CH. 40 Flashcards
What are the 5 main types of tissue in the human body?
- Water 80%
- Proteins 15%
- Lipids 2%
- Carbs 1%
- Nucleic Acids 1%
Blood in the body is made up of what?
Erythrocytes- 5 million
Leukocytes - 7500/mm^3
This type of cell generates tissues for specific organs.
-Blast cells
This type of cell is non-functional or “worn-out”
-Clast cells
This cell is much more sensitive to radiation than mature cells in produces due to its rapid reproduction rate.
any -blast cell
This type of cell is a “body” cell of regular organ tissues
- soma, somatic cells
This type of cell is a reproduction or “beginning” cell.
-genesis, genetic cells
What are 2 types of genetic cells?
- sperm
2. ova
What are the 2 reproductive stages of a cell?
- Mitosis
2. Interphase
This involved identical cell reproduction of somatic cells only.
Mitosis
This is the cell reproductive interim/ vegetating stage.
Interphase
What are the 3 stages of interphase?
- G1- gap 1
- Synthesis- S
- G2- gap 2
During this stage of interphase the cell is metabolically active duplicating organelles but not DNA. Chromatin fibers are organized into chromatids held together by centromere.
Gap 1 G1
During this stage of interphase all genetic material doubles. Each DNA molecule is replicated into 2 identical daughter molecules. They are still held together by the centromere in a way that the 2 chromatid structures become 4.
Synthesis S
During this stage of interphase the cell growth continues and enzymes and proteins are formed in preparation for cell division. The cell now becomes ready to divide through mitosis.
Gap 2 G2
What stage of interphase is the most sensitive time during a cells entire life cycle for exposure to radiation?
The very beginning of S-phase.
What are the 4 stages of Mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
During this stage of mitosis the nucleus swells and the chromosomes plump while the nuclear envelope disappears.
Prophase
During this stage of mitosis the chromatin tightens and condenses while the nucleus elongates. The chromosomes line up in the middle of the cello and mitotic spindle fibers attaches to the centromeres of each chromosome.
Metaphase
During this stage of mitosis the double chromosomes are split and each complete set of new chromosomes are pulled by the spindle fibers to each end of the nucleus.
Anaphase
During this stage of mitosis the nuclear membrane is temporarily dissolved while new cell membrane forms through the middle of the cell mass dividing it into 2 new cells.
Telophase
During which stage of mitosis does polarizing of 2 identical copies of genetic material occur?
Anaphase
During which stage of mitosis do the chromosomes become visible under a microscope?
Metaphase
This is a map of chromosomes that is made during metaphase.
Karyotypes
What is the most radiosensitive stage of mitosis?
Metaphase because the densely packed chromosomes are vulnerable to damage from ionizing interactions caused by X-ray which is visible microscopically.
This law states that cells which divide more and cells that are less highly differentiated tent to be more sensitive to radiation.
Law of Bergonie and Tribondeau
This is the most radiosensitive cell in the body.
Lymphocytes
This is a graphing of the degree of a biological response to increasing doses of ionizing radiation.
Radiation Response Curves
Radiation Response Curve graphs can have what 2 types of responses?
- The number of cases occurring within a population.
2. The severity of a particular effect on a single organism.
Radiation response curve graphs can be characterized in which 2 ways?
- Linear or non-linear
2. Threshold or non-threshold
What does a linear graph show?
a proportional relationship between dose and response.
What does a non-linear graph show?
The rate of response changes at different levels of exposure.
What does threshold, non-threshold mean?
This is the point you are able to see the response. Non threshold shows no response point.
Most somatic radiation effect follow which type of graph>
Sigmoid s-shaped non-linear curve with a toe, body, and shoulder portion. The slope of the body can be averaged.
Most cancers and genetic effects of radiation follow which type of graph?
Linear non-threshold curve.
With no threshold there is no safe what?
There is no safe amount of exposure for which we can be certain the effect will not occur.
Our main concern at diagnostic radiology dose levels is for what?
Genetic and Carcinogenic effects to the general population.
This amount of somatic damage from radiation is reparable by he bodies natural mechanisms.
90%
These are certain molecules critical to the survival of the cell.
Target molecules
This is defined as unprepared, functional damage to a chromosome resulting in deactivation of a portion of the genetic code. It is not just a single ionizing event.
A “hit”
Two hits to a single critical molecule does not kill the cell but this will?
Deactivation of two critical molecules by a single hit.
The higher the amount of radiation then the greater the what?
The greater the probability of multiple targets in a single entity meaning more hits causing lethality.
The steeper the slope on a dose graph then what happens to the sensitivity level of the cells?
The sensitivity level of the cells is greater.
Indirect hits consist of what?
The creation from water of chemical compounds which then attack the target molecule rendering it ineffective.
Radiolysis of water is also called what?
Hydrolysis
Hydrolysis ionization causes the chemical breaking down of what into what 2 variations?
- Ions
2. Free Radicals
If free radicals combine they form what?
H2O2= Hydrogen Peroxide which kills the cell
The hydroxyl radical caused how much of all damage?
2/3rds of all damage
Cell death can also occur from ionizing radiation damage breaching what?
The cell membrane
The cell membrane is composed of what?
phospholipids- 1 phosphate and 2 lipids
Irradiation of macromolecules causes what?
main- chain scission
What is main chain scission?
- Breaks into smaller molecules
2. Decreased viscosity within the cell
What is cross linking?
- Chain is attached at middle points.
2. Increased viscosity of the cell.
What is point lesions?
Cellular damage resulting from late effects of radiation effects.
Studies of changes to DNA/RNA are done in which 2 ways?
- In-vitro- “in glass” test tube or on microscope slide
2. In- vivo- “in life” living cells in organism or petri dish
This is a break in the sugar phosphate “rails” molecule structure.
Main Chain Scission
What are the two broad types of damage to DNA?
Main Chain Scission
Rung Damage
This is a break in the nitrogenous base pairs that make “rungs”.
Rung Damage
These are changes in the actual sequence of the genetic code and are of greatest concern causing permanent damage.
Frame Shift Mutations
This type of main chain scission can be repaired quickly and easily and usually are such that the rail at this point is chemically reattached with the correct molecule.
Single-strand break
This can occur when large alpha particles plow through the region or when by chance a scattered x-ray from the original break strikes the second rail of the DNA structure. The odds of reattachment are slim and are irreparable.
Double-Strand Break
Double- strand break can result in this causing permanent damage.
Frame Shift Mutation
This results in point mutation.
Single-Strand Breaks
This is very rare from a scattered x-ray and is typically from a direct effect of radiation.
Double-strand Break
This is separation of the 2 base molecules and are easily reparable since they are held in place by the rails and can re-attach.
Rung Damage
Loss or change of base is irreparable and replacement by a similar molecule still results in a change of genetic code or this.
Frame Shift Mutations
This is any unrepaired change to the genetic code. none are unique to radiation and most are recessive in hereditary.
Mutations
Mutations follow what type of rate change? What does this mean? What type of increase is this?
Linear Non-threshold curve
- This states that any amount of radiation no matter how small may cause genetic mutation.
- Proportional increase
What are the three single hit effects of visible chromosome aberrations?
- Acentric (isochromatid) fragments
- Dicentric Chromosomes
- Translocations
This is a “map” of chromosomes organizing longest to shortest taken during metaphase. Structural damage to chromosomes from radiation “hits” can be visible during metaphase.
Karyotype
This results in an arise from a single chromosome being broken in two locations.
Multi-hit Effects
In addition to translocations, a centric and dicentric fragments, can cause what?
- Deletions
- Rings
- Cross- Linking - Inversions and multi radius configurations
What is LET?
Linear Energy Transfer
This is the amount of energy deposited in tissue per unit length of the radiations travel and is one indicator of how harmful or how effective a particular type of radiation is.
Linear Energy Transfer (LET)
LET measures what?
energy deposited per mm or per micrometer as the radiation penetrates into the body
LET is an indicator of what? Always inverse to what?
- Indicator of how harmful the radiation is.
- Always inverse to penetration.
What is the most appropriate LET unit for diagnostic x-rays?
Kilovolts per micron
With higher LET the damage to tissue is more what?
Concentrated
This is the effectiveness of a certain type of radiation in causing a specified effect or disease.
Relative Biological Effectiveness (RBE)
What does RBE stand for?
Relative Biological Effectiveness
What is the RBE formula?
dose of 250 kvp x-rays required/dose of radiation z required
What is the RBEs for the following:
- Diagnostic X-ray
- 10 MeV protons
- 5 MeV alpha particles
- Heavy Recoil nuclei (particle accelerators)
- 1
- 5
- 20
- 30
This is the rate at which radiation is delivered to cells or tissues and is directly related to the effect on the organism.
Dose Rate
____ exposure to deleterious substances or effect is always more harmful to the organism than ___ exposure. (dose rate)
Acute: Chronic
This is the amplifying effect of oxygen to the damage cause by radiation exposure. It is specifically defined as the ratio of the radiation dose required to cause a particular biological effect without additional oxygen present to the dose required with added oxygen.
Oxygen Enhancement Ratio (OER)
What does OER stand for?
Oxygen Enhancement Ratio
This is dose that is delivered continuously but at a lower dose rate it is said to be what?
Protracted
This refers to extending the time over which a particular dose of radiation is delivered.
Protraction of dose
Protraction of Dose does what to dose rate and effectiveness of dose?
Reduces it
OER applies to only what type of damage indirect or direct?
Indirect
The lower the LET radiation the ____ the OER.
Higher
Higher LET radiations are more likely to cause direct or indirect damage to target molecules?
Direct
This is breaking the total delivered dose into several separated or discrete portions, allowing time periods between each exposure allowing tissue to recover.
Fractionation
Fractionation is the basis for what?
Radiation Therapy
Fractionation reduces effectiveness of the radiation in what 2 ways?
- extend delivery time effectively protracting the dose.
2. separation of dose into discrete treatments.
The reduced effectiveness of he radiation caused by fractionation can be compensated in which way?
By increasing the total dose.
What are the 3 biological factors that effect sensitivity?
- Age of Organism
- Gender
- Chemical Agents
What are the 2 types of chemical agents and examples of each that cause radio sensitivity?
- Radiosensitizers- Vit K, pyrimidines, methotrexate= x2
2. Radioprotectors- sulfhydrilis= too toxic for human use
Which gender is more resilient to radiation?
Women and the reasons are unknown.
What ages result in higher radio sensitivity?
- Extremely old- due to degenerative processes
2. Extremely young- due to law of Bergonie and Tribondeau
Highly- penetrating radiations are predominantly associated with?
- Low LET and RBE
- Indirect Effect
- Oxygen Enhancement
- Single strand breaks
- Sublethal, reparable chromosome damage
- Point Mutations
Low- penetrating radiation are predominantly associated with?
- High LET and RBE
- Direct Effect
- Double Strand breaks
- Lethal irreparable chromosome damage
- Frameshift Mutations
This is the theory that very small amounts of radiation may actually produce health benefits by stimulating vitamin D production and other chemical reactions that are beneficial to cell viability.
Radiation Hormesis
