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Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

Origin of heart beat and its conduction is represented by

  1. AV node $\rightarrow$ Bundle of His $\rightarrow$ SA node $\rightarrow$ Purkinje fibres
  2. SA node $\rightarrow$ Purkinje fibres $\rightarrow$ AV node $\rightarrow$ Bundle of His
  3. Purkinje fibres $\rightarrow$ AV node $\rightarrow$ SA node $\rightarrow$ Bundle of His
  4. SA node $\rightarrow$ AV node $\rightarrow$ Bundle of His $\rightarrow$ Purkinje fibres
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • The impulse for heart beat is originated in SA node. It is known as the pace maker of heart and situated in upper right corner of right atrium. 
  • The electrical impulses generated by SA node are conducted to Atrio Ventricular or AV node. 
  • From the AV node, the impulses are transmitted to AV bundle, known as bundle of His which convey the impulses of contraction to the apex of myocardium. 
  • The impulses cause the Purkinje fibres to sweep upwards and outwards which results in pumping of blood into aorta and pulmonary artery.
  • So, the correct sequence of propagation of cardiac impulse is SA node, AV node, Bundle of His, Purkinje fibres.
So, the correct answer is 'SA node →→ AV node →→ Bundle of His →→ Purkinje fibres'.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

Typical 'lubb-dup' sounds heard in heart beat are due to

  1. Closing of bicuspid and tricuspid valves

  2. Closing of semilunar valves

  3. Blood under pressure through aorta

  4. Closure of bicuspid-tricuspid valves followed by semilunar valves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Heart produces two distinct sounds that can be heard with the help of stethoscope. These are 'lubb' and 'dup'.
  • Lubb is the first sound which has a low pitch and produced by the closure of tricuspid and bicuspid valves (collectively called atrioventricular valves) at the beginning of ventricular systole.
  • Dup is the second sound which is sharp and has a high pitch. It is produced by closure of semilunar valves by the end of ventricular systole and beginning of ventricular diastole).
So, the correct answer is 'Closure of bicuspid-tricuspid valves followed by semilunar valves'.
Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

The first heart sound is

  1. Lubb during closure of semilunar valves

  2. Dupp during closure of semilunar valves

  3. Lubb during closure of atrioventricular valves

  4. Dupp during closure of atrioventricular valves
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
When the heart beats, it produces sounds that can be heard by stethoscope. There are four heart sounds which are designated as S1, S2, S3 and S4.
  • S1: It is the first sound 'lubb'. It has slow pitch and produced by closure of atrioventricular valves at the beginning of ventricular systole.
  • S2: It is the second sound 'dup'. It is sharper and has high pitch. It is produced by closure of semilunar valves by the end of ventricular systole. 
  • S3 and S4 are usually faint and may not be audible. S3 is produced during ventricular filling of heart and S4 is produced during atrial systole.
So, the correct answer is 'Lubb during closure of atrioventricular valves'.
Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

What will be the number of heart beats per minute, if the stroke volume of heart increases, with total volume of blood remains same

  1. Remains constant

  2. Decreases

  3. Increases

  4. Become erratic.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cardiac output is the product of stroke volume and heart rate. If cardiac output remains relatively constant and stroke volume increases, the heart rate must decrease to maintain the same output.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

Doctors use stethoscope to hear the sounds produced during each cardiac cycle. The second sound in heard when :

  1. AV valves open up

  2. Ventricular walls vibrate due to gushing in of blood from artia.

  3. Semilunar valves close down after the blood flows into vessels from ventricles.

  4. AV node recives signal from SA node.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
During each cardiac cycle, two prominent sounds are produced which can be easily heard through a stethoscope. The first sound (lub) is associated with the closure of the tricuspid and bicuspid valves during ventricular systole to prevent the backflow of blood to atria. The second sound (dub) is associated with the closure of semilunar valves during ventricular diastole to prevent the backflow of blood to ventricles.
Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

The rate of heart beat is determined by

  1. SA node

  2. AV node

  3. Purkinie fibre

  4. Papillary muscles
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The SA node acts as the primary pacemaker of the heart, setting the rhythm and rate of the heartbeat. The other structures listed are part of the conduction system but do not set the primary rate.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

In which type of stole, does phloem surround the xylem both externally and internally?

  1. Amphiphloic siphonostele

  2. Ectophtoic siphonostele

  3. Haplostele

  4. Actinostle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In an amphiphloic siphonostele, the phloem is found on both the outer and inner sides of the xylem. This is a specific type of vascular arrangement in certain plants.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

The rate conduction of impulse in the conducting system of heart is fastest in

  1. Atrial muscles

  2. Bundle of His

  3. Purkinje's fibres

  4. AV node
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In the cardiac conduction system, Purkinje fibers have the fastest rate of impulse conduction, allowing the ventricles to contract rapidly and uniformly from the apex upward.

Multiple choice biology transportation in plants and circulation in animals heart beat cardiac cycle heart, blood vessels and cardiac cycle

State whether the following statements are true or false.
Human heart is neurogenic because the heart beat originates in the nodal tissues.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The heart is entirely made up of cardiac muscles. Muscle cells are also called myocytes. The control of the heart function is by a set of muscles or special node of the modified heart muscle, the sinoatrial node (SAN) located in the atria, so the heart is, therefore, called myogenic.

So, the correct option is 'False'.