Chapter 9:
Circulatory Adaptations
to Exercise
Part B

EXERCISE PHYSIOLOGY

Average Aortic Pressure
In order to eject blood, the pressure by the left ventricle must exceed the pressure from the aorta. Mean arterial pressure therefore represents an obstacle to the ejection of blood.

•Aortic pressure is ________________ related to ________________ (the higher the aortic pressure, the ________________ the stoke volume).

•High afterload results in a decreased ________________

–Requires greater force generation by the ________________ to eject blood into the aorta

•Reducing aortic pressure results in higher stroke volume

Ventricular Contractility

•Increased contractility results in ________________ stroke volume

–Circulating ________________ and ________________

–Direct sympathetic stimulation of heart

•Both of these mechanisms increase cardiac contractility by increasing the amount of ________________available to the heart cells.

Factors that Regulate Cardiac Output

Summary of Heart
Output and Input

Hemodynamics

The study of the physical principles of blood flow

Physical Characteristics of Blood

–________________

–Liquid portion of blood

–Contains ions, proteins, hormones

–________________

–Red blood cells

•Contain ________________ to carry oxygen

–White blood cells

–________________

•Important in blood clotting

________________

Hemodynamics

Based on interrelationships between:

–Pressure

–Resistance

–Flow

Hemodynamics: Pressure

•Blood flows from high ® low pressure

–Proportional to the difference between MAP and right atrial pressure (DP)

Blood Flow Through the Systemic Circuit

Hemodynamics: Resistance

•Resistance depends upon:

–________________ vessel (important)

–________________ of the blood

–________________ of the vessel

•A small change in vessel diameter can have a dramatic impact on resistance!

Hemodynamics: Blood Flow

•Directly proportional to the pressure difference between the two ends of the system

•Inversely proportional to resistance

Sources of Vascular Resistance

•MAP ________________ throughout the systemic circulation

•Largest drop occurs across the ________________

–Arterioles are called “________________ vessels”

Pressure Changes Across the Systemic Circulation

Oxygen Delivery During Exercise

•Oxygen demand by muscles during exercise is many times greater than at rest

•Increased O₂ delivery accomplished by:

–Increased ________________

–________________ of blood flow to skeletal muscle

Changes in ________________

•Cardiac output ________________ due to:

–Increased HR

•________________ increase to max

–Increased SV

_•Plateau at ________________VO_2max

•Oxygen uptake by the muscle also increases

–Higher arteriovenous difference (________________)

Changes in Cardiovascular Variables During Exercise
These charts show the changes with ________________________________

Redistribution of Blood Flow
Dependent on exercise ________________ (metabolic rate)

•Muscle blood flow ________________ working skeletal muscle

•Splanchnic blood flow (viscera circulation) ________________less active organs

–Liver, kidneys, GI tract

Changes in Muscle and Splanchnic Blood Flow During Exercise

Increased Blood Flow to ________________ _________ During Exercise
(Regulated by local factors = Autoregulation)

•Withdrawal of sympathetic vasoconstriction

•Autoregulation

–Blood flow increased to meet metabolic demands of tissue

–O₂ tension, CO₂ tension, pH, potassium, adenosine and nitric oxide around the arterioles.

Redistribution of Blood Flow During Exercise

Circulatory Responses to Exercise

•Heart rate and blood pressure

•Depend on:

–________________

–________________ condition

–________________ (what might this include?)

Transition From Rest ® Exercise and Exercise ® Recovery

•Rapid ________________ in HR, SV, cardiac output

•Plateau in ________________ (below lactate threshold) exercise

•Recovery depends on:

–________________________________of exercise

–Training state of subject

Changes in Q, SV, HR From Rest ® Exercise ® Recovery
Note: Recovery is generally rapid

Incremental Exercise

•Heart rate and cardiac output

–________________ linearly with increasing work rate

_–Reaches plateau at ________________ VO_2max

•Systolic blood pressure

–________________ with increasing work rate

•Double product

–Increases linearly with exercise intensity

–Indicates the work of the heart

Arm vs. Leg Exercise

•At the same oxygen uptake ________________ work results in higher:

•________________

•Due to higher sympathetic stimulation

•________________

•Due to vasoconstriction of large inactive muscle mass

•The larger the muscle group - ie: legs - involved in exercise, the more resistance vessels that are dilated yielding lower peripheral resistance and BP.

•The next slide shows the comparison of average blood pressure and heart rate during submax rhythmic arm and leg exercise

Heart Rate and Blood Pressure During Arm and Leg Exercise

Prolonged Exercise

•Cardiac output is ________________

–Gradual decrease in ________________

–Gradual increase in ________________

•Cardiovascular drift (increase in HR occurring during prolonged exercise).

–Due to ________________ and ________________ skin blood flow (rising body temperature)

HR, SV, and CO During Prolonged Exercise

S

ummary of Cardiovascular Responses
to Exercise

Summary of Cardiovascular Control During Exercise

•Initial signal to “drive” cardiovascular system comes from higher brain centers.

•Fine-tuned by feedback from:

–Chemoreceptors (in muscle)

–Mechanoreceptors (Golgi tendon organs and muscle spindles)

–Baroreceptors (sensitive to changes in arterial BP

–All send information to higher brain centers to aid in modification of the CV responses to a given exercise task.

A Summary of Cardiovascular Control During Exercise

Chapter 9:
Circulatory Adaptations
to Exercise