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anatomy/physiology
study guide chapter 6
| Term | Definition |
|---|---|
| contractility | ability of skeletal muscle to shorten with force |
| excitability | capacity of skeletal muscle to respond to a stimulus |
| extensibility | ability to be stretched |
| elasticity | ability to recoil to their original resting length after they have been stretched. |
| epimysium | connective tissue sheath that surrounds the skeletal muscle. |
| Fascia | another connective tissue located outside the epimysium that surrounds and separates muscles. |
| perimysium | loose connective tissue that surrounds fascicle |
| muscle fasciculi | numerous visible bundles that the muscles are composed of. |
| fibers | single muscle cells that the fasciculi are composed of. |
| endomysium | connective tissue sheath that surrounds fibers |
| myofibrils | threadlike structure that extends from one end of the fiber to the other |
| actin myofilaments | thin myofilaments |
| myosin myofilaments | thick myofilaments |
| sarcomeres | 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 sarcomere. |
| H zone | light area in the center of each sarcomere |
| M line | dark staining band anchored in the center of the sacromere |
| resting membrane potential | change difference across the membrane |
| action potential | the brief reversal back of the charge |
| Motor neurons | nerve cells that carry action potentials to skeletal muscle fibers |
| axons | enter the muscles and branches |
| neuromusclular junction or synapse | each branch that connects to the muscle froms ____ near the center of the cell |
| motor unit | single motor neuron and all the skeletal muscle fibers it innervates |
| single muscle | many motors unit form ___ |
| presynaptic terminal | enlarged nerve terminal |
| Synaptic cleft | space between the presynaptic terminal and the muscle cell. |
| postsynaptic terminal | muscle fiber |
| synaptic vesicles | secrete a neurotransmitter |
| acetylcholine | neurotransmitter that diffuses across synaptic cleft and binds to the postsynaotic terminal causing change in the postsynaptic cell. |
| acetylcholinesterase | enzymes that break down acetylcholine released into the synaptic cleft between the neuron and 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 more muscle fibers. |
| threshold | point in which the muscle fiber will contract mazimally |
| all-or-none response | phenomenon of threshold |
| lag phrase | time between applicatin of the stimulus to a motor neuron and the beginning of a contraction |
| `contraction phase | time of contraction |
| relaxation phase | time during which the muscle relaxes |
| tetany | where the muscle remains contracted without relaxing. |
| recruitment | increase in number of mototr units being activated |
| adenosine triphosphate (ATP) | needed for energy for muscle contraction |
| ATP | produced in the mitochondria, short-lived and unstable, it degenerates to the more stable ADP plus phosphate. |
| ADP | more stable enegry |
| 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 muscle cells |
| two types of muscle contractions | Isometric Isotonic |
| Isometric (equal distance) | length of the muscle does not change, but the amount of tension increases during the contraction process |
| Isotonic (equal tension) | the amount of tension produced by the muscle in 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. (Keeps head up and back straight) |
| fast-twithch fibers | Well adapted to perform anaerobic metabolism. contract quickly and fatigue guickly. (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 (Dark meat of a duck's breat; legs of a chicken) |
| origin | the most stationary end of the muscle. (head) |
| insertion | end of the muscle undergoing the greatest movement |
| belly | portion of muscle between the origin and the indertionsynergists |
| synergists | muscles that work together to accomplish movements |
| antagonists | muscles that work in opposition to one another |
| prime mover | among a group of synergists, if one muscle plays the major role in accomplishing the desired movement, it is the _____ |
| Muslces | named according to their location, size, orientation of fibers, shape, origin, insertion, and function, etc. |
| Muscles help what? | to produce heat essential for maintenance or normal body tempeature |
| What is each muscle fiber? | single cylindrical cell containing several tissue |
| Cytoplasm of each fiber is__ | filled with myofibils |
| Myofibrils consist of ? | to major protein fibers -actin myofilaments -myosin myofilaments |
| Actin and Myosin myofilaments from what? | highly ordered units called sarcomeres |
| neuromusclular 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 each muscle | origin and insertion |
| two characteristics of skeletal Muscle | -Four Major Functional Characteristics -Structure |
| outside of most cell membranes is... | positively charged compared to the inside of the cell memeberane, which is negatively charged. |
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