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Chapter 25 Exercise Physiology
Terms in this set (19)
During exercise, what is the advantage of using the anaerobic glycolytic pathway? What are the disadvantages?
Adv: 2.5 times faster than aerobic
Dis: only provides 2 ATP (in comparison to 30-32), also produces H+ which leads to metabolic acidosis
About how much muscle and liver glycogen are stored in the human body?
Enough to provide energy to release about 2000kcal
Explain the reason for shifting from fat to carbohydrate metabolism when a person increases exercise intensity. Does this mean that fat oxidation ceases?
As exercise intensity increases and ATP is consumed more rapidly, the muscle fibers begin to use a larger proportion of glucose, so carbohydrates become the primary source of energy. However, fat oxidation still continues.
Why does insulin secretion by B-cells of the pancreas decrease during exercise?
Less insulin means that cells other than muscle fibers reduce their glucose uptake, sparing blood glucose for use by muscles. Actively contracting muscle cells are not affected by low levels of insulin because they do not require insulin for glucose uptake.
How does blood glucose enter cells if insulin concentration is decreasing?
Muscle contraction stimulates the insulin-independent translocation of GLUT4 transporters to muscle membrane, increasing glucose uptake in proportion to contractile activity.
How can the intensity of an aerobic exercise bout be determined? What is VO2 max?
-Physiologists traditionally quantify the intensity of a period of exercise by measuring oxygen consumption (VO2)
-VO2 max is a person's maximal rate of oxygen consumption and an indicator of the ability to perform endurance exercise.
What is EPOC?
Excess post-exercise oxygen consumption; EPOC represents oxygen being used to metabolize lactate, restore ATP and phosphocreatine levels, and replenish the oxygen bound to myoglobin.
How do we know that ventilation of the lungs during exercise is not a limiting factor under normal circumstances?
Ventilation is only 65% of its maximum when cardiac output has reached 90% of its maximum; heart is limiting not lungs.
How do both feed-forward and sensory feedback mechanisms control ventilation?
1. When exercise begins, mechanoreceptors and proprioceptors in muscles and joints send information about movement to the motor cortex. Descending pathways from the motor cortex to the respiratory control center of the medulla oblongata then immediately increase ventilation (gets you in the range)
2. As muscle contraction continues,
sensory information feeds back
to the respiratory control center to ensure that ventilation and tissue oxygen remain closely matches (fine-tuning)
Give a value for an average cardiac output of an untrained individual during rest and during heavy exercise. How is this different for a very well trained athlete?
-5L/min at rest, 20L/min during heavy exercise
-for athletes this number goes up 6 to 8 times, reaching as much as 40L/min
How do we increase heart rate from 80 to 100 beats/min? How do we further increase the rate?
-First increase: removal of parasympathetic activity
-Second: up sympathetic activity
How do we preferentially distribute blood to muscle during exercise?
1. Sympathetic signals from the CV control center cause vasoconstriction in peripheral tissues.
2. As muscles become active, changes in the microenvironment of muscle tissue take place: O2 concentrations decrease, while temperature, CO2, and acid in the interstitial fluid around muscle fibers increase.
3. These factors act as paracrine causing local vasodilation that overrides the sympathetic signal for vasoconstriction. 4. The net result is shunting of blood flow from inactive tissues to the exercising muscles where it is needed.
During progressive aerobic exercise, what happens to systolic blood pressure?
-It increases. Degree to which depends on the individual and the type of exercise.
-Diastolic stays about the same.
What are the two thermoregulatory mechanisms which are triggered by exercise-induced increases in body temperature?
Sweating, increased cutaneous blood flow
What is heat stroke? Explain a few of the symptoms?
A potentially fatal condition that results from strenuous exercise in hot, humid environments that can severely impair normal thermoregulatory mechanisms. Some symptoms are extremely high fever, flushed face, dry skin, sometimes appearance of goosebumps.
Describe acclimatization of the sweating response to prolonged heat exposure
-As the body adjusts to exercise in the heat, sweating begins sooner and doubles or triples in volume, enhancing evaporative cooling.
-Sweat also becomes more dilute, as salt is reabsorbed from the sweat glands under the influence of increase aldosterone.
Exercise improving type 2 diabetes
With regular exercise, skeletal muscle fibers up-regulate both the number of GLUT 4 glucose transporters and the number of insulin receptors on their membrane. The addition of insulin-independent GLUT 4 transporters decreases the muscle's dependence on insulin for glucose uptake. Glucose uptake into the exercising muscle also helps correct the hyperglycemia of diabetes
Exercise improving CV disease
Exercise reduces blood pressure, decreases triglyceride levels, and raises plasma HDL-cholesterol levels.
What is the J-shaped curve relating exercise and immunity?
Moderate exercise enhances immunity, but strenuous exercise is a form of stress that depresses immunity
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