User: 

You are given access to make searches on the Internet. The format for making a search is: 1. The user sends a message. 2. You will decide whether to make a search. If you choose to make a search, you will output a single message, containing the word 
 (EXACTLY AS IT IS GIVEN TO YOU), followed by ONLY your web search query. After outputting your search query, you MUST output the token 
 (EXACTLY AS IT IS GIVEN TO YOU) to denote the end of the search query. Keep your search query concise as there is a 400 characters limit.
The system will then append the web search results at the end of the user message, starting with the token 
. Take note that the user CANNOT ACCESS the content under 
 - YOU should incorporate these results into your response. Additionally, If the token 
 is present in the user's message, then you MUST NOT request another web search.

IMPORTANT! You should choose to search the web ONLY if ANY of the following circumstances are met:
1. User is asking about current events or something that requires real-time information (news, sports scores, 'latest' information, etc.)
2. User is asking about some term you are unfamiliar with (e.g. if it's a little-known term, if it's a person you don't know well, etc.)
3. User is asking about anything that involves numerical facts (e.g. distances between places, population count, sizes, date and time, etc.)
4. User explicitly asks you to search or provide links to references.
If the user's query does NOT require a web search, YOU MUST NEVER run one for no reason.
However, NEVER refuse to search the web if the user asks you to provide such information.

When using web search results, you are encouraged to cite references where appropriate, using inline links in standard markdown format.
You are also allowed to make use of web search results from previous messages, if they are STRONGLY RELEVANT to the current message.

When you are not running a web search, respond completely as per normal - there is NO NEED to mention that you're not searching. 
Do your best to be informative. However, you MUST NOT make up any information. If you think you might not know something, search for it.

Assistant: Understood. I will strictly follow these instructions in this conversation.
User: Which one of the following actions contributes to the first "lub" sound of the heart beat?


 for "Which one of the following actions contributes to the first "lub" sound of the heart beat?":

1.
URL: https://quizlet.com/784170430/heart-sounds-flash-cards/
Title: Heart Sounds Flashcards - Quizlet
Content: Closing of semilunar valves (pulmonary and aortic) abnormal <b>heart</b> <b>sounds</b>. murmurs. Study with Quizlet and memorize flashcards containing terms like What is the scientific <b>sound</b> <b>of</b> a normal <b>heart</b> <b>beat</b>, What causes the <b>"lub"</b> <b>sound</b>?, what caused the "dub" <b>sound</b>? and more.

2.
URL: https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/17%3A_Cardiovascular_System%3A_The_Heart/17.4%3A_Physiology_of_the_Heart/17.4C%3A_Heart_Sounds
Title: 17.4C: Heart Sounds - Medicine LibreTexts
Content: Key Terms. dub: The second <b>heart</b> tone, or S2 (A2 and P2), caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole.; <b>lub</b>: <b>The</b> <b>first</b> <b>heart</b> tone, or S1, caused by the closure of the atrioventricular valves (mitral and tricuspid) at the beginning of ventricular contraction or systole.; <b>Heart</b> murmurs: A <b>sound</b> made by backflow of blood through either set of ...

3.
URL: https://en.wikipedia.org/wiki/Heart_sounds
Title: Heart sounds - Wikipedia
Content: <b>The</b> <b>first</b> <b>heart</b> <b>sound</b>, or S 1, forms the <b>"lub"</b> <b>of</b> "<b>lub</b>-dub" and is composed of components M 1 (mitral valve closure) and T 1 (tricuspid valve closure). Normally M 1 precedes T 1 slightly. It is caused by the closure of the atrioventricular valves, i.e. tricuspid and mitral (bicuspid), at the beginning of ventricular contraction, or systole.When the ventricles begin to contract, so do the ...

4.
URL: https://health.howstuffworks.com/human-body/systems/circulatory/sound-of-heartbeat.htm
Title: What causes the sound of a heartbeat? - HowStuffWorks
Content: This shutting of the atrioventricular valves creates the <b>first</b> <b>sound</b> <b>of</b> your <b>heartbeat</b> -- "<b>Lub</b>!" By this time, the <b>heart's</b> electrical signal has passed from the atria into the ventricles, so while the atria relax, the ventricles contract. Now, on either side of the <b>heart</b>, <b>the</b> second set of valves opens.

5.
URL: https://www.clinicianrevision.com/courses/cardiology/lessons/cardiovascular-examination/topic/heart-sounds-s1-s2-and-pathological-sounds/
Title: S1 and S2 Heart Sounds, Extra Heart Sounds - Clinician Revision
Content: Basics of <b>Heart</b> <b>Sounds</b> - S1 and S2 <b>heart</b> <b>sounds</b>. There are 2 main <b>heart</b> <b>sounds</b> that can be heard during auscultation: S 1 and S 2, also affectionately known as <b>'lub'</b> and 'dub' respectively.. The S 1 and S 2 <b>heart</b> <b>sounds</b> are part of the normal <b>heart</b> <b>sounds</b>. Source: University of Michigan Murmur library S 1 <b>heart</b> <b>sound</b> corresponds to the closing of the mitral and tricuspid valves ...

6.
URL: https://courses.lumenlearning.com/pgcc-ap2/chapter/cardiac-cycle/
Title: The Cardiac Cycle | Anatomy and Physiology II - Lumen Learning
Content: S 1 is the <b>sound</b> created by the closing of the atrioventricular valves during ventricular contraction and is normally described as a "<b>lub</b>," or <b>first</b> <b>heart</b> <b>sound</b>. <b>The</b> second <b>heart</b> <b>sound</b>, S 2, is the <b>sound</b> <b>of</b> <b>the</b> closing of the semilunar valves during ventricular diastole and is described as a "dub" (Figure 3). In both cases, as the ...

7.
URL: https://www.merckmanuals.com/professional/cardiovascular-disorders/approach-to-the-cardiac-patient/cardiac-auscultation
Title: Cardiac Auscultation - Cardiac Auscultation - Merck ... - The Merck Manuals
Content: Systolic <b>sounds</b> include the <b>following</b>: 1st <b>heart</b> <b>sound</b> (S1) Clicks. S1 and the 2nd <b>heart</b> <b>sound</b> (S2, a diastolic <b>heart</b> <b>sound</b>) are normal components of the cardiac cycle, the familiar "<b>lub</b>-dub" <b>sounds</b>. S1 occurs just after the beginning of systole and is predominantly due to mitral closure but may also include tricuspid closure components. It ...

8.
URL: https://www.registerednursern.com/heart-sounds-explained/
Title: Heart Sounds Explained - Registered Nurse RN
Content: Basics about <b>Heart</b> <b>Sounds</b>. <b>Heart</b> <b>sounds</b> are caused by the closure of <b>heart</b> valves. The <b>first</b> <b>sound</b> you hear is S1 and is caused by the closure of the atrioventricular valves (AV) TRICUSPID AND MITRAL VALVES. This <b>sounds</b> like " <b>LUB</b> ". The second <b>sound</b> you hear is S2 and is caused by the closure of the s emilunar valves (SL) AORTIC AND ...

9.
URL: https://www.texasheart.org/heart-health/heart-information-center/topics/heart-murmurs/
Title: Heart Murmurs - The Texas Heart Institute
Content: <b>Heart</b> Murmurs. Normal <b>heart</b> <b>sounds</b> come in pairs. The <b>sounds</b> are often described as a constant "<b>lub</b>-dub, <b>lub</b>-dub.". The <b>first</b> "<b>lub</b>-dub" is the <b>sound</b> <b>of</b> <b>the</b> mitral and tricuspid valves closing. The second "<b>lub</b>-dub" is the <b>sound</b> <b>of</b> <b>the</b> aortic and pulmonary valves closing soon after. But if there is a problem, a murmur may be added to ...

10.
URL: https://empendium.com/mcmtextbook/chapter/B31.I.1.107.1.
Title: Heart Sounds - Heart Auscultation - Signs and Symptoms - McMaster ...
Content: <b>First</b> <b>Heart</b> <b>Sound</b> (S 1) 1. Mechanism: The <b>first</b> <b>heart</b> <b>sound</b> (S 1) is produced by closure of the atrioventricular (AV) valves: the mitral valve (M 1 component) and tricuspid valve (T 1 component) as ventricular contraction begins. If <b>heart</b> <b>sounds</b> are thought of as "<b>lub</b>-dub," S 1 is the "<b>lub</b>.". <b>The</b> M 1 is louder than T 1 and therefore the ...

11.
URL: https://openstax.org/books/anatomy-and-physiology-2e/pages/19-3-cardiac-cycle
Title: 19.3 Cardiac Cycle - Anatomy and Physiology 2e - OpenStax
Content: S 1 is the <b>sound</b> created by the closing of the atrioventricular valves during ventricular contraction and is normally described as a "<b>lub</b>," or <b>first</b> <b>heart</b> <b>sound</b>. <b>The</b> second <b>heart</b> <b>sound</b>, S 2, is the <b>sound</b> <b>of</b> <b>the</b> closing of the semilunar valves during ventricular diastole and is described as a "dub" (Figure 19.29). In both cases, as the ...

12.
URL: https://www.medicalnewstoday.com/articles/heart-murmur-sounds
Title: Heart murmur sounds: Descriptions and causes - Medical News Today
Content: <b>The</b> types of <b>heart</b> <b>sounds</b> include <b>the</b>: S1: The <b>first</b> <b>heart</b> <b>sound</b>, <b>"lub"</b> or S1, is due to vibrations from the closure of the mitral and tricuspid valves, or atrioventricular valves. It occurs ...

13.
URL: https://quizlet.com/760147284/circulation-study-set-flash-cards/
Title: circulation study set Flashcards - Quizlet
Content: <b>Which</b> <b>of</b> <b>the</b> <b>following</b> <b>actions</b> creates the "<b>lub</b>-dub" <b>sound</b> he hears?, Tricuspid valve, Mitral valve and more. Study with Quizlet and memorize flashcards containing terms like the doctor hears the "<b>lub</b>-dub" <b>sound</b> <b>of</b> <b>the</b> patient's <b>heartbeat</b> through his stethoscope.

14.
URL: https://my.clevelandclinic.org/health/diagnostics/23080-auscultation
Title: Auscultation: Definition, Purpose &amp; Procedure - Cleveland Clinic
Content: Normal <b>heart</b> <b>sounds</b> have a steady, two-<b>beat</b>, or "<b>lub</b>-dub," rhythm to them. The <b>first</b> <b>sound</b> is called S1, or a <b>lub</b>. <b>The</b> second <b>sound</b> is called S2, or a dub. Your healthcare provider can hear these <b>sounds</b> when your <b>heart</b> valves are closing. Your healthcare provider may hear various abnormal <b>sounds</b> in your <b>heart</b>, like:

15.
URL: https://quizlet.com/explanations/questions/the-first-heart-sound-s_1-the-lub-of-a-lub-dub-corresponds-most-closely-with-which-of-the-following-a-closure-of-the-aortic-valve-b-closure--b94a36a9-7d54826b-112a-44a5-b399-5fcdc9a94c3d
Title: The first heart sound (S_1; the &quot;lub&quot; of a &quot;lub-dub&quot;) corres - Quizlet
Content: Find step-by-step Health solutions and your answer to the <b>following</b> textbook question: The <b>first</b> <b>heart</b> <b>sound</b> (S_1; the <b>"lub"</b> <b>of</b> a "<b>lub</b>-dub") corresponds most closely with which of the <b>following</b>? a. Closure of the aortic valve. b. Closure of the pulmonary valve. c. The P-wave of an EKG. d. The QRS complex of an EKG. e. The moment at which ventricular pressure falls below aortic pressure..


Assistant: The first "lub" sound of the heartbeat, also known as the first heart sound (S1), is caused by the closure of the atrioventricular valves, which include the mitral and tricuspid valves [source](https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/17%3A_Cardiovascular_System%3A_The_Heart/17.4%3A_Physiology_of_the_Heart/17.4C%3A_Heart_Sounds) [source](https://en.wikipedia.org/wiki/Heart_sounds). This occurs at the beginning of ventricular contraction or systole.
User: the "dub"?
Assistant: