What steps are required for smooth muscle to relax?
Smooth muscle relaxation occurs either as a result of removal of the contractile stimulus or by the direct action of a substance that stimulates inhibition of the contractile mechanism. Regardless, the process of relaxation requires a decreased intracellular Ca2+ concentration and increased MLC phosphatase activity.
What is the first step to muscle contraction and relaxation?
The first step in the process of contraction is for Ca++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands. This allows the myosin heads to bind to these exposed binding sites and form cross-bridges.
What are the 10 steps of muscle contraction?
Terms in this set (10)
- signal from motoneuron gets to synapse.
- motoneuron releases acetylcholine (Ach) which is a neurotransmitter.
- Ach meets its receptor on the muscle cell.
- muscle cell membrane is permeable to Na+ at that moment only.
- Na+ rush creates an electrical current: action potential.
What are the 8 steps of muscle contraction?
Terms in this set (8)
- 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.
- myosin pulls on actin causing to slide over myosin.
How do muscles contract and relax?
When the stimulation of the motor neuron providing the impulse to the muscle fibers stops, the chemical reaction that causes the rearrangement of the muscle fibers’ proteins is stopped. This reverses the chemical processes in the muscle fibers and the muscle relaxes.
What is smooth muscle contraction?
Contraction. Smooth muscle contraction is caused by the sliding of myosin and actin filaments (a sliding filament mechanism) over each other. Contraction is initiated by a calcium-regulated phosphorylation of myosin, rather than a calcium-activated troponin system.
What is responsible for muscle relaxation?
Relaxation: Relaxation occurs when stimulation of the nerve stops. Calcium is then pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. Actin and myosin return to their unbound state causing the muscle to relax.
How do smooth muscle cells respond to stimuli?
Smooth muscle cells also develop tonic and phasic contractions in response to changes in load or length. Regardless of the stimulus, smooth muscle cells use cross-bridge cycling between actin and myosin to develop force, and calcium ions (Ca 2+) serve to initiate contraction.
What causes the contraction of the smooth muscle?
Phorbol esters, a group of synthetic compounds known to activate PKC, mimic the action of DG and cause contraction of smooth muscle. Finally, L-type Ca 2+ channels (voltage-operated Ca 2+ channels) in the membrane also open in response to membrane depolarization brought on by stretch of the smooth muscle cell.
What happens to the band during muscle contraction?
The A band stays the same width. At full contraction, the thin and thick filaments overlap completely. Tropomyosin is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin. Tropomyosin binds to troponin to form a troponin-tropomyosin complex.
How is tropomyosin used to start muscle contraction?
To initiate muscle contraction, tropomyosin has to expose the myosin-binding site on an actin filament to allow cross-bridge formation between the actin and myosin microfilaments. The first step in the process of contraction is for Ca ++ to bind to troponin so that tropomyosin can slide away from the binding sites on the actin strands.