Lecture #5 Flashcards
What is threshold stimulus in muscle contractions?
The minimum strength of a stimulus required for a muscle to contract
What happens when the threshold stimulus is reached?
An action potential is generated
What is a twitch?
A contractile response to a single impulse
What are the three phases of a twitch?
Latent, contraction, relaxation
What determines the amount of force a muscle fiber can generate?
The length of the muscle fiber before stimulation
What is the optimal starting length of a muscle fiber?
The resting length of a muscle fiber
Why do stretched muscle fibers generate Less force?
The myosin heads are too far apart
What is summation in muscle contractions?
The process of combining the force generated by individual muscle fiber twitches which help produce sustained contractions
What is a motor unit?
A motor neuron and the muscle fibers it controls
What type of movements require a large number of muscle fibers within a motor unit?
Course movements
What type of movement requires a smaller number of muscle fibers with an motor units?
Precise movements
What is recruitment in muscle fibers?
The increase in the number of motor units becoming activated to help produce additional force
What are the types of contractions?
Isotonic, concentric, Ecentric, and isometric
Isotonic?
Muscle contractions with changing lengths but equal force
Concentric?
Shortening muscle contractions
Ecentric?
Lengthening muscle contractions
Isometric?
Muscle contractions without a change in length
What Is another name for type one fibers?
Slow twitch fibers
What are characteristics of Type one fibers?
Resistant to fatigue and are stimulated by aerobic exercise
What is another name for type 2A fibers?
Fast twitch fatigue resistant fibers
What are characteristics of type 2A fibers?
Stimulated by forceful exercise and are fatigue resistant and quicker than type one muscle fibers
What is another name for type 2B fibers?
Fast twitch glycolytic fibers
What are characteristics of type 2B fiber?
Contract rapidly and susceptible to fatigue
What are 4 differences between smooth and skeletal muscles?
Smooth muscles have shorter fibers relative to skeletal muscle, Smooth muscles are slower in contraction and relaxation, smooth muscles are more resistant to fatigue, and smooth muscles have no observable striations
