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KIN Exercise Physiology

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      PEP418
Exercise Physiology

Section #2A: Cardiovascular
          System
                                        Overview
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•   http://www.niaaa.nih.gov/Resources/GraphicsGallery/CardiovascularSystem/269f1.htm
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              Cardiovascular System
Heart, Lungs, Arteries, Veins
Supply body with:
• O2 and nutrients
Removes from body:
• CO2 and waste products

 So, the questions we are interested in are:
1. How do the heart and lungs work together to
   exchange gasses in the blood?
2. How does the CV system change with exercise?
3. How does the CV system adapt to training?
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                 Heart and Lungs
Heart pumps blood to:
• Pulmonary system (_____________ side)
   – receive deoxygenated blood
• Rest of the body (______________ side)
   – pump oxygenated blood to the rest of the body
Lungs:
• Primary function is to exchange CO2 and O2 with the
  bloodstream
• Although the lungs only weigh 1 kg:
   – surface area for gas exchange is equal to 1/2 of a
     tennis court!
             How Do You Breathe?                          5


• The lungs do not physically “suck” air in;
   – works on pressure gradients

                              • Expanding rib-cage
                                and lowering
                                diaphragm reduces
                                pressure in thoracic
                                cavity
                                 – pressure is less
                                   than the outside air
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Pressure of outside air _______ Pressure in
              thoracic cavity
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Pressure of outside air ______ Pressure in
              thoracic cavity
    How are CO2/O2 exchanged in the lungs?
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• Works on O2 _____
  _________________
  (PO2)
   – O2 gas molecules
     move at high speeds
   – high speed means
     they exert pressure on
     any surface they make
     contact with


   This exchange occurs in the alveoli
                 Pressure Gradients
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• Partial pressure is a measure of the total number of
  molecules of a gas species in a space.
• Partial pressure is directly proportional to the
  concentration of gas molecules within a mixture of
  gases.
                 _______________
• F= fractional concentration of a gas
• PB= barometric pressure
e.g. PIO2= 760 mmHg*0.2093= 159.1 mm Hg
Partial pressure of inspired O2 at sea-level
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Pressure Gradients
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                O2 Delivery to blood
• O2 will only move into the blood
  if the PO2 in the blood is less
  than the lungs
• PO2 in the lungs is around 150
  mm Hg
   – depends on _____________
• PO2 in venous blood is about 40
  mm Hg
 This means O2 will move into
  the blood from the lungs
CO2/O2 exchange
                Systemic Circulation
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• Once the blood is oxygenated, it
  is circulated to the rest of the
  body
Arteries: carry oxygenated blood
  away from the heart
Veins: carry deoxygenated to the
  heart and lungs
Capillaries: site of O2 and CO2
  exchange with the muscle
               Systemic Circulation..
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• Blood vessels have specialized functions
 Play an active role in maintaining blood flow and
  pressure
Vaso_____________: increasing the diameter of a
  blood vessel
Vaso_____________: decreasing the diameter of a
  blood vessel
                Arteries and Veins
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Arteries are blood vessels that leave the heart
• thick, large diameter
• capable of vasocontriction/vasodilation
• gradually get smaller and smaller (arterioles)
 play a very important role in altering blood flow
  and pressure
Veins are blood vessels that go toward the heart
• smaller, less muscular
• gradually get larger (venules)
• valves
           ________________________
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•   “End-point”
•   Exchange of O2/CO2 and nutrients to muscle
•   Very small, single layer thick
•   Only 1 RBC thick
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Blood Vessels
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  How Are Arteries and Veins Important to
                 Exercise?

• Skeletal muscle accounts for 20% of blood flow at
  rest
   – increases to 85% during maximal exercise!
• If all muscles in the body accepted as much flow
  as they could:
   – heart would have to pump blood at 50-60
     l/min. (30 l/min possible with elite athletes!!!)
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          Blood Flow Re-Distribution
            Rest       Exercise      Change in
          5, 000 ml    25, 000 ml    Blood Flow
Unit       %    ml     %     ml

Muscle     20   1000   84   21,000

Liver      27   1350   2     500

Kidneys    22   1100   1     250

Other      7    350    3     780

Brain      14   700    4     900

Skin       6    300    2     600

Heart      4    200    4     1000
              Exercise Blood Flow
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• Exercise increases the O2 demand in muscle
   – therefore an increase in blood flow
• Heart cannot possibly circulate enough blood to
  accommodate the necessary vasodilation
• If not, you would pass-out during exercise!
 Blood flow is shunted away from ____________
  regions
Structure of the heart
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         Components of Blood Flow


______________(Q) = HR x SV
• amount of blood pumped (usually in l/min)
• comprised of Heart Rate and Stroke Volume
   – Resting: 5 l/min
   – Exercise: 22-35 l/min
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   Heart Rate (HR) and _______________
HR:
Number of heart beats: usually in beats/min (BPM)
• Rest: 50-70 BPM
• Exercise: 220 - age (?)

______________:
Amount of blood ejected from the left ventricle per
  heart beat (mL)
• Rest: 70-100 ml
• Exercise: 110-180 ml
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          Oxygen Consumption (VO2)
              ______________ Equation
 Essentially, O2 consumption is a function of how
  much blood flow (Q) and how much oxygen is
  extracted from the blood (a-v O2 difference)

VO2 (l/min) = Q (l/min) x a-v O2 difference
            = HR (bts/min) x SV (ml/bt) x a-vO2
            difference (ml/100ml)
            =2 - 6 l/min

a-vO2 difference
• O2 difference on arterial vs. venous side
   Calculation of oxygen consumption (VO2)
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• Essentially the difference in the amount of O2 that
  comes in the body - the amount of O2 that leaves

VO2 (L/min)= (VI x 0.2093) – (VE x %O2)
VI= volume of inspired air
0.2093= fraction of O2 in room air (20.93%)
VE= volume of expired air
%O2= fraction of oxygen in expired air, expressed as
  a decimal
   16.01% is expressed as 0.1601 in the equation
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       Dynamics During Exercise

 30

 25

 20

 15

 10

  5

  0
         Rest      Mod      Stren.


4000
3500
3000
2500
2000
1500
1000
500
  0
          Rest     Mod       Stren.
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      Dynamics During Exercise...
 180
 160
 140
 120
 100
  80
  60
  40
  20
   0
          Rest     Mod       Stren.


170
165
160
155
150
145
140
135
130
125
         Rest      Mod       Stren.
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     Dynamics During Exercise


20
18
16
14
12
10
 8
 6
 4
 2
 0
       Rest      Mod      Stren.
                      Summary
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• As exercise intensity increases certain variables
  increase in a reasonably linear manner
   – ________
   – ________
   – ________

• _______ does not!
   – ________ peaks at moderate intensities
   – more energy efficient for the body to do this

				
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