cardiovascular system6
TRANSCRIPT
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CVS changes during Exercise
• The Cardiovascular system changes to match supply and demand.Components of the CV system during exercise
heart rate strove volume cardiac output blood flowblood pressure
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Heart rate
• Measure at the radial or carotid site.• Reflects the amount of work that it is
performing to meet the demands of the body with increasing work.
• Resting HR: 60 to 80 bts/min. – Anticipatory response-prior to starting
exercise just knowing that you are going to have to start exercise.
– 220-age= predicted Max HR.
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Heart Rate
100
120
140
160
180
200
40 90 140 190 240 290 340
Treadmill Speed (m/min)
HR
(b
pm
)
trained
sedentary
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Change in HR during ExerciseChange in HR during Exercise
As exercise begins, Para-SNS withdraws influence.
SNS stimulates heart. Adrenal gland secretes catecholamines. Increase in body temperature ,as in intense
exercise.
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Stroke VolumeStroke Volume
May increase with increasing rates of work up to intensities of 40% to 60% of maximum exercise.
May continue to increase up through maximal exercise intensity, generally in highly trained athletes
Depends on position of body during exercise•upright-SV is less, supine is greater (easier to heart)upright-SV is less, supine is greater (easier to heart)
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STROKE STROKE VOLUMEVOLUME
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Cardiac Output• Resting is 5.0 L/min-
• 20 to 40 L/min during exercise.
• The need for an increase is to meet the muscle’s demands during exercise.
• An increase in HR and SV increases Q, (separate or together)
• After 40 to 60% of max, SV plateaus, Q increases due to increase in HR .
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CARDIAC OUTPUTCARDIAC OUTPUT
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Cardiac Output
0
5
10
15
20
25
30
40 90 140 190 240 290 340 390
Treadmill Speed (m/min)
Ca
rdia
c O
utp
ut
(L/m
in)
trained
detrained
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Redistribution of Blood Flow
• Blood flow to tissues is controlled in relation to tissue needs– Tissue needs may 20-30 fold, but cannot Q
that much: 5 L/min 100 -150 L/min ! ? So flow is redistributed between tissues
• Muscle blood flow to working skeletal muscle• Splanchnic blood flow to less active organs
– Liver, kidneys, GI tract, & also to non-working muscle
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Redistribution of Blood Flow During Exercise
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Redistribution of Blood Flow
Local SystemicVasodilation Vasoconstriction
PO2 PCO2 [H+] adenosine [K+] Nitric oxide
Metabolites Epinephrine
Adrenal medulla
SympatheticNervousSystem
overrides
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Blood pressure during Blood pressure during endurance activitiesendurance activities
• SBP increases in proportion to exercise intensity.
• DBP changes very little during endurance exercise.
• There is modest increase in mean arterial pressure .
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Effects of Incremental Exercise on BPEffects of Incremental Exercise on BP
0
25
50
75
100
125
150
175
200
225
250
0 50 100 150 200 250 300Workload (W)
Blo
od
Pre
ss
ure
(m
m H
g)
Systolic BP
Diastolic BP
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Cardiovascular Adjustments to Exercise
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Cardiac Output Components in Trained & Untrained Subjects
Untrained
Rest 70 72 5.0
Max Exercise 195 113 22.0
Endurance Trained
Rest 50 100 5.0
Max Exercise 195 179 35.0
Heart rate Stroke volume Cardiac outputSubject/Activity (beats/min) (ml/beat) (L/min)