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Muscular System
Muscular System Review Sheet
| Term | Definition |
|---|---|
| Tendons attach muscles to? | bones |
| Muscles do what? | contract or shorten |
| Circular layer | decreases diameter of tube or organ when contracted |
| Longitudinal layer | decreases length of tube or organ when contracted |
| Endomysium | surrounds each muscle fiber |
| Perimysium | surrounds each fascicle |
| Fascicle | a bundle of muscle fibers |
| Epimysium | surrounds each muscle |
| Tendons | epimysia blend into strong, cord-like tendons that attach muscle to bone |
| Origin | the muscle attachment to the immovable bone |
| Insertion | the muscle attachment to the movable bone (when the muscle contracts, the insertion moves towards the origin) |
| Sarcolemma | muscle cell membrane |
| Sarcoplasmic reticulum | stores calcium ions needed for contracton |
| Myofibrils | long, ribbon-like fibers of a muscle cell |
| Myofilaments | threadlike proteins in the myofibril (actin & myosin) |
| Sarcomeres | the functional unit of muscle fibers; contractile unit |
| Myosin | thich myofilament |
| Actin | thin myofilament |
| Irritability | the ability to receive and respond to a stimulus |
| Contractility | the ability to shorten |
| Producing Movement | locomotion, manipulation and facial expression are the primary functions of skeletal muscles |
| Maintaining Posture | holds body upright against gravity, stabilizes joints, maintains balance |
| Moving Substances | cardiac and smooth muscles are responsible for transporting substances like blood or food from one part of the body to another |
| Generating Heat | heat is a by-product of muscle activity, helps maintain body temperature |
| Muscles cross with how many joints? | At least one joint (with a few exceptions) |
| The bulk of the muscle is usually proximal to what? | the joint crossed |
| All muscles have at least what? | two attachments |
| Muscles can only pull but they can't? | push |
| During contraction, what does the muscle insertion do? | moves towards the origin |
| Define motor unit | One motor neuron and all the skeletal muscle cells it stimulates |
| Describe the neuromuscular junction | * The synapse where the neuron and muscle cell meet * The end of each motor neuron branches into axon terminals *Each axon terminal forms a junction with the sarcolemma of a muscle cell |
| Discuss the role of acetylcholine | *it is the neurotransmitter responsible for muscle contraction * stored in vesicles in the axon terminal *released into the synapse when a nerve impulse reaches the axon terminal *diffuses across the synaptic cleft to bind with receptors on sacrolemma |
| An ? is an electrical current generated by the "upset" or change in charge across the muscle cell membrane or sarcolemma | action potential |
| The result of this electrical impulse traveling from one end of the cell to the other is ? of the muscle cell | contraction |
| A single nerve impulse produces only ? contraction because ACh is broken down by ? to prevent continued contraction of the muscle cell | 1 ; acetylcholinesterase |
| The ? pump helps the cell return back to its resting state | sodium-potassium |
| When muscle fibers are activated by the nervous system, the ? attach to binding sites on the thin filaments | myosin heads |
| Energy is provided by ? so that each crossbridge (myosin head link to actin) attaches and detaches several times during a ? pulling each thin filament toward the center of the ? | ATP ; contraction ; sacomere |
| This event occurs simultaneously in sarcomeres throughout the cell, causing the entire muscle cell to? | shorten |
| The attachment of myosin crossbridges to actin requires ? which is stored in and released by the? | calcium ions ; sarcoplasmic reticulum |
| When the action potential ends, calcium ions are immediately reabsorbed into the SR storage areas, and the muscle cell ? and return to its original ? | relaxes ; length |
| Defined fused tetanus | Successive contractions are added together to produce a smooth, sustained contraction |
| What does the "all-or-none" law state? | When stimulated adequately, the muscle cell will contract to its fullest extent; it never partially contracts |
| List the two ways in which graded muscle contractions can be produced | 1. By changing the frequency of muscle stimulation 2. By changing the number of muscle cells being stimulated |
| What factor determines how forcefully a muscle contracts? | * The number of muscle cells that are stimulated * Fewer cells are stimulated when you are move a pen compared to when you swing a baseball bat |
| Describe muscle fatigue and its cause | * Occurs when the muscle becomes unable to contract * Caused by oxygen debt |
| Compare and contrast isotonic and isometric contractions | * Isotonic contractions occur when the muscle shortens and movement occurs * Isometric contractions occur when the muscles do not shorten; no movement occurs |
| How does regular exercise affect muscles? | Increases muscle size, strength, and endurance |
| Describe the results of aerobic exercise on muscles | Muscles become stronger, more flexible, and develop greater resistance to fatigue |
| Describe the results of resistance or isometric exercise on muscles | Muscles increase in size and strength; new filaments are made |
Created by:
DanariaW