Muscle Contraction Flashcards
What is the primary role of calcium ions (Ca2+) in muscle contraction?
Calcium ions bind to troponin, causing a conformational change that allows myosin to bind to actin.
True or False: ATP is required for muscle contraction.
True
Fill in the blank: The stages of muscle contraction include __________, where the muscle fiber generates tension.
twitch
What is the role of ATP in muscle contraction?
ATP provides energy for the myosin heads to perform the power stroke and is necessary for detaching myosin from actin.
What happens during the relaxation phase of muscle contraction?
Calcium ions are pumped back into the sarcoplasmic reticulum, and the muscle fiber returns to its resting state.
What is the first step in muscle contraction?
The release of acetylcholine at the neuromuscular junction.
In what structure is calcium stored in muscle cells?
Sarcoplasmic reticulum
True or False: Muscle relaxation occurs when calcium ions bind to troponin.
False
What is a muscle twitch?
A brief contraction and relaxation cycle of a muscle fiber in response to a single stimulus.
What initiates the cross-bridge cycle in muscle contraction?
The binding of calcium to troponin.
During muscle contraction, what happens to the sarcomere?
The sarcomere shortens as actin filaments slide over myosin filaments.
What is the term for the period of time between stimulus and the beginning of muscle contraction?
Latent period
What is the role of myosin in muscle contraction?
Myosin heads bind to actin and pull the filaments during the power stroke.
True or False: ATP is not required for muscle relaxation.
False
What happens to myosin heads during the power stroke?
They pivot and pull the actin filaments toward the center of the sarcomere.
What is the effect of a lack of ATP on muscle contraction?
Muscles cannot relax, leading to rigor mortis.
Which ion is essential for the exposure of binding sites on actin?
Calcium ions (Ca2+)
What are the three phases of a muscle twitch?
Latent period, contraction phase, and relaxation phase.
What occurs during the contraction phase of a muscle twitch?
Muscle fibers actively shorten and generate force.
Fill in the blank: The primary source of energy for muscle contraction is __________.
ATP
What is the relationship between calcium and the sarcoplasmic reticulum during contraction?
Calcium is released from the sarcoplasmic reticulum into the cytoplasm.
True or False: The relaxation phase is longer than the contraction phase in a muscle twitch.
True
What effect does repeated stimulation have on muscle contraction?
It can lead to summation and tetanus, resulting in increased muscle tension.
What is the function of troponin in muscle contraction?
Troponin binds calcium and regulates the interaction between actin and myosin.
During the relaxation phase, which enzyme helps break down acetylcholine?
Acetylcholinesterase
What is meant by ‘tetanus’ in muscle physiology?
A sustained muscle contraction due to rapid, repeated stimulation.
