Human Response to Radiation – Exam Notes

Deterministic Effects

These effects happen only if a certain dose of radiation (a threshold) is reached. If the dose is below this threshold, they won't occur. The severity of these effects increases as the radiation dose goes up, and they usually appear relatively quickly, within days or weeks after exposure.

Acute Radiation Syndrome (ARS)

A severe set of symptoms that occur after a high dose of radiation affects the whole body, with distinct forms.

Hematologic Syndrome

Damage to the bone marrow, leading to a severe drop in all types of blood cells, making a person vulnerable to infections and bleeding.

Gastrointestinal Syndrome

Damage to the lining of the digestive system, causing severe nausea, vomiting, diarrhea, and dehydration.

Central Nervous System (CNS) Syndrome

The most serious form of ARS, occurring after extremely high doses, quickly leading to the failure of the circulatory and nervous systems and rapid death.

Local Tissue Injury

Damage observed in specific parts of the body.

Skin (Local Tissue Injury)

Reddening (erythema), peeling (desquamation), or hair loss (epilation) due to radiation exposure.

Gonads (Local Tissue Injury)

Damage to reproductive organs from radiation.

Extremities (Local Tissue Injury)

Injury to arms or legs from radiation.

Hematologic Depression

A general decrease in the number of blood cells, especially white blood cells (lymphocytes are very sensitive), red blood cells, and platelets.

Cytogenetic Damage

Visible changes or abnormalities in the structure of chromosomes within cells, such as breaks or abnormal arrangements.

Stochastic Effects

Effects that have no threshold dose; even a very small amount of radiation carries a slight chance of causing them. The probability increases with dose, but severity doesn't depend on dose. They appear after a long latency period.

Malignancies (Cancers)

The main concern of stochastic effects, where radiation can increase the risk of various cancers like leukemia, bone cancer, lung cancer, thyroid cancer, and breast cancer.

Local Late Damage

Long-term problems in specific tissues, such as skin thinning (atrophy), cataracts (clouding of the eye lens), and long-lasting damage to the reproductive organs.

Life-span Shortening

A general observation that groups exposed to radiation, on average, tend to live slightly shorter lives, even without developing a specific radiation-induced disease.

Genetic Effects

Damage to the DNA in sperm or egg cells, which could potentially lead to mutations or health problems in future offspring.

Prenatal or neonatal death

Death before or shortly after birth due to fetal radiation exposure.

Severe congenital malformations

Birth defects, especially during the stage when organs are forming, caused by fetal radiation exposure.

Growth retardation

Slower development in an exposed fetus.

Increased risk of childhood cancers

A potential outcome for children exposed to radiation in utero, particularly leukemia.

American radiologists (Human Evidence Group)

Early medical professionals who received significant occupational radiation exposures.

Japanese A-bomb survivors (Human Evidence Group)

A group that provided crucial long-term data on cancer incidence and other health effects due to high radiation exposure.

Accident victims (Human Evidence Group)

Individuals involved in radiation accidents (e.g., Chernobyl, Goiania) whose cases contributed to understanding radiation effects.

Marshall Islanders (Human Evidence Group)

A population exposed to radioactive fallout from nuclear testing, providing data on radiation effects.

Uranium miners (Human Evidence Group)

A group that showed an increased risk of lung cancer due to radon exposure.

Radium painters (Human Evidence Group)

A group that developed bone cancer from ingesting radium.

Medical cohorts (Human Evidence Group)

Patients who received therapeutic radiation for medical conditions, studied to understand health outcomes.

Hydrogen (H) in body

The most abundant atom in the human body, constituting 60.0\%
.

Oxygen (O) in body

An atom that constitutes 25.7\%
of the human body.

Carbon (C) in body

An atom that constitutes 10.7\%
of the human body.

Nitrogen (N) in body

An atom that constitutes 2.4\%
of the human body.

Calcium (Ca) in body

An atom that constitutes 0.2\%
of the human body.

Phosphorus (P) in body

An atom that constitutes 0.1\%
of the human body.

Sulfur (S) in body

An atom that constitutes 0.1\%
of the human body.

Trace elements in body

Other minor elements that constitute 0.8\%
of the human body.

Water in tissue

The most abundant molecule in tissue, constituting 80\%
.

Protein in tissue

A molecule that constitutes 15\%
of tissue.

Lipid in tissue

A molecule (fats) that constitutes 2\%
of tissue.

Carbohydrate in tissue

A molecule (sugars/starches) that constitutes 1\%
of tissue.

Nucleic acid in tissue

A molecule (DNA/RNA) that constitutes 1\%
of tissue.

Other molecules in tissue

Other organic and inorganic molecules that constitute 1\%
of tissue.

Water (Macromolecule)

The most abundant molecule in cells (80\%
), vital for regulating body temperature, acting as a solvent, and participating in biochemical reactions.

Proteins (Macromolecule)

Complex molecules built from amino acids, performing various jobs like enzymes, hormones, antibodies, and providing structural support.

Enzymes (Protein function)

Speed up chemical reactions in the body.

Hormones (Protein function)

Act as chemical messengers, signaling between cells.

Antibodies (Protein function)

Part of the immune system, helping to fight off infections.

Structural support (Proteins)

A function of proteins to support cells and tissues.

Lipids (Macromolecule)

A group including fats and oils, important for building cell membranes, storing energy, and providing insulation.

Building cell membranes (Lipids)

A function of lipids, forming the outer layer of cells.

Storing energy (Lipids)

A function of lipids, providing energy supply for long periods.

Providing insulation (Lipids)

A function of lipids, helping to keep the body warm.

Carbohydrates (Macromolecule)

The body's main source of quick energy (e.g., glucose, glycogen).

DNA (Deoxyribonucleic Acid)

The most crucial molecule in terms of radiation sensitivity; carries the entire genetic code, organized into a double helix, and responsible for passing traits.

Nucleus (Cell Structure)

The control center of the cell, containing genetic material (DNA) in chromosomes, RNA, proteins, and water, enclosed by a nuclear envelope.

Cytoplasm

Everything inside the cell membrane except for the nucleus, consisting of cytosol and organelles.

Cytosol

The jelly-like substance that fills the cell.

Organelles

Various small structures suspended in the cytosol, each with a specific job.

Endoplasmic Reticulum (ER)

A network of membranes forming a communication system, involved in making lipids and proteins, with rough and smooth types.

Rough ER

ER with ribosomes attached, involved in synthesizing and modifying proteins.

Smooth ER

ER involved in lipid synthesis and detoxifying harmful substances.

Mitochondria

Often called the "powerhouses" of the cell, responsible for producing most of the cell's energy (ATP) through cellular respiration.

Ribosomes

Tiny structures responsible for protein synthesis (making proteins).

Lysosomes

Organelles containing digestive enzymes that break down waste materials and cellular debris.

Protein synthesis

The process of making proteins, involving transcription and translation.

Transcription

The step in protein synthesis where the DNA's genetic code is copied into a messenger RNA (mRNA) molecule in the nucleus.

Translation

The step in protein synthesis where mRNA travels to a ribosome, and tRNA delivers amino acids to assemble a protein chain.

Somatic cells

Body cells that reproduce through mitosis, creating two identical daughter cells for growth, repair, and replacement.

G*1 (Gap 1)

The cell grows and carries out its normal functions, preparing for DNA replication.

S (Synthesis) phase

The cell synthesizes (copies) its DNA, so each chromosome now consists of two identical sister chromatids.

G*2 (Gap 2) phase

The cell continues to grow and synthesizes proteins necessary for cell division, preparing for mitosis.

M (Mitosis) phase

The actual cell division phase of mitosis.

Prophase

Phase of mitosis where chromosomes condense and become visible.

Metaphase

Phase of mitosis where chromosomes align in the middle of the cell.

Anaphase

Phase of mitosis where sister chromatids separate and move to opposite poles.

Telophase

Phase of mitosis where new nuclear envelopes form around separated chromosomes, and the cell begins to divide into two.

Genetic cells (Meiosis)

Germ cells (like sperm and egg) that reproduce through meiosis, creating four genetically unique cells with half the number of chromosomes.

First meiotic division

In meiosis, a single cell divides into 2 cells, each containing 46 chromosomes (still duplicated).

Second meiotic division

In meiosis, 2 cells divide again, resulting in 4 cells, each with 23 unduplicated chromosomes, including a process of crossing-over.

Tissue categories

Groups of similar cells working together.

Epithelium

Tissues that cover body surfaces, line internal organs and cavities, and form glands (e.g., skin, lining of intestines).

Connective/Supporting tissue

Tissue that provides support and connects other tissues (e.g., bone, cartilage, blood, fat).

Muscle tissue

Tissue responsible for movement.

Nervous tissue

Tissue that transmits electrical signals throughout the body.

Parenchyma (Organ part)

The functional cells of an organ (e.g., liver cells in the liver).

Stroma (Organ part)

The supporting framework of an organ, including connective tissue, blood vessels, and nerves.

Nervous system (System example)

A body system responsible for transmitting electrical signals.

Reproductive system (System example)

A body system responsible for reproduction.

Digestive system (System example)

A body system responsible for processing food.

Respiratory system (System example)

A body system responsible for gas exchange.

Endocrine system (System example)

A body system responsible for hormone production and regulation.

High Radiosensitivity cells

Cells that divide rapidly and are immature, therefore highly sensitive to radiation.

Lymphocytes (High Sensitivity)

A type of white blood cell highly sensitive to radiation.

Spermatogonia (High Sensitivity)

Precursor cells to sperm, highly sensitive to radiation.

Erythroblasts (High Sensitivity)

Precursor cells to red blood cells, highly sensitive to radiation.

Intestinal crypt cells (High Sensitivity)

Rapidly dividing cells lining the intestines, highly sensitive to radiation.

Intermediate Radiosensitivity cells

Cells with moderate sensitivity to radiation.

Endothelial cells (Intermediate Sensitivity)

Cells lining blood vessels, with intermediate radiosensitivity.

Osteoblasts (Intermediate Sensitivity)

Bone-forming cells, with intermediate radiosensitivity.

Spermatids (Intermediate Sensitivity)

Developing sperm cells, with intermediate radiosensitivity.

Fibroblasts (Intermediate Sensitivity)

Cells that produce connective tissue, with intermediate radiosensitivity.