Target type: biologicalprocess
A process in which the extent of muscle contraction is reduced. Muscle relaxation can involve a number of processes including the removal of calcium from the cytoplasm to the sarcoplasmic reticulum lumen through the action of Ca2+ ATPases. In some muscles, calcium-independent pathways also play a role in muscle relaxation by decreasing the phosphorylation state of myosin light chain. [GOC:BHF, GOC:rl, PMID:19996365]
Muscle relaxation is a complex process involving the coordinated actions of several components:
1. **Neural Inhibition:** Relaxation begins with the cessation of nerve impulses from the brain and spinal cord to the muscle fibers. This signal is transmitted through motor neurons and is mediated by neurotransmitters like acetylcholine.
2. **Calcium Ion Removal:** With the absence of nerve stimulation, calcium ions (Ca2+) are actively pumped back into the sarcoplasmic reticulum (SR), a network of internal membranes within muscle cells. This removal of Ca2+ from the cytoplasm is crucial for muscle relaxation.
3. **Troponin-Tropomyosin Complex Shift:** Calcium ions bind to troponin, a protein complex attached to tropomyosin. This binding causes a conformational change in troponin, which in turn shifts tropomyosin away from the myosin-binding sites on the actin filaments.
4. **Myosin-Actin Dissociation:** The removal of tropomyosin exposes the myosin-binding sites on actin filaments. Myosin heads, which were previously attached to actin, detach and release the stored energy (ATP).
5. **Sarcomere Lengthening:** Without the continuous cross-bridge cycling between myosin and actin, the muscle fibers passively lengthen due to the elastic properties of the muscle tissue and the opposing forces of antagonist muscles.
6. **Muscle Fiber Relaxation:** The combined effects of calcium removal, the shift in the troponin-tropomyosin complex, and the dissociation of myosin and actin lead to the relaxation of individual muscle fibers.
7. **Overall Muscle Relaxation:** When a sufficient number of muscle fibers relax, the entire muscle relaxes, allowing for movement, posture control, and recovery from contraction.'
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| Protein | Definition | Taxonomy |
|---|---|---|
| P2Y purinoceptor 1 | A P2Y purinoceptor 1 that is encoded in the genome of human. [PRO:WCB, UniProtKB:P47900] | Homo sapiens (human) |
| Compound | Definition | Classes | Roles |
|---|---|---|---|
| pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid | 5'-phosphopyridoxal-6-azobenzene-2,4-disulfonic acid : An arenesulfonic acid that is pyridoxal 5'-phosphate carrying an additional 2,4-disulfophenylazo substituent at position 6. pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid: a novel antagonist that selectively blocks P2 purinoceptor receptors; a useful tool to study co-transmission in tissues when ATP and coexisting neurotransmitters act in concert | arenesulfonic acid; azobenzenes; methylpyridines; monohydroxypyridine; organic phosphate; pyridinecarbaldehyde | purinergic receptor P2X antagonist |
| adenosine diphosphate | Adenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position. | adenosine 5'-phosphate; purine ribonucleoside 5'-diphosphate | fundamental metabolite; human metabolite |
| uridine diphosphate | Uridine Diphosphate: A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety. | pyrimidine ribonucleoside 5'-diphosphate; uridine 5'-phosphate | Escherichia coli metabolite; mouse metabolite |
| adenosine monophosphate | Adenosine Monophosphate: Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position. | adenosine 5'-phosphate; purine ribonucleoside 5'-monophosphate | adenosine A1 receptor agonist; cofactor; EC 3.1.3.1 (alkaline phosphatase) inhibitor; EC 3.1.3.11 (fructose-bisphosphatase) inhibitor; fundamental metabolite; micronutrient; nutraceutical |
| uridine triphosphate | Uridine Triphosphate: Uridine 5'-(tetrahydrogen triphosphate). A uracil nucleotide containing three phosphate groups esterified to the sugar moiety. | pyrimidine ribonucleoside 5'-triphosphate; uridine 5'-phosphate | Escherichia coli metabolite; mouse metabolite |
| methylthio-adp | |||
| diquafosol | diquafosol: purinoceptor P2Y(2) receptor agonist P(1),P(4)-bis(uridin-5'-yl) tetraphosphate : A pyrimidine ribonucleoside 5'-tetraphosphate compound having 5'-uridinyl residues at the P(1)- and P(4)-positions. | pyrimidine ribonucleoside 5'-tetraphosphate; uridine 5'-phosphate | mouse metabolite; P2Y2 receptor agonist |
| 2-chloro-atp | 2-chloro-ATP: new ATP analog; relaxes mammalian gut preparations; structure | ||
| adenosine 5'-o-(1-thiodiphosphate) | adenosine 5'-O-(1-thiodiphosphate): do not confuse with ADP beta S | ||
| nitro-bis(2,4-pentanedionato)(pyridine)cobalt(iii) | nitro-bis(2,4-pentanedionato)(pyridine)cobalt(III): structure given in first source P(1),P(5)-bis(5'-adenosyl) pentaphosphate : A diadenosyl pentaphosphate having the two 5'-adenosyl residues attached at the P(1)- and P(5)-positions. | diadenosyl pentaphosphate | Escherichia coli metabolite; vasoconstrictor agent |
| salvianolic acid a | salvianolic acid A: a nootropic depside from Salvia miltiorrhizia | stilbenoid | |
| 2-methylthio-atp | 2-methylthio-ATP: purinergic receptors agonist; relaxes mammalian gut preparations; structure given in first source | ||
| adp beta s | adenosine 5'-O-(2-thiodiphosphate): partial agonist toward platelet aggregation; see also record for 1-thiodiphosphate cpd | ||
| acid blue 25 | |||
| acid blue 129 | |||
| mrs2500 |