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Muscles Anatomy
| Question | Answer |
|---|---|
| 4 Major functional characteristics | Contractility, Excitability, Extensibility, Elasticity |
| the ability of skeletal muscle to shorten with force | contractility |
| the capacity of skeletal muscle to respond to a stimulus | Excitability |
| the ability to be stretched | extensibility |
| ability to recoil to their original resting length after they have been stretched | elasticity |
| each skeletal muscle is surrounded by a connective tissue sheath called the | epimysium |
| another connective tissue located outside the epimysium. It surrounds and separates muscles | fascia |
| A muscle is composed of numerous visible bundles called muscle fasciculi (fascicle), which are surrounded by loose connective tissue called the | perimysium |
| The fasciculi are composed of single muscle cells called | fibers |
| Each muscle fiber is a single cylindrical cell containing several | nuclei |
| Each fiber is surrounded by a connective tissue sheath called the | endomysium |
| The cytoplasm of each fiber is filled with | myofibrils |
| a threadlike structure that extends from one end of the fiber to the other | myofibrils |
| Myofibrils consist of 2 major kinds of protein fibers | actin myofilaments, myosin myofilaments |
| thin myofilaments. They resemble 2 minute strands of pearls twisted together | actin myofilaments |
| thick myofilaments. They resemble bundles of minute golf clubs | myosin myofilaments |
| Actin and myosin myofilaments form highly ordered units called | sarcomeres |
| sarcomeres | joined end to end to form the myofibril |
| is the basic structural and functional unit of the muscle | the sarcomere |
| Each Z line is an attachment site for | actin |
| The arrangement of actin and myosin give a | banded appearance |
| On each side of the Z line is a light area called an I band, it consists of | actin |
| The A band extends the length of the myosin. It is the darker central region in each | sarcomere |
| In the center of each sarcomere is another light area called the | H-zone |
| The H-zone | consists of only myosin |
| The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the | M-line |
| The outside of most cell membranes is positively charged compared to the inside of the | cell membrane |
| The cell membrane is | negatively charged |
| The charge difference across the membrane is called the | resting membrane potential |
| When a muscle cell is stimulated the membrane characteristics change | briefly |
| The brief reversal back of the charge is called | action potential |
| Motor neurons | nerve cells that carry action potentials to skeletal muscle fibers |
| axons enter the | muscles and branch |
| Each branch that connects to the muscle forms a | neuromuscular junction |
| synapse | near the center of the cell |
| A single motor neuron and all the skeletal muscle fibers it innervates are called a | motor unit |
| Many motor units form a | single muscle |
| A neuromuscular junction is formed by an | enlarged nerve terminal |
| rests in an indentation of the muscle cell membrane | enlarged nerve terminal |
| the enlarged nerve terminal is the | presynaptic terminal |
| the space between the presynaptic terminal and the muscle cell is the | synaptic cleft |
| the muscle fiber is the | postsynaptic terminal |
| Each presynaptic terminal contains | synaptic vesicles |
| synaptic vesicles | secrete a neurotransmitter called acetylcholine |
| It diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell | acetylcholine |
| When an action potential reaches the nerve terminal, it causes the synaptic vesicles to releases acetylcholine into the synaptic cleft by | exocytosis |
| The acetylcholine diffuses across the synaptic cleft and binds to receptor molecules in the muscle cell membrane | sacrolemma |
| causes an influx of sodium ions into the muscle fiber | The combination of acetylcholine with its receptor |
| This influx initiates an action potential in the muscle cell, which causes it to | contract |
| The acetylcholine released into the synaptic cleft between the neuron and muscle cell is rapidly broken down by an enzymes | acetylcholinesterase |
| When the sarcomeres shorten it causes the muscle to | shorten |
| Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten | muscle contraction |
| The sliding of actin myofilaments past myosin myofilaments during contraction is called the | sliding filament mechanism |
| The H and I bands shorten, but the A bands do not change in | length |
| muscle twitch | a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers |
| A muscle fiber will not respond to stimulus until that stimulus reaches a level called | threshold |
| threshold | at which point the muscle fiber will contract maximally |
| This phenomenon is called the | all-or-none response |
| The time between application of a stimulus to a motor neuron and the beginning of a contraction is the | lag phase |
| The time of contraction is the | contraction phase |
| The time during which the muscle relaxes is the | relaxation phase |
| tetany | where the muscle remains contracted without relaxing |
| 10. The increase in number of motor units being activated is called | recruitment |
| needed for energy for muscle contraction | ATP(adenosine triphosphate) |
| produced in the mitochondria | ATP |
| short-lived and unstable | ATP |
| It degenerates to the more stable | ADP(Adenosine diphosphate) |
| It is necessary for muscle cells to constantly produce | ATP |
| When at rest they can’t stockpile ATP but they can store another high-energy molecule, called | creatine phosphate |
| without oxygen | anaerobic respiration |
| with oxygen (more efficient) | aerobic respiration |
| oxygen debt | the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells |
| muscle tone | Muscle tone refers to constant tension produced by muscles of the body for long periods of time. Keeps head up and back straight |
| fast-twitch fibers | contract quickly and fatigue quickly. Well adapted to perform anaerobic metabolism. Ex. white meat of a chicken’s breast |
| slow-twitch fibers | contract more slowly and are more resistant to fatigue. They are better suited for aerobic metabolism. Ex. dark meat of a duck’s breast or the legs of a chicken). |
| Muscles that work together to accomplish specific movements are called | synergists |
Created by:
ammille13
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