Cardiovascular Control During Exercise

SEKOLAH TINGGI ILMU KESEHATAN KOTA SUKABUMI

Program Study S1 Keperawatan

https://stikeskotasukabumi.wordpress.com

Cardiovascular Functions

Delivery• Oxygen and nutrients

Removal• CO2 and metabolic wastes

Transport• hormones

Maintenance• Body temperature• Fluid leves and pH

Prevention• infection

The Heart

Blood flow through the heart (fig

8.1)

The myocardium• interconnected cardiac muscle• hypertrophy of left ventrical

The cardiac conduction system (fig 8.3)• Autoconduction: the ability to generate its own

electrical signal rythmically without neural stimuation.

• SA node: (pacemaker) sends the electrical impulse to the atria and reaches the AV node.

• AV node: conducts the impulse from the atria into the ventricals through the ....

• AV bundle and Perkinji fibers where it travels along the septum and to the ventrical walls starting at the Apex.

The Heart

Extrinsic control of heart activity• the parasympathetic nervous system

– decreases H.R. & force of heart contraction

• the sympathetic nervous system – increases H.R. & force of heart

contraction• the endocrine system: release

norepinephrine and epinephrine to increase H.R.

The ECG (fig 8.4)

• records the electrical activity of the heart– the P wave: atrial depolarization

– the QRS complex: ventricular depolarization

– the T wave: ventricular repolarization

The ECG

Cardiac Arrhythmias

Bradycardia: “slow heart”• Resting H.R. < 60

Tachycardia: “fast heart”• Resting H.R. > 100• Symptoms include– Fatigue–Dizziness– Lightheadedness– Fainting

Premature ventricular contraction: “skipped beat”

Ventricular Fibrillation: “uncoordinated beat”

The Heart

The Cardiac Cycle: includes all of the events between two consecutive cycles

• Diastole: relaxation phase• Systole: contraction phase

Stroke Volume (SV): the amount of blood ejected from the left ventrical (fig 8.5).• SV = EDV - ESV

• end diastolic volume (EDV)• end systolic volume (ESV)• ejection fraction (EF) =

(SV / EDV) X 100%• cardiac output (Q) = HR X SV

The Vascular System Method: Aorta --> Arteries -->

Arterioles --> Capillaries -->Venuoles --> Veins --> Vena Cava

Coronary arteries Return of blood to the heart• breathing increases thoracic

pressure• muscles create a pumping action• valves prevent backflow

The Vascular System

Distribution of blood (fig 8.6)

• autoregulation: the vessels ability to detect the local chemical changes and regulate its own blood flow to meet the needs of the tissues.

• extrensic neural control: regulated largely by the sympathetic nervous system by constricting blood vessels of lesser need.

• redistribution of venous blood: creating more available blood to meet the needs of the body.

During Exercise: blood is redirected to the areas where it is needed most• Muscles receive up to 80%

The Vascular System

Redistribution of Venous Blood• 64% of blood pools in the veins

waiting for the need.

Blood pressure• systolic / diastolic

– Measured sitting and supine/prone

• control: weight loss, diet, exercise, med’s

• Hypertension: 140 / 100• Hypotension: 100 / 60

The Blood Functions• Transportation of nutrients,

hormones, etc.• Temperature regulation• Maintain (pH) balance

Blood volume and composition• Men 5 - 6 L, Women 4 - 5 L• composition (fig 8.8)– 55% plasma• 90% water

– 45% hematocrit• red blood cells: transport

oxygen primarily bound to their hemoglobin (iron).• White blood cells• platelets

The Blood

Blood viscosity: refers to the thickness of the blood.• increased viscosity restricts blood

flow but increases oxygen carrying capacity.

• decreased viscosity increases blood flow but decreases oxygen carrying capacity.

Cardiovascular Response to Exercise

Increased stroke volume

• only up to 40%-60% of maximal capacity & then plateaus (caused by reduced filling time at higher h.r. ?)

• increased volume of venous blood return– increased muscle pumping of venous

blood– increased breathing (thoracic pressure)– supine positions

• increased ventrical enlargement capacity– Frank-Starling law: when the ventricle

stretches more, it will contract with more force.

• increased ventrical contractility• aortic or pulmonary artery pressure

Cardiovascular Response to Exercise

Increased heart rate / cardiac output (fig 8.10)

Anticipatory response (increased heart rate before exercise) • Caused by the release of epinephrine

Steady state heart rate: during steady exercise

Maximum heart rate = 220 - age

Cardiovascular Response to Exercise

Redistribution of blood to the working muscles by reducing blood flow to the kidneys, stomach, liver and intestines.

Redistribution of blood to the skin in order to maintain body temperature.

Increased metabolic rate of working muscles

Autoregulation is triggered by low muscle Po2

Cardiovascular drift: increased H.R. compensates for a decreased S.V. from a decreased total blood volume to maintain Q.• redistribution• decreased blood plasma

Cardiovascular Response to Exercise

Systolic B.P. increases with intensity• valsalva during resistance

exercise• increased use of upper body

musculature Diastolic B. P. does not change

Cardiovascular Responses to Exercise

Increased A-V O2 difference: representing the amount of O2 extracted from the blood to be used by the muscles.

Decreased plasma volume =decreased performance increased blood pressure forces water from the vascular system to the interstitial spaces.• increased intramuscular osmotic

pressure attracts fluid to the muscles.• sweating

Increased blood viscosity• decreasing O2 transport

Decreased blood pH level