Exercise Physiology - Cardiovascular system: The Heart

• Heart
• Blood vessels that carry blood through body

Powerful, fatigue-resistant organ that acts as a pump to drive blood returning from all parts of the body;

Travels through lungs first to be oxygenated

Main muscle of heart that contracts to pump blood

• Delivering the oxygen and nutrient rich blood ejected from the heart to all needy tissues of the body;
• Returning oxygen-depleted blood carrying metabolic by-products from those tissues back to heart

• Right Atrium -- upper chamber;
• Left Atrium -- upper chamber;
• Right Ventricle -- lower chamber;
• Left ventricle -- lower chamber;

• Left atrium receives blood from lungs;
• Right atrium receives blood from all other parts of the body;

General function is to pumpt blood into the right and left ventricles, which drives blood to lungs and rest of the body

Seperates the left and right sides of the heart

True

• While blood is being delivered to the ventricles, those chambers are in their resting phase;
• During contraction of the ventricles, the atria are at rest;

Specialized circulation to provide oxygen to the heart and feed highly oxidative myocardium with oxygen-rich blood

Sequence of events during the heart's pumping action

• Systole - Contractile phase of the myocardium;
• Diastole - Relaxtion phase between contractions

• Volume of blood ejected from each ventricular contraction;
• Resting SV = 70 mL/beat

• Number of times the heart contracts with each ventricular contraction;
• At rest, HR is 72 beats/min

• Amount of blood pumped from the heart by each ventricle per minute;
• Q = HR * SV;
• Resting Q: 72 beats/min * 70 mL/beat = 5 L/min

• Amount of blood in each ventricle at the end of the resting phase (diastole) of the cardiac cycle;
• EDV at rest is125 mL

• EDV will significantly affect SVbecause the greater the volume of blood in the ventricle, the greater the stretch imparted on the myocardium;
• As stretch increases, so does contractile force, both by elastic recoil of the muscle and by optimizing the length of the fibers in the myocardium

• Volume of blood remaining in each ventricle following it's contraction;
• At rest, ESV is 55 mL

• Percentage (%) of blood in the ventricle during diastole that is actually pumped out during systole; A ratio of SV to EDV.
• EF = SV / EDV;
• Resting EF is 60%, although in healthy adults can range between 50% and 75%

• 1) Greater demand for blood
• 2) Increased cardiac output directly linked to exercise intensity
• 3) Increased SV and HR
• 4) Increased EDV

• 5 - 6 times resting output (25 - 30 L/min vs. 5 L/min);
• Brought about by increase in both HR and SV

• Until is reaches about 50% of VO_2max at which it levels off;
• Further increases in cardiac output (Q) will result in increased HR only;
• SV increases to 100 mL/beat

• Linear relationship exists between HR and exercise intensity;
• Monitoring HR is a common method of assessing exercise intensity during submaximal efforts

• As greater amounts of blood are pumped to the working muscle, the amount of blood returing to heart is similarly enhanced;
• EDV can reach 160 mL when SV is at peak value;
• As EDV increases so does SV

Increase its contractility which results in ejection fraction (EF) change from 60% at rest to peak of 70%

• Has no effect on Maximal HR;
• Significantly lowers Resting HR after prolonged training;

• Because resting cardiac output (Q) remains the unchanged, SV increases to counteract HR decrease;
• At rest SV could be almost 85mL following prolonged training, depending on resting HR;
• SV coul be as high as 170 mL in trained athletes

Cardiac output remais unaltered and can be sustained with lower HR and higher SV values than in untrained people.

Greatly affects bood return to the heart

• Allow more efficient return of blood from the legs;
• SV is greater during exercise in supine position (swimming) at any given intensity than during upright exercise (running, cycling);
• HR is lower during exercise in supine position than during upright exercise

Pericardium in the mediastinum

Marks the border between the atria and the ventricles

This muscular wall of the atria -- only called this when the walls are not filled with blood

Marks the boundry between the right and left ventricles

At the base of the heart

Send blood to the right atrium

Return venous blood from the myocardium to the coronary sinus which opens into the right atrium

• Allow each atrium to communicate with the ventricle;
• Right AV is called tricuspid valve;
• Left AV is bicuspid valve

• 1) Superior and inferior cavae;
• 2) right atrium;
• 3) tricupid valve;
• 4) right ventricle;
• 5) pulmonic semilunar valve;
• 6) pulmonary arteries;
• 7) lungs

• 1) Left pulomonary vein;
• 2) Left atrium;
• 3) bicuspid valve;
• 4) left ventricle;
• 5) aortic semilunar valve;
• 6) ascending aorta;
• 7) systemic circulation