Lecture 7 - DA Flashcards
(55 cards)
Define radiation.
Energy that can be transferred from one body to another through vacuum.
What are the two types of radiation? Give 3 examples for both.
Non-ionising - low energy photon: infrared, visible, UV, radiowaves
Ionising - high energy: alpha, beta, gamma
What happens when beta and gamma rays penetrate matter?
They dissipate their energy through collisions, and the absorbing ions become ionised, breaking molecular bonds.
Define the two sources of ionising radiation.
Natural - produced in nuclei within naturally occurring unstable atoms as they decay.
Artificial - unstable nuclei created by bombarding them with high energy particles, and which will later decay.
Define isotope.
Atoms of an element with the same proton number, but atomic mass.
Which is worse, external or internal irradiation, and why?
Internal, as external can be blocked or removed, while internal cannot. Also makes alpha radiation dangerous.
What are the two molecular impacts of radiation?
Ionisation - may cause unstable fragments - free radicals.
Excitation - elevates electrons to a higher state, causing potential dissociation or transfer of energy when it returns to the lower state.
Define the two forms of biological damage.
Direct - radiation strikes a molecule, causing damage.
Indirect - radiation strikes a molecule, causing it to release free radicals, which then cause damage.
Define a free radical.
Free uncombined atom, molecule, or atomic group, carrying an unpaired electron.
Which is worse, neutral free radicals, or charged free radicals?
Charged free radicals.
Define somatic damage and genetic damage.
Somatic - damage to enzymes, membranes, organelles, and in DNA leading to cancer.
Genetic damage - damage to DNA and chromosomes in reproductive tissue, leading to birth defects.
Most radiation damage occurs as mutations and cancers, rather than damage to proteins. Explain why.
A high dose is required for direct damage, so mostly causes mutations leading to cancer, which requires a low dose.
Name the three syndromes that collectively cause acute radiation syndrome, and describe the response for each. List them in order of the dose needed to be induced.
Haemopoietic syndrome - recovery or death
Gastrointestinal syndrome - death
Neurovascular (CNS) syndrome - death
What is the true cause of death in gastrointestinal syndrome? What is the underlying cause of this outcome?
Infection rather than gastrointestinal dysfunction. The higher chance of infection is due to the loss of the lymphocyte population from haemopoietic syndrome.
What are the two possible explanations of neurovascular (CNS) syndrome?
Leakage of blood vessels into the brain (ie a haemorrhage) causing pressure
Changes in neuronal permeability, leading to loss of action potential
What are the three pathologies of gastrointestinal syndrome and what does it lead to (4)?
Death of GIT mucosa
Increased shedding of mucosal cells
Decreased replacement of mucosal cells
Leads to a denuded GIT, starvation, water loss, and electrolyte loss.
Define alpha radiation.
Identical to a helium nuclei - 2 protons, 2 neutrons.
Define beta radiation.
Energetic electron ejected from an atom following the conversion of a neutron to a proton.
Define gamma radiation.
EM radiation ejected from a nucleus.
Describe what materials are needed to block alpha, beta, and gamma radiation.
Alpha - stopped by paper
Beta - goes through paper, stopped by 3mm Al foil
Gamma - goes through paper, Al foil, stopped by slab of lead
Define decay rate.
Number of nuclei decaying per unit time.
Define half-life.
Time taken for half the radioactive atoms to decay.
Describe the following formula:
At = Ao/2n
At=activity after time
Ao = activity at time 0
n = number of half lives
How can isotopes be differentiated? What else does this feature reveal?
Each isotope has a characteristic half-life. Also explains why some are more dangerous than others.
