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Ch. 9: Muscles Notes
Chapter 9 Muscular System Notes Review
| Question | Answer |
|---|---|
| What are the three types of muscle tissue? | Smooth, Cardiac, Skeletal |
| Where is smooth muscle located? | Located in the walls of hollow organs and blood vessels |
| What does smooth muscle do? | Moves materials through organs and regulates blood flow |
| What does smooth muscle cell look like? | Cylindrical cells with pointed ends; Each cell is uninucleate |
| Is smooth muscle contraction voluntary or involuntary? | Involuntary |
| Where is cardiac muscle found? | The walls of the heart |
| What does cardiac muscle look like? | Fibers are uninucleated, striated, tubular, and branched |
| How do cardiac muscle fibers connect? | Fibers interlock at intercalated disks, which permit contractions to spread quickly throughout the heart |
| Is cardiac muscle contraction voluntary or involuntary? | Involuntary |
| How do nerves affect cardiac muscles? | Nerves affect heart rate and the strength of contraction |
| Where is skeletal muscle found? | Skeletal muscle is found throughout the body, attached to bones |
| Is skeletal muscle contraction voluntary or involuntary? | Voluntary |
| What are fascia? | Layers of dense connective tissue that hold a muscle in position |
| What is a tendon? | Connects muscle to bone; tough and cord-like |
| What are aponeuroses? | Sheets of connective tissue that connect to bone and other muscles; delicate, thin sheaths |
| What is epimysium? | Surrounds entire muscle |
| What is a fascicle? | Bundles of muscle fibers (cells) |
| What is perimysium? | Separates/surrounds the fascicles |
| What is endomysium? | Surrounds each individual muscle fiber |
| What is deep fascia? | Surrounds and penetrates muscle |
| What is subcutaneous fascia? | Lies just between the skin |
| What is a sarcolemma? | Plasma membrane |
| What is a sarcoplasm? | Cytoplasm |
| What is sarcoplasmic reticulum? | Similar to endoplasmic reticulum |
| What are myofibrils? | Protein strands running through the sarcoplasm; produces striations and sarcomeres |
| What is myosin? | Thick filaments; made up of two twisted strands with globular cross-bridges (heads) |
| What is actin? | Thin filaments; have binding sites for myosin attachment |
| What is sarcomere? | Functional unit of muscle cell; where the myofibrils join together |
| What are I bands? | Light bands of actin |
| What are Z band? | I bands are attached to them; sarcomere extends from one Z line to the next |
| What are A bands? | Dark bands of myosin |
| What is titin? | Attaches myosin to Z lines |
| What are transverse tubules? | Membranous channels, are invaginations of the sarcolemma; run between parts of the SR |
| What are motor neurons? | Control effectors (skeletal muscle); each skeletal muscle fiber is connected functionally to an axon of a motor neuron (they don't physically touch) |
| What is a synapse? | The space between the muscle fiber and the axon |
| What are neurotransmitters? | Chemicals released from the axon so that the nerve cell can communicate with the muscle cell |
| What is a neuromuscular junction? | Site where an axon and a muscle fiber meet/synapse; sarcolemma specializes to form a motor end plate |
| What is a motor unit? | Motor neuron and the muscle fiber it controls |
| What is acetylcholine (ACh) | Neurotransmitter that motor neurons use to control skeletal muscle |
| What are synaptic vesicles? | Store ACh in the distal end of the axon; ACh is released into the synaptic cleft when a nervous impulse reaches the end of the axon, it diffuses across the synaptic cleft and combines with the ACh receptors on the motor endplate of the muscle fiber |
| What is a muscle impulse? | Response of the muscle; an electrical signal like a nerve impulse |
| What does sarcoplasmic reticulum store? | SR is full of calcium ions due to a calcium pump |
| How do calcium ions respond to muscle impulses? | Calcium ions diffuse out of SR cisternae into the sarcoplasm |
| What happens to actin when a muscle is at rest? | Troponin-tropomyosin complexes block the binding sites on the actin molecules |
| How do calcium ions expose binding sites? | Calcium binds to troponin, changing its shape, which moves the troponin out of the way of the binding site |
| What are cross bridges? | Linkages formed between the myosin heads and the actin binding sites |
| Explain the sliding filament model of muscle contractions. | The sarcomere shortens; Z bands are pulled closer together; myosin and actin slide past each other; actin filaments move closer to the center of the sarcomere, myosin doesn't move; |
| Explain cross bridge cycling. | Myosin heads attach to the actin, pulls it towards the center of the sarcomere, release them, and reattach; ATP is needed for this to occur |
| What is acetylcholinesterase? | Enzyme that breaks down ACh; prevents a single nerve impulse from continuously stimulating a muscle fiber |
| What are the energy sources for contraction? | ATP, creatine phosphate, aerobic cellular respiration |
| Why do muscles have myoglobin? | To store myoglobin |
| What is oxygen debt? | Amount of oxygen necessary to metabolize lactic acid |
| What is muscle fatigue? | Loss of ability to contract |
| What causes muscle fatigue? | Accumulation of lactic acid, decreased blood flow, ion imbalances, etc. |
| What are cramps? | Sustained, painful, involuntary muscle contraction |
| What is heat? | Heat is a by-product of cellular respiration |
| What is a threshold stimulus? | The minimum strength which is required for muscles to respond to stimuli |
| What happens when the threshold stimulus is reaches? | Action potential is generated and a muscle impulse spreads along the muscle fiber, causing contraction |
| What is a twitch? | The contractile response of a single muscle fiber to a muscle impulse |
| What is a latent period? | Brief delay between the impulse and the contraction |
| What controls the force of a contraction? | The frequency at which individual muscle fibers are stimulated; how many fibers take part in the overall contraction of the muscle |
| What is sustained contraction? | The summation of individual twitches cause a prolonged response |
| What is tetanic contraction (tetanus)? | Sustained contraction without any relaxation |
| What is a motor unit? | A neuron and all the muscle fibers it stimulates |
| What are the four types of contractions? | Isotonic, concentric, eccentric, isometric |
| What is slow-twitch? | Since its oxidative, it is resistant to fatigue; red fibers (contains myofibril) |
| What is fast-twitch? | Since its glycolytic, it is fatigable; white fibers due to little myoglobin |
| What are the two major types of smooth muscle? | Multiunit smooth muscle and visceral smooth muscle |
| What is multiunit smooth muscle? | Muscle fibers act independently |
| What is visceral smooth muscle? | Composed of sheets of cells connected by gap junctions; act as a single unit |
| What is calmodulin? | A protein to activate actin-myosin contraction in smooth muscle |
| Describe smooth muscle fibers. | Cells elongated with tapering ends; one nucleus per cell |
| Describe cardiac muscle fibers. | Cells are striated, branching; have one nucleus; found only in the heart |
| What is an origin? | Immovable end of the muscle |
| What is a insertion? | Movable end of the muscle; pulled toward the origin |
| What is a prime mover/agonist? | Provides major force for movement |
| What is a synergist? | Assist the prime mover |
| What is an antagonist? | Resist the prime mover's action, cause movement in the opposite direction |
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