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2/20 quiz LEC
muscle tissue - 2/20 quiz LEC
| Question | Answer |
|---|---|
| Muscle Tissue Functions (3) | Movement, Posture, Heat Production |
| Skeletal Muscle Tissue type is | Connective Tissue (Fibrous) |
| CT types found in skeletal tissue (3) | Epimysium, Perimysium, Endomysium |
| Epimysium, Perimysium, Endomysium combine to form | tendon that combines with periosteum of bone |
| Epimysium | surrounds entire muscle |
| Perimysium | surrounds muscle fiber bundles |
| Endomysium | surrounds each muscle fiber |
| the merging of the tendon and periosteum of bone is | strong bond, slow to heal |
| muscle cells are called | muscle fibers (myofibers) |
| within each muscle cell we have (5) | sarcolemma, sarcoplasm, sarcoplasmic reticulum, transverse tubules (T tubules), myofibrils |
| sarcolemma | cell membrane |
| sarcoplasm | cytoplasm |
| sarcoplasmic reticulum | smooth ER with dilaetd sacs called terminal cristernae which contain calcium ions |
| transverse tubules (T tubules) | extensions of the sarcolemma that run perpendicular to the sarcolemma |
| myofibrils | small fibers within the myofiber |
| each myofibril consists of | a series of repeating sarcomeres, the basic unit of contraction |
| sarcomeres | the basic unit of contraction |
| sarcomeres run from | Z line to Z line |
| Sarcomeres consist of | alternating A (dark) and I (light) bands |
| In the center of the A band | is a slightly lighter H zone |
| when the muscle (sarcomere) contracts (4) | 1. the Z lines come closer 2. the I band gets smaller 3. the H zone disappears 4. the A band remains the same |
| the I band components must slide over the A band components | Sliding Filament Theory |
| thin filaments | extend from the Z lines. Make up the I band and A band, which is exclusive of the H zone |
| Thin filaments are made up of | Proteins: Actin, Tropomyosin, Troponin |
| Actin | globular proteins that possess a myosin binding site |
| Tropomyosin | strands that cover the myosin binding site on the actin |
| Troponin | located at regular intervals on the tropomyosin |
| Thick Filaments | make up the A band |
| Thick filaments are made up of | myosin: club-shaped protein |
| Thick filaments possess a | cross-bridge (head) |
| cross-bridge (head) consist of | an actin-binding site and an ATP binding site |
| During contraction, a nerve impulse causes | synaptic vesicles in the motor axon end bulbs to release acetylcholine by exocytosis |
| During contraction, the impulse does not simply "jump" from neuron to muscle. What happens? | ACh diffuses across the synaptic cleft within the NMJ and initiates an impulse that spreads over the surface of the sarcolemma. |
| the impulse enters the T tubule and | stimulates the sarcoplasmic reticulum to open channels to release calcium ions from storage into the sarcoplasm |
| calcium ions combine with | the tropinin which changes shape. This causes the troponin-tropomysoin complex to move, thus exposing the myosin binding sites on the actin |
| the cross bridge is energized with | energy from an ATP |
| the actin binding site combines with | the myosin binding site |
| the cross bridge then uses its energy to | Powerstroke: bend the bridge which pulls the actin along (sliding filament) |
| the sliding draws the z lines | closer together thus shortening the sarcomere and the muscle |
| ATP binds with the | ATP binding site thus breaking the bridge and energizing the bridge for another power stroke |
| once the impulses stop, | calcium ions are actively transported back to the sarcoplasmic reticulum. |
| To relax the muscle | It takes ATP |
| The (high or low?) calcium ion concentration in the sarcoplasm allows | low. the tropomyosin/troponin complex to cover the myosin binding sites. Myosin cross bridges seperate from the actin. |
| sarcomeres return to their resting lengths | and the muscle relaxes |
| Neuromuscular Junction (NMJ) | the joining of a nerve cell (neuron) and a muscle cell. No physical contact. Only one per muscle. |
| Motor end plate | region of the sarcolemma adjacent to the neuron terminal |
| the neuron terminal contains | vesicles filled with neurotransmitter |
| the motor end plate contains | many neurotransmitter receptors |
| the space between the neuron and the muscle fiber | cleft |
| a nerve impulse causes | calcium ions channels to open allowing calcium to enter the axon. This somehow causes the vesicles to fuse with the neuronal membrane releasing the neurotransmitter, ACh, into the cleft |
| ACh combines with | the receptor sites and alters the membrane's permeability to Na and K ions (ie generates an impulse on the muscle membrane) |
| ACh in inactivated by the | sarcolemma protein, no acetylcholinesterase (AChE). As a result, ACh no longer affects the NMJ |
| curare | drug that acts as competitive inhibitor with acetylcholine |
| botulinum toxin | a toxin from a bacterium that prevents the release of ACh |
| Myasthenia gravis | an autoimmune disease that destroys the muscle Ach receptors. Causes muscle weakness, not life threatening |
| autoimmune disease | diseases whereby we produce antibodies that attack our own tissues |
| idiopathic | unknown cause |
| motor unit | the motor neuron and all the muscle fibers it stimulates |
| motor unit range | 10 (precision) to 2000 (gross) fibers per unit |
| ALL-OR-Nothing Principle | When a muscle fiber* contracts, it contracts all-the-way given the same starting point. (gun trigger) |
| all muscle fibers of a given unit will | contract all the way |
| recruitment | increasing the number of active motor units. Brain does this. Thus, more muscle strength of contraction |
| muscle tone | minimum number of motor units that are always active. Enough to make the muscle tense, but not enough to produce movement. more active=more active units |
| 100 motor units and 50 fibers/unit = | 5000 fibers/muscle |
| flacid | cut the *NMJ |
| twitch | single muscle response to a single stimulus |
| twitch consists of (3) | latent period, period of contraction, period of relaxation |
| tetanus | a sustained contraction in response to frequent stimuli |
| refractory period | a period of time following a stimulus whereby the muscle fiber loses its excitability and connot respond to another stimulus. refuses to respond |
| wave summation | occurs when a stimulus is applies AFTER the refractory period but the muscle has not completely relaxed. The second wave adds on to the first. different starting points. |
| incomplete tetanus | a sustained contraction in response to high frequency stimuli but with attempts at relaxation. These are out everyday activities |
| complete tetanus | a sustained contraction (with no relaxation) in response to a very high frequency of stimulation. Perhaps seen when lifting an elephant. |
| isotonic contraction | Movement: muscle shortening with little increase in tension. Increases strength |
| isometric contraction | No Movement: minimal shortening with great increase in tension. 2 sets muscle contractions. increases size |
| how does length influence strength of a contraction | muscle fibers contract minimally when at optimal length, attained when muscle is slightly stretched. stregth of contraction reflects degree of overlap of the thick and thin filaments. over-stratching produces a decrease in the strength of a contraction |
| muscle fibers do NOT | undergo mitosis. Only size of the CELL gets larger or smaller |
| Atrophy | decrease in individual muscle cell size |
| Hypertrophy | increase in individual muscle cell size |
| immediate energy source for a contraction | ATP |
| ATP energy time for exercise | 5-6 seconds |
| after 15 seconds | glycolysis kicks in |
| 5-15 seconds | Phosphocreatine (PC): high energy molecule that replenishes ATP stores |
| ADP + PC ---> | ATP + C |
| Oxygen debt | build up of lactic acid - need O2 to get rid of pyruvic acid |
| Glycolysy (anaerobic provides | 2 ATP molecules/glucose.. |
| The Krebs Cycle (aerobic) provides | 36 ATPs/glucose. But it is limited by the availability of oxygen and NAD+ |
| during intense exercise,Krebs cycle | cant keep up |
| krebs cycle limitation is overcome by | catabolizing many molecules of glucose by glycolysis (anaerobic) |
| pyruvic acid begins to build up and is converted to | lactic acid (pain, fatigue) |
| lactic acid is disposed of by | the taking in of additional oxygen after exercise (heavy breathing). This build up of acid creates oxygen debt. Heavy breathing after exercuse pays back the debt. |
Created by:
la66
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