Muscle tissue
skeletal muscle (voluntary )
cardiac muscle (involuntary )
smooth muscle (function involuntary )
functions of skeletal muscles
Organization of Connective Tissues
3 layers of connective tissues:
1. epimysium
2. perimysium
3. Endomysium
Epimysium
wraps skeleton muscles
- exterior collagen layer
- connected to deep fascia
- separates muscle from surrounding tissues
Perimysium
the clear thin skin of a fascicle
- surrounds muscle fiber bundles (fascicles)
- contains blood vessel and nerve supply to fascicles
Endomysium
Surrounds individual muscle cells (muscle fibers)
contains capillaries and nerve fibers contacting muscle cells
contains satellite cells (stem cells) that repair damage
Muscle Attachements
Endomysium, perimysium, and epimysium come together:
- at ends of muscles
- to form connective tissue attachment to bone matrix
- examples. tendon(bundle) or aponeurosis(sheet)
Formation of Skeletal Muscle Fibers
skeletal muscle cells are called fibers
The Sarcolemma
The cell membrane of a muscle cell
Surrounds the sarcoplasm (cytoplasm of muscle fiber)
A change in transmembrane potential begins contractions
Transverse Tubules (T tubules)
Transmit action potential through cell
Allow entire muscle fiber to contract simultaneously
Myofibrils
Types of Myofilaments
Thin filaments:
- made of protein actin
Thick filaments:
- made of protein myosin
Sarcoplasmic Reticulum
A membranous structure surrounding each myofibril
Helps transmit action potential to myofibril
Similar in structure to smooth endoplasmic reticulum
Sarcomeres (structural components)
The contractile units of muscles
Structural units of myofbrils
form visible patterns within myofibrils
Muscle Striations
A striped or striated pattern within myofibrils:
- alternating dark , thick filaments (a band) and light, thin filaments (I bands)
Sarcomere structure (levels)
Skeletal Muscle Contraction
Sliding filament theory:
- thin filament of sarcomere slide toward M line
- between thick filaments
- z lines move closer together
The neuromuscular junction
types of skeletal muscle tension (2)
Isotonic Contraction
Skeletal muscle changes length:
- resulting in motin
If muscle tension resistance:
- muscle shortens (concentric contraction)
if muscle tension < resistance:
- muscle lengthens (eccentric contraction)
Isometric Contraction
Skeletal muscle develops tension, but is prevented by changing length
Note: iso = same, metric = measure
Muscle Relaxation
after contraction, a muscle fiber returns to resting length by:
- elastic forces
- opposing muscle contractions
- gravity
Elastic Forces
Opposing muscle contractions
reverse the direction of the original motion
are the work of opposing skeletal muscle pairs