These notes for CBSE Class 11 Biology, Chapter 17, cover Breathing and Exchange of Gases. They define breathing as the exchange of atmospheric O2 with cellular CO2, and respiration as the assimilation and oxidation of nutrients. Key terms like diaphragm, pharynx, and Adam's apple are explained. The notes detail respiratory volumes such as Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), and Residual Volume (RV). Pulmonary capacities like Inspiratory Capacity (IC), Expiratory Capacity (EC), Functional Residual Capacity (FRC), Vital Capacity (VC), and Total Lung Capacity are also covered. The mechanism of breathing, including inspiration and expiration driven by diaphragm and intercostal muscle movements, is explained. Finally, the transport of gases, particularly CO2 in the blood via bicarbonates and carbaminohemoglobin, is discussed. These notes are ideal for students preparing for their exams.
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Breathing : (External respiration) The process of exchange of O
from the atmosphere
with CO 2 [110] 2 produced by the cells.
Inspiration : Oxygen from fresh air taken by lungs and diffuses into the blood.
Expiration : CO
given up by venous blood in the lungs is sent out to exterior.
Respiration : The sum total of physical and chemical processes by which oxygen 2 and carbohydrates (main food nutrient) etc are assimilated into the system and the
oxidation products like carbon dioxide and water are given off.
Diaphragm : A muscular, membranous partition separating the thoracic cavity from
the abdominal cavity.
The pressure contributed by an individual gas in a mixture of gases. It is represented as pO for carbondioxide.
Pharynx : The tube or cavity which connects the mouth and nasal passages with 2 oesophagus. It has three parts
(i) Nasopharynx (anterior part)
(ii) Oropharynx (middle
part) and
(iii) Laryngopharynx (posterior part which continues to larynx)
Adam’s Apple : The projection formed by the thyroid cartilage and surrounds the
larynx at the front of the neck.
Tidal volume (TV) : volume of air during normal respiration (500 ml.)
Inspiratory Resrve colume (IRV) : Additional volume of air inspired by a forcible
inspiration. 2500 ml to 300 ml.
Expiratory Reserve Volume (ERV) : Additional volume of air, a person can expire
by a forcible volume (RV) volume of air remaining in the lungs even after a forciable
expiration (1100 mL to 1200 mL)
PURMONARY CAPACITES : Use in clinical diagnosis.
Inspiratory capacity (IC) = (TV + 1 RV)
Expiratory Capacity (E.C) = (T.V + ERV)
Functional Residual Capacity (FRC) = (ERV + RV)
Vital Capacity (VC ) = ( ERV + TV + IRV ) or the maximum volume of air a
person can breathe out after a forced inspiration.
Total Lung Capacity : It is cludes RV, ERV,TV and IRV or vital capacity + residual
volume.
Steps involved in respiration –
(i) Breathing or pulmonary respiration
(ii) Diffusion of gases (O 2 and CO
) across alveolar membrane.
(iii) Transport of gases by the blood
(iv) Diffusion of O 2 and CO 2 2
between blood and tissues.
(v) Utilisation of O
by the cells for catabolic reactions and resultant release of CO . 2 MECHANISM OF BREATHING
Inspiration : It the pressure with is the lungs (intro pulmonary pressure) is less than the at
maspheric pressure, ie there is negative pressure in the lungs with respect to the
atmospheric pressure.
? The contraction of diaphragm increases the volume of thoracic chamber in
antero-posterior axis.
? The contraction of external intercostal muscles lifts up the ribs and the sternum
causing an increase in the volume of thoracic chamber in the dorso ventral axis.
? It causes an increase in pulmonary volume decrease the intra-pulnonary
pressure to less than the atmospheric pressure.
? It forces the air out side to move in to the lungs, i.e, inspiration.
Expiration : Relexation of diaphragm and sternum to their normal positions and reduce the
thoracic and pulmonary volume.
It increases in intrapulmonary pressure slightly above the atmospheric pressure.
It causes the expulsion of air from the lungs, i.e, expiration.
Transport of CO
CO + HO 22 2
in the blood :- Carbonic anhydrase
about 20% of CO 2 H CO (Carbonic acid) 23 is transported by combining
with free amino group of Haemoglobin, in RBC.
HbNHCOOH (Carbamino haemoglobin)
Carbonic anhydrase
CO + HbNH 22 70% of CO 2 is transported as bicarbonates of sodium (NaHCO
) and
potassium (KHCO ) 3
Breathing, or external respiration, is defined as the process of exchanging oxygen (O2) from the atmosphere with carbon dioxide (CO2) produced by the cells.
Breathing is the physical exchange of gases, while respiration is the sum of physical and chemical processes where oxygen is assimilated for oxidation, and carbon dioxide and water are released.
The main respiratory volumes are Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), and Residual Volume (RV).
Carbon dioxide is transported in the blood mainly as bicarbonates (about 70%), combined with hemoglobin as carbaminohemoglobin (about 20%), and dissolved in plasma.
The contraction of the diaphragm increases the volume of the thoracic cavity in the antero-posterior axis, which is crucial for inspiration.
Vital Capacity (VC) is the maximum volume of air a person can breathe out after a forced inspiration, calculated as ERV + TV + IRV.
The steps include breathing, diffusion of gases across the alveolar membrane, transport of gases by blood, diffusion between blood and tissues, and utilization of oxygen by cells.
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