Lecture 3: Muscular System Flashcards
Skeletal muscle
- 40% of human body mass
- ability to develop tension (defining characteristic)
Skeletal muscle functions
Locomotion
Voluntary contraction
Relaxation
Characteristics of skeletal muscle
Irritability
Contractility
Extensibility
Elasticity/flexibility
Functions of muscle
Produce movement
Maintain postures/positions
Stabilize joints
Anatomical cross section (ACS)
Measurement of cross-sectional area perpendicular to longitudinal axis of muscle
Physiologic cross section (PCS)
Sum total of all the cross sections of fibers
*at largest point
Fusiform muscle fibers
- Parallel fibers and fascicles
- high speed of contact force production
- ACS = PCS
Penniform muscle fibers
PCS > ACS
Unipennate, bipennate, multipennate
Type I muscle fibers
- Slow twitch, oxidative
- slow contraction times, well suited for long, low intensity work
Type IIa muscle fibers
- intermediate fast twitch, oxidative glycolysis
- sustain activity for a long period of time OR contract with burst of force and then fatigue
Type IIb muscle fibers
- fast twitch, glycolysis
- provide rapid force production and then fatigue quickly
Myofibril
Contractile element of muscle fiber Contains sarcomeres (found between Z lines, functional contractile unit)
Sliding filament theory
- Explains production of tension in the muscle
- Myosin (thick filament) and actin (thin filament) create cross bridge, slide past one another, causing sarcomere to contract
- Force developed is sum of pulling forces that each myosin bridge exerts on actin filament
Aponeurosis
Sheath of fibrous tissue
Can connect muscle to bone
Tendons
- Connective tissue cord that connects muscle to bone
- transmits muscle force to bone
- can withstand high tensile loads
- viscoelastic stress-strain response
Torque
Tendency of a force to produce rotation about a specific axis
- moment arm of a force is the perpendicular distance from the force’s line of action to the axis of rotation
Isometric training modality
No visible movement
Used in rehabilitation
Isotonic training modality
Same weight used throughout range of motion
Isokinetic training modality
Same velocity, varied resistance
Close-linked training modality
Isotonic movements where one segment is fixed in place
Variable resistive training modality
Loads muscle throughout range of motion
