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Chapter 6
Muscles
| Term | Definition |
|---|---|
| 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 | The ability to recoil to their original resting length after they have been stretched |
| Epimysium | Each skeletal muscle is surrounded by a connective tissue sheath |
| Fascia | Another connective tissue located outside the epimysium. It surrounds and separates muscles |
| Perimysium | Loose connective tissue that surrounds the fasciculi |
| Myofibrils | A threadlike structure that extends from one end of the fiber to the other |
| Fasciculi | Composed of numerous visible bundles |
| 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 | Actin and myosin myofilaments form highly ordered units called |
| Actin & myosin myofilaments | 2 major kinds of protein fiber |
| Sarcomere | Basic structural and functional unity of the muscle |
| one Z-line disc to another | Each sarcomere extends from |
| A banded appearance | Arrangement of actin and myosin give |
| Actin | Each Z-line is an attachment for |
| Myosin | The A band extends the length of the |
| A band | Darker, central region in each sarcomere |
| H-Zone | Light area in the center. Consists of only myosin |
| M line | Myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called |
| Positively charged | The outside of most cell membranes is |
| negatively charged | inside of the cell membranes |
| Resting membrane potential | The charge difference across the membrane is called |
| action potential | The brief reversal back of the charge |
| Motor neurons | nerve cells that carry action potentials to skeletal muscle fibers |
| Axons | enters the muscles and branch |
| neuromuscular junction | Each branch that connects to the muscle forms |
| synapse | Another word for neuromuscular junction |
| Motor unit | A single motor neuron and all the skeletal muscle fibers it innervates are called |
| neuromuscular junction | formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane |
| presynaptic terminal | enlarged nerve terminal |
| synaptic cleft | the space between the presynaptic terminal and the muscle cell is the |
| postsynaptic terminal | muscle fiber is the |
| synaptic vesicles | secrete a neurotransmitter. Each presynaptic terminal contains one |
| Acetylcholine | neurotransmitter |
| Sarcolemma | The acetylcholine diffuses across the synaptic cleft and binds to receptor molecules in the muscle cell membrane |
| Acetylcholinesterase | the acetylcholine released into the synaptic cleft between the neuron and the muscle cell is rapidly broke down by an enzyme |
| sliding filament mechanism | the sliding of actin myofilaments past myosin myofilaments during contraction |
| A Bands | do not change in length |
| H and I Bands | shorten |
| Muscle twitch | contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers |
| threshold | a muscle fiber will not respond to stimulus until that stimulus reaches a level called |
| all-or-none | phenomenon |
| lag phase | the time between application of a stimulus to a motor neuron and the beginning of a contraction |
| contraction phrase | the time of contraction |
| relaxation phase | time during which the muscle relaxes |
| tetany | where the muscles remains contracted without relaxing |
| recruitment | the increase in number of motor units being activated |
| Adenosine triphosphate | ATP |
| ATP | needed for energy for muscle contraction |
| ATP | produced in the mitochondria |
| ATP | short-lived and unstable. It degenerates to the more stable |
| ADP | adenosine diphosphate |
| ADP | plus phosphate |
| creatine phosphate | Can't stockpile ATP but can store another high-energy molecule |
| Anaerobic respiration | without oxygen |
| aerobic respiration | with oxygen (more efficient) |
| oxygen debt | amount of oxygen needed in chemical reactions to covert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells |
| Muscle fatigue | occurs after exercising our muscles strenuously for a long time |
| Flexion | movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones close together |
| extension | opposite of flexion, so it is a movement that increase the angle, or the distance, between two bones or parts of the body |
| rotation | movement of a bone around its longitudinal axis |
| abduction | moving a limb away from the midline, or median plane, of the body |
| adduction | opposite of abduction, so it is the movement of a limb toward the body midline |
| circumduction | combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints such as the shoulder |
| Frontalis | raises eyebrows |
| orbicularis oculi | blinks and closes eyes |
| orbicularis oris | closes and protrudes lips |
| temporalis | closes jaw |
| zygomaticus | raises corner of mouth |
| masseter | closes jaw |
| buccinators | compresses cheek as in whistling and sucking; holds food between teeth during chewing |
| sternocleidomastoid | flexes neck; rotates head |
| platysma | pulls corners of mouth inferiorly |
| pectoralis major | adducts and flexes humerus |
| rectus abdominis | flexes vertebral column |
| biceps brachii | flexes elbow and supinates forearm |
| triceps brachii | extends elbow |
| deltoid | abducts humerus |
| trapezius | extends neck and adducts scapula |
| latissimus dorsi | extends and adducts humerus |
| erector spinae | extends back |
| gluteus maximus | extends hip |
| soleus | plantar flexes foot |
Created by:
hale
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