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Muscles
Anatomy/Physiology Chapter 6 - Muscles
| Term | Definition |
|---|---|
| Contractility | ability to shorten skeletal muscles with force |
| Excitability | capacity to respond to a stimulus |
| Extensibility | ability to be stretched |
| Elasticity | ability to recoil after muscles have been stretched |
| Epimysium | connective tissue sheath surrounding the skeletal muscle |
| Fascia | connective tissue located outside the epimysium; surrounds and separates muscles |
| Muscle Fasiculi | numerous visible bundles inside muscles |
| Perimysium | loose connective tissue surrounding the muscle fasiculi |
| Fibers | the fasiculi are composed of these single muscle cells |
| Endomysium | connective tissue sheath surrounding each fiber |
| Myofibrils | threadlike structure that extends from one end of the fiber to the other |
| Actin Myofilaments | thin; resemble two minute strands of pearls twisted together |
| Myosin Myofilaments | thick; resemble bundles if minute golf clubs |
| Sacromeres | basic structural and functional unity of the muscle |
| Z line | attachment site for actin |
| I band | light area on each side of the Z line that consists of actin |
| A band | extends the length of the myosin and is the darkest central region in each sacromere |
| H zone | light area in the center of each sacromere |
| M line | dark staining band anchored in the center of the sacromere |
| Resting Membrane Potentisl | charge difference across the membrane |
| Action Potential | brief reversal back of the charge |
| Motor Neurons | nerve cells that carry action potentials to skeletal muscle fibers |
| (Occipito)Frontalis | moves the eyebrows |
| Zygomaticus | used for smiling |
| Buccinator & Orbicularis Oris | used for kissing |
| axons | enter the muscles and branches |
| neuromuscular junction or synapse | each branch that connects to the muscle forms _____ near the center of the cell |
| motor unit | single motor neuron and all the skeletal muscle fibers it innervates |
| synaptic vesicles | secrete a neurotransmitter |
| postsynaptic terminal | muscle fiber |
| presynaptic terminal | enlarged nerve terminal |
| synaptic cleft | space between the presynaptic terminal and the postsynaptic terminal, or muscle cell |
| single muscle | many motor units form ____ |
| acetylcholine | neurotransmitter that diffuses across synaptic cleft and binds to the postsynaptic terminal causing change in the postsynaptic cell |
| acetylcholinesterase | enzymes that break down acetylcholine released into the synaptic cleft between the neuron and the muscle cell |
| sliding filament mechanism | sliding of actin myofilaments past myosin myofilaments during contraction |
| muscle twitch | contraction of an entire muscle in response to a stimulus that causes the action potential in one or muscle fibers |
| threshold | point in which the muscle fiber will contract maximally |
| all-or-none response | phenomenon of threshold |
| lag phase | time between application of the stimulus to a motor neuron and the beginning of a contraction |
| contraction phase | time of contraction |
| relaxation phase | time during which the muscles relax |
| tetany | condition in which the muscle remains contracted without relaxing |
| recruitment | increase in number of motor units being activated |
| adenosine triphosphate (ATP) | needed for energy for muscle contraction |
| ATP | produced in the mitochondria, short-lived and unstable, it degeneratesto the more stable ADP plus phosphate |
| ADP | more stable energy |
| creatine phosphate | high-energy molecules that muscle cells can store |
| anaerobic respiration | without oxygen |
| aerobic respiration | with oxygen and is more efficient |
| oxygen debt | 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 fatigue | results when ATP is used during muscle contraction faster than it can be produced in the muslce cells |
| two types of muscle contraction | isotonic, isometric |
| isometric (equal distance) | length of the muscle does not change, but the ampunt of tension increases during the contraction process |
| isotonic (equal tension) | the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes |
| muscle tone | refers to constant tension produced by muscles of the body for long periods of time |
| fast-twitch fibers | well adapted to perform anaerobic metabolism contract quickly |
| slow-twitch | contract more slowly and more resistant |
| origin(head) | most stationary part of the muscle |
| insertion | part of the muscle that undergoes the greatest movement |
| belly | located between the origin and the insertion |
| synergists | muscles that work together |
| antagonists | muscles that work opposite of each other |
| prime mover | in a group of synergists, it plays the major role |
| muslces | named according to location, direction, size, shape, etc. |
| muscles help what? | to produce heat essential for maintenance or normal body temperature |
| what is each muscle fiber? | single cylindrical cell containing several tissues |
| cytoplasm of each fiber is ____ | filled with myofibrils |
| myofibrils consist of... | two major protein fibers- actin myofilaments and myosin myofilaments |
| actin and myosin myofilaments form what? | highly ordered units called sarcomeres |
| meuromuscular junction | formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane |
| muscle contraction | occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten |
| during sliding filament mechanism... | H and I bands shorten, but the A bands do not change in length |
| if successive stimuli are given... | you get successive twitches that occur so frequently the muscle does not have time to fully relax |
| during period of inactivity | energy contained in ATP is used to synthesize creatine phosphate |
| points of attachment of the muscle | origin(head) and insertion |
| two characteristics of skeletal muscle | voluntary and are striated |
| outside of most cell membranes... | positively charged compared to the inside of the cell membrane, which is negatively charged |
| gastrocnemius | calf muscle |
| triceps brachii | back of the arm and flexes the arm |
| biceps brachii | front of the arm |
| quads | front of the thigh |
| hamstrings | back of the thigh |
| rectus abdominus | abs |
| buttocks | gluteus maximus |
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haleyskye96
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