transfers its energy to the DNA & RNA molecule directly.
indirect effect initial, ionizing event occurs on a distant, noncritical molecule & energy is then transferred to DNA.
Target Theory There is one master or key molecule which maintains cell function. (DNA)
Created by: rieste