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63 Cards in this Set
- Front
- Back
Muscles |
Distinguished by their ability to transform chemical energy (ATP) into directed mechanical enregy. In doing so, they become capable of exerting force |
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- Can send an action potential - Can contract - Can stretch |
Characteristics of muscle tissue (3) |
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Skin (Epidermis & Dermis) Hypodermis (Adipose tissue & superficial fascia {another layer of loose fatty connective tissue}) Deep Fascia (Dense regular connective tissue) |
To get to the muscle we must get through 3 layers |
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Fascicles Muscle Fibers Myofibrils Myofilaments |
Muscle is an organ composed of ____________, which are made of _____________, which are made of ___________________, which are made of _________________. |
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Fascicles |
Bundle of Muscle Fibers (Cell) |
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Muscle Fibers |
Made up of myofibrils, |
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Myofibrils |
Contain the contractile elements of skeletal muscle cells, the sarcomere, which contain even smaller rod like structures called of myofilaments |
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Myofilaments |
Filaments of myofibrils, constructed from proteins, principally myosin or actin |
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Actin: Thin filaments Myosin: Thick filaments |
Myofilaments (2 types) |
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Endomysium |
What is the membrane that encloses individual muscle fascicles? |
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Perimysium |
What is the membrane that encloses all the muscle fascicles in a muscle? |
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Epimysium |
What is the membrane enclosing the skeletal muscle? |
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Sarcomere |
Region of a myofibril between two successive Z discs - Smallest contractile unit of a muscle fiber - the functional unit of skeletal muscle - Contains an A band flanked by half an I band at each end |
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Sarcolemma |
Analogous to the Cell membrane, but of the skeletal muscle fiber |
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Sarcoplasm |
Analogous to Cytoplasm of a muscle cell - Contains unusually large amounts of glycosomes (stored glycogen granules) and myoglobin (red pigment that stores oxygen) |
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Sarcoplasmic Reticulum |
- Analogous to Endoplasmic Reticulum - Surround each myofibril - Stores calcium and releases it on demand for muscle contraction |
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Striations Think MHAIZ |
Arrangement of myofilaments in the cell into sarcomeres, dark A bands and light I bands - Each dark A band has a lighter region in the middle called H zone) - Each H zone is bisected vertically by dark line called M line formed by myomesin proteins - Each light I bind also has midline interruption, darker area called Z disc |
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I Band |
- Region with Actin filaments only, with Z disc in middle - Thus appears "lighter" |
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H Band |
- Region in the Middle of A Band, contains vertical M line - Consists of thick filaments |
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A Band |
- Region of sarcomere with Thick and thin filaments with the vertical M line in the middle - Thus appears "darker" |
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Tropomyosin Troponin |
2 Types of regulatory proteins holding actin in place |
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Tropomyosin |
- Rod-like protein that spirals about the acting core to help stiffen and stabilize it - Block myosin-binding sites on actin |
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Troponin |
- Globular protein on the actin filament that binds calcium ions |
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Titin |
- Elastic filament composed of a giant protein that extends from Z disc to the thick filament myosin, then runs within the thick filament to attach to M line - Helps muscle spring back into shape after stretching |
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Myosin |
- Thick type of myofilament with the ability to break down ATP - Ability to pivot - Ability to attach to actin - Extend entire length of A band, connected in the middle of the sarcomere at the M line |
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Actin |
- Thin filaments extend across the I band and part way into A band, Z band anchors the thin filaments |
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T-Tubule |
At each A band, I band junction, the sarcolemma of the muscle protrudes deep into the cell interior, forming an elongated tube vertically - Increase the muscle fiber's surface area - Conduct impulses to the deepest regions of the muscle cell and every sarcomere for the release of calcium |
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Sliding filament theory |
- Action potential down sarcolemma - Calcium release - Calcium binds to troponin - Twists tropomyosin off binding sites - Myosin binds to actin - Myosin heads (cross bridges) ratchet - Sarcomere shortens Describes what theory? |
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- I Bands shorten - Distance between Z disc shortens - H zones disappear - A bands move closer together, but length does not change |
When muscle cell contracts, what are the 4 things that happen along the sarcomere? |
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Path of action potential |
- Calcium binds to and enters the synaptic bulb of motor neuron - Acetylcholine released into synaptic cleft - Acetylcholine binds to acetylcholine receptors - Action potential sent across sarcolemma and down T-tubules - This occurs because Na+ which is normally outside cell gets pumped into cell membrane - Changes to more positively charged inside membrane and this charge travels down - This action potential then triggers Calcium release from sarcoplasmic reticulum which diffuses into cell and acts further in muscle contraction |
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Excitation of Muscle Cell |
- Nerve signal arrives at synaptic bulb - Calcium enters synaptic bulb through voltage gated calcium channels - Acetylcholine released from synaptic bulb by exocytosis - ACH binds to ligand (chemically) gated ion channels at sarcolemma, channels change shape and open - Na diffuses in, K diffuses out - Causes voltage change inside sarcolemma - Voltage gated ion channels open - more Na comes in - Action potential, muscle fiber excited - Action potential travels along sarcolemma down T-tubules - Voltage gated ion channels in T-tubules open and calcium channels in sarcoplasmic reticulum open - Calcium rushes into cytosol of muscle cell |
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After calcium release |
- Calcium binds to troponin - Causes tropomyosin to change position - Myosin binding sites are exposed on actin - Myosin heads attach, thus contraction occurs - After, calcium goes back into sarcoplasmic reticulum (ATP required) |
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Calcium Pump (Into sarcoplasmic reticulum) Na/K Pump Kinking of myosin head |
ATP is required for 3 processes in the muscle fiber/cell? |
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- Anaerobic & Aerobic Pathways - Stored glycogen in cell |
ATP comes from? (2) |
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Muscles at rest |
- Minimal ATP needed - Excess ATP will donate phosphate to creatine - CREATINE PHOSPHATE formed - Held in reserve for use later |
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High muscle activity Anaerobic |
- Not enough oxygenated cells - Glycogen in sarcoplasm breaks down to glucose - Glucose into Pyruvic acid and 2 ATPs formed in the process - Pyruvic acid turns into lactic acid - Creatine phosphate donates phosphate to ADP forming ATP - Used for quick, powerful contractions - Muscle fatigues quickly |
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Moderate activity Aerobic |
- Enough oxygen in cells stored by the protein myoglobin - Glycogen to Glucose to Pyruvic acid (2 ATPs made) - Pyruvic acid to Mitochondria to 34 ATPS - Used for longer periods of contraction - No fatigue |
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Anaerobic Pathway to create ATP |
- Creatine phosphate + ADP => Creatine + ATP - Glucose broken down to 2 Pyruvic acid molecules (releasing 2 ATP per glucose), then during no oxygen, converts to lactic acid |
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Aerobic Respiration |
Glucose + O2 => CO2 + H2O + ATP Provides about 32 ATP per glucose, but slower process than anaerobic |
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Fast glycolytic fibers |
- Most muscles fibers are these - Large diameter - No myoglobin - White color - Anaerobic ATP production - Quick powerful contraction, short-term intense |
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Slow oxidative fibers |
- Fibers are smaller in diameter - Lots of Myoglobin - Red color - Aerobic ATP production - Longer contraction for endurance |
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Type I (slow-oxidative) Fibers |
- Fiber color: Red
- ATPase activity: Low - Contraction speed: Slow - Glycolytic enzymes: Low - Mitochondrial content: Packed - Fatigue resistance: High - Vascularization: Extensive |
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Type IIa (fast-oxidative) Fibers |
- Fiber color: Red -Motor unit size: 2-6 fibers - ATPase activity: High - Myoglobin content: High - Glycolytic enzymes: Intermediate |
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Type IIb (fast-glycolytic) Fibers |
- Fiber color: White - Vascularization: Average -Motor unit size: 2-6 fibers - ATPase activity: High - Contraction speed: Fast - Fatigue resistance: Low - Myoglobin content: Low - Mitochondrial content: Sparse |
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Motor Unit |
1 motor neuron and all of the muscle fibers it innervates |
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Change the number of motor units stimulated |
How do we vary the degree of contraction? |
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Small Motor Unit |
- Motor neuron controls only 5-6 muscle fibers - Allows precise control - Ex: Eye and finger muscles |
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Large Motor Unit |
- Motor neuron controls 1000-2000 muscle fibers - Less precise control - Ex: Leg muscle |
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Muscle Tone |
- Due to spinal reflexes that activate first one group of motor units and then another in response to activated stretch receptors in the muscles - Motor units "switching" on and off |
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Hypertrophy |
- Muscle cells enlarge - More myofibrils |
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Atrophy |
- Smaller muscle cells |
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Muscle Twitch |
- Motor unit's response to a single action potential of its motor neuron |
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Myogram |
- "Picture" of the contraction of a motor unit - Typically depicts three phases Period of Contraction Period of relaxation |
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Wave Summation / Incomplete Tetanus |
- More than one stimuli are delivered to a muscle in rapid succession, the second twitch will be stronger than the first, because it occurs before the muscle has completely relaxed - Contractions are added together |
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Complete Tetanus |
- Sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate - Reaches maximal tension, all evidence of muscle relaxation disappears and contractions fuse into smooth, sustained contraction plateau |
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Treppe |
- The graduated series of increasingly vigorous contractions that results when a corresponding series of identical stimuli is applied to a rested muscle—called also staircase effect, staircase phenomenon Ex: Lifting small weights repeatedly |
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Isometric Contraction |
When weight applied and tension increases: - Muscle length is constant - Because Weight exceeds muscle's maximal tension - Ex: Carrying a bag of groceries |
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Isotonic Contraction |
When weight applied and tension increases: - Muscle length shortens - Ex: Lifting an object, running |
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Cardiac Muscle |
Characteristics: Branched cells, intercalated disks (Gap junctions, desmosomes) Sarcomeres: Yes Motor Neurons: No (Involuntary) Energy Source: Lactic acid Role of calcium: Yes Tetanus: No, contractile strength increases with degree of stretch |
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Cardiac Muscle |
Sarcomeres: Yes Motor Neurons: No (Involuntary) Energy Source: Lactic acid Role of calcium: Yes Tetanus: No, contractile strength increases with degree of stretch |
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Smooth Muscle |
- Dense bodies anchor actin filaments instead of tropomyosin, tethered to sarcolemma, act like Z discs of skeletal muscle - No T-tubules, only caveolae - Underdeveloped sarcoplasmic reticulum - Calmodulin in cytosol regulates calcium instead of troponin - Lattice-like intermediate filaments |
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Caveolae |
Pouch like in foldings containing large number of Ca2+ channels, allowing Calcium influx more so than the underdeveloped sarcoplasmic reticulum in the smooth muscle fiber |
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Stripes |
When describing muscle, what does "striated" mean? |