Cardiovascular/Hematopoietic System

Question 1

Splenic contraction

Answer 1

increases oxygen carrying capacity in the blood

Ht 60-70% is physiologic, higher than this = blood doping, blood too viscous = sludging

Question 2

Cardiac output

Answer 2

CO = HR x SV
- from 25L/min at rest to 300L/min
HR increase = fastest way to increase CO
rest HR = 25-45bpm, max HR = 220-250bpm

Question 3

Stroke volume

Answer 3

myocardial contractility - ejection fraction
venous return - vasoconstriction, muscle contraction, changes in air pressure within the thorax
blood volume - splenocontraction can increase volume by 12L
increased stroke volume is limited

Question 4

Limiting factor for maximal exercise is

Answer 4

getting oxygen from the air into the blood

Question 5

Oxygen from air to blood

Answer 5

respiratory system

• gas exchange (O2 extraction, high A-V O2 gradient), right shift of O2 dissociation curve)
• ventilation (increasing tidal volume)
• increase in RR
• perfusion to lungs
• ventilation:perfusion ratio
• diffusion

Question 6

Ventilation

Answer 6

80L/min at rest to 1800L.min during exercise
increasing tidal volume
- increase diaphragm contractions, pleural pressure changes, flow
- limit to muscular activity - energy needed to increase ventilation uses more oxygen than it delivers

Question 7

Increasing respiratory rate

Answer 7

gallop and cantor - resp rate coupled with stride frequency 1:1

• RR limited to maximum rate related to foot movement ~130/min
• visceral contents act as a pump - limb touches down during exhalation, limb comes up starts inhalation

Question 8

Limiting factors for maximal exercise

Answer 8

The ability of a horse’s muscle mass to consume O2 far exceeds ability of the heart and lungs to provide oxygenated blood

• conditions resulting in improved cardiac output positively impact performance
• extreme HR reduces ventricular filling time (reduced CO)
• hypoxemia at 65% VO2 max because diffusion limitation, RBC passing too quickly through capillary, can’t fully saturate with O2

Question 9

Training improves oxygen delivery by

Answer 9

increase in heart mass, SV, PV, RBC volume, increased capillary supply to muscles, transit time, more O2 unloaded

Question 10

Training changes to muscle

Answer 10

more type IIA fibers
volume of mitochondria
oxidative enzymes
glycogen stores