Illinois State University The Cardiovascular System The Cardiovascular System Cardiovascular Control During Exercise Chapter 11 and 12

Illinois State UniversityIllinois State University

The Cardiovascular SystemThe Cardiovascular System

Cardiovascular Control Cardiovascular Control During ExerciseDuring Exercise

Chapter 11 and 12Chapter 11 and 12


Heart Structure and Blood FlowHeart Structure and Blood Flow

The The atriaatria receive receive blood into the heart; blood into the heart; the the ventriclesventricles eject eject blood from the blood from the heart.heart.

Atria

Ventricles


The MyocardiumThe Myocardium

Because the left Because the left ventricle must ventricle must produce more power produce more power than other than other chambers, its chambers, its myocardium is myocardium is thicker due to thicker due to hypertrophy.hypertrophy.


Cardiac ConductionCardiac Conduction

Cardiac tissue is capable of Cardiac tissue is capable of autoconductionautoconduction..

It initiates its own pulse without neural It initiates its own pulse without neural control.control.


Cardiac ConductionCardiac Conduction

The The sinoatrial (SA) sinoatrial (SA) node is the heart’s node is the heart’s pacemaker, establishing the pulse and pacemaker, establishing the pulse and coordinating activity throughout the coordinating activity throughout the heart.heart.


Extrinsic Control Extrinsic Control of Heart Activityof Heart Activity

Heart rate and contraction strength can Heart rate and contraction strength can be altered by the autonomic nervous be altered by the autonomic nervous system or the endocrine system.system or the endocrine system.


Electrocardiography (ECG)Electrocardiography (ECG)

The The ECGECG is a recording of the heart’s is a recording of the heart’s electrical functioning.electrical functioning.

An exercise ECG may reveal underlying An exercise ECG may reveal underlying cardiac disorders.cardiac disorders.

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Cardiac FunctionCardiac Function

The cardiac cycle:The cardiac cycle:• RelaxationRelaxation = diastole. = diastole.• ContractionContraction = systole. = systole.• ECG waves: ECG waves: P, QRS, T.P, QRS, T.

Stroke volume.Stroke volume.


Cardiac FunctionCardiac Function

Ejection fraction Ejection fraction from left ventricle from left ventricle (60% at rest).(60% at rest).

Cardiac output Cardiac output (4.8-6.4 L(4.8-6.4 L.. min min-1-1))


Vascular System:Vascular System:

Arteries.Arteries. Arterioles.Arterioles. Capillaries.Capillaries. Venules.Venules. Veins.Veins.


Venous ReturnVenous Return

Blood returns to the heart through the Blood returns to the heart through the veins, assisted by:veins, assisted by:• Breathing.Breathing.• Muscle pump.Muscle pump.• Valves.Valves.

Valsalva ManueverValsalva Manuever


Distribution of BloodDistribution of Blood

Activity dictates distribution.Activity dictates distribution. Vasoconstriction.Vasoconstriction. Vasodilation.Vasodilation.


Blood Pressure (NHLBI, 2003)Blood Pressure (NHLBI, 2003)PressurePressure NormalNormal Pre-Pre-

hypertensionhypertensionStage IStage I

HypertensionHypertension

Stage II Stage II HypertensionHypertension

SystolicSystolic < 120< 120 120-139120-139 140-159140-159 >> 160 160

DiastolicDiastolic < 80< 80 80-8980-89 90-9990-99 >> 100 100

Treatment

Otherwise Otherwise healthyhealthy

NoneNone NoneNone Diuretics for Diuretics for most, most, possibly other possibly other drugsdrugs

Two-drug Two-drug combo; combo; usually one is usually one is a diuretica diuretic

With other With other diseasesdiseases

NoneNone Medically treat Medically treat diseasesdiseases

Multiple Multiple medicationsmedications

Multiple Multiple medicationsmedications


BloodBlood

Blood Blood and and lymphlymph are the substances are the substances that transport materials to and from that transport materials to and from body tissues.body tissues.

Fluid from plasma enters tissues, Fluid from plasma enters tissues, becoming becoming interstitial fluidinterstitial fluid..


BloodBlood

Most interstitial fluid Most interstitial fluid returns to the returns to the capillaries, but some capillaries, but some enters the lymphatic enters the lymphatic system as lymph, system as lymph, eventually returning eventually returning to the blood.to the blood.


BloodBlood

Blood is about 55% Blood is about 55% to 60% plasma and to 60% plasma and 40-45% formed 40-45% formed elements including elements including RBCs, WBCs, etc.RBCs, WBCs, etc.

HematocritHematocrit – ration – ration of blood cells to total of blood cells to total blood volume.blood volume.


BloodBlood

Oxygen is primarily transported bound Oxygen is primarily transported bound to the hemoglobin in red blood cells.to the hemoglobin in red blood cells.

As blood viscosity increases, so does As blood viscosity increases, so does resistance to flow.resistance to flow.


Total Peripheral ResistanceTotal Peripheral Resistance

TPR = length x viscosityTPR = length x viscosity

____________________________

(Radius)(Radius)44


Response to ExerciseResponse to Exercise

As exercise intensity increases, HR As exercise intensity increases, HR increases.increases.


ExerciseExercise

The heart ejects blood more often, thus The heart ejects blood more often, thus speeding up circulation.speeding up circulation.



Stroke volume Stroke volume also increases, so the also increases, so the amount of blood ejected with each amount of blood ejected with each contraction increases.contraction increases.

Increases in HR and SV increase Increases in HR and SV increase cardiac output.cardiac output.



More blood is forced out of the heart More blood is forced out of the heart during exercise then when at rest, and during exercise then when at rest, and circulation speeds up.circulation speeds up.



This insures that adequate supplies of This insures that adequate supplies of the needed materials - the needed materials - oxygen and oxygen and nutrients nutrients - reach the tissues and that - reach the tissues and that waste products, which build up much waste products, which build up much more rapidly during exercise, are more rapidly during exercise, are quickly cleared away.quickly cleared away.


Major Changes in Blood Major Changes in Blood During ExerciseDuring Exercise

The The a-vOa-vO22 difference difference increases.increases. Increased extraction of oxygen from the Increased extraction of oxygen from the

blood for use by the active muscles.blood for use by the active muscles.



Plasma volume decreases during Plasma volume decreases during exercise. exercise.

Water is forced into tissues by Water is forced into tissues by increased blood pressure. increased blood pressure.

Water also evaporates.Water also evaporates.



Hemoconcentration occurs as plasma Hemoconcentration occurs as plasma fluid (water) is lost.fluid (water) is lost.

Although the actual number of red blood Although the actual number of red blood cells might not increase, the relative cells might not increase, the relative number of red blood cells per unit of number of red blood cells per unit of blood increases, which increases Oblood increases, which increases O22

carrying capacity.carrying capacity.



pH pH levels drops from resting values of levels drops from resting values of 7.4 to 7.0 or lower.7.4 to 7.0 or lower.

Muscle pH decreases even further.Muscle pH decreases even further. The decrease in pH results primarily The decrease in pH results primarily

from increased blood lactate from increased blood lactate accumulation with increasing exercise accumulation with increasing exercise intensity.intensity.

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Illinois State University The Cardiovascular System The Cardiovascular System Cardiovascular Control During Exercise Chapter 11 and 12