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44 Cards in this Set
- Front
- Back
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What are the three types of muscles? |
Smooth, skeletal, and cardiac |
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What is a voluntary muscle and an example of one? |
Consciously controlled and are innervated by somatic nerve fibers. (skeletal muscle- striated and voluntary) |
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What is an involuntary muscle and an example of one? |
Innervated by autonomic nerve fibers nd are not under conscious control. (cardiac- striated, smooth- non-striated) |
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What type of muscles are found in body organs like stomach, intestine, esophagus etc.
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Smooth |
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What is the main function or property of all types of muscles
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Contraction and relaxation |
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Is nerve stimulation required for smooth muscle contraction? |
Yes, self excitation. |
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What is the "self excitation" process of smooth muscles? |
Because smooth muscles are not stimulated by somatic nerve fibers and have their own pace makers that initiate a wave of depolarization to stimulate the cells for contraction. |
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What is ephatic conduction? |
Because the plasma membrane of smooth muscle cells are closely attached to each other (synctial connection), this creates a direct transmission of depolaraization wave from one cell to another. |
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What is the internal structure of skeletal muscle (muscle fiber - myofibrils - thick and thin myofilaments)
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Myofibrils make up the muscle and are made up of thick/thin filaments. Myosin- thick Actin- thin |
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Why do the skeletal muscle fibers appear to be striated?
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Arrangement of light/dark bands are due to the difference in density and overlapping of the thick (myosin) and thin (actin) filaments.
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Why are the smooth muscles less fatigue prone as compared to skeletal muscle fibers
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Because the Na+ and Ca++ channels operate very slowly and the process of myosin and actin molecules are slow as well. Only require 25% as much oxygen and energy in comparison. |
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Cardiac muscles have what type of properties (voluntary or involuntary; striated or unstriated)
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Involuntary, striated |
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Which muscle fibers have intercalated discs interposed at the gap junctions?
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Cardiac muscle |
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What is the pace maker of the cardiac muscles called?
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SA node |
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Why is the contraction time longer in cardiac muscle fibers?
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The action potential spreads through the cardiac muscle very slowly. This helps the heart to provide more time to pump blood out of ventricles and fill them up again. |
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What is I-band? |
The portion of skeletal muscle filament that is the lighter zone consisting of thin filaments only. |
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What is A-band? |
The portion of skeletal muscle filament that is the dark zone and consists of the overlapping of thick and thin filaments. |
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What is Z-line? |
The portion of skeletal muscle filament is the anchor line, one end of thin filament is attached to Z-line. |
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What is sarcomere? |
It is the segment of myofibril between the two Z-lines. Sarcomere is the structural and fundamental unit of contraction of a muscle fiber.
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What is the structural and functional unit of contraction of a striated muscle fiber?
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Sarcomere |
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Calcium ions (Ca++) are stored in which part of the skeletal muscle fiber?
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Sarcoplasmic reticulums |
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What is the neurochemical substance released at a neuromuscular junction?
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Acetylcholine |
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In skeletal muscle fibers, the action potential spreads through the t-tubules and reaches to the sarcoplasmic reticulums and causes what action?
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The release of Ca++ ions in sarcoplasm |
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Which ions are the most important for muscle contraction and relaxation?
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Ca++ |
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Name the two segments of a thick filament (Ultrastructure)
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HMM (Heavy Meromyosin) and LMM (Light Meromyosin) |
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Name the three components of a thin filament (Ultrastructure)
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G-actin, tropomyosin, and troponin |
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What are the steps of cross-bridging process? |
1. The Ca++ ions released by the sarcoplasmic reticulum attach to the troponin molecules. 2. This attachment brings the change in position of tropomyosin-troponin complex, moving it away from the binding sites to uncover them. 3. Now the heads of HMM molecules can attach to the binding sites on G-actin molecules. 4. As the heads of HMM attach to binding sites, they utilize the energy by converting the ATP into ADP. 5. As each head gets the energy, it makes a power stroke bending the arm, that moves the thin filament toward the center of sarcomere and that is called contraction. |
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Calcium ions bind to what part of the thin filament?
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Troponin |
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What is essential in order for a contracted muscle to relax?
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The Ca++ ions must be pumped back to the sarcoplasmic reticulum.
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What is the effect of organo-phosphate compounds on neuromuscular junction?
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Can cause inhibition of enzyme acetylcholinesterase at the synapse.
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What is the effect of curariform drugs on neuromuscular junction?
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Binds with the receptor sites of acetylcholine on muscle sarcolemma and does not allow the acetylcholine to depolarize the membrane (no action potential, no contraction).
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What is the effect of botulinum toxins on neuromuscular junction?
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Prevents the terminal knobs to release acetylcholine (no action potential, leads to muscle spasm).
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What are the sources of energy utilized by the muscle fibers for relaxation/contraction?
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ATP, creatine phosphate, glucose |
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What is the end product of glucose metabolism in presence of oxygen?
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38 ATP's |
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What will happen, if muscle contraction outstrips the mitochondria's ability to produce ATP's aerobically?
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In absence of oxygen, the pyruvic acid can not enter the kreb cycle. Instead it follows the anaerobic pathway. Now the pyruvic acid is converted into lactic acid. Excess lactic acid builds up rapidly bringing about muscle fatigue.
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What is tetany? |
A stage of maximum contraction, when a higher frequency of stimulation does not increase the tension of contraction.
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What is fatigue? |
The decreased work capacity of muscles due to lack of energy. No energy available for muscle contraction and relaxation. |
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What is rigor mortis? |
Extreme state of fatigue is called rigor mortis, when ATPs become completely depleted in the muscles. This stage is seen after death. |
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What is tone? |
It is the slight tension in the muscles due to continues transmission of nerve impulses from the spinal cord. This keeps the muscles active even during the resting stage.
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What are the characteristic features of Type I muscle fibers (Red Muscle Fibers)?
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Rich in myoglobin and blood supply and have plenty of mitochondrias but low in glycogen contents.
These muscles utilize krebs cycle (mitochondria) for energy (ATPs). Slow twitch and fatigue resistant (e.g. back muscle). |
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What are the characteristic features of Type II muscle fibers (White Muscle Fibers)?
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Rich in glycogen but are low in myoglobin, mitochondria and blood supply.
Due to limited oxygen supply, they mainly depend on glycolysis for ATP production. Have few mitochondria , therefore get less ATP from kreb cycle. Fast twitch and fatigue prone (e.g. thigh muscle). |
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What is isotonic contraction? |
When muscle length shortens on contraction. |
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What is isometric contraction? |
When muscle length does not shorten during contraction.
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What is myasthenia gravis? |
It is a disorder in canines that can causes megaesophagus by blocking acetylcholine receptors at the postsynaptic neuromuscular junction. |
