Exam 2 Flashcards
Phosphocreatine in the muscle
donates a phosphate group to make ATP quickly
Glycogen in the muscle
can generate ATP both aerobically and anaerobically
Bucking horses work for, at most 8 seconds. To power this effort for ATP would be synthesized
predominantly anaerobically
To facilitate powerful movements such as going over a fence or breaking out of a head horse box or turning a barrel the horse would use
large motor units (large number of muscle fibers controlled by one motor neuron)
Lactic acid in the muscle
is the product of anaerobic synthesis if ATP using glycogen
There are breed differences in the proportion of Type I, Type IIA, and typer IIX muscle fibers expressed in the gluteal muscles of the horse. The quarter horse is known for its speed and power in the short distance. It would be expected that the quarter horses would have proportionally increased expression of
Type IIX fibers
Muscles in the shoulder are important to maintain posture and help hold the neck and head up. Because of this role these muscles have to work for a long time without fatigue. It would be expected that most of the ATP used for theses activities would be derived from the
Aerobic ATP production using fatty acid
Horses which suffer from mitochondrial myopathy are unable to move protons from the mitochondrial matrix to the inter-memebrane space (the mitochondria are dysfunctional). A filly with this disorder could not trot for more than 10 min and was unable to exceed 7 m/sec (slow lope). Which best accounts for these symptoms
high lactic acid synthesis since ATP cannot be made anaerobically
Mutation of the glycogen synthase 1 gene (GLY1) is one cause of polysaccharide storage myopathy (PSSM). Mutation of this gene causes an increase in muscle glycogen and limits its exercise. What best accounts for theses symptoms
metabolic stress limits exercise since aerobic metabolism of glycogen (pyruvate) is dysfunctional
In the first few seconds of any exercise ATP will be synthesized predominantly from
anaerobic pathways
Muscle capillary density increases with increasing fitness. This increase in density would facilitate exercise by
increased surface are, increasing oxygen delivery
With increased fitness, more ATP will be generated aerobically at any given speed. This will improve performance and delay fatigue because
aerobic pathways spares muscle glycogen
With training and increased fitness, the muscle has an increase in aerobic and a decrease in aerobic ATP synthesizing enzymes. This change in enzymes would facilitate exercise by
increasing the capacity of aerobic ATP synthesis
With training and increased fitness, number of IIA and IIX muscle fibers increase. This change delays fatigue since
These fibers derive more of their ATP from aerobic (oxidative) pathways
Packed cell volume is a measure of RBC content of blood, and increases from resting values of 0.3 to a 0.6 at exercise. This increase in RBC reflects
The increased O2 carrying capacity at exercise
Ventilation increases linearly with speed (or effort). This increase in ventilation is accomplished by
increased breath frequency at low speeds and greater tidal volume at high speeds
In 2012 I’ll have another raced with a nasal strip, but was intending to run in the Belmont without it-the nasal strip was considered illegal at the Belmont. This nasal strip decreases nasal resistance which accounts for
approx. 50% of the airway resistance
In a fit horse at intense exercise, supply of oxygen limits exercise capacity. Venous return blood is more deoxygenated and there is a decreased transit time in the pulmonary system compared to at rest. What causes these limitations
More O2 is consumed and increased pulmonary pressure decreases transit time
The increase in VO2 with training is most likely influenced by
increased numbers of mitochondria
If a horse had recurrent airway obstruction (RAO) developed from exposure to dusty stables or moldy hay, what would be the exercise limitation
limited gas exchange at the alveoli
cross sectional are occupied by capillaries is much greater than that of arteries or veins training increases the number of capillaries which increase exercise capacity by
increased area for gas exchange
V4, or the velocity a horse is going when it reaches 4 mmole lactate/ liter of blood, is an important measure of fitness because
V4 is the velocity after which most of the ATP must be synthesized anaerobically
At exercise there is an increase in the number of RBC. There is not an additional increase in RBC with training. What is the best explanation for this
A further increase is packed cell volume would increase blood viscosity and pressure
With training lung capacity
remains unchanged
