Question
The first sound (S$_1$) 'lubb' is caused by blood turbulence associated with:
This question was previously asked in
CUET PG 2026 Agri-Business Management Question Paper (25-Mar-2026) (Shift 2)
The correct answer is
Closing of atrioventricular valves
First Heart Sound S1 Lubb Causes
The first heart sound, referred to as S1 and often described as 'lubb', originates from the events occurring at the beginning of ventricular systole (the heart's contraction phase).
Mechanism of S1 Production
S1 is primarily caused by the:
- Closing of the atrioventricular (AV) valves: This includes the mitral valve (between the left atrium and left ventricle) and the tricuspid valve (between the right atrium and right ventricle). The closure of these valves prevents the backflow of blood into the atria as the ventricles begin to contract. The resulting vibrations and turbulence generate the 'lubb' sound.
Analysis of Options
- Opening of atrioventricular valves: This event occurs during diastole (heart relaxation) and is not the cause of S1.
- Closing of atrioventricular valves: This correctly explains the origin of S1 ('lubb').
- Opening of semilunar valves: These valves (aortic and pulmonary) open after the AV valves close and ventricular pressure exceeds that in the aorta and pulmonary artery. Their opening does not cause S1.
- Closing of semilunar valves: The closure of the aortic and pulmonary valves marks the end of ventricular systole and causes the second heart sound (S2), 'dub'.
Therefore, the turbulence associated with the closing of the atrioventricular valves is the source of the first heart sound (S1) 'lubb'.
Was this answer helpful?
Similar Questions
- The attachment site for microtubules that separates chromosomes during cell division:
- The process of synthesizing ATP from ADP and Pi coupled with electron transport chain is:
- The functionally active form of Vitamin D is:
- Sexual dimorphism is seen in:
- Match the LIST-I with LIST-II
LIST-I LIST-II A. Moss I. Wolffia B. Pteridophyte II. Sequoia C. Gymnosperm III. Selaginella D. Angiosperm IV. Sphagnum
Choose the correct answer from the options given below: - Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: 12-20% acrylamide in PAGE restricts the migration of large molecules.
Reason R: Pore size of the gel affects the separation of molecules.
In the light of the above statements, choose the most appropriate answer from the options given below - Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Spectroscopy technique is used for the study of interaction of electromagnetic radiation with matter.
Reason R: It is used for the identification of substances through the spectrum emitted or absorbed by them.
In the light of the above statements, choose the most appropriate answer from the options given below - Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: The amino acid sequences of Histones H$_3$ and H$_4$ are not highly conserved.
Reason R: Nearly all of the amino acids in a histone molecule are engaged in an interaction with either DNA or another histone.
In the light of the above statements, choose the most appropriate answer from the options given below - Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: X chromosome is acrocentric and Y chromosome is submetacentric.
Reason R: This is based on the position of centromere on the chromosome.
In the light of the above statements, choose the most appropriate answer from the options given below - Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Electron transport chain (ETC) and ATP synthesizing system are located on the inner mitochondrial membrane.
Reason R: The inner surface of the inner mitochondrial membrane possess phosphorylating subunits.
In the light of the above statements, choose the most appropriate answer from the options given below
Important Questions from Mixed Topic (CUET PG)
- Kalpsutra, the illustrated canonical text is from:-
- The Harappan city almost exclusively devoted to craft production was-:
- Mohandas Karamchand Gandhi launched quit India movement after the failure of:-
- The "Objectives Resolution" was introduced in constituent assembly by:-
- Who among the following was not a member of the constituent assembly:-
Need Expert Advice?
Upcoming Exams
GATE
February 06, 2027
Test Series
CUET
CUET PG Psychology (HUQP20) 2026 Mock Test Series
10 Tests
781 Attempts
3.7(15)
English
More Questions from CUET PG
