The Muscular System

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Health

12th

106 Terms

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Organs of the muscular system include:
Approximately 650 skeletal muscles, the heart, and organs containing smooth muscle like the stomach, bladder, blood vessels, etc.
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What are the functions of the muscular system?
Producing movement by contracting (shortening) and relaxing (elongating), maintaining posture, stabilizing joints, and generating heat
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What are the three types of muscles tissues?
Skeletal, cardiac, and smooth
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Skeletal and smooth are elongated and are called
Fibers
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Nonstriated; involuntary
Smooth Muscle
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Spindle-shaped with a single nucleus.
Smooth Muscle
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Contraction is slow and sustained.
Smooth Muscle
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Striated; Involuntary
Cardiac Muscle
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Found only in the heart.
Cardiac Muscle
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Branching cells joined by special junctions called intercalated discs.
Cardiac Muscle
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Contract slowly and in close coordination.
Cardiac Muscle
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Striated; Voluntary
Skeletal Muscle
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Contract rapidly and with great force, but tire easily and must rest after short periods of activity.
Skeletal Muscle
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Muscle fibers are bundled together to form a fascicle which is wrapped by the epimysium.
Skeletal Muscle
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Epimysia blend into strong tendons, which attach muscles indirectly to bones, cartilages, or connective tissue coverings. 
Skeletal Muscle
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Functions of skeletal muscle:
Maintains posture, stabilizes joints, and generates heat
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The 5 Golden Rules: 1st Rule
All skeletal muscles cross at least one joint
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The 5 Golden Rules: 2nd Rule
The bulk of a skeletal muscle lies proximal to the joint crossed
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The 5 Golden Rules: 3rd Rule
All skeletal muscles must have at least two attachments: the origin, and the insertion
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The 5 Golden Rules: 4th Rule
Skeletal muscles can only pull; they never push
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The 5 Golden Rules: 5th Rule
During a contraction, a skeletal muscle insertion moves toward the origin
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Point attached to the immovable or less movable bone
Origin
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Point attached to the movable bone
Insertion
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Large muscles consist of thousands of single _______ that are contractile units.
Muscle fibers (muscle cells)
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Muscle fibers are bound together by a connective tissue called __________.
Endomysium
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**__________** wrap around a bundle of muscle fibers.
Perimysium
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A bundle of muscle fibers is called a ________.
Fascicle
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Many fascicles are bound together by the _________.
Epimysium
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Epimysia blend into _______ which connect to bones, cartilages and other connective tissue coverings.
Tendons
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**______** covers the epimysium to cover the entire muscle and runs into the tendon.
Fascia
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The specialized plasma membrane of muscle cells.
Sarcolemma
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Long organelles filling the cytoplasm of muscle cells.
Myofibrils
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Contains only thin filaments called ______.
Actin
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A darker midline interruption of the light I band.
Z disc
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Contains entire length of thick filaments called ________.
Myosin
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Lighter central area of the dark A band.
H zone
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The center of the H zone
M line
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Smallest unit of a muscle fiber that contracts
Sarcomere
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What goes here?
What goes here?
Muscle
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What goes here?
What goes here?
Fascicles
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What goes here?
What goes here?
Muscle Fibers (Cells)
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What goes here?
What goes here?
Myofibrils
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What goes here?
What goes here?
Thick and Thin Filaments
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What is A?
What is A?
Tendon
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What is B?
What is B?
Epimysium
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What is C?
What is C?
Fascicle
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What is D?
What is D?
Muscle Fiber
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What is E?
What is E?
Sarcolemma
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What is F?
What is F?
Myofibril
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What is G?
What is G?
(A) Band
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What is H?
What is H?
(I) Band
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What is I?
What is I?
Sarcomere
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What is J?
What is J?
Thin (actin) myofilament
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What is K?
What is K?
Thick (myosin) myofilament
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Ability to receive and respond to a stimulus.
Irritability
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Ability to shorten when adequate stimulus is received.
Contractility
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Ability of muscle cells to be stretched.
Extensibility
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Ability of muscle cells to recoil and resume resting length after being stretched.
Elasticity
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Muscles shorten and contract as the actin and myosin interact through a crossbridge formation
Sliding Filament Theory
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Myosin heads attach to binding sites on the thin filaments forming a ___________.
Cross bridge
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When a muscle is relaxed, regulatory proteins called ______ __and__ _______ cover part of the actin that myosin needs to bind to, preventing it from forming a cross bridge.
Troponin, tropomyosin
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________are needed to bind to these regulatory proteins and change their shape and position on the actin. This Ca²⁺ is released from the _______.
Calcium ions, sarcoplasmic reticulum
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In order for the myosin heads to release, energy from ______________ is needed.
Adenosine Triphosphate (ATP)
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Without ATP, the myosin cannot release the actin so the muscle stays contracted
Rigor Mortis
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One motor neuron and all the skeletal muscle cells it stimulates.
Motor Unit
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Long, thread-like extensions of the neuron that reach the muscle cell and branch into axon terminals.
Axons
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Branches of axons that form junctions with the sarcolemma of a muscle cell to form neuromuscular junctions.
Axon Terminals
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Junctions between the nerve and muscle, specifically the motor neuron and sarcolemma, that contain vesicles filled with a chemical referred to as a neurotransmitter.
Neuromuscular Junctions
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Chemical released by nerve upon arrival of nerve impulse in the axon terminal.
Neurotransmitter
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The neurotransmitter that stimulates skeletal muscle.
Acetylcholine
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Although the nerve endings and the sarcolemma are very close, they never touch. This gap between them is filled with tissue fluid and is called the ___________.
Synaptic Cleft
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Naming Skeletal Muscles: Direction of muscle fibers
Rectus Femoris, Transversus Abdominis
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Naming Skeletal Muscles: Relative size of the muscle
Gluteus Maximus, Gluteus Medius
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Naming Skeletal Muscles: Location of the muscle
Temporalis, Frontalis
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Naming Skeletal Muscles: Number of origins
Triceps Brachii, Biceps Brachii
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Naming Skeletal Muscles: Location of the muscle’s origin and insertion
Sternocleidomastoid, Brachioradialis
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Naming Skeletal Muscles: Shape of the muscle
Trapezius, Deltoid
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Naming Skeletal Muscles: Action of the muscle
Flexor Carpals Ulnaris, Adductor Muscle
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Movement that decreases the angle of the joint and brings two bones closer together; typical of a hinge joint
Flexion
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Movement that increases the angle or distance between two bones or parts of the body; the opposite of flexion; typical of straightening elbow or knee
Extension
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Extensions beyond 180°
Hyperextension
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Movement of a bone around its longitudinal axis; common of ball-and-socket joints; example is moving the atlas around the axis (shaking your head “no”)
Rotation
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Movement of a limb away from the midline or median plane of the body
Abduction
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Movement of a limb towards the body midline; opposite of abduction
Adduction
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A combination of flexion, extension, abduction, and adduction; common of ball-and-socket joints; proximal end of bone is stationary, and distal end  moves in a circle
Circumduction
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Lifting the foot so that the superior surface approaches the shin (towards the dorsum)
Dorsiflexion
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Depressing the foot (pointing the toes); “planting” the foot toward the sole
Plantar Flexion
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Turning sole of the foot medially
Inversion
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Turning the sole of the foot laterally
Eversion
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Forearm rotates laterally so palm faces anteriorly; radius and ulna are parallel
Supination
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Forearm rotates medially so palm faces posteriorly; radius and ulna cross each other like an X
Pronation
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Moving the thumb to touch the tips of the fingers on the same hand
Opposition
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Muscle that has major responsibility for causing a particular movement
Primer Mover
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Muscles that oppose or reverse a movement
Antagonist
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Help prime movers by producing the same movement or reducing undesirable movements
Synergist
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Myofilaments are able to slide past each other during contractions, shortening the muscle and movement occurs.
Isotonic Contractions
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tension in the muscle increases due to myosin “spinning their wheels”; myosin is trying to slide, but the muscle is pitted against some immovable object ending in the muscle being unable to shorten or produce movement.
Isometric Contractions
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Continuous partial contractions of muscle fibers as a result of a staggered series of nerve impulses being delivered to different muscle cells.
Muscle Tone
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If the nerve supply is damaged, the muscle is no longer stimulated in this manner and loses tone, becomes paralyzed, and begins to _______: waste away.
Atrophy
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Result in stronger, more flexible muscles with greater resistance to fatigue thanks to an increase in the number of blood vessels; improves digestion and coordination
Aerobic (Endurance) Exercises