1. Types of Muscle Fibers and Contractions

2. Muscular System Muscles are the organs that move body parts.
_________________
___________________.
More than 600
muscles in the body
35–40% of body mass
is muscle

3. Muscular System
Muscle—organ that __________ and becomes shorter or __________ and becomes longer
Result = Body parts move, energy is used, and work is done.

4. Muscles at Work
_________________________________________________________________.
One muscle contracts while
the other muscle relaxes.
Muscles always ________;
they never push.

5. Motor neurons and muscle contraction
Motor neurons stimulate muscle contraction
Motor neurons are branched and can stimulate more than one muscle fiber
_________________________________________________________
_________________= the synapse between a motor neuron and a muscle fiber

6. Fig 30.10A

7. Motor neurons and muscle contraction
The strength of a muscular contraction is controlled by the number of motor units activated. _________________________________________________
Muscles requiring precise control have one motor neuron per muscle fiber

8. Muscles at Work Results of Muscle Action Muscles contract
This produces thermal energy, and it uses chemical energy.
Thermal energy produces heat that helps keep body temperature constant.
Chemical energy is from glucose. (When glucose is used up, muscles are tired and need to rest.)

9. Muscles at Work Results of Muscle action (cont.)
Over time, muscles become _______ or _______, depending on how much work they do.

10. TYPES OF MUSCLE CONTRACTIONS

11. Types of Muscle Contractions
________________: when the ms. does not shorten during contraction while tension is increasing.
Isotonic contraction: _________________________________________________________________________________.

12. Isometric Contraction
Isotonic Contraction
Isometric Contraction
Tension is constant
Tension n the ms. Rises markedly
Length is decreased or lengthened
______________________
_________________
No work is done
less energy used/muscle contraction
More energy used/muscle contraction

14. Types of Isotonic Contractions
Concentric: ___________________________________________________________________________________
Eccentric: ______________________________________________________________________________________

16. Slow- and Fast-Twitch Fibers
Skeletal muscle fibers can be divided on basis of contraction speed:
______________________
Fast-twitch (type II fibers).
Differences due to different myosin ATPase isoenzymes that are slow or fast.

17. Slow- and Fast-Twitch Fibers
Slow-twitch (type I fibers):
Red fibers (high myoglobin content).
___________________________________________________
Resistant to fatigue.
________________.
Numerous mitochondria and aerobic enzymes.

18. Slow- and Fast-Twitch Fibers
Fast-twitch (type IIB fibers):
_______________________
Adapted to respire anaerobically.
Have large stores of glycogen.
_________________
Have few mitochondria.

19. Slow- and Fast-Twitch Fibers
Intermediate (type IIA) fibers:
________________
Resistant to fatigue.
People vary genetically in proportion of fast- and slow-twitch fibers in their muscles.