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130 Cards in this Set
- Front
- Back
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What are the primary tissue types of muscle tissue?
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Skeletal muscle tissue Cardiac muscle tissue Smooth muscle tissue |
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What is skeletal muscle?
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Allows us to move The muscular system -Includes only skeletal muscles |
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What are the six functions of skeletal muscle tissue?
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Maintain posture and body position Support soft tissues Guard entrances and exits Maintain body temperature Store nutrient reserves |
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What is skeletal muscle composed of?
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Connective tissues Nerves Blood vessels |
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What are the three layers of connective tissues within the muscles?
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Perimysium Endomysium |
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What is Epimysium?
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Connected to deep fascia Separates muscle from surrounding tissues |
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What is Perimysium?
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Contains blood vessels and nerve supply to fascicles |
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What is Endomysium?
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Contains capillaries and nerve fibers contacting muscle cells Contains myosatellite cells (stem cells) that repair damage |
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Where and why do the Endomysium, perimysium, and epimysium come together?
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i.e., Tendon (bundle)or aponeurosis (sheet) |
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What do the vascular systems of muscles do?
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Supply large amounts of oxygen, supply nutrients, and carry away waste |
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Skeletal muscles are considered what type of muscle and are controlled by what?
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Voluntary muscles controlled by nerves of the central nervous system (brain and spinal cord) |
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Describe skeletal muscle cells
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Develop through fusion of mesodermal cells (myoblasts), become very large, and contain hundreds of nuclei |
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What is the sarcolemma?
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Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions |
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What are transverse tubules or T tubules?
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Transmit action potential through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma |
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What are myofibrils?
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Made up of bundles of protein filaments called myofilaments |
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What are myofilaments responsible for?
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Muscle contraction |
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What are the two types of myofilaments?
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-Made of the protein actin Thick filaments: -Made of the protein myosin |
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What is the sarcoplasmic reticulum (SR)?
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Helps transmit action potential to myofibril Similar in structure to smooth endoplasmic reticulum Forms chambers (terminal cisternae) attached to T tubules |
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What is a triad within the sarcoplasmic reticulum?
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Is formed by one T tubule and two terminal cisternae |
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What is a cisternae?
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Release Ca2+ into sarcomeres to begin muscle contraction |
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What are sarcomeres?
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Structural units of myofibrils Form visible patterns within myofibrils A striped or striated pattern within myofibrils -Alternating dark, thick filaments (A bands) and light, thin filaments (I bands) |
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What are the components of the A Bands
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H band Zone of overlap |
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What is the M line of the A Bands?
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The center of the A bands At midline of sarcomere |
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What are H bands of the A Bands?
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The area around the M line Has thick filaments but no thin filaments |
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What is the zone of overlap in the A Bands?
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The densest, darkest area on a light micrograph Where thick and thin filaments overlap |
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What are the components of the I Bands?
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Titin |
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What are the Z lines in the I Bands?
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The centers of the I bands At two ends of sarcomere |
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What are Titins in the I Bands?
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Strands of protein Reach from tips of thick filaments to the Z line Stabilize the filaments |
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What are the components of thin filaments?
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Nebulin Tropomyosin Troponin |
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What are F-actins in thin filaments?
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Filamentous actin
Is two twisted rows of globular G-actin The active sites on G-actin strands bind to myosin |
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What are Nebulin in thin filaments?
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Holds F-actin together
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What are tropomyosin in thin filaments?
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Prevents actin-myosin interaction |
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What are troponin in thin filaments?
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Binds tropomyosin to G-actin Controlled by Ca2+ |
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How are contractions initiated?
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Troponin-tropomyosin complex changes Exposes active site of F-actin |
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Describe thick filaments
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Contain titin strands that recoil after stretching |
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Describe the mysosin molecule
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Binds to other myosin molecules Head: Made of two globular protein subunits Reaches the nearest thin filament |
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What happens to myosin heads during contractions?
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Pivot, producing motion |
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What is sliding filament theory?
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The width of A zone stays the same Z lines move closer together |
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Explain the process of muscle contraction
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-Causes excitation-contraction coupling Muscle fiber contraction -Interaction of thick and thin filaments Tension production |
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What is the neuromuscular junction (NMJ)?
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Special intercellular connection between the nervous system and skeletal muscle fiber Controls calcium ion release into the sarcoplasm |
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Describe excitation-contraction coupling
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Action potential reaches a triad -Releasing Ca2+ -Triggering contraction Requires myosin heads to be in "cocked" position -Loaded by ATP energy |
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What are the 6 steps to the contraction cycle?
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2. Active-Site Exposure 3. Cross-Bridge Formation 4. Myosin Head Pivoting 5. Cross-Bridge Detachment 6. Myosin Reactivation |
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What is fiber shortening?
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Muscle shortening can occur at both ends of the muscle, or at only one end of the muscle -This depends on the way the muscle is attached at the ends |
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The duration of a contraction depends on what?
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Number of free calcium ions in sarcoplasm Availability of ATP |
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What happens during the relaxation of muscles?
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Ca2+ detaches from tropomyosin Active sites are re-covered by tropomyosin |
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What is rigor mortis?
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Caused when: -Ion pumps cease to function; ran out of ATP -Calcium builds up in the sarcoplasm |
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Summary of contraction & relaxation Just read it over :) |
-Skeletalmuscle fibers shorten as thin filaments slide between thick filaments -Free Ca2+ in the sarcoplasm triggers contraction -SR releases Ca2+ when a motor neuron stimulates the muscle fiber -Contraction is an active process -Relaxation and return to resting length are passive |
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Explain tension production by muscle fibers
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As a whole, muscle fiber is either contracted or relaxed |
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What does tension within muscle fibers depend on?
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The fibers resting length at the time of stimulation The frequency of stimulation |
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In length-tension relationships what does the number of pivoting cross-bridges depend on?
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The amount of overlap between thick and thin fibers
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What produces the greatest amount of tension?
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-Too much or too little reduces efficiency |
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What is the normal resting sarcomere length? |
75-130% of optimal length |
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What does a single neural stimulation produce?
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A single contraction or twitch which lasts about 7-100 msec. |
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What does a sustained muscular contraction require? |
Many repeated stimuli
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What are the stages of a "twitch"
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2. Contraction phase 3. Relaxation phase |
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Explain what happens in the latent period of a twitch
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The action potential moves through sarcolemma causing Ca2+ to release |
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Explain what happens in the contraction period of a twitch |
Calcium ions bind and tension builds to peak |
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Explain what happens during the relaxation phase of a twitch |
Ca2+ levels fall, active sites are covered and tension falls to resting levels |
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What is a treppe?
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Repeated stimulations immediately after relaxation phase -Stimulus frequency <50/second Causes a series of contractions with increasing tension |
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What is wave summation?
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Repeated stimulations before the end of relaxation phase -Stimulus frequency >50/second Causes increasing tension or summation of twitches |
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What is incomplete tetanus?
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If rapid stimulation continues and muscle is not allowed to relax, twitches reach maximum level of tension |
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What is complete tetanus?
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If stimulation frequency is high enough, muscle never begins to relax, and is in continuous contraction |
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Tension production by skeletal muscles depend on what?
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Internal tension produced by muscle fibers External tension exerted by muscle fibers on elastic extracellular fibers Total number of muscle fibers stimulated |
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Explain motor units in a skeletal muscle
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Explain recruitment or multiple motor unit summation
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In a whole muscle or group of muscles, smooth motion and increasing tension are produced by slowly increasing the size or number of motor units stimulated |
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Explain maximum tension
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Can be sustained only a very short time |
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Explain sustained tension
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Less than maximum tension and allows motor units to rest in rotation |
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What is muscle tone?
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Muscle units actively maintain body position, without motion Increasing muscle tone increases metabolic energy used, even at rest |
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Based on the pattern of tension production contractions are classified as either...?
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What is an isotonic contraction?
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-resulting in motion If muscle tension is greater than load (resistance) the muscle shortens (concentric contraction If muscle tension is less than load (resistance) muscle lengthens (eccentric contraction) |
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What is an isometric contraction?
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iso= same, metric= measure |
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How are load and speed of contraction related?
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What are the function of elastic forces in muscle relaxation?
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Expands sarcomeres to resting length |
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Describe opposing muscle contractions
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Are the work of opposing skeletal muscle pairs |
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What is the affect of gravity on muscle relaxation?
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Can take the place of opposing muscle contraction to return a muscle to its resting state |
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What does ATP do for muscle contraction?
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-Sustained muscle contraction uses a lot of ATP -Muscles store enough energy to start contraction -Muscle fibers must manufacture more ATP as needed |
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What is ATP?
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-The active energy molecule |
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What is CP?
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-The storage molecule for excess ATP energy in resting muscle |
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How does energy recharge ADP to ATP? |
When CP is used up, other mechanisms generate ATP |
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How do cells produce ATP?
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Anaerobic glycolysis in the cytoplasm |
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What is Aerobic Metabolism?
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Breaks down fatty acids Produces 34 ATP molecules per glucose molecule |
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What is Glycolysis?
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Produces two ATP molecules per molecule of glucose Breaks down glucose from glycogen stored in skeletal muscles |
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What do skeletal muscles do when they are at rest?
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What happens to muscles during light activity?
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Muscles generate ATP through anaerobic breakdown of carbohydrates, lipids, or amino acids |
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What happens to muscles during peak activity? |
Energy is provided by anaerobic reactions that generate lactic acid as a byproduct |
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What is muscle fatigue?
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When muscles can no longer preform a required activity, they are fatigued |
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What are the results of muscle fatigue?
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Damage to sarcolemma and sarcoplasmic reticulum Low pH (lactic acid) Muscle exhaustion and pain |
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What is the recovery period for muscles?
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Oxygen becomes available Mitochondria activity resumes |
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What is the Cori Cycle?
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Liver converts lactate to pyruvate Glucose is released to recharge muscle glycogen reserves |
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Explain the oxygen debt after exercise or other exertion
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Results in heavy breathing Also called excess postexercise oxygen consumption (EPOC) |
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Active muscles produce what?
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How much energy can be lost as heat, raising body temperature? |
70% |
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What hormones effect muscle metabolism?
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Testosterone Thyroid hormones Epinephrine |
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What is force in muscle performance?
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The maximum amount of tension produced |
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What is endurance in muscle performance?
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The amount of time an activity can be sustained |
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What do force and endurance depend on?
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Physical conditioning |
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What are the three major types of skeletal muscle fibers?
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Slow fibers Intermediate fibers |
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Explain fast fibers
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Have large diameter, large glycogen reserves, few mitochondria Have strong contractions, fatigue quickly |
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Explain slow fibers
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Have small diameter, more mitochondria Have high oxygen supply Contain myoglobin (red pigment, binds oxygen) |
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Explain intermediate fibers
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Have low myoglobin Have more capillaries than fast fibers, slower to fatigue |
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What are white muscle?
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Pale (e.g., chicken breast) |
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What are red muscles?
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Mostly slow fibers Dark (e.g., chicken legs) |
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What kind of muscles are most human muscles (color)?
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Pink |
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What is muscle hypertrophy?
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-Increases diameter of muscle fibers -Increases number of myofibrils Increases mitochondria, glycogen reserves |
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What is muscle atrophy?
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-Reduces muscle size, tone, and power |
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How does physical conditioning help us?
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What are anaerobic activities in physical conditioning and how do they help us?
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50-meter dash, weightlifting, etc. --Use fast fibers --Fatigue quickly with strenuous activity -Improved by frequent, brief, intensive workouts -Causes hypertrophy |
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What are aerobic activities in physical conditioning and how do they help us?
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-Supported by mitochondria -Requires oxygen and nutrients Improves endurance by training fast fibers to be more like intermediate fibers, cardiovascular performance |
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Why is it important to exercise?
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Muscle tone indicates base activity in motor units of skeletal muscle Muscles become flaccid when inactive for days or weeks Muscle fibers break down proteins, become smaller and weaker With prolonged inactivity, fibrous tissue may replace muscle fibers |
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Explain cardiac muscle tissues
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They are striated and only found in the heart Striations are similar to that of skeletal muscle because the internal arrangement of myofilaments is similar |
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What are the structural characteristics of cardiac muscle tissue?
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Are small Have a single nucleus Have short, wide T tubules -Have no triads Have SR with no terminal cisternae Are aerobic (high in myoglobin, mitochondria) Have intercalated discs |
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What are intercalated discs?
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Join cell membranes of adjacent cardiocytes (gap junctions, desmosomes) |
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What are the functions of intercalated discs?
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Enhance molecular and electrical connections Conduct action potentials |
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How do intercalated discs effect coordination of cardiocytes?
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Because intercalated discs link heart cells mechanically, chemically, and electrically, the heart functions like a single, fused mass of cells |
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What is automaticity in cardiac muscle tissue?
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Contraction without neural stimulation controlled by pacemaker cells |
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What is variable contraction tension in cardiac muscle tissue?
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Controlled by nervous system |
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What are extended contraction times in cardiac muscle tissue? |
Ten times as long as skeletal muscle |
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What is a long refractory period in cardiac muscle tissue? |
Prevention of wave summation and tetanic contractions by cell membranes |
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Where does smooth muscle form in body systems?
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Around other tissue |
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Function of smooth muscle in integumentary system?
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Arrector pili muscles cause "goose bumps" |
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Function of smooth muscle in blood vessels and airways?
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Regulates blood pressure and airflow |
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Function of smooth muscle in reproductive and glandular systems?
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Produces movements |
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Function of smooth muscle in digestive and urinary systems? |
Forms sphincters and produces contractions |
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What are structural characteristics of smooth muscle tissue?
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Different internal organization of actin and myosin Different functional characteristics |
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What are the characteristics of smooth muscle cells?
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Have a single, central nucleus Have no T tubules, myofibrils, or sarcomeres Have no tendons or aponeruoses Have scattered myosin fibers Myosin fibers have more heads per thick filament Dense bodies transmit contractions from cell to cell |
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What are the functional characteristics of smooth muscle tissue?
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Length-tension relationships Control of contractions Smooth muscle tone |
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Explain excitation coupling
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Ca2+ binds with calmodulin in the sarcoplasm and activates myosin light chain kinase Enzyme breaks down ATP, initiates contraction |
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Explain length-tension relationships
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Resting length not related to tension development Functions over a wide range of lengths (plasticity) |
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Explain control of contractions
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In multiunit smooth muscle cells -Connected to motor neurons In visceral smooth muscle cells -Not connected to motor neurons -Rhythmic cycles of activity controlled by pacesetter cells |
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Explain smooth muscle tone
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Modified by neural, hormonal, or chemical factors |
