Class 12 biology MCQs chapter 8 (Respiration and Circulation)


Choose the correct alternatives from those given below and complete the statements.


1. The muscular structure that separates the
thoracic and abdominal cavity is _______.
    a. pleura
    b. diaphragm
    c. trachea
    d. epithelium

Answer : Diaphragm
Explanation : The diaphragm separates the thoracic cavity, containing the heart and lungs, from the abdominal cavity and performs an important function in respiration: as the diaphragm contracts, the volume of the thoracic cavity increases, creating a negative pressure there, which draws air into the lungs.



2. What is the minimum number of plasma membrane that oxygen has to diffuse across to pass from air in the alveolus to haemoglobin inside a R.B.C.?
    a. Two
    b. Three
    c. Four
    d. Five

Answer : Five 



3. ________ is a sound producing organ,
    a. Larynx
    b. Pharynx
    c. Tonsils
    d. Trachea

Answer : Larynx
Explanation : Sound producing organ of human being is the larynx. It is a cartilaginous box and is also known as the sound box. There are two vocal cords in the box which vibrate on the passage of air through them and hence produce sound.



4. The maximum volume of gas that is inhale during breathing in addition to T.V is _____.
    a. residual volume
    b. I.R.V.
    c. G.R.V.
    d. vital capacity

Ans : I.R.V.



5. ________ muscles contract when the external intercostal muscles contract
    a. Internal abdominal
    b. Jaw
    c. Muscles in bronchial walls
    d. Diaphragm

Answer : diaphragm



6. Movement of cytoplasm in unicellular organisms is called __________.
    a. diffusion
    b. cyclosis
    c. circulation.
    d. thrombosis.

Answer : Cyclosis 
Explanation : Cytoplasmic streaming, also called protoplasmic streaming and cyclosis, is where there is flow inside the cytoplasm.[1] It is typically observed in large plant and animal cells. Here flow means that the cytoplasm is moving inside the cell, it is not stationary. 



7. Which of the following animals do not have closed circulation?
    a. Earthworm.
    b. Rabbit
    c. Butterfly
    d. Shark

Answer : Butterfly
Explanation : All other orgnanism have closed circulatory system and Organisms with an open circulatory system typically have a relatively high volume of hemolymph and low blood pressure. Examples of animals with open circulatory systems include insects, spiders, prawns and most mollusks.



8. Diapedesis is performed by _________.
    a. erythrocytes
    b. thrombocytes
    c. adipocytes
    d. leucocytes

Ans : Leucocytes 


9. Pacemaker of heart is _________.
    a. SA node
    b. AV node
    c. His bundle
    d. Purkinje fibers

Answer : SA Node
Explanation : The sinoatrial (SA) node or sinus node is the heart's natural pacemaker. It's a small mass of specialized cells in the top of the right atrium (upper chamber of the heart). It produces the electrical impulses that cause your heart to beat.


10. Which of the following is without nucleus?
    a. Red blood corpuscle
    b. Neutrophill
    c. Basophill
    d. Lymphocyte

Answer : Red blood carpuscle 


11. Cockroach shows which kind of circulatory system?
    a. Open
    b. Closed
    c. Lymphatic
    d. Double

Ans : Open 
Explanation : cockroach consist open circulatory system.


12. Diapedesis can be seen in _________ cell.
    a. RBC
    b. WBC
    c. Platelet
    d. neuron

Ans : WBC



13. Opening of inferior vena cava is guarded by __________.
    a. bicuspid valve
    b. tricuspid valve
    c. Eustachian valve
    d. Thebesian valve

Answer : Eustachian valve 
Explanation : The inferior vena cava, larger than the superior, returns the blood from the lower half of the body, and opens into the lowest part of the atrium, near the atrial septum, its orifice (Opening of inferior vena cava) being directed upward and backward, and guarded by a rudimentary valve, the valve of the inferior vena cava (Eustachian valve).



14. ___________ wave in ECG represent atrial depolarization.
    a. P
    b. QRS complex
    c. Q
    d. T

Ans : P


15. The fluid seen in the intercellular spaces in Human is _________
    a. blood
    b. lymph
    c. interstitial fluid
    d. water

Answer : Interstitial fluid 
Explanation : Interstitial fluid is found in the interstitial spaces, also known as the tissue spaces. Interstitial mixes with and becomes intercellular fluid when it flows between cells.

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