Term
| What are the three kinds of muscle cells? |
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Definition
| Cardiac, Smooth, and Skeletal. |
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Term
| How do skeletal muscles attach to bones? |
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Definition
| Tendons (connective tissue) |
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Term
| Why are skeletal muscles striated? |
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Definition
| (thick and thin filaments). |
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Term
| Skeletal muscles cells are under _____ control and are _____-nucleated. |
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Definition
| Voluntary control; multi-nucleated. |
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Term
| How many muscles are in the human body? |
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Definition
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Term
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Definition
| Muscle cells. They run the entire length of the cell. They are held together and in parallel by connective tissue. They are 10-100 micrometers long. |
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Term
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Definition
| Contractile elements found in muscle cells (muscle fibers). They are composed of thick and thin filaments. |
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Term
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Definition
| A basic unit of contraction in a myofibril, the region between two Z lines. |
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Term
| Muscles are made up of ______ of muscle cells. |
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Definition
| Bundles. Connective tissue and bloody vessels run between the bundles. It is highly vascularized. |
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Term
| What are the thick and thin muscle filaments called? |
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Definition
| Thick: myosin filament. Thin: actin filament. |
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Term
| Actin has two ends: a ___end and a ___ end. |
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Definition
| A plus end and a minus end. |
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Term
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Definition
| NH2, COOH, and ATP (ADP when in filament.) |
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Term
| What are Myosin motor proteins? |
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Definition
| A type of actin based protein. |
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Term
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Definition
| A motor protein found in skeletal muscle; it generates force for muscle contraction. |
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Term
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Definition
| Formed from 2 heavy chains, 2 copies each of 2 light chains. The head binds and hydrolyzes ATP and generates force for movement; the Tail is formed from coiled-coil interaction of 2 alpha-helices of heavy chains. |
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Term
| What are Myosin Thick Filaments? |
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Definition
| Large, bipolar filaments formed from tail-tail interactions between myosin molecules. |
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Term
| Myosin Thick Filaments contain _____ |
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Definition
| several hundred myosin heads. |
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Term
| What direction are myosin heads oriented in Myosin Thick Filaments? |
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Definition
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Term
| Thick filaments can slide _________ oriented pairs of actin filaments past each other. |
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Definition
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Term
| What is the bare zone of the Myosin II thick filament? |
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Definition
| A place within the filament that has no head domains. |
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Term
| Where is motor activity containined within Myosin? |
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Definition
| The myosin head. Intact head domains move actin and ATP |
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Term
| What is the Sliding Filament Mechanism of Muscle Contraction? |
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Definition
| Thin filaments slide over thick filaments simultaneously on each side of sarcomeres. This shortens the sarcomeres and muscles fibers and produces forces that contracts the muscle. |
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Term
| How does a muscle conract? |
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Definition
1) Action potential arrives at the neuromuscular junction, causing release of acetylcholine.
2) Acetylcholine triggers an action potential in the muscle fiber that spreads over its plasma membrane and stimulate the sarcoplasmic reticulum to release Ca2+ into the cytosol.
3) Ca2+ combines with troponin, inducing a conformational change that moves tropomyosin away from myosin-binding sites on thin filaments.
4) Exposure of sites on actin allows myosin crossbridges to bind and initiate the crossbridge cycle.
5) Myosin heads of thick filaments attach to a thin filament, pull, and release in cyclic reactions powered by ATP hydrolysis. |
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Term
| What happens in a neuron to neuron synapse? |
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Definition
1) Need a lot of synaptic input from a lot of presynaptic cells to get to threshold: a lot of integration, a lot of EPSPs to reach threshold.
2) It can have an inhibitory input. |
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Term
| What happens at a Neuromuscular junction? |
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Definition
1) One action potential in a motor neuron almost always causes an action potential in the muscle cell.
2) No inhibitory input. Have a large excitatory end plate potential (EPP) that reaches threshold for an action potential.
3) Since neuromuscular junctions are in the middle of a muscle cell, the action potential generated can go out in both directions to cover the entire muscle cell. |
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Term
| Action Potential goes along the membrane into ________ |
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Definition
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Term
| What are the 4 steps of the Cross Bridge Cycle? |
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Definition
1) Myosin cross bridge has ATP bound, not in contact with actin.
2) Myosin binding site on actin becomes available.
3) ATP -> ADP+P and myosin head attaches to actin and initiates the "power stroke" (bending of the myosin head and movement of the actin filament) and releasing ADP
4) Myosin head binds to a new ATP and detaches from actin. |
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Term
| What happens when the system is reset? |
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Definition
1) Action potentials to the muscle stop.
2) Ca2+ is removed from the troponin and actively transported (via Ca2+ pumps) back (from the cytosol) into the sarcoplasmic reticulum.
3) Tropomyosin moves to its orginal location on the actin, blocking myosin binding sites.
4) Think filaments slide back to their original position. |
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Term
| What end of actin does myosin move toward? |
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Definition
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Term
| What end of actin is the leading end? |
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Definition
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Term
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Definition
| It blocks acetylcholine release at the neuromuscular junction -> muscles are unable to contract. |
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Term
| How does the venom of the Black Widow work? |
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Definition
| Muscles go into convulsive contractions due to the massive release of acetylcholine. |
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Term
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Definition
| A poison that blocks receptors for acetylcholine in muscle fibers, resulting in Paralysis, respiratory failure, and death. |
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Term
| What do the muscles do in Rigor Mortis? |
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Definition
| Ca2+ leaks into the cytoplasm, causing the myosin head to attach to actin -> muscle contraction. Myosin head cannot be released from the actin because there is no ATP. |
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Term
| What causes a muscle twitch? |
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Definition
| A single action potential arriving at a neuromuscular junction. |
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Term
| What causes a second muscle twitch? |
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Definition
| Restimulation of muscle fiber before it relaxes completely. This is added to first and causes a summed STRONGER CONTRACTION. |
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Term
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Definition
| A peak level of contraction caused by the rapid arrival of Action Potentials. Tetanus increases the force of contraction of individual fibers. |
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Term
| What are the three types of muscle twitches? |
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Definition
| Single twitches, summed twitches, and Tetanus. |
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Term
| How do muscle fibers differ? |
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Definition
| Number of mitochondria and capacity to produce ATP. |
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Term
| What are the 3 types of muscle fibers? |
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Definition
1) Slow Muscle Fibers
2) Fast Aerobic Fibers
3) Fast Anaerobic Fibers |
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Term
| Describe Slow Muscle Fibers. |
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Definition
1) They contract relatively slowly.
2) The intensity of the contraction is low because the ATP on the myosin head is hydrolyzed slowly.
3) They do not fatigue rapidly; they can remain contracted for long periods (postural muscles).
4) They have high concentrations of myoglobin (an oxygen storing protein) so they have a good supply of oxygen. |
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Term
| Describe Fast Aerobic Muscle Fibers. |
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Definition
| They contract relatively quickly and powerfully. They fatigue more quickly than slow fibers. |
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Term
| Describe Fast anaerobic fibers. |
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Definition
| They contract more rapidly and powerfully than fast aerobic fibers, but they fatigue more rapidly than fast aerobic fibers. |
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Term
| What kind of fibers do most muscles contain? |
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Definition
| A mixture of the 3 types. Some muscles have more of one type than nother. Postural Muscles have more of the slow type. |
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Term
| What is the optimal length of a muscle fiber? |
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Definition
| The length where the maximum number of cross bridges are available to pull, there's a good overlap between thick and thin filaments, but the thin filaments don't get in each other's way at all. |
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Term
| What happens when a muscle fiber is longer than its optimal length? |
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Definition
| There is very little overlap between thick and thin filaments and not very many cross bridges can pull. |
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Term
| What happens when the muscle fiber is shorter than the optimal length? |
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Definition
| Thin filaments start to overlap and get in each other's way. All the myosin binding sites are not available to bind with myosin heads, resulting in less effective pulling of the cross bridges. |
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Term
| Why can we not change our muscle lengths? |
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Definition
| Our muscles are attached to bones. |
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Term
| What are the two types of muscle contraction? |
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Definition
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Term
| What is an Isomeric muscle contraction? |
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Definition
| The muscle is at the same length. The muscle can contract, but it only exerts force or tension. It doesn't shorten. |
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Term
| What is an isotonic muscle contraction? |
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Definition
| The muscle shortens and lifts the load. |
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Term
| What happens in Endurance training? |
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Definition
| Fast muscle fibers are converted from anaerobic to aerobic. Fast anaerobic fibers fatigue more rapidly than fast aerobic fibers. |
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Term
| What happens in weight lifting? |
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Definition
| Fast muscle fibers are converted from aerobic to anaerobic. Fast anaerobic fibers contract more rapidly and powerfully than fast aerobic fibers. |
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Term
| Skeletal muscles are divided into functional ____ |
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Definition
|
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Term
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Definition
| A group of muscle fibers activated by branches of a single motor neuron. |
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Term
| How do you determine the total force produced by a skeletal muscle? |
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Definition
| By the number of motor units activated. |
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Term
| What is a motor unit made up of? |
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Definition
| Motor neurons and muscle cells. |
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Term
| What happens when more motor units are excited? |
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Definition
| This is called Recruitment. More muscle fibers will contract at the same time. |
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Term
| Bones act as _____ when moved by skeletal muscles. |
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Definition
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Term
| How does the bone-lever work? |
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Definition
1) The joint at one end forms the fulcrum of the lever.
2) The load is at theopposite end.
3) The force is applied by attachment of a muscle at a point between the ends. |
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Term
| What kind of muscle causes movement at a joint? |
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Definition
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Term
| What is an Antagonistic pair? |
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Definition
| The way most skeletal muscles are arranged. Members of a pair pull a bone in opposite directions. When one member of the pair contracts, the other member relaxes and is stretched. |
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Term
| Muscles are _____ for animal activities. |
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Definition
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Term
| Where is Smooth muscle found? |
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Definition
| Bladder, reproductive tracts, gastrointestinal tracts, respiratory tracts, and surrounding the blood vessel. |
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Term
| Why does the contraction of one smooth muscle cell invoke some degree of contraction in an adjoining cell? |
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Definition
| Cells are coupled together. |
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Term
| What facilitates the spread of chemicals or action potentials between smooth muscle cells? |
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Definition
| Gap junctions coupling adjacent cells chemically and electrically. |
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Term
| A smooth muscle can do what to a much greater extent than skeletal muscles? Why? |
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Definition
| It can shorten because there is more distance between thin and thick filaments. |
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Term
| Why is a smooth muscle's ability to shorten important? |
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Definition
| Smooth muscles often surround structures that change in diameter. They can contract and be very long or they can contract and be much shorter. |
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Term
| Can contraction in smooth muscles be non-linear? |
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Definition
| Yes. Fibers are in a slanted position; there is a bulging appearance when the filaments slide and shorten the muscle. |
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Term
| What does Neural Input from the ANS do to Smooth Muscle? |
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Definition
| It can induce or inhibit contraction. (Sympathetic and Parasympathetic nervous systems often have opposing effects.) |
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Term
| What does Hormonal Input do to smooth muscle? |
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Definition
| Hormones will stimulate a second messenger molecular which leads to calcium release. |
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Term
| How is activation by calcium in smooth muscles different? |
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Definition
1) In some smooth muscles, calcium enters from outside the cell via voltage or ligand gated channels.
2) In other smooth muscle, the calcium comes from the sarcoplasmic reticulum.
3) There are no T tubules.
4) Calcium calmodulin -> activates an enzyme that can phosphorylate the cross bridges -> cross bridges can bind and can pull on the thin filaments. |
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Term
| What are two important characteristics of Smooth Muscle Contractions? |
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Definition
1)They tend to be slower.
2) They tend not to fatigue.
EX: Muscles that control the diameter of blood vessels can remain contracted for a long time. |
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