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U2: Muscles
| Question | Answer |
|---|---|
| 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. |
| Types of muscle tissue | skeletal muscle, cardiac muscle, smooth muscle |
| Muscle fibers | what muscle cells are called because of their elongated, thread-like shape. |
| 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. |
| 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. |
| 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. |
| Skeletal muscle functions | produce movement, maintain posture, generate heat. |
| Connective tissue wrappings or skeletal muscle | epimysium, perimysium, endomysium |
| 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 |
| Perimysium | connective tissue wrapping around a bundle of skeletal muscle fibers/cells; such a bundle is called a fascicle. |
| Endomysium | connective tissue wrapping around a single skeletal muscle cell/fiber |
| Muscle attachments | origin and insertion; attach via strong fibrous connective tissue arranged in form of tendons or aponeuroses. |
| Origin | attachment of a skeletal muscle that remains fixed/stationary/immobile when the muscle contracts |
| Insertion | moveable attachment of a skeletal muscle; in muscles of the limbs insertion lies distal to origin. |
| Prime mover/agonist | muscle that’s largely responsible for causing a given movement |
| Antagonist | muscle that opposes or reverses a particular movement produced by a prime mover/agonist; relaxed when a prime mover is contracted/shortened. |
| Synergists | help prime movers by producing the same movement or by reducing undesirable movement when a prime mover contracts. |
| Microscopic & Functional Anatomy of Skeletal Muscle Tissue | cells elongated and multinucleated, striated; have sarcolemma (plasma membrane) and sarcoplasm. |
| Sarcoplasm | cytoplasm of muscle cells/fibers. Contains myofibrils (train) which consists of sarcomeres (cars of train). |
| 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. |
| 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. |
| Skeletal muscle disorders | myasthenia gravis, muscular dystrophy |
| 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. |
| 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. |
| 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. |
| 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. |
| 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. |
| Fast oxidative fibers | intermediate in many characteristics in comparison to slow oxidative and fast glycolytic fibers. |
| 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 |
| 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 |
| Frontal belly of epicranius | overlies frontal bone; pulls scalp forward, furrows brow |
| Occipital belly of epicranius | overlies occipital bone; pulls scalp backward |
| Orbicularis oculi | surrounds anterior aspect of eye; closes eye, produces blinking and squinting |
| Orbicularis oris | encircles and forms core of lips; moves lips in a variety of ways, including puckering and closing; “kissing muscle” |
| Zygomaticus | origin is zygomatic bone; insertion skin at corners of mouth; draws corners of mouth upward; “smiling muscle” |
| 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 |
| 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. |
| 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 |
| Superior rectus | moves eyeball upward |
| Inferior rectus | moves eyeball downward |
| Medial rectus | moves eyeball medially (toward nose) |
| Superior oblique | helps rotate eyeball |
| Inferior oblique | helps rotate eyeball |
| Muscles that move mandible (lower jaw) | provide for mastication/chewing; masseter, temporalis |
| 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 |
| 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 |
| 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 |
| 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. |
| Pharyngeal constrictor muscle | after suprahyoid muscles; in wall of pharynx. Squeeze food inferiorly through pharynx and into esophagus |
| Infrahyoid muscles | after suprahyoid and pharyngeal; located below hyoid bone. Pull the hyoid and larynx inferiorly to resting positions as swallowing ends. |
| Muscles that move head and neck | sternoceidomastoid, splenius muscles |
| 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 |
| Splenius muscles | two muscles in posterior neck; lie deep to trapezius. Insertion-occipital bone; action-extend and hyperextend head |
| Muscles that move vertebral column & neck | erector spinae/sacrospinalis |
| 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! |
Created by:
mbtrimm
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