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U2: Muscles

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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