Muscular System - midterm 2 Flashcards
Muscular system:
- refers to skeletal muscle system
- primarily attached to bone
- produce movement by contracting - byproduct = heat
Skeletal muscle
- cells called fibers
- fascicle = group fibers
- whole muscle = group of fascicles
CT components of skeletal muscle: (2)
1) Fascia = CT
2) Tendons + Aponeuroses
Fasia = CT types (3)
a) Epimysium - surrounds entire muscle
b) perimysium - surrounds fascicles
c) endomysium - surrounds each muscle fiber
Tendons + Aponeuroses
- extensions of epi-,peri-, + endomysium
- anchors to bone (periosteum), cartilage, skin, or fascia
- tendon = rope-like
- aponeurosis = sheet like
Skeletal muscle fiber structure
large multinucleate cells parts: 1) sarcolemma = cell membrane 2) sarcoplasm = cytoplasm 3) Myofibrils (intracellular structures) - hundreds to thousands -composed of sarcomeres 4) T-tubules 5) Sarcoplasmic Reticulum
Sarcomere structure (composed of proteins):
made of 2 types of myofilaments: a) thin filaments: composed of: i. actin - functions in contraction ii. tropomyosin + iii. troponin - regulate contraction (regulatory proteins)
b) thick filaments
- composed of:
i. myosin - fxns in contraction
- attached to Z discs by titin
- has rod-like tail with 2 globular heads
> head extends towards actin - forms crossbridge
- the myofilaments create dark + light bands (striations) of the sarcomere
- sarcomeres join end to end )at Z discs) to for myofibrils
Banding pattern of myofilaments, in muscle fiber structure
a) A band
dark = length of thick filament - myosin + actin (with troponin + tropomyosin)
b) H zone
lighter band at centre of A band - myosin only
c) I band
light = actin (with troponin + tropomyosin) + titin
d) Z discs (in center of I band)
-actin + titin attach
- connect sarcomeres: between 2 z-discs = 1 sarcomere
e) M line
where myosin tails (thick myofilaments) attach to each other (centre of sarcomere)
T-tubules (skeletal muscle fibre)
- continuations of sarcolemma that extend deep into fiber (cell)
- directly encircle myofilaments of myofibrils at junction of A & I bands (2/sarcomere)
Sarcoplasmic Reticulum (skeltal muscle fibre)
- = smooth ER
- triad = 2 enlarged areas of SR (terminal cistern) & T-tubule
how muscles produce movement (3)
1) Pulling on bones when they contract
2) Using group action
3) lever system
Pulling on bones when they contract
a) origin = attachment of tendon to stationary bone
b) insertion = attachment of tendon to movable bone
Using group action to produce muscle movement
a) agonist = major muscle producing the movement
b) synergists = help the agonist action
c) antagonist = produces opposite action of agonist (contraction inhibited when agonist contracts)
Lever systems to produce movement
- bone/muscle interaction at a joint parts: a) levers = bone b) fulcrum = joint - effort = contraction og agonist - resistance = opposed movement - effort must be greater than resistance to get movement
eg. flexion of forearm
- agonist = biceps brachii
- antagonist = triceps brachii
- synergists = brachialis, brachioradialis
- lever = redius (insertion of agonist)
- fulcrum = elbow joint
- effort = muscle contraction
- resistance - weight of forearm
eg. extension of forearm
- agonist - triceps brachii
antagonist = biceps brachii
Naming skeletal muscles
1) action they preform
2) shape of muscle
3) origin + insertion
4) location
5) relative size
6) direction of fibers
7) number of origins
