Topic 11: Muscular System 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
List the CT component of skeletal muscle
1) Fascia
2) Tendons + Aponeuroses
Fascia
= CT
Epimysium
– surrounds entire muscle
Perimysium
– surrounds fascicles
Endomysium
– surrounds each muscle fiber
Tendons + Aponeuroses
extensions of epi-, peri-, + endomysium
anchors to bone (periosteum), cartilage, skin, or fascia
tendon
= rope-like
o e.g. Achilles tendon
connect muscle to bone
aponeurosis
e. g. galea aponeurotica = epicranial aponeurosi
- sheet like
Describe the structure of Skeletal Muscle Fiber
large multinucleate cells parts: 1) Sarcolemma = cell membrane 2) Sarcoplasm = cytoplasm 3) Myofibrils (intracellular 4) T-tubules structures) 5) Sarcoplasmic Reticulum
Myofibrils
within each fibre there are several hundreds to thousands
composed of sarcomeres:
Describe the structure of sarcomeres
(composed of proteins):
o made of 2 types of myofilaments:
a) thin filaments:
thick filaments
thin filaments
composed of:
i. actin – functions in contraction
2
ii. tropomyosin + iii. troponin – regulate
contraction (regulatory proteins)
thick filaments
composed of:
i. myosin – functions in contraction
attached to Z discs by titin
has rod-like tail with 2 globular heads
o head extends toward actin and attaches to it
– forming a crossbridge
A band
dark = length of thick filament – myosin + actin
with troponin + tropomysosin
H zone
lighter band at center of A band – myosin only
I band
light = actin (with troponin + tropomyosin) + titin
Z discs
(in center of I band)
actin + titin attach
connect sarcomeres: between 2 z-discs = 1 sarcomere
M line
where myosin tails (thick myofilaments) attach to each other (center of sarcomere
T-tubules
continuations of sarcolemma that extend deep into fiber (cell)
directly encircle myofilaments of myofibrils at junction of A & I bands
(2/sarcomere)
Sarcoplasmic Reticulum
= smooth ER
triad = 2 enlarged areas of SR (terminal cisternae) & T-tubule