Exam 4 Flashcards
SKELETAL MUSCLES & PHYSICAL PERFORMANCE
Myology
scientific study of muscles & their parts
Generally speaking, 2 main units exist in the muscular system… what are they?
structural unit: muscle fiber or muscle cell
functional unit: motor unit
Skeletal muscle fibers are comprised of 2 primary constituents
- sarcoplasm: muscle cytoplasm
- myofibrils: sarcomeres in series-contractile elements
Gross muscles may be comprised of how many muscle fibers?
only a few or as many as 1 million
Structural unit
muscle fiber/muscle cell
Functional unit
motor unit
All muscle fibers are supplied with nerves (innervated) by terminal branches of a single ___ ___ ___?
alpha efferent axon
How many motor units are located in each gross muscle?
multiple
What does it mean if a motor unit is recruited?
all fibers w/in it are concurrently contracting
As force demands increase…
more motor units are recruited
Muscles containing a small # of muscle fibers per motor unit are capable of smaller/larger gradations (degrees, stages) in force output?
smaller
Sarcoplasm
~25% protein in a non-contractile configuration
~75% fluid
Myofibrils
various protein filaments configured to enable the contractile process
-series of sarcomeres
Main filaments involved in contractions
myosin & actin
Smaller filaments loosely bound to actin when the myofibril is relaxed
troponin & tropomyosin
Muscle fibers have how many nuclei?
multiple
multi-nucleated
Muscle fibers have a cell wall called the…
sarcolemma
Sarcolemmas have 3 major substructures:
- Transverse Tubules (T Tubules)
- Terminal Cisternae
- Sarcoplasmic Reticulum (SR)
Transverse Tubules
- inlets w/in the sarcolemma that provide for neural input
- Run roughly perpendicular to sarcomere
Terminal Cisternae
- Storage vesicles for calcium
- Located parallel & contiguous (share a border) to transverse tubules
- May be referred to as vesicles of the SR
Sarcoplasmic Reticulum
- conduit for calcium
- oriented roughly parallel to the sarcomere
Sarcomere
structural unit of the myofibril
Sarcomere contains the contractile elements between each pair of ___?
Z-disks
Z-disks are ___ ____?
connective tissue
In a relaxed sarcomere you have the following…
I-band
A-band
H-zone
M-line
I-band
light zone
A-band
dark zone
H-zone
in middle of A-band
M-line
in middle of H-zone
Connective tissue found within each ___ ____ and at ___ ____ outside of it.
muscle fiber
multiple levels
Connects sarcomeres?
z line / z disc
Endomysium surrounds…
surrounds muscle fibers
Perimysium surrounds…
surrounds fascicles
Epimysium/fascia surrounds…
surrounds whole muscle
Tendon is…
coalescing (coming together of) of epimysium and fascia that connects muscle to bone
2 main types of extracellular protein fiber that affect elasticity of musculo-tendinous unit
collagen & elastin
Collagen
- fibrous insoluble protein
- found within connective tissue in muscle, skin, bone, ligaments, & cartilage
- stiffens tissue
- greater than or equal to 20 isoforms exist
Elastin
- stores mechanical energy
- albuminoid protein (yellow elastic tissue found in connective tissue)
Connective tissue fill where?
spaces b/w organs & tissues in the body
Connective tissue mainly comprised of
- tough protein fibers embedded in a polysaccaride gel (extracellular matrix)
- mainly secreted by fibroblasts
Parallel elastic components made up of…
- sarcolemma
- endomysium
- perimysium
- epimysium
Other tissues that affect elasticity of musculo-tendinous unit
- parallel elastic components
- series elastic components
