Excitation-contraction coupling involves the
transformation of depolarizing events in the sarcolemma into the initiation of mechanical shortening of the myofibrils within the myofiber by calcium ions released from the terminal cisternae of the sarcoplasmic
reticulum (SR).
What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated?
Thus, there is a
one-to-one relationship
between a muscle and a motor neuron pool. Each individual muscle fiber in a muscle is innervated by one, and only one, motor neuron (make sure you understand the difference between a muscle and a muscle fiber). A single motor neuron, however, can innervate many muscle fibers.
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers?
Acetylcholine
. Action potentials.
What is directly responsible for muscle contraction?
Muscle contraction thus results from an
interaction between the actin and myosin filaments
that generates their movement relative to one another. The molecular basis for this interaction is the binding of myosin to actin filaments, allowing myosin to function as a motor that drives filament sliding.
Which ions are responsible for the coupling of excitation to the contraction of muscle?
Sodium ions
enter the muscle fiber, and an action potential rapidly spreads (or “fires”) along the entire membrane to initiate excitation-contraction coupling.
What are the steps in excitation contraction coupling?
The sequence of events in twitch skeletal muscle involves: (1)
initiation and propagation of an action potential along the plasma membrane, (2) spread of the potential throughout the transverse tubule system (T-tubule system)
, (3) dihydropyridine receptors (DHPR)-mediated detection of changes in membrane potential, (4) …
What is the order of excitation contraction coupling?
The EC-coupling cycle involves the following sequence of events: (1) depolarization of the plasma membrane and its membrane invaginations (the t-tubular system) by an action potential; (2) transduction of the depolarization signal to the sarcoplasmic reticulum (SR) membrane; (3) activation of Ca
2 +
release from the SR …
What is the main function of tropomyosin in skeletal muscle?
Tropomyosin is a protein involved in
skeletal muscle contraction and that wraps around actin and prevents myosin from grabbing it
. This prevents muscle contractions until the proper signal arrives. When the nervous system tells the muscle cell to contract, calcium is released.
Which ion is important for muscle contraction?
Thus,
Calcium
plays an important role in muscle contraction. The role of magnesium is to form a MgATP complex to bind to a myosin active site, thus promoting actomyosin dissociation. Both calcium and magnesium are required during chemical events and muscle contraction.
Why is calcium important for muscle contraction?
Nerve and Muscle Function
Calcium’s positive molecule is important to the transmission of nerve impulses to the muscle fiber via its neurotransmitter triggering release at the junction between the nerves (2,6). Inside the muscle,
calcium facilitates the interaction between actin and myosin during contractions
(2,6).
What are the steps of muscle contraction?
- action potential to muscle.
- ACETYLCHOLINE released from neuron.
- acetylcholine binds to muscle cell membrane.
- sodium diffuse into muscle, action potential started.
- calcium ions bond to actin.
- myosin attaches to actin, cross-bridges form.
What is the process of a muscle contraction?
Muscle contraction occurs when
the thin actin and thick myosin filaments slide past each other
. … In this conformation the cross-bridge binds weakly to actin and attaches and detaches so rapidly that it can slip from actin site to actin site, offering very little resistance to stretch.
What is required for muscle contraction?
For a contraction to occur there must first be a stimulation of the muscle in the form of
an impulse (action potential) from a motor neuron
(nerve that connects to muscle). … When an impulse reaches the muscle fibres of a motor unit, it stimulates a reaction in each sarcomere between the actin and myosin filaments.
What is the process of excitation?
The process of excitation is one of the major means by which
matter absorbs pulses of electromagnetic energy (photons)
, such as light, and by which it is heated or ionized by the impact of charged particles, such as electrons and alpha particles.
Is important in skeletal muscle contraction because?
Binds to troponin to remove the masking of active sites on actin for myosin
. Activates the myosin ATPase by binding to it. Prevents the formation of bonds between the myosin cross bridges and the actin filament.
What is the role of ATP in muscle contraction?
ATP
prepares myosin for binding with actin by moving it to
a higher- energy state and a “cocked” position. … ATP must bind to myosin to break the cross-bridge and enable the myosin to rebind to actin at the next muscle contraction.
