Cardiovascular Control During Exercise

1. Cardiovascular Control During Exercise

2. Cardiovascular Functions • Delivery • Oxygen and nutrients • Removal • CO2 and metabolic wastes • Transport • hormones • Maintenance • Body temperature • Fluid leves and pH • Prevention • infection

3. 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.

4. 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

5. The ECG

6. 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”

7. 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

8. 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

9. 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%

10. 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

11. 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

12. 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.

13. Cardiovascular Response to Exercise • Increased stroke volume(fig 8.11) • 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

14. 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

15. 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

16. 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

17. 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