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A&P Lecture 6
Muscle tissue, muscular system
| Term | Definition |
|---|---|
| Types of muscle tissue | skeletal, cardiac, smooth |
| Muscular system | includes only skeletal muscles |
| Function of skeletal muscles | produce skeletal movement, maintain body position, support soft tissues, guard openings, maintain body temperature, store nutrient reserves |
| Structures in skeletal muscle | muscle fibers, connective tissues, nerves, blood vessels |
| Three layers of connective tissue within muscles | epimysium, perimysium, endomysium |
| Epimysium | an exterior collagen layer connected to deep fascia; separates muscle from surrounding tissues |
| Perimysium | connective tissue that surrounds fascicles; contains blood vessel and nerve supply to fascicles |
| Fascicle | a bundle of muscle fibers |
| Endomysium | connective tissue that surrounds individual muscle fibers, and contains capillaries and nerve fibers contacting muscle cells; also contains myosatellite cells that repair damage |
| Myosatellite cell | a muscle stem cell |
| Muscle attachment | connective tissue at the end of muscles made of the combined epimysium, perimysium, and endomysium that forms a connective tissue attachment to the bone matrix, either as a tendon or an aponeurosis |
| Tendon | bundle of connective tissue that attaches muscle to bone matrix |
| Aponeurosis | sheet of connective tissue that attaches muscle to bone matrix |
| Function of nerves in the muscular system | connect muscles to the central nervous system, allowing voluntary control |
| Nomenclature of skeletal muscles | a descriptive name followed by a location name |
| Function of blood vessels in the muscular system | form an extensive vascular network that supplies nutrients and large amounts of oxygen, and carries away waste products |
| Properties of skeletal muscle fibers | are very long; develop through fusion of myoblasts; contain hundreds of nuclei |
| Myoblast | mesodermal stem cell that forms skeletal muscle cells |
| Sarcolemma | cell membrane of a muscle fiber; maintains transmembrane potential to allow contractions |
| Sarcoplasm | cytoplasm of a muscle fiber |
| T tubule | transverse tubule; transmits action potential through the muscle fiber; allows entire fiber to contract simultaneously, and has same properties as the sarcolemma |
| Myofibril | lengthwise subdivision within muscle fiber made up of myofilaments |
| Myofilament | a protein filament responsible for muscle contractions |
| Types of myofilaments | thin filaments made up of actin; thick filaments made up of myosin |
| Sarcoplasmic reticulum | membranous structure surounding each myofibril that helps transmit action potential and forms terminal cisternae attached to the T tubule; similar structure to smooth endoplasmic reticulum |
| Terminal cisterna | concentrates calcium ions via ion pumps, and releases them into sarcomeres to begin muscle contraction |
| Triad | internal structure of a muscle fiber formed by one T tubule and two terminal cisternae |
| Sarcomere | contractile unit of muscle that forms the structural unit of a myofibril, and forms visible patterns within the myofibril |
| Muscle striations | a pattern of light (I band) and dark (A band) filaments within myofibrils |
| A band | a dark, thick filament within the myofibril |
| I band | a light, thin filament within the myofibril |
| M line | the center of the A band, at the midline of the sarcomere |
| Z line | the center of the I band, at the ends of the sarcomere |
| Zone of overlap | the darkest area visible in the myofibril, where the A and I bands overlap |
| H band | area around the M line that has thick filaments but no thin filaments |
| Titin | a strand of protein that reaches from the tips of the thick filaments to the Z line, stabilizing the filaments |
| Function of sarcomeres | contracts when calcium ions released by the sarcoplasmic reticulum cause the thin and thick filaments to interact |
| Four proteins of thin filaments | F-actin, nebulin, tropomyosin, troponin |
| Mnemonic for remembering thick and thin filaments | the "tin" in actin corresponds to the thIn filaments, which look lIght and form the I band; the A band looks dArk |
| Types of fascicle organization | parallel, convergent, pennate |
| Types of attachment sites for convergent muscles | tendon, aponeurosis, raphe |
| Types of pennate muscles | unipennate (extensor digitorum), bipennate (rectus femoris), multipennate (deltoid) |
| Sphincter | circular muscles that open and close to guard entrances of the body |
| Orbicularis oris | the muscle that closes and opens the mouth |
| Orbicularis oculis | the muscle that closes and opens the eye |
| Lever | rigid, moving structure |
| Fulcrum | fixed point |
| Three functions of levers | changes direction of applied force, distance and speed of movement, effective strength of applied force |
| First-class lever | fulcrum is in the center between the applied force and the resistance; for example, nodding yes |
| Second-class lever | centers resistance between fulcrum and applied force, to move a large weight with a small force; for example, tiptoeing |
| Third-class lever | centers applied force between resistance and fulcrum, to maximize speed and distance traveled; for example, flexion of the elbow |
| Types of muscle functions | agonist, antagonist, synergist, fixator |
| Agonist muscle | produces a particular movement |
| Antagonist muscle | opposes movement of a particular agonist |
| Synergist muscle | smaller muscle that assists a larger agonist |
| Fixator muscle | stabilizes point of attachment of an agonist muscle |
| Only two muscles without the word "muscle" in their correct names | platysma, diaphragm |
| Platysma | flat muscle of the lower jaw |
| Diaphragm | umbrella-shaped muscle that separates the thoracic and abdominal cavities |
| Ways muscles are named | location in the body, origin and insertion, fascicle organization, relative position, structural characteristics, action |
| Muscles of the eye | six extrinsic muscles (sclera), two intrinsic |
| Six extrinsic muscles of the eye | superior rectus, medius rectus, inferior rectus, lateral rectus, superior oblique, inferior oblique |
| Intrinsic muscles of the eye | ciliary, iris |
| Ciliary muscle of the eye | controls the shape of the lens to focus vision |
| Iris muscle | controls the size of the pupils |
| Divisions of the muscular system | axial (60% of muscles), appendicular (40%) |
| Six muscle groups of the head and neck | facial expression, extrinsic eye muscles, mastication, muscles of the tongue, muscles of the pharynx, anterior muscles of the neck |
| Process of initiating contraction | Ca2+ ion binds to receptor on troponin molecule; troponin-tropomyosin complex changes, expressing the active site of F-actin |
| Sliding filament theory | thin filaments slide along thick filaments toward the M line at the center of the sarcomere; width of the A zone stays the same, Z lines move closer together |
| Five steps of the contraction cycle | exposure of active sites; formation of cross-bridges; pivoting of myosin heads; detachment of cross-bridges; reactivation of myosin |
| Process of relaxation | Ca2+ concentrations fall; Ca2+ ions detach from troponin; active sites are re-covered by tropomyosin; tension gradually falls to resting levels; titin proteins recoil after stretching |
| Neuromuscular junction | location of neural stimulation; action potential causes release of neurotransmitters into the synaptic cleft |
| Action potential | electrical signal that travels along the nerve axon and ends at synaptic terminal |
| Synaptic terminal | part of the neuron that releases acetylcholine into the synaptic cleft |
| Acetylcholine | neurotransmitter that transmits action potential from a motor neuron to a muscle fiber by binding to membrane receptors on the sarcolemma, making it more permeable to sodium ions |
| Synaptic cleft | gap between the synaptic terminal and motor end plate, where acetylcholine is released by the neuron and attaches to the motor end plate |
| Motor end plate | portion of the sarcolemma that receives acetylcholine |
| Cardiac muscle tissue | striated muscle tissue found only in the heart, notable for containing intercalated discs |
| Intercalated discs | specialized contact points between cardiocytes made up of gap junctions and desmosomes that enhance molecular and electrical connections and conduct action potentials |
| Smooth muscle tissue | nonstriated tissue with different functional characteristics from skeletal muscle; causes involuntary movement in the body, mainly in the cardiovascular (regulating blood pressure and flow), digestive (peristalsis, sphincters), and integumentary systems |
| Muscles of the shoulders and upper limbs | position the pectoral girdle, flex and extend the shoulder and elbow, abduct and adduct the shoulder, and rotate the shoulder |
| Muscles that position the pectoral girdle | trapezius, rhomboid, levator scapulae, serratus anterior, subclavius, pectoralis minor |
| Muscles that abduct the shoulder | deltoid (agonist), supraspinatus (synergist) |
| Muscle that adducts the shoulder | coracobrachialis |
| Muscles that rotate the shoulder | subscapularis and teres major (medial), infraspinatus and teres minor (lateral) |
| Muscle that extends the shoulder | latissimus dorsi |
| Muscle that flexes the shoulder | pectoralis major |
| Muscles of the rotator cuff | supraspinatus, subscapularis, infraspinatus, teres minor |
| Muscles that flex the elbow | biceps brachii (agonist), brachialis and brachioradialis (synergists), triceps and anconeus (antagonists) |
| Muscles that extend the elbow | triceps brachii (agonist), anconeus (synergist), biceps and brachioradialis (antagonists) |
| Muscles that move the thigh | gluteal, lateral rotators, adductors, iliopsoas |
| Gluteal muscles | gluteus maximus, gluteus medius and minimus, tensor fasciae latae |
| Lateral rotators of the thigh | piriformis, obturator |
| Adductors of the thigh | adductor magnus, adductor brevis, and adductor longus; pectineus, gracilis |
| Hip flexors | psoas major, iliacus |
| Extensors of the knee | four muscles of the quadriceps femoris |
| Quadriceps femoris | vastus medialis, vastus intermedius, and vastus lateralis; rectus femoris |
| Flexors of the knee | hamstring |
| Hamstring muscles | biceps femoris, semitendinosus, semimembranosus |
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ekolmus
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