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Muscles Terms
| Question | Answer |
|---|---|
| contractility | the ability of skeletal muscle to shorten with force. |
| excitability | the capacity of skeletal muscle to respond to a stimulus. |
| extensibility | the ability to be stretched. |
| elasticity | ability to recoil to their original resting length after they have been stretched. |
| epimysium | connective tissue sheath surrounding skeletal muscle. |
| fascia | connective tissue located outside the epimysium. It surrounds and separates muscles. |
| perimysium | Surrounds muscle fascicles. |
| fascicles | bundles of muscle tissue. |
| endomysium | surrounds each muscle fiber (cell). |
| muscle cells | muscle fibers |
| myofibrils | a threadlike structure that extends from one end of the fiber to the other. |
| actin myofilaments | thin myofilaments. They resemble 2 minute strands of pearls twisted together. |
| myosin myofilaments | thick myofilaments. They resemble bundles of minute golf clubs. |
| sarcomeres | units formed by Actin and myosin myofilaments which are joined end to end to form the myofibril. basic structural and functional unit of the muscle. |
| Z line | borders of sarcomeres. attachment site for actin. |
| cause of banded appearance of muscles | arrangement of actin and myosin |
| I band | On each side of the Z line is a light area, [term]. Consists of actin. |
| A band | extends the length of the myosin. It is the darker central region in each sarcomere. |
| H zone | In the center of each sarcomere is another light area called the [term], which consists of only myosin. |
| M line | The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the [term]. |
| resting membrane potential | The outside of most cell membranes is positively charged compared to the inside of the cell membrane, which is negatively charged. The charge difference across the membrane is called the [term]. |
| action potential | When a muscle cell is stimulated the membrane characteristics change briefly. The brief reversal back of the charge is called [term]. |
| motor neurons | nerve cells that carry action potentials to skeletal muscle fibers. |
| synapse | neuromusclular junction |
| neuromusclular junction | Axons enter the muscles and branch. Each branch that connects to the muscle forms a [term]. formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane. |
| motor unit | single motor neuron and all the skeletal muscle fibers it innervates. |
| presynaptic terminal | enlarged nerve terminal. |
| synaptic cleft | space between the presynaptic terminal and the muscle cell. |
| postsynaptic terminal | the receiving part of the connection (synapse) between two nerve cells (neurons). muscle fiber. |
| synaptic vesicles | vesicles that secrete a neurotransmitter called acetylcholine |
| acetylcholine | neurotransmitter which causes muscle contraction. |
| acetylcholinesterase | enzyme that breaks down acetylcholine. |
| Muscle Contraction | Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten. When the sarcomeres shorten it causes the muscle to shorten. |
| sliding filament mechanism | The sliding of actin myofilaments past myosin myofilaments during contraction. The H and I bands shorten, but the A bands do not change in length. |
| threshold | point at which stimulus becomes strong enough for muscle to respond by contracting maximally. This phenomenon is called the all-or-none response. |
| lag phase | The time between application of a stimulus to a motor neuron and the beginning of a contraction. |
| contraction phase | The time of contraction. |
| relaxation phase | The time during which the muscle relaxes |
| Tetany | where the muscle remains contracted without relaxing. |
| recruitment | The increase in number of motor units being activated. |
| ATP | (adenosine triphosphate) is needed for energy for muscle contraction. |
| mitochondria | produces atp |
| ADP | (adenosine diphosphate) plus phosphate. what atp degenerates into. |
| creatine phosphate | more stable high energy molecule stored in muscles. |
| 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 fatigue | results when ATP is used during muscle contraction faster than it can be produced in the muscle cells. |
| isometric | (equal distance) – the 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 is constant during contraction, but the length of the muscle changes. |
| 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). |
| origin | (head) is the most stationary end of the muscle. |
| insertion | the end of the muscle undergoing the greatest movement. |
| belly | The portion of the muscle between the origin and the insertion. |
| synergists | Muscles that work together to accomplish specific 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. |
| Occipitofrontalis | raises the eyebrows. |
| Orbicularis oculi | closes the eyelids and causes “crows feet” wrinkles in the skin at the lateral corners of the eye. |
| Orbicularis oris | puckers the lips. |
| Buccinator | flattens the cheeks. Trumpeter’s muscle. Orbicularis oris and buccinator are the kissing muscles. |
| Zygomaticus | smiling muscle. |
| Levator labii superioris | sneering |
| Depressor anguli oris | frowning |
| Mastication | chewing |
| 4 pairs of mastication muscles | 2 pair of pterygoids, temporalis, and masseter. |
| Intrinsic Tongue Muscles | change the shape of the tongue. |
| Extrinsic Tongue Muscles | move the tongue. |
| Sternocleidomastoid | lateral neck muscle and prime mover. Rotates and abducts the head |
| Erector spinae | group of muscles on each side of the back. Responsible for keeping the back straight and the body erect. |
| Thoracic Muscles | muscles that move the thorax |
| External intercostals | elevate the ribs during inspiration |
| Internal intercostals | contract during forced expiration. |
| Diaphragm | accomplishes quiet breathing. Dome-shaped muscle. Aids in breathing. |
| Trapezius | rotates scapula |
| Serratus anterior | pulls scapula anteriorly |
Created by:
onjarre
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