KOMPAS.com – Otot merupakan alat gerak aktif yang sangat penting bagi manusia. Otot bekerja dengan cara berkontraksi, menggerakkan tulang dan sendi, membuat manusia dan hewan bisa menggerakkan anggota tubuhnya.
Namun, bagaimana mekanisme terjadinya kontraksi otot? Menurut B. Brenner dan E. Eisenberg dalam jurnal The Mechanism of Muscle Contraction: Biochemical, Mechanical, and Structural Approaches to Elucidate Cross-bridge Action in Muscle (1987) kontraksi otot teradi ketika filament aktin tipis dan filament miosin tebal saling bergesekan.
Mekanisme kontraksi otot dimulai dari sistem saraf pusat sebagai pusat kendali tubuh. Sistem saraf pusat, baik otak maupun sumsum tulang belakang mengeluarkan impuls atau potensial aksi ke neuron motorik.
Potensial aksi kemudian akan menjalar hingga ke ujung serat otot memicu pelepasan asetilkolin. Dilansir dari BioNinja, asetilkolin kemudian memulai depolarisasi di dalam sarkolema dan menyebabkan retikulum sarkoplasma melepaskan ion kalsium (Ca2+).
Pembentukan jembatasan silang aktin dan miosin
Setelah pelepasan ion kalsium, mekanisme otot masuk ke tahap selanjutnya yaitu pembentukan jembatan sialng antara aktin dan miosin. Ion kalsium yang dilepaskan kemudian berikatan dengan troponin.
Hal tersebut mengaktifkan aktin dan memberikan jalan untuk berikatan miosin. Miosin yang berikatan dengan aktin membentuk suatu struktur yang dinamakan dnegan jembatan silang.
Miosin kemudian mengikat aktin dan menariknya ke dalam, tahapan ini mengonsumsi energi dalam bentuk ATP. Ikatan ini melepaskan ADP dan juga fosfat. Kepala miosin kemudian berikatan dengan ATP yang baru, membuatnya melepaskan aktin.
Kepala miosin kemudian berada dalam konfigurasi energi yang tinggi dan siap berikatan dengan aktin selanjutnya.
NURUL UTAMI Pergeseran jembatan silang aktin dan miosin yang menyebabkan kontraksi otot
Dilansir dari Medicine Libretexts, kepala miosin bergerak menarik aktin bersamanya menyebakan sarkomer memendek dan otot berkontraksi. Penarikan aktin oleh miosin inilah yang membuat serat otot memendek dan berkontraksi sesuai dengan impuls yang diberikan.
Pergeseran aktin dan miosin terus berlanjut, membuat otot berkontraksi dan memungkinkan manusia untuk bergerak juga mempertahankan kerja organ. Dilansir dari Lumen Learning, kontraksi otot baru akan berhenti jika sinyal dari neuron motorik berakhir.
Berakhirnya sinyal akan menghentikan retikulum sarkoplasma untuk melepaskan ion kalsium. Dan semua ion kalsium yang masih tersisa dipompa kembali ke dalam retikulum sarkoplasma. Hal tersebut menyebabkan ikatan kalsium dengan troponin berhenti yang secara otomatis juga menutup situs pengikatan antara aktin dan miosin.
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Pilihan Untukmu
`); var wSpecStop = createElementFromHTML(`
Konten disembunyikan. Muat ulang halaman untuk perbarui rekomendasi.
`); reactionPopup.querySelector('.buttonShare').setAttribute('data-title', item.title); reactionPopup.querySelector('.buttonShare').setAttribute('data-url', itemUrl); reactionPopup.querySelector('.buttonShare').setAttribute('data-campaign', 'AIML_Widget_Desktop'); let userFeedback = new UserFeedback(resultObj.engine['tracker_algsrc'], itemUrl + tracker_params, jxRecHelper, index); reactionPopup.querySelector('.buttonBookmark').addEventListener('click', function() { do_bookmark(itemUrl, index, userFeedback); }); reactionPopup.querySelector('.buttonShare').addEventListener('click', function() { userFeedback.event('share'); }); reactionPopup.querySelector('.buttonNotInterest').addEventListener('click', function() { if (getCookie('kmps_usrid')) { hideThisArt(this); userFeedback.event('not-interested'); } else { const parentAction = this.parentElement.parentElement.parentElement if (!!parentAction) { let indexElement = parentAction.getAttribute('data-index') if (indexElement != 'undefined') { localStorage.setItem('reaction_not_interest_temp', JSON.stringify({ urlpage: items[indexElement].url })) } } window.location.href = "" + btoa(window.location.href); } }); /** * trigger action "userFeedback" that user not interest item before, when not interest without login */ if (getCookie('kmps_usrid') && localStorage.getItem('reaction_not_interest_temp')) { const tempUrlNotInterest = JSON.parse(localStorage.getItem('reaction_not_interest_temp')) if (itemUrl == tempUrlNotInterest.urlpage) { userFeedback.event('not-interested'); localStorage.removeItem('reaction_not_interest_temp'); } } wSpecStop.querySelector('.wSpec-stop-undo').addEventListener('click', function() { showThisArt(this); userFeedback.event('un-not-interested'); }); recItem.appendChild(buttonOption); recItem.appendChild(reactionPopup); recItem.appendChild(wSpecStop); } var recItemWrapperA = createElement('a', null, null, null); recItemWrapperA.setAttribute('href', itemUrl + tracker_params); var titleDiv = createElement('h4', null, null, [cssClasses.title]); var titleTextNode = document.createTextNode(item.title); if (item.itemType == 'video') { var iconVideo = createElement('div', null, null, ['icoInline', 'icoVideo']); iconVideo.style.marginRight = '5px'; titleDiv.appendChild(iconVideo); } titleDiv.appendChild(titleTextNode); var sourceDiv = null; if (item.hasOwnProperty('method')) { sourceDiv = createElement('div', null, null, [cssClasses.source], resultObj.engine['type'] + ' . ' + item.method.toUpperCase()); } else { var sourceDiv = createElement('div', null, null, [cssClasses.source], resultObj.engine['type']); } var textWrapper = createElement('div', null, null, [cssClasses.text_wrapper]); textWrapper.appendChild(categoryDiv); textWrapper.appendChild(titleDiv); textWrapper.appendChild(sourceDiv); recItemWrapper.appendChild(imgWrapper); recItemWrapper.appendChild(textWrapper); recItemWrapperA.appendChild(recItemWrapper); recItem.appendChild(recItemWrapperA); widgetWrapper.appendChild(recItem); // hook up the click handler for this item // recItem.onclick = handleClick.bind(null, jxRecHelper, itemUrl + tracker_params, index); recItemWrapperA.onclick = handleClick.bind(null, jxRecHelper, itemUrl + tracker_params, index); }); } // end while var endDate = new Date(); var loadtime = (endDate.getTime() - startDate.getTime()); trackEventGa('AIML Article Recommendation', 'Content Loaded', 'algsrc='+algsrc+',site=SKOLA,device=desktop,loadtime=' + loadtime) let domain = window.location.hostname; if(domain=='){ var url=window.location.href.split("/"); domain=url[2]+'/'+url[3] } let user_subs_type = "Gues"; let subs_type = ""; let is_lgn = 0; let engine = algsrc; if(getCookie('kmps_usrid')){is_lgn=1}; let time_load = loadtime; resolve(); /*** * JXRECSDK NOTES 3 of 5 - * pass all the info about the items to the rec helper * each one is an object: ALL MANDATORY * div * id * pos */ jxRecHelper.items(widgetItemArr); /*** * JXRECSDK NOTES 4 of 5 - * Call the ready() of the helper object when the recommendation * results have been populated to the widget * (This will register the action=ready event) */ if (resultObj.engine['type'] == 'api-1') { jxRecHelper.ready(resultObj.options.algo + ":" + resultObj.options.version); } else { jxRecHelper.ready(resultObj.engine['type']); } } else { jxRecHelper.error(204); console.error("Error: no recommendation items"); return; } } catch (err) { jxRecHelper.error(901); console.log(err.stack); let domain = window.location.hostname; if(domain=='){ var url=window.location.href.split("/"); domain=url[2]+'/'+url[3] } let user_subs_type = "Gues"; let subs_type = "" let is_lgn = 0; let engine = algsrc; if(getCookie('kmps_usrid')){is_lgn=1}; let endDate = new Date(); let time_load = (endDate.getTime() - startDate.getTime()); } }); } const _jxRecSdkURL = ' var startDate = new Date(); class OneWidget { constructor() { //this is also the one we will pass to the JX rec helper object when //we instantiate it: //In this implementation most of these come from the options obj //on the publisher page. this._options = { accountid: '9262bf2590d558736cac4fff7978fcb1', pageurl: ' widget_id: '1000183-6xWeiWZFIM', type: 'pages', container: 'rekomendasi-konten-pilihan-untukmu-aiml', keywords: content_tags, title: title, customid: "69", count: 14, }; this._containerId = this._options.container; this._container = document.getElementById(this._containerId); this._engines = [{"url":"https:\/\/recommendation.jixie.media\/v1\/recommendation","method":"GET","pageurl":"https:\/\/","system":"jx","type":"api-1","tracker_params":"?source=widgetML","tracker_algsrc":"V","count":14,"page_status":"read","excludeitemids":"20220121150516269"}]; } kickOff() { startDate = new Date(); const rand = Math.floor(Math.random() * 1000); /*const randSystem = Math.floor(Math.random() * 3); this._engine = this._engines[randSystem] if (location.hostname.indexOf('lestari') != -1) { this._engine = this._engines[1] }*/ this._engine = this._engines[0]; this._options.system = this._engine['system'] trackEventGa('AIML Article Recommendation', 'Widget load', 'algsrc=' + this._engine['tracker_algsrc'] + ',site=SKOLA,device=desktop') let promJXSDK = fetchJSFileP(_jxRecSdkURL); let thisObj = this; // first we wait on the JX REC SDK to be loaded and initialized let recHelperObj = null; let recResults = null; promJXSDK .then(function() { /*** * JXRECSDK NOTES 1 of 5 - INSTANTIATION OF A JX REC HELPER OBJECT * Call this AFTER JX REC SDK is loaded but BEFORE you call your REC * backend. * * param: MANDATORY options object * options object must at a minimal have * accountid: get from jixie * widgetid: get from jixie * container: DIV ID of the destination div to house the widget * (for jixie widget this is just the options object passed from the page) * * (This will also register the action=load event) */ recHelperObj = jxRecMgr.createJxRecHelper(thisObj._options); let basicInfo = thisObj._options; basicInfo.engine = thisObj._engine if (basicInfo.engine.type == 'api-1') { var options = { count: basicInfo['count'], adpositions: "", keywords: basicInfo['keywords'], title: basicInfo['title'], date_published: "2022-01-21", pagecategory: "SKOLA", algo: "mixed" }; if(getCookie('kmps_usrid')){ var kg = { pagetype:basicInfo.engine.page_status, uid:getCookie('kmps_usrid'), ukid:getCookie('kmp_uid') } if(basicInfo.engine.page_status=='read'){ kg['excludeitemids'] = basicInfo.engine.excludeitemids; kg['multiFormat'] = true; } options['additional'] = { kg:kg }; } return recHelperObj.getJxRecommendations(options); } else { return fetchRecommendationsP(basicInfo, recHelperObj.getJxUserInfo()); } }) .then(function(resp) { if (thisObj._engine.type == 'api-3') { recResults = new Object recResults.items = resp.docs.result; } else { recResults = resp; } recResults.engine = thisObj._engine; if (!resp || !recResults.items || recResults.items.length == 0) { /*** * JXRECSDK NOTES 2 of 5 - * Call the error() function on the recHelper when either an error * has occured in the fetching or there are no recommended items * * (This will register the action=error event) */ recHelperObj.error(204); throw "no recommendation results"; } }) .then(function() { // everything is ready (recommendation results, css): document.getElementById("rekomendasi-konten-pilihan-untukmu-aiml").classList.remove("-loading"); document.querySelector('.wSpec-list').remove(); createDisplay(rand, thisObj._container, recResults, recHelperObj) .then(function() { toggleDropdown(); //observe lozad lozad('.lozad', { load: function(el) { el.src = el.dataset.src; el.onload = function() { el.classList.add('fade') } } }).observe() }) }) .catch(function(error) { console.log(`Unable to create recommendations widget ${error.stack} ${error.message}`); }); } } var limit_gtm_ready = 1; function check_gtm_ready() { if ('ga' in window) { // create a new instance of our widget based on the options const newW = new OneWidget(); newW.kickOff(); } else { const timeout_gtm_ready = setTimeout(check_gtm_ready, 500) limit_gtm_ready += 1; if (limit_gtm_ready > 10) { clearTimeout(timeout_gtm_ready); const newW = new OneWidget(); newW.kickOff(); } } } check_gtm_ready() document.querySelector('.wSpec-secret').addEventListener('click', function(e) { e.preventDefault(); let wSl = document.querySelectorAll('.wSpec-source'); if (wSl.length > 0) { for (let i = 0; i < wSl.length; i++) { wSl[i].classList.toggle('show') } } }) function trackEventGa(category, action, label) { if ("ga" in window) { ga(function() { tracker = ga.getAll()[0]; if (tracker) { tracker.send("event", category, action, label); console.log('track event ', category, action, label) } }) } } function formBody(obj) { let formBody = []; for (var property in obj) { let encodedKey = encodeURIComponent(property); let encodedValue = encodeURIComponent(obj[property]); formBody.push(encodedKey + "=" + encodedValue); } return formBody.join("&"); } function getCookie(name) { var name = name + '='; var cookies = decodeURIComponent(document.cookie).split(';'); for (var i = 0; i < cookies.length; i++) { var c = cookies[i]; while (c.charAt(0) == ' ') { c = c.substring(1); } if (c.indexOf(name) == 0) { return c.substring(name.length, c.length); } } } function get_guid(url) { const videoPath = url.match(/\/watch\/(\d+)/); if (videoPath) { return `video.${videoPath[1]}`; } let arrayUrl = url.split('/'); let readPath = arrayUrl.indexOf('read'); if (arrayUrl[readPath + 1] == 'xml') { readPath += 1; } let year = arrayUrl[readPath + 1]; let month = arrayUrl[readPath + 2]; let date = arrayUrl[readPath + 3]; let id = arrayUrl[readPath + 4]; let guid = `.xml.${year}.${month}.${date}.${id}`; return guid; } function toggleDropdown() { let tdd = document.querySelectorAll('[data-dropdown]') if (!!tdd) { tdd.forEach((el) => { el.addEventListener('click', function() { el.parentElement.classList.toggle('-active') let saved = el.parentElement.getAttribute('data-saved') let kmps_usrid = getCookie('kmps_usrid'); if (kmps_usrid && !saved && el.parentElement.classList.contains('-active')) { let url = el.parentElement.getAttribute('data-url'); let guid = get_guid(url); check_bookmark( kmps_usrid, guid ).then(function(resp) { if (resp.hasOwnProperty('total_data')) { if (resp.total_data > 0) { el.parentElement.querySelector('.buttonBookmark').classList.add('-active'); el.parentElement.querySelector('.buttonBookmark').innerHTML = 'Hapus dari tersimpan'; el.parentElement.setAttribute('data-saved', 'true'); } else { el.parentElement.setAttribute('data-saved', 'false'); } } }) } }) document.addEventListener("click", function(e) { // console.log(e.target) if (el.contains(e.target)) { // console.log(tdd) } else { el.parentElement.classList.remove('-active') } }); }); } } function check_bookmark(kmps_usrid, guid) { let url = ` return new Promise(function(resolve, reject) { var xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { resolve(JSON.parse(this.responseText)) } }; xmlhttp.open("GET", url, true); xmlhttp.send(); }); } function do_bookmark(pageurl, pos, userFeedback) { const wSpecItem = document.querySelector(`.wSpec-item[data-index="${pos}"]`); const btnBookmark = wSpecItem.querySelector('.buttonBookmark'); const kmps_usrid = getCookie('kmps_usrid'); const guid = get_guid(pageurl); const type = pageurl.match(/\/watch\/(\d+)/) ? 'video' : 'article'; if (kmps_usrid) { if (btnBookmark.classList.contains('-active')) { set_unbookmark({ guid: guid, kmps_usrid: kmps_usrid, type: type }).then(function(resp) { btnBookmark.classList.remove('-active'); btnBookmark.innerHTML = 'Simpan artikel'; reactionToast('Artikel berhasil dihapus dari list yang disimpan'); userFeedback.event('un-save'); }).catch(function(resp) { // message: "Data doesn't exists" if (resp.hasOwnProperty('message') && resp.message.includes('exist')) { btnBookmark.classList.remove('-active'); btnBookmark.innerHTML = 'Simpan artikel'; reactionToast('Artikel berhasil dihapus dari list yang disimpan'); } }) } else { const user_bookmark_url = ""; set_bookmark({ guid: guid, kmps_usrid: kmps_usrid, type: type, publisher: 'kompas', platform: 'desktop' }).then(function(resp) { btnBookmark.classList.add('-active'); btnBookmark.innerHTML = 'Hapus dari tersimpan'; reactionToast('Artikel berhasil disimpan', user_bookmark_url); userFeedback.event('save'); }).catch(function(resp) { // message: "Data already exist" if (resp.hasOwnProperty('message') && resp.message.includes('exist')) { btnBookmark.classList.add('-active'); btnBookmark.innerHTML = 'Hapus dari tersimpan'; reactionToast('Artikel berhasil disimpan', user_bookmark_url); } }) } } else { const login_url = "" + btoa(window.location.href); window.location.href = login_url; } } function set_bookmark(data) { const url = ""; return new Promise(function(resolve, reject) { const xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 201) { resolve(JSON.parse(this.responseText)); } else if (this.readyState == 4 && this.status == 400) { reject(JSON.parse(this.responseText)); } }; xmlhttp.open("POST", url, true); xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8"); xmlhttp.send(formBody(data)); }); } function set_unbookmark(data) { const url = ""; return new Promise(function(resolve, reject) { const xmlhttp = new XMLHttpRequest(); xmlhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { resolve(JSON.parse(this.responseText)); } else if (this.readyState == 4 && this.status == 400) { reject(JSON.parse(this.responseText)); } }; xmlhttp.open("POST", url, true); xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8"); xmlhttp.send(formBody(data)); }); } class UserFeedback { constructor(engine, pageurl, jxRecHelper, pos) { this.engine = engine; this.pageurl = pageurl; this.jxRecHelper = jxRecHelper; this.pos = pos; } event(feedback) { if (this.engine == 'C') { const xmlhttp = new XMLHttpRequest(); let params = { domain: 'kompas.com', ce_userid: getCookie('kmps_usrid'), ce_sessionid: getCookie('ukid'), ce_pageurl: this.pageurl, engine: 'C', ce_feedback: feedback } xmlhttp.open("GET", ' + formatParams(params)); xmlhttp.send(); } else if (this.engine == 'V') { if (feedback == 'share') { this.jxRecHelper.shared(this.pos); } else if (feedback == 'save') { this.jxRecHelper.bookmarked(this.pos); } else if (feedback == 'not-interested') { this.jxRecHelper.hidden(this.pos); } else if (feedback == 'un-not-interested') { this.jxRecHelper.unhidden(this.pos); } } } } function formatParams(params) { return "?" + Object .keys(params) .map(function(key) { return key + "=" + encodeURIComponent(params[key]) }) .join("&") } document.addEventListener("click", function(e){ let dx = document.querySelectorAll('[data-dropdown]') if(dx) { dx.forEach(function(el){ if(el.contains(e.target)) { el.parentElement.classList.toggle('-active') } else { el.parentElement.classList.remove('-active') } }) } })
