Cardiovascular/Hematopoeitic Systems

Question 1

What are the majority of exercise intolerance issues due to?

Answer 1

Musculoskeletal problems, respiratory issues, cardiovascular issues

(in that order)

Question 2

What does splenic contraction do for the horse?

Answer 2

Increases circulating blood volume which increases oxygen carrying capacity of the blood

Question 3

What how much does hematocrit increase doe splenic contraction result in?

Answer 3

from 40% (resting) to 60-70%

Question 4

What can be an issue with increased PCV?

Answer 4

Also increases the viscosity of the blood which can decrease the perfusion

More reasons why blood doping is dumb

Question 5

What is the issue with exogenous EPO administration in order to boost blood production?

Answer 5

Immune mediated reaction that results in bone marrow suppression and lifelong/fatal anemia

Question 6

What is cardiac output a product of?

Answer 6

Heart rate and stroke volume

Question 7

How much does cardiac output increase from rest to exercise?

Answer 7

25L/min to 300L/min

Question 8

What is the typical exercise HR of a horse?

Answer 8

200-250BPM

Question 9

What factors contribute to increased stroke volume?

Answer 9

• Myocardial contractility
• Venous return
• Blood volume
• Filling time

Question 10

What is venous return enhanced by?

Answer 10

Vasoconstriction, muscular contraction, air pressure changes in the thorax

Air pressure likely the most important component

Question 11

How much volume can splenic contraction contribute?

Answer 11

12L

~25% of normal circulating BV

Question 12

What cardiac event dysfunction is most likely to contribute to exercise intolerance and poor performance?

Answer 12

Atrial contraction dysfunction

Question 13

How much does SV increase with submaximal exercise?

Answer 13

20-50%

Question 14

T/F: Increased heart rate will always have a positive effect on stroke volume.

Answer 14

False- if heart rate is high enough to decrease diastolic filling time it will negatively impact it

Question 15

What system is believed to be the primary limiting factor to maximal exercise?

Answer 15

Respiratory system

Question 16

What pathology supports the thought that the respiratory system is the limiting factor for maximal exercise?

Answer 16

Exercise induced pulmonary hemorrhage

Question 17

What is the difference in respiratory volume between rest and exercise?

Answer 17

80L/min vs 1800L/min

Question 18

How is tidal volume increased?

Answer 18

1. Increasing diaphragm contraction
2. Increasing pleural pressure changes
3. Increasing flow
4. Limiting muscular activity

Question 19

Why does limiting muscular activity help increase tidal volume?

Answer 19

The energy needed to increase ventilation uses more oxygen than it delivers.

Question 20

At what speeds does the horses respiratory rate match the stride frequency?

Answer 20

Gallop and canter

Feet cannot go faster than the breathing

Question 21

What is the respiratory rate limited to at a gallop and canter?

Answer 21

~130 breaths/min

Question 22

What acts as a pump to assist breathing at a gallop and canter?

Answer 22

Visceral contents

As the front feet hit the ground the contents hit the diaphragm which causes the horse to exhale and visa versa

Question 23

What A-V O2 gradient favors diffusion of gases?

Answer 23

High gradient- improves O2 extraction

Question 24

What what kind of shit of the O2 dissociation curve favors offloading?

Answer 24

Right shift due to hypercarbia, high temps, or tissue acidosis

Question 25

T/F: The horse has more muscle mass than the cardiovasular and respiratory systems can reasonably maintain during maximal exercise

Answer 25

True- reasons why horses have been selectively breed for bigger hearts

Question 26

At what percentage of VO2 max does hypoxemia ensue?

Answer 26

65%- passage of the RBCs in pulmonary capillaries is too fast for them to get adequate oxygenation

Question 27

What two things will have a negative impact on performance in the cardiovascular system?

Answer 27

Limited SV increase and extreme HR increase

Question 28

What is the most significant limitation to respiratory function?

Answer 28

Resistance to flow in the upper airways

Question 29

What are the limitations of the respiratory system?

Answer 29

Limit to increase in rate
Limit to ventilation
Resistance to upper airway flow

Question 30

What muscle fibers fatigue fastest in endurance horses?

Answer 30

Type I and then type 2 aerobic metabolism

Question 31

What muscle fibers fatigue fastest in race horses?

Answer 31

Type 2 anaerobic metabolism

Question 32

What does training and conditioning improve oxygen delivery by?

Answer 32

• Increase in heart mass
• Increase in SV
• Increase in PCV
• Increase in total RBC volume
• Increase capillary supply to muscles
• Redistribution of blood
• Increased capillary surface area
• Increase delivery to working muscles

Question 33

Training a horse increases which metabolic pathway?

Answer 33

Aerobic- more 2A fibers, increased mitochondria and glycogen stores

Question 34

When is exercise evaluation performed?

Answer 34

Poor performance- sudden onset or never reached potential
Exercise intolerance- suboptimal performance of a usually good perfoming horse
Fitness assessment- to assess general fitness and potential

Question 35

T/F: Horses with exercise intolerance do not appear sick under normal condition or at rest.

Answer 35

True