Ch. 10 Muscle Tissue Flashcards
What are the 6 functions of skeletal MUSCLES?
- Produce skeletal movement
- Maintain posture & body position
- Support soft tissues (abdominal wall and floor of pelvic cavity)
- Guard entrances and exits
- Maintain body temperature
- Store nutrient reserves
What are the three layers of muscle?
- epimysium
- perimysium
- endomysium
What are the components of skeletal muscle?
- muscle tissue (cells or ‘fibers’)
- connective tissue
- nerves
- blood vessels
A dense layer of collagen fibers that surround the entire muscle. Separates the muscle from nearby tissues and organs.
Connected to deep fascia, a dense connective tissue layer.
Epimysium
- Divides the skeletal muscle into a series of compartments; surrounds muscle fiber bundles
- Contains blood vessels and nerve supply to fascicles
Perimysium
A bundle of muscle fibers surrounded by the perimysium
fascicle
- Surrounds individual muscle cells (muscle fibers)
- Contains capillaries and nerve fibers contacting muscle cells
- Contains myosattelite cells (stem cells) that repair damage
Endomysium
a bundle at the end of each muscle that usually attaches it to bones
tendon
a broad sheet at the end of muscle tissue that usually attaches it to bone
aponeurosis
a group of embryonic cells that fuse and form individual multinucleate skeletal muscle fibers.
myoblast
Where does each nucleus in multinucleate muscle cells originate?
myoblasts
Where do myosattelite cells come from?
Myoblasts that did not fuse with developing muscle fibers
the plasma membrane of muscle fiber
sarcolemma
cytoplasm of a muscle fiber
sarcoplasm
Why is sarcoplasm different from other plasma membranes?
It has a membrane potential due to the unequal distribution of positive and negative charges
- Transmit action potential through cell
- Allow simultaneous contraction
- Same properties as sacolemma
Transverse tubules
(T tubules)
- Lengthwise subdivisions within muscle fibers
- Made up of bundles of protein filaments
- Actively shorten. Responsible for muscle contraction
- 100s - 1,000s per fiber
myofibrils
protein bundles that make up myofibrils. Two types.
myofilaments
(thin and thick)
composed of actin
thin filaments
(myofilaments that make up myofibrils)
composed of myosin
thick filaments
(myofilaments that make up myofibrils)
Provide energy (ATP) for short-duration, maximum intensity muscular contractions
glycolysis
mitochondria and granules of glycogen scattered among the myofibrils of each muscle fiber
– A membranous structure surrounding each myofibril
– Helps transmit action potential to myofibril
– Similar in structure to smooth endoplasmic reticulum
– Forms chambers (terminal cisternae) attached to T tubules
sarcoplasmic reticulum
- Chambers next to T-tubules where the SR enlarges, fuses and forms expanded chambers
- Concentrate Ca2+ (via ion pumps)
- Release Ca2+ into sarcomeres to begin muscle contraction
terminal cisternae
formed by one T tubule and two terminal cisternae
Triad
- The contractile units of muscle
- Structural units of myofibrils
- Form a striated pattern within myofibrils
- Alternating dark, thick filaments (A bands) and light, thin filaments (I bands)
Sarcomeres
Three components A Band
1. M line
2. The H Band
3. Zone of overlap
– The densest, darkest area on a light micrograph
– Where thick and thin filaments overlap
- Where triads surrounding sarcomeres are located; calcium ions released here
Zone of overlap
The H Band
– The area around the M line
– Has thick filaments but no thin filaments
M line
– The center of the A band
– At midline of sarcomere
Zone of overlap
– The densest, darkest area on a light micrograph
– Where thick and thin filaments overlap
- Where triads surrounding sarcomeres are located; calcium ions released here
– The area around the M line
– Has thick filaments but no thin filaments
The H Band
– The center of the A band
– At midline of sarcomere
M line
contains thin but not thick filaments
The I band
Marks the boundary between adjacent sarcomeres
Z lines
