Muscle_Physiology_Brainscape Flashcards
(36 cards)
What triggers cross-bridge formation in muscle fibers?
A motor nerve signal that activates the fiber.
What happens during cross-bridge formation?
Myosin heads temporarily attach to actin filaments, shortening the sarcomere.
Why is sarcomere length important?
Optimal length allows the most cross-bridges to form, generating maximum force.
What happens if sarcomeres are too far apart?
Fewer cross-bridges form, producing less force.
What happens if sarcomeres are too close together?
Cross-bridges interfere with each other, reducing force production.
At what elbow angle is muscle tension most powerful during flexion?
Between 30 and 120 degrees.
What is the sarcoplasmic reticulum?
A network of tubules inside muscle fibers that stores and releases calcium.
What are T-tubules (transverse tubules)?
Structures that connect the sarcoplasmic reticulum to the sarcolemma.
What surrounds all myofibrils, fibers, and bundles?
Connective tissue made mostly of collagen.
What is a motor unit?
A motor neuron and all the muscle fibers it innervates.
What is an action potential in muscle contraction?
An electrical signal that initiates muscle contraction.
What neurotransmitter is used at the neuromuscular junction?
Acetylcholine.
Where does the action potential arrive to trigger muscle contraction?
The motor end plate (neuromuscular junction).
What causes calcium to be released into the muscle fiber?
The action potential travels through T-tubules, triggering calcium release from the sarcoplasmic reticulum.
What does calcium do in muscle contraction?
It enables cross-bridging between actin and myosin.
What happens when a neural signal stops?
Calcium is reabsorbed into the sarcoplasmic reticulum, ending contraction.
What are characteristics of Type I (slow-twitch) muscle fibers?
Slow to contract, fatigue-resistant, lower power output.
What are characteristics of Type II (fast-twitch) muscle fibers?
Contract quickly and forcefully, but fatigue rapidly.
Which fiber type is better for endurance activities?
Type I (slow-twitch).
Which fiber type is better for power and strength activities?
Type II (fast-twitch).
Which fiber type is recruited first in activity?
Slow-twitch fibers (Type I).
What determines the ratio of fast to slow twitch fibers?
Genetics.
How does training affect muscle fibers?
Increases recruitment and efficiency of specific fiber types.
Can muscle fibers change type with training?
Training can enhance characteristics, but does not convert fiber types.
