Ch 1-2: Common Measurements & Homeostasis Flashcards
Work
work= force x distance
work : J force: N distance: m
conversion factor
9.81 N/kg
1 Nxm = 1 J
Power
power= work/ time
Power: W work: J time: s
1 W= 1 Jxs-1
Work rate or power output provides the intensity of exercise
Ergometers
used to measure human work output and power
Distance
Rate(speed) x Duration
Incline of a treadmill is expressed in
% grade
- Amt of vertical rise per 100 units of belt travel
Calculating work on a treadmill
- cannot be easily determined when treadmill is horizontal
- can be calculated when running/walking on a slope
work= body weight x total vertical distance
Vertical Displacement
Vertical displacement= % grade x distance
Energy expenditure
metabolic rate
- commonly measured in calories (calorimetry)
I kcal= 1000 calories = 4186 J
1 kilocalorie (kcal) = 1,000 calories used to express energy expenditure and energy value of foods
Direct calorimetry
Measurement of heat production as an indication of metabolic rate
Indirect calorimetry
Used to measure oxygen consumption (VO2) as an estimate of resting metabolic rate
- there is a direct relationship between oxygen consumption and heat production
1 MET
1 MET= 3.5 mlx kg-1 x min-1… resting metabolic rate
The energy cost of horizontal treadmill walking or running can be estimated because the O2 requirements for both walking and running, increase as a
linear function of speed
VO2
Volume of O2 consumed
Net efficiency
ratio of work output divided by energy expended above rest
High exercise efficiency improves exercise performance by
increasing the power output produced per amount of ATP used
Net efficiency decreases as work rate(power)
increases
With an increase in work rate, energy expenditure…
increases in a curvilinear fashion
factors that influence exercise efficiency
work rate, speed of movement, and muscle fiber types affect efficiency
Which muscle fiber type is more efficient?
Slow muscle fibers
Which muscle fiber type require less ATP per unit of work?
Slow muscle fibers
less ATP= more efficient
Running Economy
Oxygen cost of running at given speed
- lower VO2 at same speed indicates better running economy
- about 10% better in elite, compared to untrained runners
To achieve maximal efficiency at any work rate, there is an optimal
speed
Homeostasis
Maintenance of a constant and normal (resting) internal environment
- constant over time (dynamic constancy)
Steady state
Unchanging level of a physiological variable but not equal to the “homeostatic” resting value
- constant during movement
- when the body is in steady state, a balance has been achieved between the demands placed on the body and the body’s response to those demands
Intracellular control systems vs Organ control systems
Intracellular
- Protein breakdown and synthesis
- Energy production
- Maintenance of stored nutrients
Organ
- Pulmonary and circulatory systems
- replenish oxygen and remove carbon dioxide
Negative feedback loop
effect goes in opposite direction of the stimulus… responds to the stimulus to “fix” what happened
-primary method used to maintain homeostasis
Parts of biological control systems
- sensor or receptor: detects changes in variable
- control center: assesses input from sensor and initiates response
- effector: changes internal environment back to normal
Positive feedback loop
acts to increase the original stimulus (same direction as the stimulus)
Gain of Control Systems
- also known as precision
- a system’s capability to correct a deviation from homeostasis
- control systems that deal with life/death have large gains
How does exercise challenge homeostasis?
- increased O2 demand by working muscles
- increased CO2 produced by working muscles
- increased heat produced by working muscles
- heavy exercise—> lactic acid—> increased acidity
- most biological control systems can maintain a steady state during submaximal (mild) exercise in a cool environment
- during heavy exercise or prolonged exercise in a hot or humid environment, disturbances to homeostasis are too great for control systems to overcome… steady state can’t be reached
Adaptation
- change in structure or function of cell or organ system (in response to exercise)
- results in improved ability to maintain homeostasis
Acclimation
- Adaptation to repeated environmental stresses
- Results in improved function of existing homeostatic system
- “getting used to the environment”
Cell signaling
- communication between cells using chemical messengers
- coordinates cellular activities
- important for maintaining homeostasis
- five different cell signaling pathways exist
What are the 5 Cell signaling mechanisms?
- Intracrine signaling
- Juxtracrine signaling
- Autocrine signaling
- Paracrine signaling
- Endocrine signaling
Intracrine signaling
chemical messenger inside cell triggers response
Juxtacrine signaling
chemical messenger passed between two connected cells
Autocrine signaling
chemical messenger released in extracellular fluid and acts on that same cell
Paracrine signaling
chemical messengers act on nearby cells
Endocrine signaling
Chemical messengers released into blood
- only affect cells with specific receptor
Stress proteins assist in
regulation of homeostasis
- repair the damaged proteins
Cellular stress response
a biological control system in cells that manufactures proteins to defend against stress (maintain homeostasis)
- cells synthesize protective proteins called stress proteins
Stresses that induce stress proteins… and what kinds of exercise produce these stresses
aka affect homeostasis
- heat
- abnormal pH
- low cellular energy levels
- alterations in cell calcium
- free radical damage
- etc.
High intensity or prolonged exercise can produce these stresses
If speed is too low then efficiency is _______ due to ______
low; inertia
If speed is too high then efficiency is _____ due to _____
low; increased muscular friction
High power outputs result in _______ to result in greater efficiency
higher speeds
