Term
| Describe how heart rate, stroke volume and cardiac output respond to increasing rates of work. Illustrate how these three variables are interrelated. |
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Definition
| Heart rate increases proportionately to the increase in exercise intensity until near-maximal exercise is achieved. Stroke volume increases above resting rates during exercise up to intensities reaching approximately 40% to 60% of VO2max, where it remains relatively unchanged until exhaustion, but may have the capability of increasing through maximal exercise intensities. Cardiac output also increases when responding to exercise intensity. The three are related because the increased heart rate will bring in more oxygen, reaching the 40-60% point of VO2max, increasing stroke volume to its maximum rate. |
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Term
| How do we determine HRmax? What are alternative methods using indirect estimates? What are the major limitations of these indirect estimates? |
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Definition
| HRmax can be predicted by having someone exercise in an all-out effort until fatigued. Indirect estimates include subtracting one's age from 220, subtracting 208 from 0.7*age. The limitation is that heart rates can vary between individuals, so estimating runs an increase risk of an error in estimating. |
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Term
| Describe two important mechanisms for returning blood back to the heart during exercise in an upright position. |
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Definition
| Gravity makes blood pool in the lower extremities when upright, forcing stroke volume to increase to push blood further throughout the body. The two mechanisms are stroke volume and gravity. |
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Term
| What is the Fick principle, and how does this apply to our understanding of the relationship between metabolism and cardiovascular function? |
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Definition
| The Fick principle states that oxygen consumption of a tissue is dependent on blood flow to that tissue and the amount of oxygen extracted from the blood by the tissue. It's applied to both the whole body and regional circulations. It's related to metabolism and cardiovascular function because it illustrates how using specific tissues forces the heart to pump more blood to those areas, using more energy to keep up with increased demands in the process. |
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Term
| Define the Frank-Starling mechanism. How does this work during exercise? |
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Definition
| The Frank-Starling mechanism is an increased force of contraction, allowing increased venous return and better ventricular filling. Done to eject a higher volume of blood by forming more actin-myosin cross bridges to develop greater force with a greater stretch. During exercise, the increased blood flow fills and stretches the ventricle, making it contract more forcefully and increasing stroke volume in the process. |
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Term
| How does blood pressure respond to exercise? |
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Definition
| Endurance exercise leads to an increase of systolic blood pressure correlated to increasing exercise intensity, but doesn't change, (or can even lower) diastolic pressure. This leads to mean arterial pressure increasing. |
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Term
| What are the major cardiovascular adjustments that the body makes when someone is overheated during exercise? |
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Definition
| When overheating, the body will increase blood flow to the skin to help dissipate body heat by creating an initial reduction in sympathetic vasoconstriction, causing a passive vasodilation. Once a particular body core temperature threshold is reached, skin blood flow dramatically increases by activation of the sympathetic active vasodilator system. |
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Term
| What is the cardiovascular drift? What two theories have been proposed to explain this phenomenon? |
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Definition
| Cardiovascular drift is the collective alterations during prolonged aerobic exercise or aerobic exercise in a hot environment at a steady state intensity. SV gradually increases while heart rate increases, yet arterial blood pressure declines. The two theories explaining it are that HR increases to compensate for the decrease in SV or that there is less time to fill ventricles with an increased HR, lowering SV during prolonged exercise.. |
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Term
| Describe the primary functions of blood. |
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Definition
| The primary functions of blood include carrying oxygen and nutrients to the tissues and clearing waste products of metabolism. |
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Term
| What changes occur in the plasma volume and red blood cells with increasing levels of exercise? With prolonged exercise in the heat? |
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Definition
| As exercise increases, plasma volume decreases while red blood cells shrink in size, leading to dehydration and impairing performance when blood flow to muscles is decreased. |
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Term
| How does pulmonary ventilation respond to increasing intensities of exercise? |
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Definition
| As exercise intensity increases, increased breathing leads to changes in the chemical status of the arterial blood. More CO2 and H+ is generated, enhancing oxygen unloading in the muscles in the process.. Chemoreceptors primarily in the brain then send signals that stimulate the inspiratory center, increasing depth and rate of breathing. |
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Term
| Define the terms dyspnea, hyperventilation, Valsalva maneuver and ventilatory threshold. |
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Definition
Dyspenea: The sensation of shortness of breath during exercise typically found in people with poor aerobic fitness levels who attempt to exercise at intensities that significantly elevate arterial CO2 and H+ concentrations.
Hyperventilation: An increase in ventilation in excess of the need from exercise.
Valsalva maneuver: A potentially dangerous respiratory procedure typically during heavy lifting. It occurs when the individual closes the glottis, increases the intra-abdominal pressure by forcibly contracting the diaphragm and the abdominal muscles, and increases the intrathoracic pressure by forcibly contracting the respiratory muscles.
Ventilatory threshold: The point during increased exerecise intensity where ventilation increases disproportionately to oxygen consumption, typically between 55-70% of VO2max. |
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Term
| What role does the respiratory system play in acid-base balance? |
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Definition
| As H+ increases, it stimulates the respiratory center to increase ventilation, facilitating the binding of H+ to bicarbonate to remove carbon dioxide. This decreases free H+ and increases blood pH, providing short term means of neutralizing acute effects of exercise acidosis. |
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Term
| What is the normal resting PH for arterial blood? For muscle? How are these values changed as a result of exhaustive sprint exercise? |
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Definition
| The resting pH for arterial blood is 7.4. For muscle, it's 7.1. In an exhaustive sprint exercise, muscle glycolysis generates a large amount of lactate and H+, which lowers muscle pH to les s than 6.7 while blood pH drops to about 7.1. |
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Term
| What are the primary buffers in blood? In muscles? |
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Definition
| Primary buffers in blood include bicarbonate, hemoglobin, proteins and phosphates. Buffers in muscles include phosphates such as phosphoric acid and sodium phosphate. |
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