Tbl Cardiovascular Adaptation to Muscular Exercise

8/2/2019 Tbl Cardiovascular Adaptation to Muscular Exercise

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CARDIOVASCULARADAPTATION TO

MUSCULAR EXERCISE


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Cardiovascular changes during muscular exercise


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CARDIOVASCULAR ADAPTATIONTO MUSCULAR EXERCISE

The blood flow of resting skeletal muscles islow (900 ml/min). During exercise, the flow is greatly increased to as much as

20-fold. Exercise produces increased H+ ion, excess

metabolites, excitement, adrenaline-secretion,

rise of temperature and so on these factors alter the activity of the different systems bytheir central and peripheral actions and regulate theirfunctional level according to the needs of the body.


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CARDIOVASCULAR ADAPTATIONTO MUSCULAR EXERCISE

The cardiovascular changes produced areeither: general

or local


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A) General effects

I. Heart rate: Heart rate is increased and may reach 140 to 180 beats per

minute or more.

The increase in heart rate is presumably due to: irradiation of impulses from the higher centers (cerebral cortex,

respiratory center etc....) to the cardiovascular centers (CVCs).

The rise of temperature and increased acidity stimulate thecardiovascular centers further.

The increased venous return sets up the Atrial stretch reflex. Also the muscular system (through the muscle spindles and the other

proprioceptors) sends impulses to the higher centers via the sensorynerves.


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A) General effects

I. Heart rate:(cont.) The net result of all the discharge to the CVCs is to produce

marked depression of vagal tone and increase of thesympathetic tone.

There is only one factor which tends to slow the heart duringexercise, namely the rise in the ABP, according to Mareys

law.

But the vagal neurons of the CVCs become so inhibited by the

various mentioned factors this may be explained by assuming that during exercise the

baroreceptors become out of function


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A) General effects

II. Venous return This is increased by about 5 or 6 folds due to:

the arteriolar dilatation in skeletal muscles

the increase in sympathetic venomotor tone

the activated muscle pump

the thoracic pump action


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A) General effects

III. Cardiac output The cardiac output is increased up to 25 L/min. and in very

well trained athletes to 35 L/min.

The mechanisms responsible for this increase are : increased heart rate

increased venous return and stroke volume

The heart muscle contracts more forcibly to achieve asmaller end-systolic volume, i.e.

EDV is increased while the ESV is decreased.

The chronotropic and inotropic effects on the heart are dueto increased activity in the noradrenergic sympathetic nervesto the heart and the decreased vagal tone.


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Cardiac

output

(L/min)

Heart rate

(beat/min)

Stroke

(volumeml)

EDV(ml)

ESV (ml)

Non-athleteRest 5 70 70 130 60

Maximum

exercise

22

Diff. (*3.4)

180 (*2.5) 120 (*1.7) 140 (+10) 20 (- 40)

TrainedathleteRest 5 40 120 200 80

Maximum

exercise

36

Diff. (*6.2)180 (*4.5) 200 (*1.6) 220 (+20) 20 ( -60)

Cardiacvariables at rest & at maximum exercise for non-athlete & trained athlete


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A) General effects

IV. Blood pressure: In spite of the marked increase in the cardiac output, there is

a fall in the total peripheral resistance due to vasodilatationof the exercising muscles

Consequently, systolic blood pressure rises only moderately,whereas the diastolic pressure may remain unchanged or even falls

Evidence of such vasodilatation is that:

CO increases five times but the ABP is increased only at the most to

two-folds. ABP = CO X Peripheral resistance


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B) Local effects

I. Local blood vessels Vasodilatation takes place in arterioles, capillaries and

venules in the muscles. Many capillaries which were collapsed at rest become

patent. These actions are caused by :

O2 lack increased CO2 and increased H+ ion concentration in skeletal muscles. Potassium is another substance that accumulates locally and has a dilator action.

A rise in temperature exerts a direct vasodilator effect. Adrenaline dilates muscular vessels

it is secreted from the adrenal medulla exclusively. Noradrenaline is secreted mainly from the noradrenergic postganglionic

sympathetic fibers and a little from the adrenal medulla.

The net effect of all these local changes is to increase the

O2 utilization


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B) Local effects

II. Tissue fluid and lymph: Tissue fluid formation is increased because the capillary

blood pressure rises, and the filtering force is increased.

The dilatation of the capillaries increases their permeabilityand so more lymph is drained by the lymphatics.


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1. Blood flow in skeletal muscles of the legsshould increase tremendously during vigorous

running.

Which of the following mechanismscontributes to increased skeletal muscle blood

flow?

A) Local metabolites dilate skeletal muscleblood vessels

B) Resistance of the veins and venules

decreases

C) Total peripheral resistance increases

D) Circulating epinephrine constricts skeletal


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2-The increase in blood flowing throughcoronary vessels during exercise is largely

due to a regulation involving:

a) Adrenergic relaxation of the tension

exerted by myocardial fibers.b) Increase in coronary pressure due to aconcomitant higher aortic pressure.

c) Oxygen dependent mechanism.

d) All of the above.


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3-In muscular exercise, cardiac

output depends primarily on:

a) Heart acceleration.

b) Smaller end diastolic volume.

c) Greater end systolic volume.

d) Marked increase in strokevolume


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4-During exercise, total peripheralresistance decrease because of the

effect of:a) the sympathetic nervous system on

splanchnic arterioles.

b) the parasympathetic nervous system onskeletal muscle arterioles.

c) local metabolites on skeletal musclearterioles.

d) local metabolites on cerebral arterioles.


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5-During muscular exercisetachycardia is due to all the

following EXCEPTa- increase arterial blood pressure

b- impulses from skeletal muscles.c- increase body temperature.

d- increase venous return.


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6-In a healthy subject, running is usually associated with adecrease in the end-systolic volume of the right and leftventricles and with an increase in their stroke volume.

The mechanism for this response is probably thefollowing:

A) Starlings law of the heart

B) Decrease in sympathetic tone toventricles

C) A Decrease in venous return to the

heart

D) An increase in pulmonary and systemic

resistance


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7-Local metabolic activity is themain factor determining the rate

of blood flow to all of thefollowing except:

A) Heart

B) Skin

C) Skeletal muscle

D) Brain


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8-Each of the following tends toincrease lymph flow, EXCEPT:

a) Increased plasma colloid osmoticpressure

b) Increased capillary pressure

c) Increased muscular activityd) Increased permeability of the

capillaries


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9-All of the following factors can cause

an increase in cardiac output EXCEPT:

a) exercise

b) deep inspiration

c) Ischemia of the cardiacmuscles

d) Arteriolar dilatation. e ncrease n s ro e


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- e ncrease n s ro evolume which results from

greater diastolic volumedepends primarily on:

a)the initial length of myocardial

fibres

b) increased coronary blood flow

c) decreased aortic resistance

d) parasympathetic nervous system


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11-Which of the following are

incorrectly paired?

a) loss of blood: hypotension.

b) increased cardiac output :exercise.

c) increased total peripheral resistance :

fainting

d) adenosine: coronary vasodilatation.


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12- Venous return to the heart isfacilitated by:

a) The amount of blood filling thecirculatory system

b) The tone of sympathetic system on theveins

c) The activity of skeletal muscles

d) All of the above

13 The most important variable


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a) Impulses from cardiovascular centers

b) Compression of abdominal muscles which

reduces the vascular bed by a purelymechanical effect and raises the meansystemic filling pressure

c) Increased myocardial contractility due toincreased circulating epinephrine

d) Increased metabolism of muscle that

13-The most important variablewhich increases cardiac output

during exercise is the:


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during moderate exercise:-

a- Heart rate.

b- Cardiac output.

c- Pulse pressure.

d- Total peripheral resistance.


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15-During exercise, all of the

following increase EXCEPT:a- The total peripheral resistance.

b- The systolic BP.

c- The stroke volume.

d- The heart rate.


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16-The increase in blood flowingthrough coronary vessels during

exercise is due to:

a) Parasympathetic mediated

vasodilatation

b) Direct sympathetic stimulation of

adrenergic receptorsc) Increase in coronary pressure

d) Local accumulation of vasodilator


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17-Venous return to the heart is

facilitated by:a) The tone of sympathetic system on

veins

b)The negativity of the thoracic pressure


d) All of the above

D.


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1 Bl d fl i k l t l l f th l


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1. Blood flow in skeletal muscles of the legsshould increase tremendously during vigorous

running.

Which of the following mechanismscontributes to increased skeletal muscle blood

flow?

A) Local metabolites dilate skeletal muscleblood vessels

B) Resistance of the veins and venules

decreases

C) Total peripheral resistance increases

D) Circulating epinephrine constricts skeletal


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2-The increase in blood flowing throughcoronary vessels during exercise is largely

due to a regulation involving:

a) Adrenergic relaxation of the tension

exerted by myocardial fibers.b) Increase in coronary pressure due to aconcomitant higher aortic pressure.

c) Oxygen dependent mechanism.

d) All of the above.


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3-In muscular exercise, cardiac

output depends primarily on:

a) Heart acceleration.

b) Smaller end diastolic volume.

c) Greater end systolic volume.

d) Marked increase in strokevolume

D i i l i h l


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4-During exercise, total peripheralresistance decrease because of the

effect of:a) the sympathetic nervous system on

splanchnic arterioles.

b) the parasympathetic nervous system onskeletal muscle arterioles.

c) local metabolites on skeletal musclearterioles.

d) local metabolites on cerebral arterioles.


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5-During muscular exercisetachycardia is due to all the

following EXCEPTa- increase arterial blood pressure

b- impulses from skeletal muscles.c- increase body temperature.

d- increase venous return.


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6-In a healthy subject, running is usually associated with adecrease in the end-systolic volume of the right and leftventricles and with an increase in their stroke volume.

The mechanism for this response is probably thefollowing:

A) Starlings law of the heart

B) Decrease in sympathetic tone toventricles

C) A Decrease in venous return to the

heart

D) An increase in pulmonary and systemic

resistance

7 Local metabolic activity is the


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7-Local metabolic activity is themain factor determining the rate

of blood flow to all of thefollowing except:

A) Heart

B) Skin

C) Skeletal muscle

D) Brain


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8-Each of the following tends toincrease lymph flow, EXCEPT:

a) Increased plasma colloid osmoticpressure

b) Increased capillary pressure

c) Increased muscular activityd) Increased permeability of the

capillaries


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9-All of the following factors can cause

an increase in cardiac output EXCEPT:

a) exercise

b) deep inspiration

c) Ischemia of the cardiacmuscles

d) Arteriolar dilatation. - e ncrease n s ro e


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- e ncrease n s ro evolume which results from

greater diastolic volumedepends primarily on:

a)the initial length of myocardial

fibres

b) increased coronary blood flow

c) decreased aortic resistance

d) parasympathetic nervous system


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11-Which of the following areincorrectly paired?

a) loss of blood: hypotension.

b) increased cardiac output :exercise.

c) increased total peripheral resistance :

fainting

d) adenosine: coronary vasodilatation.


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12- Venous return to the heart isfacilitated by:

a) The amount of blood filling thecirculatory system

b) The tone of sympathetic system on theveins


d) All of the above

13-The most important variable


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a) Impulses from cardiovascular centers

b) Compression of abdominal muscles which

reduces the vascular bed by a purelymechanical effect and raises the meansystemic filling pressure

c) Increased myocardial contractility due toincreased circulating epinephrine

d) Increased metabolism of muscle that

13-The most important variablewhich increases cardiac output

during exercise is the:


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during moderate exercise:-

a- Heart rate.

b- Cardiac output.

c- Pulse pressure.

d- Total peripheral resistance.


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15-During exercise, all of the

following increase EXCEPT:a- The total peripheral resistance.

b- The systolic BP.

c- The stroke volume.

d- The heart rate.

16 Th i i bl d fl i


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16-The increase in blood flowingthrough coronary vessels during

exercise is due to:

a) Parasympathetic mediated

vasodilatation

b) Direct sympathetic stimulation of

adrenergic receptors

c) Increase in coronary pressure

d) Local accumulation of vasodilator

D


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17-Venous return to the heart is

facilitated by:a) The tone of sympathetic system on

veins

b)The negativity of the thoracic pressure


d) All of the above

.


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18-The general effect of exercise onarterial blood pressure is to:

A. Raise systolic and lower diastolic pressuresdue to an increase in peripheral resistance

B. Lower systolic and raise diastolic pressures

C. Raise systolic and lower diastolic pressuresaccompanied by, and partly due to, a

decreased peripheral resistance

D. Raise both systolic and diastolic pressuresaccompanied by, and partly due to, a

r ri h r l r i n


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Tbl Cardiovascular Adaptation to Muscular Exercise

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