Mechanism of Breathing Questions in English

(B) $(1)$ The volume of air involved in breathing is measured using an instrument called a $Spirometer$.
$(2)$ Inspiration (breathing in) is initiated by the contraction of the diaphragm,which increases the volume of the thoracic cavity in the antero-posterior axis,thereby decreasing the intra-pulmonary pressure and allowing air to flow into the lungs.
Therefore,the correct sequence is $Spirometer$ and $Contraction$.

(B) Inspiration occurs if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure,i.e.,there is a negative pressure in the lungs with respect to atmospheric pressure.
Similarly,expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure.

(N/A) Expiration occurs when the diaphragm and the external intercostal muscles relax.
This relaxation causes the diaphragm and the sternum to return to their normal positions.
As a result,the thoracic volume decreases,which leads to a decrease in pulmonary volume.
This reduction in volume causes the intra-pulmonary pressure to increase to a level slightly above the atmospheric pressure.
Consequently,air is forced out of the lungs,a process known as expiration.

(N/A) During normal respiration,the creation of a pressure gradient between the lungs and the atmosphere is primarily facilitated by the diaphragm and the external intercostal muscles.
$1$. The diaphragm contracts and flattens,increasing the volume of the thoracic cavity in the anteroposterior axis.
$2$. The external intercostal muscles contract,lifting the ribs and the sternum,which increases the volume of the thoracic cavity in the dorsoventral axis.
$3$. These combined actions increase the overall thoracic volume,which leads to a decrease in intrapulmonary pressure below atmospheric pressure,allowing air to flow into the lungs.

(B) Inspiration is the process by which atmospheric air is drawn in.
$(1)$ During inspiration,the diaphragm contracts,which increases the thoracic volume in the antero-posterior axis.
$(2)$ The external inter-costal muscles contract,lifting up the ribs and the sternum,which increases the thoracic volume in the dorso-ventral axis.
$(3)$ An increase in thoracic volume leads to an increase in pulmonary volume.
$(4)$ According to Boyle's Law,an increase in pulmonary volume causes a decrease in intra-pulmonary pressure to less than atmospheric pressure,forcing air from outside into the lungs.
Therefore,events $(a)$ and $(b)$ are correct.

(A) Inspiration (inhalation) is an active process that involves the following steps:
$1$. The diaphragm contracts,which increases the volume of the thoracic cavity in the anterior-posterior axis.
$2$. The external intercostal muscles contract,lifting the ribs and the sternum,which increases the volume of the thoracic cavity in the dorso-ventral axis.
$3$. These actions lead to an overall increase in pulmonary volume.
$4$. According to Boyle's Law,an increase in volume leads to a decrease in intra-pulmonary pressure compared to atmospheric pressure,which forces air into the lungs.
Therefore,statements $(a)$ and $(b)$ are correct,while $(c)$ and $(d)$ describe the process of expiration.

(C) Altitude sickness occurs when a person travels to high altitudes (e.g.,Rohtang Pass near Manali or Mansarovar in Tibet).
At high altitudes,the atmospheric pressure is low,which results in a decrease in the partial pressure of oxygen $(pO_2)$.
Due to this low oxygen availability,the body does not get enough oxygen,leading to symptoms like nausea,fatigue,and heart palpitations.
Therefore,the correct cause is the decrease in atmospheric pressure at high altitudes.

(C) Breathing involves the process of filling the lungs with atmospheric air and then emptying them. Breathing in is known as inspiration or inhalation,while breathing out is known as expiration or exhalation.
During inspiration,the diaphragm muscles contract,which causes the diaphragm to flatten. This movement increases the volume of the thoracic cavity in the antero-posterior axis,facilitating the entry of air into the lungs.

(B) Inspiration is initiated by the contraction of the diaphragm,which increases the volume of the thoracic chamber in the antero-posterior axis.
The contraction of the external intercostal muscles lifts up the ribs and the sternum,causing an increase in the volume of the thoracic chamber in the dorso-ventral axis.
The overall increase in the thoracic volume causes a similar increase in the pulmonary volume,leading to a decrease in intrapulmonary pressure,which draws air into the lungs.

(C) Expiration is the process by which $CO_{2}$ is expelled from the lungs.
During this process,the muscle fibres of the diaphragm relax,causing it to return to its original dome-shaped structure.
This relaxation decreases the volume of the thoracic cavity,which increases the pressure inside the lungs,forcing air out.

(C) The ventilation movements of the lungs (breathing) in mammals are primarily governed by the diaphragm and the intercostal muscles.
$1$. The diaphragm is a dome-shaped muscular sheet that separates the thoracic cavity from the abdominal cavity. Its contraction increases the volume of the thoracic cavity in the antero-posterior axis.
$2$. The intercostal muscles (external and internal) are present between the ribs. The contraction of external intercostal muscles lifts up the ribs and the sternum,causing an increase in the volume of the thoracic cavity in the dorso-ventral axis.
$3$. Together,these movements create a pressure gradient that allows air to move in and out of the lungs.

(C) Humans have the ability to increase the strength of inspiration and expiration with the help of additional muscles in the abdomen.
During forced breathing,the abdominal muscles contract to push the diaphragm upward,which helps in increasing the strength of expiration.
Similarly,the relaxation of these muscles and the use of accessory muscles allow for deeper inspiration.

(C) Breathing,commonly known as pulmonary ventilation,consists of two main stages:
$1$. $A-$ Inspiration (Inhalation): This is the process during which atmospheric air is drawn into the lungs.
$2$. $B-$ Expiration (Exhalation): This is the process by which the alveolar air (air rich in $CO_2$) is released out into the atmosphere.
Therefore,the correct sequence is $A-$ inspiration and $B-$ expiration.

(B) Hiccups occur due to the spasmodic contraction of the diaphragm. This is often caused by the irritation of the phrenic nerve,which controls the movement of the diaphragm.

(B) $1$. Breathing (ventilation) involves inhalation,which is an active process requiring the contraction of the diaphragm and external intercostal muscles. Although exhalation is generally a passive process under normal conditions,the overall process of ventilation is considered active because it requires energy expenditure for the inhalation phase.
$2$. The contraction of the diaphragm muscle pulls the diaphragm downwards,which increases the anteroposterior volume of the thoracic cavity. This increase in volume leads to a decrease in intrapulmonary pressure compared to atmospheric pressure,thereby generating the pressure gradient necessary for air to flow into the lungs.

(A) The process of expiration occurs in the following sequence:
$1.$ Relaxation of the diaphragm and the intercostal muscles returns the diaphragm and sternum to their normal positions $(I)$.
$2.$ This movement reduces the thoracic volume and,consequently,the pulmonary volume $(II)$.
$3.$ The reduction in pulmonary volume leads to an increase in intra-pulmonary pressure to a level slightly above the atmospheric pressure $(IV)$.
$4.$ This pressure gradient causes the air to be expelled from the lungs,which is known as expiration $(III)$.
Therefore,the correct sequence is $I \rightarrow II \rightarrow IV \rightarrow III$.

(B) Hiccups are the spasmodic contraction of the diaphragm followed by a spasmodic closure of the glottis,resulting in a sharp inspiratory sound.
This phenomenon is typically triggered by the irritation of sensory nerve endings in the digestive tract or the diaphragm.

(C) The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere.
Inspiration occurs when the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure.
This condition is equivalent to saying that there is a negative pressure in the lungs with respect to the atmospheric pressure.
Therefore,both statements $I$ and $II$ describe the same physical condition required for inspiration to occur.
Thus,inspiration takes place in both situations.

(D) According to the mechanism of breathing described in the $NCERT$ textbook:
$1$. Inspiration occurs when there is an $A-$ increase in the pulmonary volume.
$2$. This increase in volume leads to a $B-$ decrease in the intra-pulmonary pressure compared to the atmospheric pressure.
$3$. Because the pressure inside the lungs is lower than the pressure $C-$ outside,air is forced to move into the lungs.
$4$. This process is known as $D-$ inspiration.
Therefore,the correct sequence is $A-$ increase,$B-$ decrease,$C-$ outside,$D-$ inspiration.

(C) The thoracic cavity is anatomically an air-tight chamber. This is essential because any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity. Such an arrangement is crucial for breathing,as we cannot directly alter pulmonary volume. The contraction of external intercostal muscles (not internal) lifts the ribs. $RBCs$ transport both oxygen and carbon dioxide. $A$ healthy man inspires $500 \; mL$ of air per breath (Tidal Volume),not per minute.

(A) Exhalation (expiration) is the process by which air is expelled from the lungs.
During exhalation:
$(i)$ The diaphragm relaxes and moves upward to its dome-shaped position.
$(ii)$ The external intercostal muscles relax,causing the ribs and sternum to move downward and inward,which reduces the volume of the thoracic cavity.
$(iii)$ This increase in pressure inside the lungs relative to atmospheric pressure forces air out of the lungs.
Looking at the provided figures,Figure $A$ shows the diaphragm moving upward and the ribs moving inward/downward,which correctly represents the process of exhalation.

(C) The process of inspiration involves the following sequence of events:
$1$. Contraction of intercostal muscles $(III)$ leads to the upward and outward movement of the ribs $(II)$,which increases the volume of the thoracic chamber in the dorsoventral axis $(I)$.
$2$. Simultaneously,the contraction of the diaphragm $(V)$ increases the volume of the thoracic cavity in the anteroposterior axis $(VI)$.
$3$. These combined increases in thoracic volume lead to a decrease in intrapulmonary pressure,which causes the entry of air inside the lungs $(IV)$.
Therefore,the correct sequence is $III \rightarrow II \rightarrow I \rightarrow V \rightarrow VI \rightarrow IV$.

(B) Inspiration is the process of breathing in air.
It occurs when the intra-pulmonary pressure (pressure within the lungs) is lower than the atmospheric pressure.
This pressure gradient forces air from the outside environment into the lungs.

(D) Cardiac muscles,which are the muscles of the heart,have no role in the process of inspiration and expiration.
Abdominal muscles and internal intercostal muscles are accessory muscles that assist in forced breathing.
During forced expiration,the contraction of abdominal muscles and internal intercostal muscles increases the strength of expiration,thereby increasing the volume of air exhaled.

(D) The breathing rate (or respiratory rate) of a normal healthy adult human at rest is approximately $12-16$ times per minute. This rate can increase significantly during physical exercise or stress.

(A) During inspiration,the contraction of the diaphragm muscle causes it to become flat and lowered,thereby increasing the volume of the thoracic cavity in the antero-posterior axis.
Simultaneously,the contraction of the external intercostal muscles lifts the ribs and sternum up and outward,causing an increase in the volume of the thoracic cavity in the dorso-ventral axis.

(A) During inspiration,the contraction of the diaphragm muscle causes it to become flat and lowered,thereby increasing the volume of the thoracic cavity in the antero-posterior axis.
The contraction of the external intercostal muscles lifts the ribs and sternum up and outward,causing an increase in the volume of the thoracic cavity in the dorso-ventral axis,i.e.,the backward-forward direction.

(A) Expiration is the process of moving air out of the lungs when the pressure within the lungs is higher than the atmospheric pressure.
During normal quiet breathing,expiration occurs due to the relaxation of the diaphragm and the external intercostal muscles.
This relaxation causes the diaphragm and sternum to return to their normal positions,which decreases the thoracic volume and consequently the pulmonary volume,leading to an increase in intrapulmonary pressure and the expulsion of air.

(B) The mechanism of breathing involves changes in the volume of the thoracic cavity.
An increase in the volume of the thoracic chamber leads to a similar increase in the volume of the pulmonary cavity (lungs).
This increase in volume causes a decrease in the intrapulmonary pressure compared to the atmospheric pressure.
Consequently,air moves from the atmosphere into the lungs to equalize the pressure.

(B) When the pressure within the pulmonary cavity (intra-pulmonary pressure) is higher than the atmospheric pressure,air moves from the lungs to the outside environment.
This process is known as expiration or the expulsion of air.
Air naturally moves from a region of higher pressure to a region of lower pressure.

(A) During quiet breathing,inspiration is an active process that requires the contraction of the diaphragm and external intercostal muscles.
Conversely,normal expiration is a passive process.
It occurs when the diaphragm and external intercostal muscles relax,allowing the lungs and chest wall to return to their original position due to their inherent elastic recoil.
Therefore,both the Assertion and the Reason are correct,and the Reason provides the correct explanation for why expiration is a passive process.

(C) The human lungs are situated in the thoracic cavity,which is an anatomically airtight chamber.
Because the lungs are located in this airtight space,we cannot directly alter the pulmonary volume.
Instead,any change in the volume of the thoracic cavity will be reflected in the lung (pulmonary) cavity.
Therefore,the statement that we can directly alter the volume of the lungs is incorrect.

(D) healthy human adult breathes approximately $12$ to $18$ times per minute at rest. This rate is known as the respiratory rate or breathing rate.

(D) Forced breathing or forced expiration is an active process that requires the contraction of additional muscles beyond those used in quiet breathing.
$1$. The $Diaphragm$ and $External Intercostal$ muscles are primarily involved in normal inspiration.
$2$. During forced expiration,the $Abdominal$ muscles contract to push the diaphragm upward,and the $Internal Intercostal$ muscles pull the rib cage downward.
$3$. During forced inspiration,accessory muscles in the $Neck$ (such as the $Sternocleidomastoid$ and $Scalene$ muscles) help to further elevate the rib cage.
Therefore,all the mentioned muscle groups are involved in forced breathing processes.

(A) The given diagram represents the process of inspiration. During inspiration,the diaphragm undergoes contraction,which causes it to flatten and increases the volume of the thoracic cavity. In this process,the ribs and sternum move outwards and upwards. Therefore,'Relaxation of the diaphragm' is the incorrect statement because the diaphragm contracts during inspiration.

(D) The process of inspiration (breathing in) follows a specific physiological sequence:
$1$. $III$ - Contraction of the diaphragm and external intercostal muscles (respiratory muscles) occurs first.
$2$. $IV$ - This contraction leads to an increase in the thoracic volume.
$3$. $I$ - The increase in thoracic volume causes a corresponding increase in lung volume.
$4$. $II$ - According to Boyle's Law,an increase in volume leads to a decrease in intrapulmonary pressure compared to atmospheric pressure.
$5$. $V$ - Consequently,air rushes into the lungs from the outside to equalize the pressure.
Therefore,the correct sequence is $III \rightarrow IV \rightarrow I \rightarrow II \rightarrow V$.

(B) $1$. Inspiration is initiated by the contraction of the diaphragm,which increases the volume of the thoracic chamber in the anteroposterior axis.
$2$. The contraction of external intercostal muscles $(EICM)$ lifts up the ribs and the sternum,causing an increase in the volume of the thoracic chamber in the dorsoventral axis.
$3$. The diaphragm and external intercostal muscles $(EICM)$ are the primary muscles involved in inspiration.
$4$. Normal expiration is a passive process because it occurs due to the relaxation of the diaphragm and intercostal muscles,which returns the thorax to its original position.

(C) The diagram shows the diaphragm moving upwards (dome-shaped) and the rib cage moving inwards and downwards. This indicates a decrease in the thoracic volume,which leads to an increase in thoracic pressure,causing air to be expelled from the lungs. This process is known as expiration. Expiration occurs when the diaphragm and external intercostal muscles relax,returning the diaphragm and sternum to their normal positions.

(C) The process of inspiration (inhalation) occurs in the following sequence:
$1$. The contraction of the diaphragm makes it flat and moves it downwards $(IV)$.
$2$. Simultaneously,the contraction of external intercostal muscles causes the ribs and sternum to move upward and outward $(III)$.
$3$. These two actions combined lead to an increase in the thoracic volume $(II)$.
$4$. An increase in thoracic volume leads to a decrease in intrapulmonary pressure compared to atmospheric pressure,causing air from the atmosphere to rush into the lungs $(I)$.
Therefore,the correct sequence is $IV \rightarrow III \rightarrow II \rightarrow I$.