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Define the term "threshold dose" in radiation exposure.
A dose level below which there is no effect of radiation on the biological response.
What is the linear non-threshold (LNT) model?
A radiation protection model that assumes a direct relationship between radiation exposure and the risk of cancer.
What factors influence an organism's sensitivity to radiation?
Cells that have a high division rate, high metabolic rate, are of a non-specialized type, and are well-nourished.
Stochastic
Occurs by chance, the probability increases as exposure increases.
Deterministic
The severity of the effect varies with dose; occurs when a significant amount of radiation is absorbed, causing direct damage to the cells and tissue.
What is the latent period in the context of radiation exposure?
The asymptomatic period between the prodomal stage and the onset of symptoms.
How does ionizing radiation affect the hematopoietic system? What is the dose range?
It directly damages the hematopoietic stem cells within the bone marrow, leading to a decrease in the production of blood cells (red, white, and platelets).
stops regeneration
Dose range: 200-1000 rads.
Describe the effects of radiation on the gastrointestinal tract. What is the dose range?
Sufficiently large acute exposures lead to the reproductive death of rapidly dividing crypt cells and loss of body fluid/absorption. Villi gets sluffed off.
Dose range: 1000-5000 rads
What are the acute effects of radiation on the central nervous system? What is the dose range?
Respiratory failure and/or brain stem damage, tremors, death, brain cell damage.
Dose range: Above 5000 rads within 30 hours.
Discuss the concept of radiation hormesis.
It is the idea that low doses of ionizing radiation can have beneficial effects on biological systems.
How does age influence susceptibility to radiation?
Younger people have more cells that are dividing rapidly and tissues that are growing, making them more sensitive to radiation.
What role do free radicals play in the mechanism of cellular damage following ionizing radiation exposure?
They are very reactive chemically, and when combining can produce hydrogen peroxide (Hâ‚‚Oâ‚‚), which is a chemical poison and one of the most harmful free radical products.
What is the Law of Bergonié and Tribondeau, and what fundamental principles does it describe regarding the effects of radiation on living tissues?
"The radiosensitivity of a tissue is directly proportional to its reproductive capacity and inversely proportional to its degree of differentiation."
Discuss the implications of the Law of Bergonié and Tribondeau for understanding the effects of radiation on developing tissues, such as those found in embryos and children.
The most critical period is 2-8 weeks into gestation.
As low as 10 rads may cause effects such as deformation and retardation.
100-200 rads is enough to cause death.
List the doses and effects for the following: Cell membrane, Cytoplasm, Mitochondria, Lysosomes, Nucleus, and DNA.
Cell membrane: 3000-5000 Rads, death of the cell, “drowning”
Cytoplasm: Negligible
Mitochondria: ~3000 Rads, ATP Production slowed/stopped. “starves”
Lysosomes: Suicidal Cell component- Kills itself by eating itself, digestive enzymes released
Nucleus: Most radiosensitive part, DNA production stops
DNA: Duplicate set of chromosomes stopped
What factors affect the radiosensitivity of cells?
Division rate, metabolic rate, non-specialized type, and well-nourished state.
What cell types are most sensitive to radiation?
Germinal cells of the ovaries and testes, hematopoietic tissues, basal cells of the skin, and epithelium of the GI tract.
What cells are least sensitive to radiation?
Bone, liver, kidney, cartilage, muscle, and nervous tissue.
Somatic
Suffered by the exposed person
Hereditary
don’t appear until later generations are born
Describe the role of personal protective equipment in radiation safety
acts as a barrier to prevent workers from being contaminated with radioactive material
How does radiation affect the immune system?
Damaging bone marrow stem cells
Explain the significance of LD50/30 in radiation exposure to humans. What is the LD50/30 dose?
The dose of radiation expected to cause death(Lethal Dose) within 30 days to 50% of those exposed, without medical treatment
The best estimate for the LD 50/30 for humans is between 300 and 500 rads (3-5 gray), and is usually stated as 450 rad (4.5 gray).
Acute Radiation Exposure
Refers to one big dose of radiation received in a short period of time
Chronic Radiation Exposure
Refers to the sum of small doses received repeatedly over long periods of time
What are the main cellular effects of ionizing radiation
Damage to the DNA
How do radiation doses affect cellular repair mechanisms
The higher the dose, the less likely the cells repair will be successful
How does radiation exposure lead to mutations at the cellular level?
causes breaks in the DNA strand which can lead to genetically induced diseases
How does radiation exposure affect the digestive system?
kills the crypt cells, makes it difficult to digest food
What is the significance of using fractional doses in radiation therapy?
allow for a higher total dose to be delivered to a “tumor” while minimizing damage to healthy tissues by dividing the radiation into smaller doses, enabling cells to repair themselves between treatment
Explain how hydroxyl radicals are generated during the radiolysis of water and their significance in biological systems
through the splitting of water molecules, making them a significant factor in biological systems due to their ability to damage critical cellular components like DNA and proteins when generated within living organisms exposed to radiation; essentially acting as a potent oxidizing agent that can disrupt cellular functions
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