Muscles and Muscles Tissue Part C Flashcards
Factors of Muscle Contraction
Force of contraction depends on number of cross bridges attached, which is affected by four factors:
Number of muscle fibers stimulated
(recruitment): the more motor units recruited, the greater the force.
Relative size of fibers
the bulkier the muscle, the more tension it can develop
Muscle cells can increase in size (hypertrophy) with regular exercise
Frequency of stimulation
the higher the frequency, the greater the force.
Stimuli are added together
Degree of muscle stretch
muscle fibers with sarcomeres that are 80–120% their normal resting length generate more force
If sarcomere is less than 80%
resting length, filaments overlap too much, and force decreases.
If sarcomere is greater than 120%
of resting length, filaments do not overlap enough so force decreases
How fast a muscle contracts and how long it can stay contracted is influenced by:
Muscle fiber type
Load
Recruitment
Muscle fiber type Classified according to two characteristics
Speed of contraction.
Oxidative fibers.
Glycolytic fibers
Speed of contraction
– slow or fast fibers
According to
Speed at which
myosin ATPases split ATP
According to pattern
Pattern of electrical activity of motor neurons
Metabolic pathways
used for ATP synthesis
Oxidative fibers
use aerobic pathways
Glycolytic fibers:
use anaerobic glycolysis
skeletal muscle fibers can be classified into three types:
Slow oxidative fibers, fast oxidative fibers, or fast glycolytic fibers
Most muscles contain
contain mixture of fiber types, resulting in a range of contractile speed and fatigue resistance
All fibers in one motor unit
are the same type
Genetics dictate
individual’s percentage of each
Muscle fiber type
Different muscle types are better suited for different jobs
Slow oxidative fibers example
: low-intensity, endurance activities
Example: maintaining posture
Fast oxidative fibers and example
medium-intensity activities
Example: sprinting or walking
Fast glycolytic fibers and example
short-term intense or powerful movements
Example: hitting a baseball
Load
muscles contract fastest when no load is added