Causes of Disease Flashcards
What is the concept of aetiology?
Initial events that trigger disease. Diseases can have single cause or product of multiple factors
What is the concept of pathology?
Process of disease taking place
What are idiopathic conditions?
Conditions with no known cause
What is an intrinsic cause of disease and state some examples?
Cause of a disease that begins within the body. Mainly due to changes in an individual’s genome e.g., nuclear/mitochondrial, inherited mutations and other genetic variations (duplications, deletions, insertions, loss), de novo mutations (occur from new), epigenetic modifications (methylation etc). All typically alter function of a gene which leads to more/less protein or same amount but more/less activity.
What is the difference between cell autonomously and cell non-autonomously?
CA – cell X no longer expresses structural protein Y, so cell X is the wrong shape. Mutation affects that specific cell that expresses this protein.
CN – cell X no longer secretes protein hormone Y, so cell Z no longer functions and cell X unaffected.
What is an extrinsic cause of disease and give some examples?
Causes of disease that are due to external factors e.g., injury, infection, nutrition & diet, chemical poisoning, exposure to radiation etc.
How is age a contributing factor?
Most of the time ‘age’ refers to time e.g., cartilage damage increases with time therefore more prone to osteoarthritis.
How is age a cause?
It describes the biological process of ageing e.g., in women, risk of osteoporosis increases as there is decreased oestrogen from menopause which takes place due to increased age.
What are alternative descriptions of disease?
Intrinsic – genetics. Extrinsic – environmental.
Give some specific diseases that have intrinsic causes (in this module).
Cancer, developmental diseases, inherited anaemia, inherited metabolic diseases.
What is the cell cycle?
A cell reproduces by performing an orderly sequence of events in which it duplicates its contents and then divides in two. This cycle of duplication and division, known as the cell cycle, is the essential mechanism by which all living things reproduce.
What are the phases of the cell cycle?
The cell cycle can generally be divided into the mitotic phase and interphase. During interphase, the cell grows in size with most of the cell’s contents duplicating during this phase. The S phase (synthesis phase) of interphase is where the DNA of the cell is duplicated via DNA replication. The growth phases either side of S phase are known as G1 and G2 respectively and this is where the remainder of the cell’s contents is duplicated. During the mitotic phase, the cell divides into 2 daughter cells. Cells can leave the cell cycle, and this occurs when growth factors are no longer present. Cells that leave the cell cycle are known as quiescent cells and are said to be in the G0 phase. These quiescent cells can re-enter the cell cycle when mitogens interact with them whilst some quiescent cells can differentiate terminally upon which they can no longer enter the cell cycle. In terms of DNA content, the cell has 46 chromosomes (2n) during G1 and 92 chromosomes during G2 (4n).
What is the significance of the two gap phases?
They are more than simple time delays to allow cell growth. They also provide time for the cell to monitor the internal and external environment to ensure that conditions are suitable and preparations are complete before the cell commits itself to the major upheavals of S phase and mitosis. The G1 phase is especially important in this respect. Its length can vary greatly depending on external conditions and extracellular signals from other cells. If extracellular conditions are unfavourable, for example, cells delay progress through G1 and may even enter a specialized resting state known as G0 (G zero), in which they can remain for days, weeks, or even years before resuming proliferation. Indeed, many cells remain permanently in G0 until they or the organism dies. If extracellular conditions are favourable and signals to grow and divide are present, cells in early G1 or G0 progress through a commitment point near the end of G1 known as Start (in yeasts) or the restriction point (in mammalian cells).
What are mitogens?
There are proteins that stimulate proliferation known as mitogens and they maintain survival. Examples of mitogens include EGF (epidermal growth factor), FGF (fibroblast growth factor), IL2 and IL4 (Interleukins 2 and 4) and NGF (nerve growth factor) that are all named after the target they were initially identified on. Mitogens can also follow other naming conventions (e.g. PDGF stands for platelet-derived growth factor and IGF1 stands for insulin-like growth factor 1).
What factors control the cell cycle?
There are 3 checkpoints in the cell cycle. These checkpoints are regulated by kinases and phosphatases. The first checkpoint is at the end of G1 before entry into S phase. This restriction point checks for DNA damage, checks if the cell is the correct size and if there are sufficient numbers of metabolites and nutrient stores. The second restriction point is at the end of G2 just before mitosis. This checkpoint checks if DNA is completely replicated and that it is not damaged. The third checkpoint is during mitosis and it checks if the chromosomes are aligned on mitotic spindle with 2 copies attached to each spindle. Only cells in the G1 phase are responsive to growth factors and this is therefore the main site of control of cell growth.
