U2: Muscles
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| Muscle Tissues | all produce some kind of body movement when it contracts and shortens; have contractile protein myofilamants actin and myosin. Prefixes myo- and sarco-; many mitochondria, well vascularized.
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| Types of muscle tissue | skeletal muscle, cardiac muscle, smooth muscle
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| Muscle fibers | what muscle cells are called because of their elongated, thread-like shape.
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| Skeletal muscle tissue | packaged in skeletal muscle organs; usually attached to bones via tendons; facial muscles are attached to skin. Cells multinucleated & striated, contain myofibrils, sarcomeres, sarcoplasmic reticulum; voluntary muscle controlled by somatic motor system.
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| Cardiac muscle tissue | found only in heart; composes thick myocardium. Cells striated & in branching chains, contain myofibrils, sarcomeres, sarcoplasmic reticulum. Ends of cells=intercalated discs in which gap junctions are located. Pumping action of heart. Involuntary.
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| Smooth muscle tissue | in walls of hollow internal organs; Aka visceral muscle b/c of location. Cells=non-striated. Provide contractions to help propel stuff in tubular organs; food thru digestive tract, bowels, urinary bladder, baby delivery. Involuntary.
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| Skeletal muscle functions | produce movement, maintain posture, generate heat.
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| Connective tissue wrappings or skeletal muscle | epimysium, perimysium, endomysium
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| Epimysium | sheath of connective tissue around an entire skeletal muscle; its connective tissue extends beyond a skeletal muscle either in form of cord like tendon or broad, sheet-like aponeurosis
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| Perimysium | connective tissue wrapping around a bundle of skeletal muscle fibers/cells; such a bundle is called a fascicle.
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| Endomysium | connective tissue wrapping around a single skeletal muscle cell/fiber
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| Muscle attachments | origin and insertion; attach via strong fibrous connective tissue arranged in form of tendons or aponeuroses.
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| Origin | attachment of a skeletal muscle that remains fixed/stationary/immobile when the muscle contracts
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| Insertion | moveable attachment of a skeletal muscle; in muscles of the limbs insertion lies distal to origin.
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| Prime mover/agonist | muscle that’s largely responsible for causing a given movement
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| Antagonist | muscle that opposes or reverses a particular movement produced by a prime mover/agonist; relaxed when a prime mover is contracted/shortened.
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| Synergists | help prime movers by producing the same movement or by reducing undesirable movement when a prime mover contracts.
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| Microscopic & Functional Anatomy of Skeletal Muscle Tissue | cells elongated and multinucleated, striated; have sarcolemma (plasma membrane) and sarcoplasm.
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| Sarcoplasm | cytoplasm of muscle cells/fibers. Contains myofibrils (train) which consists of sarcomeres (cars of train).
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| Sarcomere | basic unit of contraction in skeletal muscle; portion of myofibril between two consecutive z discs. Composed of thin actin filaments and thick myosin filaments.
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| Sarcoplasmic reticulum | organelle in skeletal muscle cell that releases calcium ions upon stimulation; calcium ions allow for interaction between myosin cross bridges and actin filaments required for contraction.
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| Skeletal muscle disorders | myasthenia gravis, muscular dystrophy
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| Myasthenia gravis | autoimmune disease; attack of immune system against acetylcholine receptors on the sarcolemma of skeletal muscle cells; causes progressive loss of normal stimulation of skeletal muscles causing weakness over time.
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| Muscular dystrophy | group of inherited diseases characterized by progressive deterioration and weakening of skeletal muscles. Involves defects in genes that are responsible for coding for proteins in sarcolemma of muscle cells.
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| Types of skeletal muscle fibers/cells | slow oxidative, fast glycolytic, fast oxidative; each skel. Muscle contains a mix of all three, so can perform different tasks at different times. Amount is genetically determined.
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| Slow oxidative fibers | aka red, slow-twitch fibers; contract slowly, produce ATP by aerobic means. Abundant myoglobin, large supply mitochondria, capillaries, resistant to fatigue, thin, not much contraction power. Posture muscles.
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| Fast glycolytic fibers | white, fast-twitch fibers; contract quickly, make ATP anaerobically via glycolysis; pale b/c little myoglobin; fewer mitochondria, fewer capillaries, less resistant to fatigue; more actin and myosin, larger diameter, powerful contractions. Arm muscles.
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| Fast oxidative fibers | intermediate in many characteristics in comparison to slow oxidative and fast glycolytic fibers.
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| Muscles of Facial Expression | insertion for these muscles is skin, innervation is facial nerve. Bell’s palsy is paralysis of facial muscles associated with dysfunction of the facial nerve
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| Epicranius | two-part muscle consisting of a frontal belly and an occipital belly connected by an aponeurosis which covers the superior part of the skull
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| Frontal belly of epicranius | overlies frontal bone; pulls scalp forward, furrows brow
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| Occipital belly of epicranius | overlies occipital bone; pulls scalp backward
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| Orbicularis oculi | surrounds anterior aspect of eye; closes eye, produces blinking and squinting
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| Orbicularis oris | encircles and forms core of lips; moves lips in a variety of ways, including puckering and closing; “kissing muscle”
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| Zygomaticus | origin is zygomatic bone; insertion skin at corners of mouth; draws corners of mouth upward; “smiling muscle”
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| Buccinator | horizontally oriented cheek muscle; compresses cheeks in ways that make blowing, whistling and sucking possible; holds food between teeth during chewing; well developed in nursing infants
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| Platysma | thin, sheet-like superficial anterior neck muscle; insertion is lower margin of mandible and skin at corner of mouth; tenses skin in anterior neck; pulls mandible and skin at edge of mouth downward.
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| Muscles that move the eyeball | 6 muscles per eyeball; insertion for all is the sclera (tough white part of eyeball); four of six of the muscles are innervated by oculomotor nerve
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| Superior rectus | moves eyeball upward
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| Inferior rectus | moves eyeball downward
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| Medial rectus | moves eyeball medially (toward nose)
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| Superior oblique | helps rotate eyeball
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| Inferior oblique | helps rotate eyeball
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| Muscles that move mandible (lower jaw) | provide for mastication/chewing; masseter, temporalis
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| Masseter | covers lateral aspect of mandibular ramus; bulging of it can be felt through skin when teeth are clenched; insertion is mandible; action is chewing, biting, elevates (closes) jaw
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| Temporalis | covers parts of temporal and parietal bones; bulging of it can be felt through scalp when teeth are clenched; insertion is mandible; action is masticating/chewing, biting, elevates (closes) mandible
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| Swallowing muscles | tongue & buccinator muscles squeeze food posteriorly thru mouth toward pharynx; throat/pharynx muscles contract in sequence- suprahyoid muscles, pharyngeal constrictor muscles, infrahyoid muscles
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| Suprahyoid muscles | above hyoid bone; pull hyoid & larynx superiorly & anteriorly. Moves laryngeal opening under protective flap (epiglottis) keeping food/fluid out of respiratory tract. Anterior mvmnt of hyoid bone widens pharynx to better receive food.
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| Pharyngeal constrictor muscle | after suprahyoid muscles; in wall of pharynx. Squeeze food inferiorly through pharynx and into esophagus
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| Infrahyoid muscles | after suprahyoid and pharyngeal; located below hyoid bone. Pull the hyoid and larynx inferiorly to resting positions as swallowing ends.
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| Muscles that move head and neck | sternoceidomastoid, splenius muscles
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| Sternoceidomastoid | in anterolateral surface of neck. Origins-sternum, clavicle. Insertion-mastoid process of temporal bone. Simultaneous contraction of both such muscles flexes head and neck; contraction of one alone rotates and tilts head
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| Splenius muscles | two muscles in posterior neck; lie deep to trapezius. Insertion-occipital bone; action-extend and hyperextend head
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| Muscles that move vertebral column & neck | erector spinae/sacrospinalis
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| Erector spinae/sacrospinalis | complex group of muscles deep in back on both sides of vertebral column; Action-extension of vertebral column and trunk; provide for erect posture; contracted one at a time=bending spine laterally. Lift with your legs!
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