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Physiology Ch. 10
Skeletal Muscle Contraction and Smooth Muscle
| Term | Definition |
|---|---|
| ______ and _______ hold Ca2+ in sarcoplasmic reticulum. | Calmodulin, calsequstrin |
| Troponin | Protein that binds with Ca2+. When not bound, forces troponin to stay in place and inhibit actin-myosin bonding. |
| Actin | Thin filaments. Shorten with contraction. Has globular (G) kinds and stranded (F) together to form the whole structure. |
| Myosin | Thick filaments, has heads that bind to actin. Capable of hydrolyzing ATP for energy for muscle contraction |
| Myoglobin | Muscle version of hemoglobin |
| Triad | T-tubule and 2 terminal cisternae of sarcoplasmic reticulum |
| Connectin | Extends from Z disc to M line, stabilizes thick filaments with spring-like tension. |
| Distrophin | Anchors myofibrils to sarcolemma proteins. Abnormalities cause muscular dystrophy. |
| What is the optimal length of the sarcomere? | Length of noncontractile portion (A Band; thick filament length) |
| What are 3 ways muscle generate ATP, as they do not store much? | Creatine phosphate (Pi molecules to add to ADP), glycolysis, aerobic cellular respiration |
| Lactate formation | During low O2 levels. This formation arises from conversion of pyruvate molecules, and irritates your muscles. |
| Fast twitch fibers | Fibers that contract more powerfully, quicker but briefer. Are in high amounts in athletes like football players (fast changes in direction) |
| Slow twitch fibers | Fibers that contract longer and slower. For endurance |
| Oxidative fibers | Allows contraction for longer. Aerobic respiration occurs in these, and appear red. Ex: erector spinae |
| Tropomyosin | Rope along actin that inhibit binding with myosin heads |
| What are the 3 types of fibers? | Slow oxidative, fast oxidative, fast glycotic fibers |
| What are the 3 periods of twitch? | 1. Latent phase- diffusing of ions before action potential 2. Contraction phase- power stroke 3. Relaxation phase |
| Frequency-tension relationship | The higher the frequency, the higher the tension |
| Summation | Increase in muscle tension from successive action potentials during phase of mechanical activity. |
| Recruitement | With greater force on muscle, more fibers join to contract and press against it. Also called multiple motor unit summation |
| Muscle tone | Resting tension in a muscle. A few fibers in every muscle are contracted at all times, resulting in this. |
| Isometric contraction | Holding a weight while arm doesn't move. Muscle length stays the same. |
| Isotonic contraction | Muscle tension overcomes resistance resulting in movement. Tone is constant, muscle length changes. Can be concentric or eccentric |
| Concentric contraction | Type of isotonic contraction, where muscle shortens |
| Eccentric contraction | Type of isotonic contraction, where muscle lengthens. |
| Cross-bridge cycle of contraction | 1. Myosin heads attach to actin, forms cross bridge. 2. Pi generated in previous cycle released, initiating power stroke. Myosin pulls actin to M line, ADP released. 3. New ATP attaches to myosin head, myosin detaches. 4. ATP splits, myosin is "charged" |
| Cross-bridge cycling continues as long as ___ and ___ are present. | Ca2+, ATP |
| Length-tension relationship | Tension produced depends on its length at time of stimulation. Resting = max contractile force Shortened length and longer length = weaker force |
| What length of muscle allows for the greatest contractile force to be produced? | Resting. |
| Muscle fatigue | Decline in muscle tension as result of previous contractile activity. Due to lack of ATP, as well as increased acidity due to lactic acid production affecting enzymes. |
| Endurance exercise leads to: | Better ATP production (more mitochondria) |
| Resistance exercise leads to: | Hypertrophy. Muscle increases in size because of more contractile proteins and greater glycogen |
| Atrophy | Decrease in muscle size due to lack of use |
| Fibrosis | Muscle mass often replaced by dense ct |
| In contraction, the ______ remains the same size, and the ____ and _____ disappear. | A band, H zone, I band |
| Phasodilation | Bigger lumen for more blood to flow through |
| Phasoconstriction | Done via smooth muscle, lumen of blood vessels constricts to increase pressure and lessen blood flow. |
| Where is smooth muscle located? | Walls of arteries and veins, arrector pili muscle, GI tract, walls of bronchi in resp. tract. |
| Smooth muscle is controlled by: | ANS |
| Circular layer | Innermost layer of smooth muscle that is responsible for constricting. When it contracts, organ elongates and lumen constricts. |
| Longitudinal layer | Outer layer of smooth muscle that shortens. When contracted, organ shortens and lumen dilates |
| Peristalsis | Smooth muscle propelling substances through lumen |
| Smooth muscle forms ____ and _____, which exhibit _____ action. | sheets, layers, synchronized |
| Smooth muscles have ____ innervation from both ____ and ____ divisions of ANS. | dual, sympathetic, parasympathetic |
| Aspects of smooth muscle: | Spindly shaped w/ big central nucleus. Has no troponin or sarcomeres (no Z line, H band, etc.). Filaments are arranged diagonally to the long axis of muscle, with caveolae and gap junctions along it. |
| Caveolae | Motor end plate for smooth muscle cell |
| Smooth muscle gets calcium from ____ instead of sarcoplasmic reticulum. Uses _____ as Ca2+ channels. | ECF, gap junctions |
| Smooth muscle has more ____ and less ____ than skeletal muscle cells. | Actin, myosin. |
| Myosin light-chain kinase (MLCK) | Ca2+ regulated enzyme that phosphorylates myosin during cross-bridge cycling in smooth muscle cells |
| Steps of smooth muscle contraction (overview) | Ca2+ enters -> binds to calmodulin -> calmodulin nudges MLCK to charge ATP -> ATP can now bind to myosin head -> myosin binds to actin -> power stroke |
| Calmodulin | Smooth muscle molecule similar to tropomyosin in skeletal muscle |
| Rate of removal of Ca2+ from cytosol of smooth muscle cell is ____ than in skeletal muscle. | Slower |
| Myogenic response | Contraction in reaction to stretch |
| Stress-relaxation response | Relaxation after prolonged stretch |
| Syncytium | Group of cells working together and linked |
| Unitary tissues | Smooth muscle cells that are electrochemically linked to a single syncytium |
| Single unit muscle cells go through synchronous activity because: | They are linked by gap junctions, so molecules can flow between them. |
| Multi-unit muscle cells have ____ gap junctions. | No/few |
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RunningMads
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