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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
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