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Stabilize Joints (Skeletal)
muscles (tendons and ligaments) help to stabilize poorly articulating joints
Generate Heat (Skeletal)
mitochondria makes ATP from glucose and oxygen; skeletal muscles use ATP for contractions and creates heat as a bi-product
involuntary; located in the heart; striated; unique features: branching pattern, intercalated discs, and muscle fibers are separate
involuntary; located in walls of hollow organs (intestines, etc.); performs peristalsis; unique features: spindle shaped, and has NO striations
ONLY VOLUNTARY MUSCLE; location: attached to bones; has striations; unique features: cylindrical shaped, multinucleated, and fibers are close together
wraps around the fascicle (several muscle fibers connected together); contains collagen and elastic fibers, nerves and blood vessels
each individual muscle cell (myofiber) in the fascicle is wrapped by this connective tissue; (membrane layer on the inside) endo
Tendon or Aponeurosis
at the end of each muscle cell where the endomysium and perimysium come together to form a tendon or aponeurosis; both connect skeletal muscles to bone; aponeurosis connects muscle to muscle
'flesh husk'- the plasma membrane of a cell that surrounds the sarcoplasm of the muscle cell
extend into the cell at the right angles to the cells surface to contract the entire muscle cell at the same time
long organelles found inside the muscle cell; tiny contract units that help to shorten the muscle during contraction; have banding patterns (striations)
During muscle contraction, what happens to the sarcomere?
it shortens as the Z lines are pulled closer together
A Band (DARK BAND)
a portion of the sarcomere which contains ALL of the thick filaments and only a portion of the thin filaments
a portion within the A Band which contains only the THICK filaments; no thin filaments are found when the muscle is relaxed
During muscle contraction, what happens to the H Zone?
it disappears since the thin filaments invade the H zone
I Band (LIGHT BAND)
a portion of the sarcomere which contains the Z Line and only the THIN filaments
During muscle contraction, what happens to the I Band?
it disappears since the thick filaments invade the I Band
During muscle contraction, what happens to the Z Lines?
slides closer together since the myosin heads attach to the thin filaments and pull them
Thick Filaments/Myosin Filaments
possess heads which are crucial for muscle contraction; made of the protein, myosin; myosin heads attach to certain sites of the thin filaments so muscle contraction can occur
knobby, golf club shaped portions of the thick filaments; made of proteins that attach to a particular portion of the thin filaments during muscle contraction; often called a cross bridge
During muscle contraction, what is the role of the myosin heads?
myosin heads attach to thin filaments, pull them together, release and repeat; the thin filaments slide toward the center of the sarcomere, in turn, the Z Lines are moved closer together and the sarcomere shortens
Thin Filament/Actin Filament
anchored to the Z Line; made of actin, tropomyosin and troponin; for muscle contraction to occur, troponin-tropomyosin must change positions and expose active sites on actin
organelle wrapped around the myofibril like a lacey sleeve; calcium ions are released into the sarcoplasm for muscle contraction to occur; ions diffuse into the sarcomere, the SR reabsorbs calcium ions after muscle contraction to help the muscle relax
link between the generation of action potential and the start of muscle contraction; takes about .03 seconds for action potential to create a muscle contraction
gap between the sarcolemma of the muscle cell and the axon terminals of the nerve cell
as action potential reaches the synaptic knob, calcium ions diffuse into the axon terminal
a chemical packaged in vesicles that is released into the synaptic cleft by exocytosis
binds to receptors on the sarcolemma of the muscle cell; channel proteins open so that the voltage of the cell can change and the action potential can be transferred to the next cell; to keep it resting, the charge must be negative; action potential changes a negative charge to a positive on the interior of the muscle cell; causes sarcolemma to become selectively permeable to sodium ion (outside of cell) while potassium is inside
sodium ions that carry a positive charge, creates an electrical impulse, influx of sodium ions into the muscle cell causes the flow of an electrical current
when myosin heads form cross bridges when attaching to the binding sites on actin filaments
occurs when no ATP is available; muscles are locked in contracted state until ions drain and pool in the body
contractions that shorten and produce movement (flexion, extension, abduction, adduction)
AChE breaks down ACh, ACh is recycled and returned to the axon terminal, SR reabsorbs calcium ions, troponin-tropomyosin complex recovers the binding sites on acting and prevents the myosin heads from attaching, without cross bridge interaction, the contraction ends, muscle relaxes to its normal length
Smooth Muscles Contracting
lacks sarcomeres, troponin, and striations; uses same sliding filament theory of other muscles
different degrees of muscle shortening affected by: changing frequency in muscle stimulation and changing the number of muscles being stimulated
single, brief, jerky contraction; not a normal way to operate; result in nervous system problems
Latent Period (Twitch)
excitation period- the contraction cycle has not yet begun; action potential is sweeping across the sarcolemma; SR is in the process of releasing calcium
Contraction Phase (Twitch)
tension rises as calcium ions bind to troponin and active sites on the thin filaments are now exposed; cross bridge interactions occur
calcium levels fall and active sites are covered by tropomyosin, cross bridges detach and tension falls
skeletal muscle stimulated immediately after relaxation phase has ended; will produce a slightly higher tension than the first stimulus
Summation of Twitches
addition of twitches; if stimulation continues and the muscles is not allowed to relax completely, tension will begin to rise above treppe; reaches an imcomplete tetanus
Fused or Complete Tetanus
in most types of muscle activity; impulses sent so rapidly that the muscle doesn't get to relax completely between stimuli
resting tension; not enough tension to create movement, but enough to tense and firm the muscle
reaches peak tension is 0.01 seconds; larger fiber possess, many packed myofibrils, large amounts of glycogen, few mitochondria; fatigue quickly; found in white meat in chicken
smaller in diameter; specialized to continue contractions over longer periods of time, has mitochondria and contains a pigment called myoglobin which leads to oxygen molecules that makes it more dependent on anaerobic cellular respiration; found in dark meat chicken
Aerobic Cellular Respiration
most common way to generate ATP in a resting muscle by transforming fatty acids; exercise begins-- ATP made by pyruvic acid
glucose + oxygen > carbon dioxide + water + 34-36 ATP
fastest way to regenerate ATP when supplies run low; creatine phosphate can be stored when muscles are inactive; this type of ATP regeneration can be exhausted in 15 seconds
CP interacts with ADP > Creatine and ATP
Anaerboic Cellular Respiration
generates 2 ATP molecules for each glucose molecule broken down, glucose retrieved from glycogen stored in the sarcoplasm; lactic acid builds up during exercise
Glycogen stored in muscle cells > Glucose > 2 ATP + Lactic Acid
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