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69 Cards in this Set
- Front
- Back
How much does the body's total energy expenditure increase during high-intensity exercise? |
15 - 25 time above expenditure at rest |
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What are the two major adjustment in blood flow that must occur to meet increased demands of muscle during exercise? |
1. An increase in cardiac output 2. A redistribution of blood from inactive organs to the active skeletal muscle |
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Cardiac Output |
HR X SV (Heart rate x Stroke Volume) |
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Regulation of heart rate is controlled intrinsically by.... |
SA node (Sinoatrial node), located in the posterior wall of the right atrium |
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Regulation of heart rate is controlled extrinsically by... |
nervous and hormonal systems |
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What is the AV (atrioventricular) node? |
A small knot of tissue located in the floor of the right atrium gives off many branches that facilitate ventricular contraction. |
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Describe the vagus nerves' contribution to heart rate |
Vagus nerves are parasympathetic fibers that make contact with both the SA and AV nodes. Upon simulation they release acetylcholine which causes a decrease in the activity of both the SA and AV nodes, reducing heart rate. |
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Chronotropic response |
Heart beats faster
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Inotropic response |
Increased force of heart contractility |
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Cardiac Accelerator nerves |
Sympathetic fibers that innervate the SA node and ventricles |
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Catcecholamines |
Epinephrine and Norepinephrine |
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Frank-Starling mechanism |
The mechanism by which an increased amount of blood in the ventricle places a stretch on the cardiac muscle fibers, thereby causing a stronger ventricular contraction to increase the amount of blood ejected. |
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Autoregulation |
Local control of blood distribution (through vasodilation) in response to a tissue's changing metabolic needs. |
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Cardiac Output |
The amount of blood pumped by the heart per minute; usually expressed in liters of blood per minute. |
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Systolic Blood Pressure (SBP) |
The pressure exerted by the blood on the vessel walls during ventricular contraction |
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Diastolic Blood Pressure (DBP) |
The pressure in the arteries during the relaxation phase (diastole) of the cardiac cycle; indicative of total peripheral resistance. |
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Diastole |
The period of filling of the heart between contractions; resting phase of the heart. |
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Why is SBP affected more than DBP during exercise? (3 responses) |
1. Increased heart contractility and stroke volume increase the force with which blood leaves the heart. 2. Muscle action requires greater force or pressure to deliver blood into the exercising muscles. 3. Vasodilation within the exercising muscles allows more blood to drain from the arteries through the arterioles and into the muscle capillaries, thus minimizing changes in diastolic pressure. |
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What percentage of total cardiac output is directed toward skeletal muscle at rest? during maximal exercise? |
Rest: 15 - 20% Maximal Exercise: 80 - 85% |
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What contributes to decrease in blood volume during early stages of exercise? (3 answers) |
1. Increased hydrostatic pressure from muscle contraction (squeezes fluid out of bloodstream) 2. Increase in osmotic pressure in the interstitial fluid space around muscles cells (due to accumulation of metabolites) 3. Loss of sweat |
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What changes take place to conserve blood volume? (3 answers) |
1. Progressive increase in heart rate to maintain cardiac output and offset reduced SV 2. Vasoconstriction in non-exercising regions to increase blood pressure 3. Release of vasopressin (antidiuretic) and aldosterone... reduce water and sodium loss |
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"The pump" weighlifters feel |
Transient hypertrophy - edema in the interstitial and intracellular spaces of the muscle resulting in a feeling of fullness in the muscle. |
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What contributes to venous return during maximal exercise? |
Muscle pump: contraction of muscles compress veins forcing blood in them toward the heart. |
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Minute ventilation (V(dot)E) |
A measure of the amount of air that passes through the lungs in one minute; calculated as the tidal volume multipled by the ventilatory rate. |
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Part of the brain that controls respiration |
Medulla oblongata |
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Humoral receptors role in ventilation |
Changes in chemicals in the blood trigger changes in ventilation. (Eg: carbon dioxide, hydrogen and potassium increases in blood trigger increase in ventilation, as does a decrease of oxygen in the blood) |
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Neural influences in ventilation |
Feedback from peripheral receptors such as muscles spindles, Golgi Tendon Organs (GTOs), or joint pressure receptors can trigger a ventilation response. Also, mechanoreceptors in the right ventricle of the heart may also send signals to the respiratory control center. |
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Ventilatory threshold (VT) |
Point of transition between predominately aerobic energy production to anaerobic energy production; involves recruitment of fast-twitch muscle fibers and identified via gas exchange during exercise testing.
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What is the average breathing rate at rest? during strenuous exercise? |
Rest: 12 - 15 breaths per minute Exercise: 35 - 45 breaths per minute |
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What is typical tidal volume at rest? during strenuous exercise? |
Rest: 0.4 - 1.0L Exercise: up to 3.0L or greater |
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VT1: First ventilatory threshold occurs when? |
Approximately the first time that lactate begins to accumulate in the blood. Caused by the need to blow off the extra carbon dioxide. |
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VT2: Second ventilatory threshold occurs when? |
Occurs at the point where lactate is rapidly increasing with intensity. Probably represents the point at which blowing off carbon dioxide is no longer adequate to buffer the increase in acid that is occurring with increased exercise intensity. |
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Primary hormone released by the adrenal medulla |
Epinephrine |
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Responses to epinephrine (and norepinephrine) |
1. strength of cardiac contraction increases 2. vasoconstriction in non-exercising muscles 3. vasodilation of heart and active skeletal muscles 4. (NOT nor-e) dilation of respiratory passages, reduces digestive activity, reduces bladder emptying 5. affects CNS by promoting state of arousal 6. affects blood glucose concentration |
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gluconeogenesis |
production of glucose from non-sugar substances |
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glycogenolysis |
release of glycogen from liver and skeletal muscles |
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lipolysis |
breakdown of triglycerides in adipose tissue to free fatty acids (FFA) for use as fuel |
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How much can glucose uptake by skeletal muscles increase during exercise? |
7 - 20 times that during rest |
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glucagon |
hormone released from the pancreas that stimulates and almost instantaneous release of glucose from the liver - low blood glucose levels stimulate its release |
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cortisol |
steroid released from the adrenal cortex; plays many roles; stimulates FFA mobilization from adipose tissue, mobilizes gluconeogenesis in liver, decreases rate of glucose utilization by cells; slow acting; may play a role in tissue recovery and repair; prolonged elevations linked with many negatives, including abdominal obesity. |
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growth hormone |
released from anterior pituitary gland; plays a major role in protein synthesis; support role of cortisol |
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only macronutrient whose stored energy generates ATP anaerobically |
carbohydrates |
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Epinephrine levels generally increase at exercise intensities above what VO2 max level? |
60% |
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During exercise, glucose stored in non-exercising muscles can be delivered indirectly to the exercising muscles by what? |
glucose-alanine pathway: glucose is partially metabolized to pyruvate, to which an amino group is added to manufacture alanine (amino acid). Alanine travels to the liver where the amino group is removedand the pyruvates are reconstitued back to glucose, which are then released into circulation to the exercising muscle |
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Cori cycle |
the cycle of lactate to glucose between the muscle and the liver |
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Which type of muscle fiber produces more force? |
Fast-twitch muscle fibers product 10 - 20% more force than slow twitch (due to more myosin cross-bridges per cross-sectional area) |
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Which type of muscle fiber has a faster shortening speed? |
Fast-twitch; contain more myosin ATPase (enzyme required for the breakdown of ATP) |
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Which type of muscle fiber has higher efficiency (requires less energy to perform a given amount of work)? |
Slow-twitch: due to higher concentration of myoglobin, larger number of capillaries, and higher mitochondrial enzymes |
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Decline in muscular performance associated with a reduction in the body's glycogen reserves |
muscle fatigue |
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How much can metabolism rise during intense aerobic exercise by elite athletes? |
20 - 25 times above resting levels |
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What is the body temperature above which protein structure of enzymes may be destroyed, resulting in cellular death? |
113F |
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What is the body temperature at which the metabolism is slowed and cardiac function may be abnormal? |
93.2F |
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What is the body's primary means of losing heat during exercise? |
Evaporation |
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What are the four mechanisms the body uses to give off heat? |
1. radiation 2. convection 3. conduction 4. evaporation |
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Chronic Adaptions to Exercise: Blood Volume |
Increases: plasma volume primarily. RBC can increase, but ratio of RBC to plasma still reduced |
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Chronic Adaptions to Exercise: Blood Viscocity |
Reduced due to increased plasma, and higher plasma to RBC ratio. This enhances oxygen delivery to active skeletal muscles because blood flows more easily |
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Chronic Adaptions: Heart Size |
Increased - increased left ventricular cavity (to hold increase blood volume), and increase thickness of left ventricular walls |
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arterial-mixed venous oxygen difference |
the difference in oxygen content between arterial and mixed venous blood, which reflects the amount of oxygen removed by the whole body |
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Fick equation |
The rate at which oxygen is consumed = cardiac output x arterial-mixed venous oxygen difference |
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Chronic Adaptions: Heart Rate |
Resting and submaximal heart rate decrease - thought to be result of increase parasympathetic activity |
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Chronic Adaptions: oxygen extraction (arterial-mixed venous oxygen difference) |
Increased |
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Chronic Adaptions: Blood Flow to Active Muscles |
Enhanced: 1. increase capillarization of trained muscles 2. greater recruitment of existing capillaries 3. more effective blood flow distribution from inactive areas 4. increased blood volume |
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Chronic Adaptions: Blood Pressure |
Both systolic and diastolic blood pressures tend to be lowered in borderline or moderately hypertensive individuals who exercise regularly |
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Chronic Adaptions: Mitochondria |
Increase in quantity and size - improve the muscles ability to produce ATP, then thus the ability to use oxygen |
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Chronic Adaptions: Oxidative Enzymes |
Activity increased; as a consequence there is a slower rate of muscle glycogen utilization and an enhanced reliance on fat as fuel at any given exercise intensity. (May results in ability to maintain a higher intensity throughout duration of workout.) |
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Motor unit recruitment and synchronizations change with regular resistance training |
Motor units may act more synchronously (recruited together) enhancing contraction and increasing muscles ability to create force. Increased strength without muscle hypertrophy. |
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Rate coding (muscles) |
The process by which the force production of a given motor unit varies from that of a twitch (single electrical stimulation) to that of tetnus (peak force product of the motor unit produced by summation of multiple twitches), by increasing the frequency of stimulation of the motor unit. |
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Rate coding change with resistance training |
Rate coding may increase, which would result in an increase in the frequency of discharge of the motor units to allow a faster time to peak force production for the trained muscle. |
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General hormonal changes with regular endurance training |
Hormonal response declines with regular training; increased efficiency due to improved sensitivity and/or responsiveness to hormone. |