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47 Cards in this Set
- Front
- Back
The T, or transverse tubules, are also associated w/the highly organized smooth endoplasmic reticulum called the______ in skeletal fibers |
sarcoplasmic reticulum |
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a muscle is composed of numerous visible bundles called muscle |
Fasciculi |
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this is considered the smallest contractile unit of skeletal muscle. It extends from z-disk to z-disk. |
sarcomere |
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what is a z-disk? |
a filamentous network of protein forming a disklike structure for the attachment of actin myofilaments. |
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each______includes a z-disk and extends from each side of the z-disk to the ends of the myosin myofilaments. |
Isotropic band or I band- (light) |
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In the center of each A band is a smaller band called the _______, where the _________ and _______ do not overlap and only _______ are present. |
H-zone, actin, myosin myofilaments, myosin myofilaments |
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Three important properties of myosin heads |
1. Bind to active sites on the actin molecules to form Cross-bridges 2. Heads are attached to the rod portion by a hinge region that can bend & straighten during contraction 3. The heads are ATPase enzymes, which breakdown adenosine triphosphate (ATP), releasing energy. |
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What is part of the energy used for? |
to bend the hinge region of the myosin molecule during contraction (causes contraction). |
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The equivalent to a cytoplasm of a cell is called a _______ in muscles |
sarcoplasm |
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These channels are gated membrane channels that open and close in response to a particular membrane potential. |
Voltage-gated ion channels |
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the voltage-gated channels that play a major role in an action potential are |
voltage-gated Na+, K+, and Ca2+ channels. |
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Do voltage-gated channels allow all ions to cross the plasma membrane? |
No, they are specific to an ion. For example, the Na+ channel only allows Na+ to cross through the plasma membrane. |
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The resting membrane potential can be measured in units called______ |
millivolts (mv=1/1000 volt) |
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What are the potential differences across the plasma membranes of neurons and muscle fibers? |
Between -70 and -90 mV. |
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Why is the potential difference reported as a negative #? |
because the inner surface of the plasma membrane is negative compared with the outside. |
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The ________ of the action potential is a brief period during which further depolarization occurs & the inside of the cell becomes_______. |
Depolarization phase, positively charged. |
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Each presynaptic terminal contains numerous mitochondria and many small, spherical sacs approx. 45um in diameter, called________ |
Synaptic vesicles |
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every vesicle contains acetycholine (ACh), what is it composed of? |
It is an organic molecule composed of acetic acid and choline. |
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Acetycholine (ACh) is a _________ |
neurotransmitter |
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What is a neurotransmitter? |
A substance released from a presynaptic membrane that diffuses across the synaptic cleft and alters the activity of the postsynaptic cell. |
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How can neurotransmitters stimulate or inhibit the production of an action potential in the postsynaptic membrane? |
By binding to ligand-gated ion channels |
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Near the t-tubules the sarcoplasmic reticulum is enlarged to form |
terminal cisternae |
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What is a triad? |
A T tubule and 2 adjacent terminal cisternae |
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Is the concentration of Ca2+ higher or lower within the sarcoplasmic reticulum compared to the sarcoplasm of a resting muscle fiber? |
It is higher, approximately 2000 times higher. Since the sarcoplasmic reticulum actively transports Ca2+ into its lumen. |
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Movement of the myosin molecule while the cross-bridge is attached is called the |
Power stroke |
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Return of the myosin head to its original position after cross-bridge release is called the |
recovery stroke |
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______cycles of power & recovery during each muscle contraction. |
Many |
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What happens when Ca2+ is released from the sarcoplasmic reticulum in response to an action potential? |
The cycle of cross-bridge formation, movement, and release, which results in contraction, begins. |
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muscles performing delicate and precise movements have motor units with a ______ |
small number of muscle fibers - can be as little as 10 |
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muscles performing more powerful but less precise contractions have motor units with____ |
many muscle fibers - can be several hundred |
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The _______ fibers there are in motor units of a muscle, the _______ a person has over that muscle. |
fewer, greater control |
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what is a possible explanation for treppe (a phenomenon where a muscle fiber contracts w/greater force w/each subsequent stimulus)? |
an increase in Ca2+ levels around the myofibrils. The Ca2+ released in response to the 1st stimulus is not taken up completely by the sarcoplasmic reticulum before the 2nd stimulus causes the release of additional Ca2+, even though the muscle relaxes completely between the muscle twitches. |
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what is tetanus? |
a period of sustained contraction of muscle fibers due to the increase of action potential and contraction frequency. |
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Incomplete tetanus? |
muscle fibers partially relax between the contractions |
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complete tetanus? |
muscle fibers produce action potentials so rapidly that no relaxation occurs between them |
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as the frequency of contractions increases, the increased tension produced is called |
multiple- wave summation |
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what are eccentric contractions? |
isotonic contractions in which tension is maintained in a muscle, but the opposing resistance is great enough to cause the muscle to increase in length. |
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As a result of extreme muscle fatigue, muscles occasionally become incapable of either contracting or relaxing- a condition called |
physiological contracture |
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why is Physiological contracture caused? |
Due to lack of ATP in muscle fibers. When ATP levels are low, active transport of Ca2+ into the sarcoplasmic reticulum slows, Ca2+ accumulate in the sarcoplasm, & ATP is unavailable to bind to the myosin molecules that have formed cross-bridges w/the actin myofilaments. So, the previously formed cross-bridges cannot release, causing Physiological Contracture. |
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Slow-twitch oxidative (SO) muscle fibers (type I fibers) |
contract more slowly, have a better-developed blood supply, have more mitochondria, and are more fatigue-resistant than fast-twitch muscle fibers. |
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The enzymes on the myosin heads responsible for the breakdown of ATP are called_____, which are broken down slowly by slow-twitch fibers. |
Myosin ATPase |
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what is the primary source for ATP synthesis in slow-twitch muscles? |
Aerobic respiration-which is enhanced by plentiful blood supply and the presence of numerous mitochondria |
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Fast-twitch muscle fibers (type II fibers).... |
respond rapidly to nervous stimulation, & their myosin heads have a fast form of myosin ATPase, which allows the rapid breakdown of ATP. This allows the cross-bridges to release & form more rapidly. |
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Muscles containing a high percentage of fast-twitch fibers have a..... |
less-well-developed blood supply than muscles containing a high percentage of slow-twitch muscle fibers. Fast-twitch fibers have very little myoglobin & fewer & smaller mitochondria. |
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Fast-twitch muscle fibers have large deposits of______ and are well adapted to perform______. |
glycogen, anaerobic respiration. |
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what are the 2 forms of fast-twitch muscle fibers? |
Type IIa, or fast-twitch oxidative glycolytic fibers (FOG), which rely on both anaerobic and aerobic ATP production. Type IIb, or fast-twitch glycolytic fibers (FG), which almost exclusively rely on anaerobic glycolysis for ATP production. |
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what are the largest diameter fibers in men and women? |
Women- type I alone, or in conjunction with type IIa. Men- type IIa |