PSY333H1 Lecture Notes - Lecture 3: Phosphocreatine, Creatine Kinase, Aerobic Exercise

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11 Jul 2012
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Lecture 3
Health-Enhancing Behaviours
Exercise:
- Any physical activity (even fidgeting) will use energy and burn calories
- EXERCISE is a special class of physical activity
Four Components of Physical Activity:
1. Type: identifies the physiological systems used in a particular activity
Aerobic
Strength
Endurance
Flexibility
2. Frequency: describes how much activity is performed over a period of time
3. Intensity: describes load imposed on physiological systems
4. Duration: temporal length of physical activity
Does Type Matter?
- Many different types of exercise or physical activity, but physiologically there are 5 forms of
exercise
- Resistance related
1. Isometric exercise: contract muscle group against immovable object without movement
in body (improves muscle strength)
2. Isotonic response: place resistance on muscles by moving muscle groups; i.e. weight-
lifting (improves strength and endurance)
3. Isokinetic exercise: place resistance that overloads muscle groups through complete
range of motion with variable resistance; need special equipment (best for strength and
endurance)
- Other 2 forms:
1. Aerobic uses oxygen
Sustained exercise, prolonged oxygen
High intensity, long duration, high endurance
Stimulates and strengthens heart and lungs improves body’s oxygen usage
i.e. jogging, bicycling, swimming
2. Anaerobic does not use oxygen
High-intensity, short-duration, low-endurance
i.e. sprinting
creates deficit in oxygen
- Energy for exercise comes from burning glucose and fatty acids
o Can be in the presence of oxygen or not
o Glucose in the main fuel source of the body
How Exercise Works:
- Muscles: source of energy that keeps everything going is Adenosine triphosphate (ATP)
- Biochemical way to store and use energy
o Adenine nucleotide bound to 3 phosphates
o Every stored in the bond between the second and third phosphate groups
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o Actin and myosin allow for the contraction of muscles
How Does Body Create ATP?
- Several different systems create ATP
- Work together in phases
o Different forms of exercise use different systems, so a sprinter is getting ATP in a
completely different way from a marathon runner
- ATP comes from three different biochemical systems in the muscles, in this order:
o Phophagen system
o Glycogen-lactic acid system
o Aerobic respiration
Phosphagen System:
- Muscle cells contain a high-energy phosphate compound called creatine phosphate
- Phosphate group is removed from creatine phosphate by an enzyme called creatine kinase, and
is transferred to ADP to form ATP
- ATP levels and creatine phosphate levels = phosphagen system
o Supply energy needs of working muscle at a high rate, but only for 8 to 10 seconds
o Releases energy quickly, and after this time, there is no more energy left in that
molecule
Glycogen-Lactic Acid System:
- Muscles have big reserves of a complex carbohydrate called glycogen (chain of glucose
molecules)
- Cell splits glycogen into glucose uses anaerobic metabolism (anaerobic means “without
oxygen”) to make ATP and a by-product called lactic acid from the glucose
- 12 chemical reactions take place to make ATP under this process, so it supplies ATP at a slower
rate than phosphagen system
o Produce enough ATP to last about 90 seconds
Aerobic Respiration:
- When oxygen is present, glucose can be completely broken down into CO2 and water in a
process called aerobic respiration
- Glucose can come from 3 different places:
o Remaining glycogen supplies in the muscles
o Breakdown of the liver`s glycogen into glucose, which gets to working muscle through
the bloodstream
o Absorption of glucose from food in the intestine, which gets working muscle through
bloodstream
- Can also use fatty acids from fat reserves in muscle and the body to produce ATP
- In extreme cases (like starvation), proteins can also be broken down into amino acids and used
to make ATP
- Aerobic respiration would use carbohydrates first, than fasts and finally proteins
- Produces ATP at the slowest rate of the three systems
- Supply ATP for several hours or longer
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Does type matter?
- Sustained nature of aerobic exercise produces health bebefits
- Other forms of exercise are satisfying in their wn way, but have less effect on overall fitness
o Affect short-term glycogen stores instead of long-term energy conversion systems
A note on calories:
- # of calories in a food is a measure of how much potential energy that food possesses
- A gram of carbohydrates has 4 calories, a gram of proteins has 4 calories, and a gram of fat has 9
calories
- Our bodies “burn” calories thought metabolic processes
o Enzymes break carbohydrates into glucose and other sugars, fats into glycerol and fatty
acids and proteins into amino acids
o These molecules are then transported through the bloodstream, to cells, where they are
either absorbed for immediate use or sent on to the final stage of metabolism in which
they are reacted with oxygen to release their stored energy
Exercise:
- Only 49% of Canadians are at least moderately active during their leisure time
o Moderate = 150 calories (kcal) of energy per day, or 1,000 kcal/week
o Physical activity that is done 3.0 to 5.9 times the intensity of rest
- Common chores
o Washing and waxing car (45-60 mins)
o Washing windows or floors (45-60 mins)
o Gardening (30-45 mins)
o Pushing a stroller 1.5 miles for 30 minutes
o Shovelling snow for 25 minutes
o Stair-walking for 15 minutes
- Inactivity = more common among
o Women vs. men
o Older vs. younger adults
o Lower vs. higher incomes and education levels
o Aboriginal vs. non-aboriginal Canadians
- How much?
o Accumulate 60 minutes of physical activity/day
o 30 minutes of moderate-intensity 4 days/week
Exercise vs. Stress:
- Why exercise, which produces the release of adrenalin and other hormones has beneficial
effects on heart functioning whereas stress also produces these changes, but has adverse
effects
o 3 theories:
1. Infrequent activation and discharge of adrenalin (exercise) may be better then
chronically enhanced discharge (stress)
2. Adrenalin discharged under the intended reasons is metabolized differently
than in the stress response
3. Under stress, the HPA axis is activated which maybe be heavily responsible for
the adverse effects whereas, the SNS aroused alone or delayed HPA (common in
exercise) had fewer adverse effects
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