Topic 11: Muscular System

Question 1

what are the basics of the muscular system?

Answer 1

-refers to skeletal muscle
-primarily attached to bone
-produce movement by contracting (shortening)

Question 2

how do muscles work together?

Answer 2

-work in opposition to one another

Question 3

what is skeletal muscle?

Answer 3

-made of cells called fibers
-fibers are arranged into fascicles

Question 4

what are fascicles?

Answer 4

-groups of fibers
-the whole muscle is groups of fascicles

Question 5

what is a fascia?

Answer 5

-a connective tissue covering that holds layers together
-surrounds muscles or other organs

Question 6

what are the 3 layers of fascia?

Answer 6

-epimysium
-perimysium
-endomysium

Question 7

what is the epimysium?

Answer 7

-outermost layer of fascia
-surrounds the entire muscle

Question 8

what is the perimysium?

Answer 8

-middle layer of fascia
-surrounds fascicles

Question 9

what is the endomysium?

Answer 9

-innermost layer of fascia
-surrounds each muscle fiber

Question 10

what are tendons?

Answer 10

-extensions of the fascia layers
-anchors to bone (periosteum), cartilage, or fascia
-rope-like bundle of dense regular CT
-ex: calcaneal (achilles) tendon

Question 11

what are aponeuroses?

Answer 11

-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)

Question 12

what is the structure of skeletal muscle fibers?

Answer 12

-large + long multinucleated cells
-sarcolemma (cell membrane)
-sarcoplasm (cytoplasm)
-myofibrils (intracellular structures)
-t-tubules
-sarcoplasmic reticulum

Question 13

what are myofibrils?

Answer 13

-intracellular structures
-many to each muscle fiber
-composed of sarcomeres

Question 14

what is the structure of sarcomeres?

Answer 14

-composed of proteins
-thin filaments
-thick filaments

Question 15

what are thin filaments composed of? what are the functions of these proteins?

Answer 15

-actin
-tropomyosin (control contractions)
-troponin (control contractions)

Question 16

how do contractions occur?

Answer 16

-globular heads of thick filaments will grab sites on the actin protein
-other proteins of the thin filament can obstruct this

Question 17

what are thick filaments composed of? what is the function of this protein?

Answer 17

-myosin (functions in contraction)
-rod-like tails with 2 globular heads
-heads extend towards actin and attach to it during contraction (shortens the sarcomere)

Question 18

where and how does myosin attach to the sarcomere?

Answer 18

-Z discs by the titin protein

Question 19

what creates striations in the sarcomere?

Answer 19

-the different banding patterns of the sarcomere
-dark and light areas

Question 20

what are the different banding patterns?

Answer 20

• A band
• H zone
• I band
• Z discs
• M line

Question 21

what is the A band?

Answer 21

-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

Question 22

what is the H-zone?

Answer 22

-only myosin
-no thin filaments are present
-lighter band at the center of the A band

Question 23

what is the I-band?

Answer 23

-only the thin filaments and z-discs between each new sarcomere
-produces a lighter band

Question 24

what are Z-discs?

Answer 24

-at the end of each sarcomere
-connection points for other sarcomeres
-darkest striation in the center of the I-Band

Question 25

what is the M-line

Answer 25

-where myosin tails attach to each other (center of the sarcomere) -middle

Question 26

what do sarcomeres join to form?

Answer 26

-myofibrils -join end to end by z-discs

Question 27

what are T-tubules?

Answer 27

-continuations of the sarcolemma that extend deep into the cell/fiber -allows a close contact of extracellular fluid

Question 28

what is the sarcoplasmic reticulum?

Answer 28

-smooth ER

Question 29

what is a triad?

Answer 29

-T-tubule and 2 terminal cisternae (enlarged areas of the SR)

Question 30

how do muscles produce movement?

Answer 30

-pull on bones (skin or other muscles too) when they contract -bones allow for a certain range of motion -using group action -lever systems

Question 31

what are the types of group action in muscle movement?

Answer 31

-agonist -synergists -antagonist

Question 32

what is the origin point of a muscle?

Answer 32

-attachment of a tendon to the stationary bone -not participating in physical movement

Question 33

what is the insertion point of a muscle?

Answer 33

-attachment of a tendon to the moveable bone -participates in movement

Question 34

what is an agonist?

Answer 34

-major muscle producing a certain movement

Question 35

what are synergists?

Answer 35

-helpers for the agonist action -prevent undesirable motions -stabilizers

Question 36

what is an antagonist?

Answer 36

-produces the opposite action of the agonist -contraction is inhibited when agonist contracts -allow muscles to return to anatomical position

Question 37

what are lever systems?

Answer 37

-bone/muscle interaction at a joint -levers = bones (insertion bone) -fulcrum = joint -effort = contraction of agonist -resistance = opposes movement

Question 38

in a lever system, what must be greater to get movement?

Answer 38

-effort must be greater than resistance

Question 39

will certain muscles always be agonists or antagonists?

Answer 39

-no they switch depending on the movement

Question 40

in the flexion of the forearm while lifting a weight, what are all the different parts/roles?

Answer 40

-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

Question 41

in the extension of the forearm, what is the agonist and what is the antagonist?

Answer 41

-agonist = triceps brachii -antagonist = biceps brachii

Question 42

what are the categories of actions for skeletal muscles?

Answer 42

-flexors -extensors -abductors -adductors

Question 43

what are flexor muscles?

Answer 43

-decrease the angle between two bones -ex: biceps brachii

Question 44

what are extensor muscles?

Answer 44

-increase the angle between two bones -bring back to anatomical position after flexion -ex: tricep brachii

Question 45

what are abductor muscles?

Answer 45

-move limbs away from the midline

Question 46

what are adductor muscles?

Answer 46

-move limbs toward the midline

Question 47

what do tendons and aponeurosis act as? which is less common?

Answer 47

-connection points -aponeurosis are less common