Exercise Physiology

Explain the four phases of the Valsalva and discuss the physiologic consequences of this maneuver

1. Initial Pressure Rise 2. Reduce venous return and compensation 3. Pressure Release 4. Return of cardiac output Performing a prolonged Valsalva maneuver during static, straining-type exercise dramatically reduces venous return and arterial blood pressure Diminishes brain's blood supply, producing dizziness or fainting

List and quantify three ways for carbon dioxide transport in blood

About 80% of CO2 transports in chemical combination with water to form bicarbonate The blood carries CO2 in three ways: 1. In physical solution in plasma 2. Combined with hemoglobin within red blood cells 3. As plasma bicarbonate

List and give the function of the four major proteins of skeletal muscle

Actin: filaments have two twisted monomer chains bound by tropomyosin polypeptide chains Myosin: filaments are bundles of molecules with polypeptide tails and globular heads Tropomyosin: Tropomyosin inhibits actin and myosin interaction Troponin Tropomyosin and troponin regulate make-and-break contacts between the myofilaments during muscle action

List the partial pressures of respired gases during rest and maximal physical activity in alveoli, arterial blood, active muscles, and mixed-venous blood

As a result of humidification, the effective Po2in tracheal air decreases by 10 mm Hg from ambient value of 159 mm Hg to 149 mm Hg CO2 makes little contribution to inspired air; this means humidification exerts a negligible effect on inspired Pco2 Alveolar air composition differs from incoming breath of moist ambient air because CO2 continually enters alveoli from blood and O2 continually enters blood from the alveoli 14.5% O2, 5.5% CO2, and 80.0% N2 Average pressures exerted by O2 and CO2 against alveolar side of alveolar-capillary membrane: Po2 = 103 mm Hg Pco2 = 39 mm Hg

Describe the different arrangements of individual muscle fibers along the long axis of skeletal muscle

Complex Fusiform Arrangement (series-fibered muscle) Features individual fibers that run parallel to muscle's line of pull Arrangement features muscle fibers that terminate in muscle's midbelly, and taper to interact with connective tissue matrix and/or adjacent fibers Enables parallel packing of relatively short fibers within in a long muscle Structural specialization creates lateral tension at various points along fiber's surface

Discuss muscle fiber changes that occur with exercise training

Endurance athletes possess predominantly slow-twitch fibers; fast-twitch fibers predominate for elite sprint athletes Performance success depends not only on muscle fiber composition, but on a blending of many physiologic, biochemical, neurologic, and biomechanical "support systems" Larger muscle fibers in male athletes along with a larger total muscle mass are principal gender differences in muscle morphology

Draw and label the structures of skeletal muscle

Epimysium surrounds entire muscle and blends into intramuscular tissue sheaths to form tendons Perimysium surrounds a bundle of fibers called a fasciculus Endomysium wraps each muscle fiber and separates it from neighboring fibers Sarcolemma surrounds each muscle fiber and encloses fiber's cellular contents Sarcoplasm contains nuclei that house genes, mitochondria, and other specialized organelles Sarcoplasmic reticulum provides structural integrity

Describe events in motor unit excitation prior to muscle action

Excitation normally occurs only at NMJ When an impulse arrives at NMJ, ACh releases from vesicles in terminal axons into synaptic cleft ACh then combines with a transmitter-receptor complex in postsynaptic membrane Change in electrical properties elicits endplate potential that spreads from motor endplate to extrajunctional sarcolemma of muscle Causes action potential to travel muscle fiber length, enter T-tubule system, then spread to inner structures of muscle fiber to primethe contractile machinery for excitation

Discuss the mechanical and muscular aspects of inspiration and expiration during rest and physical activity

Expiration: Sternum and ribs drop, diaphragm rises (decreasing chest cavity volume and compressing alveolar gas), moving air from respiratory tract to the environment Inspiration: Diaphragm contracts, flattens, and moves downward toward the abdominal cavity Elongation and enlargement of the chest cavity expands air in the lungs, causing its intrapulmonic pressure to decrease slightlybelow atmospheric pressure Lungs inflate as nose and mouth suck air inward Completed when thoracic cavity expansion ceases; this causes equality between intrapulmonic and ambient atmospheric pressures

Describe motor unit facilitation and inhibition

Facilitation: Ach release excites postsynaptic membrane of its connecting neuron Enhanced facilitation (disinhibition) causes full muscle activation during all-out effort and accounts for rapid and specific strength increases early in resistance training Inhibition: Some presynaptic terminals produce inhibitory impulses that increase postsynaptic membrane's permeability to potassium and chloride ion efflux, to increase cell resting membrane potential to create an inhibitory postsynaptic potential (IPSP) IPSP hyperpolarizes the neuron making it more difficult to "fire" Neural inhibition has protective functions, and reduces input of unwanted stimuli to produce a smooth, purposeful response

Contrast slow-twitch and fast-twitch muscle fiber characteristics

Fast Twitch: Exhibit four characteristics: High capability for electrochemical transmission of action potentials High myosin ATPase activity Rapid Ca2+ release and uptake by efficient sarcoplasmic reticulum High rate of crossbridge turnover These factors contribute to this fiber's rapid energy generation for quick, powerful muscle actions Slow Twitch: Generate energy for ATP resynthesis through aerobic system of energy transfer Four distinguishing characteristics: Low myosin ATPase activity Slow calcium handling ability and shortening speed Less well-developed glycolytic capacity than fast-twitch fibers Large and numerous mitochondria

Discuss variations in twitch characteristics, resistance to fatigue, and tension development in different motor unit categories

Fast twitch, high force, and fast fatigue (type IIx) FF Fast twitch, moderate force, and fatigue resistant (type IIa) FR Slow twitch, low force, and fatigue resistant (type I)

Explain Henry's law in relation to gas exchange within the body

Henry's law: Mass of a gas that dissolves in a fluid at a given temperature varies in direct proportion to pressure of the gas over the liquid Two factors that govern the rate of gas diffusion into a fluid: Pressure differential between gas above the fluid and gas dissolved in the fluid Solubility of gas in the fluid

List two mechanisms that adjust force of muscle action

Increased number of motor units recruited muscle generates considerable force when activated by all of its motor units Increased frequency of motor unit discharge repetitive stimuli that reach a muscle before it relaxes and increases the total tension

Discuss the contributions of breathing rate and tidal volume to minute ventilation and alveolar minute ventilation at rest and physical activity

Increasing the rate and depth of breathing increases alveolar ventilation in physical activity In moderate activity, well-trained athletes maintain alveolar ventilation by increasing TV with only a small increase in breathing rate In exercise, breathing becomes deeper and alveolar ventilation increases from 70% at rest to >85% of exercise minute ventilation Each person develops their "style" of breathing; breathing rate and TV blend to provide effective alveolar ventilation

Outline distribution patterns of muscle fibertype among different groups of elite athletes

Men, women, and children on average possess 45 to 55% slow-twitch fibers in arm and leg muscles Fast-twitch fibers distribute equally between type IIa and type IIx subdivisions Although no gender differences exist in fiber distribution, large interindividual variation occurs Trend in one's muscle fiber type distribution remains fairly consistent among the body's major muscle groups

List the five levels of skeletal muscle organization

Molecular Microscopic Cellular Tissue Organ

Define the terms motor unit, neuromuscular junction, and autonomic nervous system

Motor unit: consists of anterior motor neuron and specific muscle fibers it innervates; functional unit of movement. Each muscle fiber generally receives input from only 1 motor neuron; a motor neuron may innervate many muscle fibers Neuromuscular junction:Interface between the end of a myelinated motor neuron and a muscle fiber; transmits nerve impulse to initiate muscle action

Describe myoglobin's role in oxygen delivery to the tissues during physical exertion

Myoglobin adds additional O2 to the muscle in the reaction Myoglobin facilitates O2 transfer to mitochondria when exercise begins and during intense exercise when intramuscular Po2 declines dramatically During rest and moderate exercise, myoglobin maintains high O2 saturation

Explain the role of myoglobin during intense physical activity

Myoglobin in skeletal and cardiac muscle provides an "extra" O2 store to release O2 at low Po2 During intense activity, myoglobin facilitates O2 transfer to mitochondria when intracellular Po2 in active skeletal muscle decreases dramatically

Quantify oxygen transport in arterial plasma and combined with hemoglobin under sea-level, ambient conditions

Oxygen is carried by hemoglobin

Discuss the role partial pressure plays in loading and unloading metabolic gases in the lungs and tissues

Partial pressure gradients (differences in partial pressure) allow the loading of oxygen into the bloodstream and the unloading of carbon dioxide out of the bloodstream. These two processes occur at the same time. Higher pressure to lower pressure: oxygenated.

Diagram and discuss the role of an anterior motor neuron

Permits transmission of an electrochemical impulse from spinal cord to muscle

Summarize the sliding filament model of muscle action

Proposes that muscle shortens or lengthens because thick and thin filaments slide past each other without changing length Myosin crossbridges cyclically attach, rotate, and detach from actin filaments with energy from ATP hydrolysis Produces change in relative size within sarcomere's zones and bands; and produces a force at Z bands I band decreases as the Z bands are pulled toward the center of each sarcomere In isometric muscle action the fiber's length remains unchanged so relative spacing of the I band and A band remains constant The A band widens in eccentric action as the fiber lengthens during force generation

Describe and label skeletal muscle fiber's ultrastructural components

Single multinucleated muscle fiber contains myofibrils that lie parallel to fiber's long axis Myofibrils contain smaller subunits called myofilaments that lie parallel to long axis of myofibril Myofilaments consist of actin and myosin that account for ~85% of myofibrillar complex Other proteins either serve structural function or affect protein filament interactions during muscle action Tropomyosin, troponin, α-actinin, β-actinin, M protein, and C protein

Outline the sequence of chemical and mechanical events during muscle excitation-contraction

Step 1 Generation of action potential in motor neuron causes terminal axon to release acetylcholine (ACh), which diffuses across synaptic cleft and attaches to specialized ACh receptors on sarcolemma Step 2 Muscle action potential depolarizes the transverse tubules at the sarcomere's A-I junction Step 3 Depolarization of T-tubule system causes Ca2+ release from lateral sacs of sarcoplasmic reticulum Step 4 Ca2+ binds to troponin-tropomyosin in actin filaments, releasing the inhibition that prevented actin from combining with myosin Step 5 Actin combines with myosin-ATP; this activates myosin ATPase, which splits ATP The reaction's energy produces myosin crossbridge movement and creates tension Step 6 ATP binds to myosin crossbridge which breaks actin-myosin bond, allowing actin disassociation from the crossbridge Thick and thin filaments then slide past each other and muscle shortens Step 7 Crossbridge activation continues when Ca2+ concentration remains high enough to inhibit troponin-tropomyosin system Step 8 When muscle stimulation ceases, intracellular Ca2+ concentration rapidly decreases as Ca2+ moves back into lateral sacs of sarcoplasmic reticulum through active transport; requires ATP hydrolysis Step 9 Ca2+ removal restores inhibitory action of troponin-tropomyosin In presence of ATP, actin and myosin remain in dissociated, relaxed state

Describe factors that produce the "Bohr effect"

The Bohr effect reflects alterations in molecular structure of Hb from increased acidity, temperature, CO2 concentration, and red blood cell 2,3-DPG Any increase in plasma acidity and temperature causes the oxyhemoglobin dissociation curve to shift downward and to the right

Discuss two factors that account for variations in the ventilation-perfusion ratio among healthy individuals

The ratio of alveolar ventilation to pulmonary blood flow Amount of air coming inside and amount of blood in the lungs

Describe the ventilatory system's conducting, transitional, and respiratory zones

conducting zones: trachea and terminal bronchioles function in air transport considered anatomic dead space transitional and respiratory zones: Bronchioles, alveolar ducts, and alveoli Function in gas exchange, surfactant production, molecule activation and inactivation, blood clotting regulation, and endocrine function

Diagram and label the main structures of the ventilatory system components

nose and mouth trachea (and adjusts to body temperature), is filtered and humidified two bronchi bronchioles alveoli lungs capillaries