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Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

Read the following statements regarding mechanism of respiration and choose the correct option.
$1$. Inspiration occurs only when there is negative pressure in the lungs with respect to atmosphere
$2$. Expiration takes place only when intrapulmonary pressure is lower than atmospheric pressure
$3$. Pressure gradients are generated with the help of diaphragm and intercostal muscles
$4$. Inspiration is initiated by relaxation of diaphragm
$5$. Contraction of diaphragm reduces pulmonary volume and increases intrapulmonary pressure causing expiration.

  1. $1, 2$ and $5$ correct
  2. $2$ only correct
  3. $2, 5$ correct
  4. $1, 3$ correct
  5. $1, 4$ correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement 1 is correct (negative pressure is required). Statement 3 is correct (muscles create the pressure gradient). Statements 2, 4, and 5 are incorrect because expiration is passive (relaxation) and contraction of the diaphragm increases volume, not reduces it.

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

With conscious efforts one can.

  1. Breathe out air totally without oxygen

  2. Breathe in and out by moving diaphragm alone without moving ribs at all

  3. Breathe out air through eustachian tube by closing both nose and mouth

  4. Empty the lungs completely by breathing out all air out of them
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The diaphragm and intercostal muscles are skeletal muscles, allowing for some conscious control. One can choose to breathe using only the diaphragm (abdominal breathing) or only the ribs (thoracic breathing).

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

Which of the following is the most appropriate in normal circumstances?

  1. During inspiration the intrapulmonary pressure is less than the atmospheric pressure

  2. During expiration the intrapulmonary pressure is less than the atmospheric pressure

  3. During inspiration the intrapulmonary pressure is more than the atmospheric pressure

  4. During expiration the intrapulmonary pressure is equal to atmospheric pressure
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For air to flow into the lungs during inspiration, the intrapulmonary pressure must be lower than the atmospheric pressure, creating a pressure gradient.

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

In negative pressure breathing, inhalation results from:

  1. forcing air from the throat down into the lungs

  2. contracting the diaphragm

  3. relaxing the muscles of the rib cage

  4. contracting the abdominal muscles
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

During the process of inhalation, the lung volume expands as a result of contraction of the diaphragm & intercostal muscles, thoracic cavity expands, due to this increase in volume, the pressure is decreased.

So, the correct option is 'contracting the diaphragm'.

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

During expiration the diaphragm becomes

  1. dome-shaped

  2. oblique

  3. concave

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

When the internal intercostal muscles contract and diaphragm relax, the ribs move .downward and inward and diaphragm becomes convex {dome shaped), thus decreasing the volume of thoracic cavity and increasing the pressure inside as compared to the atmospheric pressure outside. This will cause the air to move out (expiration).

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

After forceful inspiration, the amount of air that can be breathed out by maximum forced expiration is equal to

  1. Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV) + Tidal Volume (TV) + Residual Volume (RV)

  2. IRV + RV + ERV

  3. IRV + TV + ERV

  4. TV + RV + ERV
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Vital capacity is the maximum volume of air a person can breathe in after a forced expiration or the maximum volume of air a person can breathe out after a forced inspiration.This equals the inspiratory reserve volume (IRV) + expiratory reserve volume (ERV) + tidal volume (TV). Its value is 3400 mL - 4800 mL..

Multiple choice zoology respiratory system of human mechanism of respiration respiratory cycle breathing and exchange of gas

Read the following four statements (i) - (iv) with certain mistakes in two of them.
(i) A water breather expends much more energy in ventilating its respiratory surface than an air-breathing one.
(ii)   Lungs become empty after forceful expiration.
(iii) Exchange of gases in the lungs is interrupted during expiration.
(iv) Respiratory movements are controlled by $CO _{2}$ concentration of arterial blood.
Which of the above two statements have mistakes?

  1. (i) and (iv)

  2. (ii) and (iii)

  3. (i)and(ii)

  4. (iii) and (iv)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Corrected statements:

(ii) Lungs do not become empty after a forceful expiration.

(iii) The exchange of gases in the lungs is not interrupted during expiration.

So, the correct answer is '(ii) and (iii)'.