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153 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Name the 3 types of muscle tissue. |
Skeletal, Cardiac, and Smooth muscle tissue. |
SCS |
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What are the common properties of muscle tissue? |
1.) Excitability (responsiveness); 2.) Contractility (ability of cells to shorten); 3.) Extensibility (stretching); 4.) Elasticity (recoil) |
Excited Elastagirl Extends and Contracts |
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Name the 6 functions of skeletal muscle? |
Producing movement; Maintaining posture and body position; Supporting soft tissues; Guarding body entrances and exits; Maintaining body temperature; and Storing Nutrients |
Think about what skeletal muscles do in your body. |
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What do skeletal muscles contain? |
Skeletal muscle tissue (primarily); Connective tissues; Blood vessels; Nerves |
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Name the 3 layers of connective tissue that skeletal muscles have. |
Epimysium, Perimysium, and Endomysium |
Epi, Peri, Endo |
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Describe epimysium. |
Layer of collagen fibers that surrounds the muscle; connected to deep fascia; separates muscle from surrounding tissues |
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Describe perimysium. |
Surrounds muscle fiber bundles (fascicles); contains: collagen fibers, elastic fibers, blood vessels, nerves |
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Describe endomysium. |
Surrounds individual muscle cells (muscle fibers); contains: capillary networks, myosatellite cells (stem cells) that repair damage, nerve fibers |
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Collagen fibers of epimysium, perimysium, and endomysium come together at the ends of muscles to form _______. |
A tendon (bundle) or aponerosis (sheet) |
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Collagen fibers of epimysium, perimysium, and endomysium come together to attach _______ to _______. |
Skeletal muscles; bones |
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Skeletal muscles _____ only when _____ by the central nervous system. |
Contract; stimulated |
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Are skeletal muscles voluntary or involuntary? |
Voluntary |
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What is being described below? _____ are enormous compared to other cells; contain hundreds of nuclei (multinucleate); develop by fusion of embryonic cells (myoblasts); also known as striated muscle cells due to striations |
Skeletal muscle fibers (the cells) |
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What is being described below? Plasma membrane of a muscle fiber; surrounds the sarcoplasm (cytoplasm of a muscle fiber); a sudden change in membrane potential initiates a contraction |
Sarcolemma |
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What is the sarcoplasm? |
Cytoplasm of a muscle fiber |
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What is described below? Tubes that extend from the surface of muscle fiber deep into sarcoplasm; transmit action potential from sarcolemma into cell interior |
Transverse tubules (T tubules) |
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What is being described below? A tubular network surrounding each myofibril; similar to smooth endoplasmic reticulum; forms chambers (terminal cisternae) that attach to T tubules [two terminal cisternae plus a T tubule forms a triad]; specialized for storage and release of calcium ions [ions are actively transported from cytosol into terminal cisternae] |
Sarcoplasmic reticulum (SR) |
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What is being described below? Lengthwise fibrils packed within a muscle fiber; responsible for muscle contraction; made of bundles of protein filaments (myofilaments); two types of myofilaments (thin filaments and thick filaments) |
Myofibrils |
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What are the two types of myofilaments? |
Thick and thin filaments |
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Thin filaments are composed primarily of _____. |
Actin |
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Thick filaments are primarily composed of _____. |
Myosin |
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What is being described below? Smallest functional units of muscle fiber; interactions between filaments produce contraction; arrangement of filaments accounts for striated pattern of myofibrils (Dark and light bands) |
Sarcomeres |
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What are the two types of myofibril bands and describe which is light and which is dark?. |
Dark bands = A bands; light bands = I bands |
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What is found in the A band (dark band)? |
M line, H band, and Zone of overlap |
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In center of A band: proteins stabilize positions of thick filaments |
M line |
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On either side of M line; has thick filaments but no thin filaments |
H band |
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Dark region; where thick and thin filaments overlap |
Zone of overlap |
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What is found in the I band (light band)? |
Thin filaments, Z discs, and titin |
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Contains thin but no thick filaments |
I band (light band) |
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Bisects I bands; marks boundaries between adjacent sarcomeres |
Z discs |
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Elastic protein; extends from tips of thick filaments to the Z line; keeps filaments in proper alignment; aids in restoring resting sarcomere length |
Titin |
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What do thin filaments contain? |
F-actin, nebulin, tropomyosin, and troponin proteins |
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Twisted strand composed of two rows of globular G-actin molecules; active sites on G-actin bind to myosin |
Filamentous actin (F-actin) |
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Holds F-actin strand together |
Nebulin |
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Covers active sites on G-actin; prevents actin-myosin interaction |
Tropomyosin |
Blocks |
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A globular protein; binds with tropomyosin, G-actin, and Ca2+ |
Troponin |
Binds |
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Each contains about 300 myosin molecules |
Thick filaments |
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Each myosin molecule consists of a _____ and a _____. |
Tail: binds to other myosin molecules; head: made of two globular protein subunits (projects toward nearest thin filament, can bind to actin) |
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Core of titin recoils after stretching |
Thick filaments |
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What happens in the sliding-filament theory, during a contraction? |
1. H bands and I bands narrow 2. Zones of overlap widen 3. Z lines move closer together 4. Width of A band remains constant Thus, thin filaments must slide toward center of sarcomere |
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Are found in skeletal muscle fibers and neurons; depolarization and repolarization events produce action potentials (electrical impulses) |
Excitable membranes |
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What are action potentials? |
Electrical impulses |
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Skeletal muscle fibers contract due to stimulation by _____. |
Motor neurons |
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Describe the contraction cycle. |
1. Contraction cycle begins 2. Active-site exposure 3. Cross-bridge formation (myosin binds to actin) 4. Myosin head pivoting (power stroke) 5. Cross-bridge detachment 6. Myosin reactivation |
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Describe the neuromuscular junction (NMJ). |
Synapse between a neuron and a skeletal muscle fiber; axon terminal of the motor neuron releases a neurotransmitter into the synaptic cleft (the neurotransmitter is acetylcholine (ACh)); ACh binds to and opens a chemically gated Na+ channel on the muscle fiber (Na+ enters cell and depolarizes motor end plate; an action potential is generated) |
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Describe excitation-contraction coupling. |
Action potential travels down T tubules to triads (Ca2+ is released from terminal cisternae of SR); Ca2+ binds to troponin and changes its shape; troponin-tropomyosin complex changes position (exposes active sites on thin filaments); contractiom cycle is initiated |
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Describe generation of muscle tension. |
When muscle cells contract, they produce tension (pull); to produce movement, tension must overcome the load (resistance); the entire muscle shortens at the same rate (because all sarcomeres contract together; speed of shortening depends on cycling rate (number of power strokes per second)) |
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Generation of muscle tension
Duration of a contraction depends on _____ , _____ , and _____. |
Duration of neural stimulus, presence of free calcium ions in cytosol, and availability of ATP. |
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As Ca2+ is pumped back into SR and Ca2+ concentration in cytosol falls... |
1. Ca2+ detaches from troponin 2. Tropinin returns to original position 3. Active sites are re-covered by tropomyosin and the contraction ends |
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Describe rigor mortis. |
Fixed muscular contraction after death; results when ATP runs out and ion pumps cease to function and calcium ions build up in cytosol |
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The number of contracting sarcomeres in a muscle fiber is fixed so, |
A muscle fiber is either producing tension or relaxed |
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The amount of tensiom produced depends on what 3 things? |
Number of power strokes performed, fiber's resting length at time of stimulation, and freqency of stimulation |
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A single neural stimulation priduces a single contraction, or twitch lasts _______ msec. |
7-100 msec |
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Sustained muscular contractions require _____. |
Many repeated stimuli |
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A graph showing tension development in muscle fibers |
Myogram |
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A single twitch has 3 phases. What are they? |
Latent period, contraction phase, and relaxation phase |
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Action potential moves across sarcolemma; SR releases Ca2+ |
Latent period |
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Calcium ions bind to troponin and cross-bridges form; tension builds to a peak |
Contraction phase |
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Ca2+ levels in cytosol fall; cross-bridge detach and tension decreases |
Relaxation phase |
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A stair-step increase in tension |
Treppe |
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Which muscle are treppes usually seen in? |
Cardiac muscle |
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Increasing tension due to summation of twitches |
Wave summation |
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Caused by repeated stimulations immediately after relaxation phase; stimulus <50/second; produces a series of cobtractions with increasing tension |
Treppe |
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Cause by repeated stimulations before the end of relaxation phase; stimulus frequency >50/second |
Wave summation |
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_____ is maximun tension. |
Tetanus |
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Muscle produces near-maximum tension; caused by rapid cycles of contraction and relaxation |
Imcomplete tetanus |
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Higher stimulation frequency eliminates relaxation phase; muscle is in continuous contraction; all potential cross-bridges form |
Complete tetanus |
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Tension production by skeletal muscles depends on the ______. |
Number of stimulated muscle fibers |
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A _____ is a motor neuron and all of the muscle fibers it controls |
Motor unit |
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May contain a few muscle fibers or thousands (precise movement vs. Strength); all fibers in a ______ contract at the same time |
Motor unit |
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Involunary "muscle twitch"; unlike a true twitch, it involves more than one muscle fiber |
Fasciculation |
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Increase in the number of active motor units; produces smooth, steady increase in tension |
Recruitment |
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______ is achieved when all motor units reach complete tetanus (can be sustained for a very short time) |
Maximum tension |
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Produceess than maximum tension; motor units are allowed to rest in rotation |
Sustained contractions |
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The normal tension and firmness of a muscle at rest |
Muscle tone |
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Without causing movement, motor units actively... |
Amstabilize positions of bones and joints and maintain balance and posture |
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Muscle tone keeps the muscles ready to _____. |
Work |
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Elevated muscle tone increases resting ______. |
Energy consumption |
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_____ are classified based on their pattern of tension production |
Contractions |
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2 types of muscle contractions |
Isotonic and isometric |
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Skeletal muscle changes length; resulting in motion |
Isotonic contractions |
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Muscle tension > load (resistance); muscle shortens |
Isotonic concentric contraction |
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Muscle tension < load; muscle elongates |
Isotonic eccentric contraction |
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Are inversely related; the heavier the load, the longer it takes for movement to begin; tension must exceed the load before shortening can occur |
Load and speed contraction |
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Elastic forces: tendons recoil after a contraction; helps return muscle fibers to resting length Opposing muscle contractions: opposing muscles return a muscle to resting length quickly Gravity: assists opposing muscles |
Muscle relaxation and the return to resting length |
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_____ is the only energy source used directly for muscle contraction |
ATP-adenosine triphosphate |
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Contracting muscles use a lot of _____. Muscles store enough _____ to start a contraction. More _____ must be generated to sustain a concentration. |
ATP |
They are all the same answer. |
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Skeletal muscle fibers produce more ATP than needed when _____. |
At rest |
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ATP transfers energy to _____ |
Creatine |
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Used to store energy and convert ADP back to ATP |
Creatine phosphate (CP) |
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Catalyzes the conversion of ADP to ATP using energy stored in CP |
Enzyme creatine kinase (CK) |
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When CP is used up, otjer mechanisms are used to generate _____. |
ATP |
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Direct phosphorylation of ADP by creatine phosphate (CP) Anaerobic metabolism (glycolysis) - lactic acid fermentation Aerobic metabolism (critic acid cycle and electron transport chain) |
How ATP is generated |
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Anaerobic process Important energy source for peak muscular activity Breaks down glucose from glycogen stored in skeletal muscles Produces two ATP per molecules of glucose |
Glycolysis |
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Primary energy source of resting muscles Breaks down fatty acids |
Aerobic metabolism |
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Skeletal muscles at rest metabolize fatty acids and store glycogen and CP During moderate activity, muscles generate ATP through aerobic breakdown of glucose, primarily At peak activity, pyruvate produced via glycolysis is coverted to lactate |
Muscle metabolism: 3 major mechanisms |
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The time required after exertion for muscles to return to normal |
Recovery period |
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Lactate is transferred from muscles to the liver Liver converts lactate to pyruvate Most pyruvate molecules are converted to glucose Glucose is used to rebuild glycogen reserves in muscle cells |
Lactate removal and recycling (Cori cycle) |
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Oxygen Debt After exercise or other exertion the body needs more _____ that usual to normalize metabolic activities Breating rate and depth are increased |
Oxygen |
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Active skeletal muscles produce heat; release up to 85 percent of the heat needed to maintain normal body temperature |
Heat production and loss |
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What hormones increase metabolic activities in skeletal muscles? |
Growth hormones, testosterone, thyroid hormones, and epinephrine |
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Muscle Performance The maximum amount of tension produced |
Force |
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Muscle Performance The amount of time an activity can be sustained |
Endurance |
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Muscle Performance Force and endurance depend on the types of _____ and _____. |
Muscle fibers; physical conditioning |
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What are the 3 types of skeletal muscle fibers? |
Fast fibers, slow fibers, and intermediate fibers |
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What is described below? Majority of skeleyal muscle fibers Contract very easily Large diameter; large glycogen reserves; few mitochondria; produce contractions, but fatigue quickly |
Fast fibers |
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What is described below? Slow to contract and slow to fatigue Small diameter; numerous mitovhondria; high oxygen supply from extensive capillary network; contain myoglobin (red pigment that binds oxygen) |
Slow fibers |
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Are midsized; little myoglobin; slower to fatigue than fast fibers |
Intermediate fibers |
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Mostly fast fibers; pale (e.g., chicken breast) |
White muscles |
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Mostly slow fibers; dark (e.g., chicken legs) |
Red muscles |
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Contain a mixture of fiber types and are pink |
Most human muscles |
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Muscle growth from heavy training that causes increases in: Diameter of muscles fibers, number of myofibrils, number of mitochondria, and glycogen reserves |
Muscle hypertrophy |
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Reduction of muscle size, tone, and power due to lack of activity |
Muscle atrophy |
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Describe some changes in muscle tissue as get older in age. |
Skeletal muscle fibers become smaller; skeletal muscles become less elastic (fibrosis - increase in fibrous connective tissue); tolerance for exercises decreases; ability to recover from muscular injuries decreases |
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When muscles can longer perform at a required level, a person is experiencing _____. |
Muscle fatigue |
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Muscle fatigue is correlated with _____ depletion of metabolic reserves; _____ to sarcolemma and sarcoolasmic reticulum; ____ in pH, which affects calcium ion binding and alters enzyme activities; _____ due to low blood pH and pain |
Depletion; damage; decline; weariness |
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Almost all _____ muscles attach to bones |
Skeletal |
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Fixed point of attachment of a miscle to bone is the _____. |
Origin |
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Movable point of attachment is the _____. |
Insertion |
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Origin is usually _____ to insertion. |
Proximal |
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Movements produced by muscle contraction |
Actions |
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Describe muscle interactions. |
Muscles work im groups to maximize efficiency Smaller muscles reach maximum tension first, followed by larger, primary muscles |
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What 4 termz refer to how muscles wotk together? |
Agonist, antagonist, synergist, and fixator |
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Mostly responsible for producing a particular movement |
Agonist (prime mover) |
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Opposes movement of a particular agonist |
Antagonist |
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A maller muscle that assists a larger agonist |
Synergist |
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A synergist that assists an agonist by preventing movement at another joint |
Fixator |
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Explain how agonists and antagonists work in pairs and give two examples. |
When one contracts, the other stretches Flexors-extensors Abductors-adductors |
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Which systems support the muscular system? |
Cardiovascular, respiratory, intehumentary, nervous and endocrine systems |
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How does the cardiovascular system support the muscular system? |
Delivers oxygen and nutrients Removes carbon dioxide |
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How does the respiratory system support the muscular system? |
Responds to oxygen demand of muscles |
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How does the integumentary system support the muscular system? |
Disperses heat from muscle activity |
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How do the nervous and endocrine systems support the muscular system? |
Direct responses of all systems |
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Found only in the heart; have excitable membranes; striated like skeletal muscle cells |
Cardiac muscle cells |
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Name 6 characteristics about the cardiac muscle cells. |
1. They are small 2. Typically branched with a single nucleus 3. Have short, wife T tubules (no triads) 4. Have SR with no terminal cisternae 5. Are almost totally dependent on aerobic metabolism (contain lots of myoglobin, many mitochondria) 6. Contact each other via interecalated discs |
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Specialized connections; join sarcolemmas of adjacent carfiac muscle cells by gap junctions and desmosomes |
Intercalated discs |
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Describe the functions of the intercalated discs. |
Stabilize positions of adjacent cells; maintaining three-dimensional structure of tissue; allowing ions to move from one cell to another (so cardiac muscle cells beat in rhythm |
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Automaticity (auto-rhythmic) Contraction without neutral stimulation Controlled by pacemaker cells |
Functional characteristic of cardiac muscle |
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Nervous system can alter pace and tension of contractions |
Functional characteristic of cardiac muscle |
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Contractions last 10 times longer than those in skeletal muscle, and refactory periods are longer |
Funtional characteristic of cardiac muscle |
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Wave summation and tetanic contractions are prevented due to special properties of the sarcolemma |
Functional characteristic of cardiac muscle |
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What systems do smooth muscle tissues have a role in? |
Integumentary, cardiovascular, respiratory, digestive, urinary, and reproductive systems |
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What role does smooth muscle tissue play in the integumentary system? |
Arrector pili muscles erect hairs |
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What role does smooth muscle tissue play in the cardiovascular and respiratory systems? |
Regulates blood pressure and airflow |
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What role does smooth muscle tissue play in the digestive and urinary systems? |
Forms sphincters and moves materials along and out of the body |
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What role does smooth muscle tissue play in the reproductive system? |
Transports gametes and expels fetus |
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What muscle type do these structural characteristics describe? Long, slender, spindle-shaped cells; single, central nucleus; no T tubules, myofibrils, or sarcomeres; nonstriated muscle; scattered thick filaments with many myosin heads; thin filaments attached to dense bodies; dense bodies connect adjacent cells, transmitting contractions; no tendons or aponeuroses |
Smooth muscle |
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Name some functional charcacteristics of smooth muscle tissue. |
Excitation-contractiom coupling Length-tension relationships Control of contractions Smooth muscle tone |
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What is being described below? Free Ca2+ in cytoplasm triggers contraction; Ca2+ binds with calmodulin: activates myosin light chain kinase, allows myosin heads to attach to actin |
Excitation-contraction coupling |
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What is being described below? Due to the lack of sarcommeres, tensiom and resting length are not directly related; even a stretched smooth muscle can contract: plasticity - the ability to function over a wide range of lengths |
Length-tension relationships |
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What is being described? Multiunit smooth muscle cells: innervated in motor units, each cell may be connected to more than one motor neuron |
Control of contractions |
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What is being described? Visceral smooth muscle cells: not connected to motor neurons, arranged in sheets or layers, rhythmic cycles of activity are controlled by pacesetter cells |
Control of contractions |
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Normal background level of activity; can be decreased by neural, hormonal, or chemical factors |
Smooth muscle tone |
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