Lecture 5 Flashcards
Lecture 5:
What are 3 ways the relationship between cancer & PA can be explained?
1.) The indirect association b/w PA & cancer
2.) The direct effect of physical activity itself on cancer
3.) The effect of obesity on cancer (next set of slides)
Lecture 5:
When discussing PA & cancer risks reduction, what are indirect associations between cancer & PA?
The correlation b/w 2 variables due to the presence of a common third variable
- each variable closely related to a third factor
- we; lifestyle factors often related to PA & reduced cancer risk reduction
Lecture 5:
What are the effects of Pre-Existing Disease on cancer risks & PA?
- Associated disease causes person to reduce PA
- eg; smoker who gets COPD would have decreased activity levels & increased risk of lung cancer
Letcure 5:
How does dietary fibre act as a confounding variable to PA & reduced cancer risks?
Fibre reduces risk of cancer by;
- binding carcinogens, altering GI flora, & increasing speed of transit (poop transit)
- active people tend to eat more fibre but consequently it appears that PA reduces cancer risk when actually it’s the confound of a fibre filled diet
Letcure 5:
How do Antioxidants act as a confounding variable to PA & reduced cancer risks?
Active people tend to also eat more of these, but consequently it looks like it’s the PA reducing cancer risk (when actually the confound antioxidants eaten)
- Antioxidants “clean up” free radicals
Lecture 5:
What are the Free Radicals that Antioxidants “clean up”?
Oxygen molecules with single missing electrons, causing cellular damage as they take electrons from molecules in healthy cells
Letcure 5:
How do Vitamins act as a confounding variable to PA & reduced cancer risks?
Active people = more likely to take Vitamin D & other supplements
- studies show larger doses of these vitamins may decrease cancer risk
Letcure 5:
How does Socioeconomic Status act as a confounding variable to PA & reduced cancer risks?
Active people are more likely to be; wealthier, live further from polluted areas, & have less exposure to occupational carcinogens
Lecture 5:
How do high levels of Sex Hormones from PA influence cancer risk?
High sex hormone levels increase cell proliferation (cell division) & decrease apoptosis
- Overall, reduced sex hormone levels increase blood reduces risk of cancer
Lecture 5:
How does Plasma Testosterone & estrogen levels influence cancer risk?
High levels of plasma testosterone is associated with risk of some hormone sensitive cancers in men
- High plasma estrogen has same cancer risk but in women
Lecture 5:
How is the Menstrual Cycle related to PA & Cancer risk?
More menstrual cycles in a lifetime = greater risk of developing breast cancer
- late menarche, early menopause, & pregnancy = protective (more exercise delays menarche & reduces total cycles)
Lecture 5:
How does estrogen influence cancer risk?
Less estrogen exposed to breast tissue over lifetime = better
Lecture 5:
How does PA influence estrogen levels in Pre-menopausal adult women vs postmenopausal women?
Pre = PA decreases levels of circulating estrogen & progesterone
Post = PA decreases serum estrogens & androgens
Lecture 5:
How does PA influence Androgens in Men?
- PA reduces basal (resting) levels of androgens
- Androgens may be related to cancer risk (anabolic steroid use linked to liver cancer)
- PA may reduce risk of prostate cancer as it reduces circulating androgen levels (but inconclusive if for sure)
Lecture 5:
How does PA influence Insulin & Insulin like Growth Factor & cancer risk?
Insulin & IGF are growth promoters for breast & colon cancer
- these are strongly controlled by PA (more PA = less insulin)
- Increased levels of these cause increase sex hormones & then more proliferation
Lecture 5:
How does PA influence Cortisol levels & cancer risk?
Regular PA decreases resting cortisol levels
- too much cortisol depresses immune system
- immune function needed to fight off cancer cells, so lowering cortisol through PA is important
Lecture 5:
How does PA influence Prostaglandins & cancer risk?
Prostaglandins are released from exercise-induced microtrauma which may increase movement through GI tract allowing decreased risk of colon cancer
- may also reduce proliferation
Lecture 5:
What are the 2-stages of tumour formation?
1.) Normal cell gives rise to precancerous cell
2.) Further changes produce cancerous cell capable of rapid replication
Lecture 5:
How does PA & overtraining influence the immune system?
PA stimulates the immune system however, overtraining depresses the immune system
Lecture 5:
What are the 5 parts of the Immune System that Attack Cancer Cells?
1.) Macrophages
2.) Natural Killer Cells (NK cells)
3.) Lymphocytes
4.) Neutrophils
5.) Lymphokine-activated killer cells (LAK cells)
Lecture 5:
What are Macrophages & how do they work in the immune system to protect/fight against cancer?
Have a phagocytic role as they eat/engulf cancer cells & act as a dominant role in cancer prevention
- normally low activity, but become primed when inflammation occurs, thus microtrauma from PA can make macrophages more active
Lecture 5:
What are Natural Killer Cells & how do they work in the immune system to protect/fight against cancer?
Surveillance role as they attack most cancer cells types as they scan the body for unknown things
- single round of vigorous PA increases NK levels
- regular exercisers have higher NK cell activity @ rest than non-exercisers
Lecture 5:
What are Cytolytic T Lymphocytes & how do they work in the immune system to protect/fight against cancer?
They kill tumour cells & activity is enhanced by regular moderate PA
Lecture 5:
What are Interferons (IFN-a) & their role in the immune system for reducing cancer risk/amount?
Inhibit growth & division of tumour cells (levels increase with PA)
- activates macrophages & NK cells
Lecture 5:
What are Tumour Necrosis Factors (TFNs) & their role in the immune system for reducing cancer risk/amount?
Damage tumour cells
- levels increase after endurance activities
Lecture 5:
What are 4 things that PA & reduced cancer risk may be linked to?
1.) indirect relationships
2.) Decreased circulating sex hormones
3.) better regulated insulin & IGF
4.) Decreased cortisol & prostaglandins
