Topic 11: Muscular System Flashcards
what are the basics of the muscular system?
-refers to skeletal muscle
-primarily attached to bone
-produce movement by contracting (shortening)
how do muscles work together?
-work in opposition to one another
what is skeletal muscle?
-made of cells called fibers
-fibers are arranged into fascicles
what are fascicles?
-groups of fibers
-the whole muscle is groups of fascicles
what is a fascia?
-a connective tissue covering that holds layers together
-surrounds muscles or other organs
what are the 3 layers of fascia?
-epimysium
-perimysium
-endomysium
what is the epimysium?
-outermost layer of fascia
-surrounds the entire muscle
what is the perimysium?
-middle layer of fascia
-surrounds fascicles
what is the endomysium?
-innermost layer of fascia
-surrounds each muscle fiber
what are tendons?
-extensions of the fascia layers
-anchors to bone (periosteum), cartilage, or fascia
-rope-like bundle of dense regular CT
-ex: calcaneal (achilles) tendon
what are aponeuroses?
-extensions of the fascia layers
-anchors to bone (periosteum), cartilage, or fascia
-flat sheet of dense regular CT
-ex: epicranial aponeurosis (scalp) (connects frontal and occipital bellies)
what is the structure of skeletal muscle fibers?
-large + long multinucleated cells
-sarcolemma (cell membrane)
-sarcoplasm (cytoplasm)
-myofibrils (intracellular structures)
-t-tubules
-sarcoplasmic reticulum
what are myofibrils?
-intracellular structures
-many to each muscle fiber
-composed of sarcomeres
what is the structure of sarcomeres?
-composed of proteins
-thin filaments
-thick filaments
what are thin filaments composed of? what are the functions of these proteins?
-actin
-tropomyosin (control contractions)
-troponin (control contractions)
how do contractions occur?
-globular heads of thick filaments will grab sites on the actin protein
-other proteins of the thin filament can obstruct this
what are thick filaments composed of? what is the function of this protein?
-myosin (functions in contraction)
-rod-like tails with 2 globular heads
-heads extend towards actin and attach to it during contraction (shortens the sarcomere)
where and how does myosin attach to the sarcomere?
-Z discs by the titin protein
what creates striations in the sarcomere?
-the different banding patterns of the sarcomere
-dark and light areas
what are the different banding patterns?
- A band
- H zone
- I band
- Z discs
- M line
what is the A band?
-extends to the whole length of the thick filament
-includes some thin filament
-dark band
-darker in the area containing thin filament proteins
-includes all sarcomere proteins
what is the H-zone?
-only myosin
-no thin filaments are present
-lighter band at the center of the A band
what is the I-band?
-only the thin filaments and z-discs between each new sarcomere
-produces a lighter band
what are Z-discs?
-at the end of each sarcomere
-connection points for other sarcomeres
-darkest striation in the center of the I-Band
what is the M-line
-where myosin tails attach to each other (center of the sarcomere)
-middle
what do sarcomeres join to form?
-myofibrils
-join end to end by z-discs
what are T-tubules?
-continuations of the sarcolemma that extend deep into the cell/fiber
-allows a close contact of extracellular fluid
what is the sarcoplasmic reticulum?
-smooth ER
what is a triad?
-T-tubule and 2 terminal cisternae (enlarged areas of the SR)
how do muscles produce movement?
-pull on bones (skin or other muscles too) when they contract
-bones allow for a certain range of motion
-using group action
-lever systems
what are the types of group action in muscle movement?
-agonist
-synergists
-antagonist
what is the origin point of a muscle?
-attachment of a tendon to the stationary bone
-not participating in physical movement
what is the insertion point of a muscle?
-attachment of a tendon to the moveable bone
-participates in movement
what is an agonist?
-major muscle producing a certain movement
what are synergists?
-helpers for the agonist action
-prevent undesirable motions
-stabilizers
what is an antagonist?
-produces the opposite action of the agonist
-contraction is inhibited when agonist contracts
-allow muscles to return to anatomical position
what are lever systems?
-bone/muscle interaction at a joint
-levers = bones (insertion bone)
-fulcrum = joint
-effort = contraction of agonist
-resistance = opposes movement
in a lever system, what must be greater to get movement?
-effort must be greater than resistance
will certain muscles always be agonists or antagonists?
-no they switch depending on the movement
in the flexion of the forearm while lifting a weight, what are all the different parts/roles?
-agonist = biceps brachii
-antagonist = triceps brachii
-synergists = brachialis, brachioradialis
-lever = radius (insertion point)
-fulcrum = elbow joint
-effort = muscle contraction
-resistance = weight of object + forearm + hand
in the extension of the forearm, what is the agonist and what is the antagonist?
-agonist = triceps brachii
-antagonist = biceps brachii
what are the categories of actions for skeletal muscles?
-flexors
-extensors
-abductors
-adductors
what are flexor muscles?
-decrease the angle between two bones
-ex: biceps brachii
what are extensor muscles?
-increase the angle between two bones
-bring back to anatomical position after flexion
-ex: tricep brachii
what are abductor muscles?
-move limbs away from the midline
what are adductor muscles?
-move limbs toward the midline
what do tendons and aponeurosis act as? which is less common?
-connection points
-aponeurosis are less common
