At hills, the pressure of air falls and the person cannot get enough oxygen in the lungs for diffusion into the blood.Due to deficiency of oxygen, the person feels breathlessness, headche, dizziness, nausea, mental fatigue and a bluish colour on the skin, nails and lips.

Carbonic anhydrase is an fastest enzyme known so far. It is found in RBC.

It is the additional volume of air that can be expired forcibly after normal expiration. It is about 1000-1100 mL.

Difference between oxyhaemoglobin and carbaminohaemoglobin are

Increase in pCO₂ tension in blood brings rightward shift of the oxygen-dissociation curve of haemoglobin thereby decreasing the affinity of Hb for O₂ .this effect is called Bohr's effect.
It plays a crucial role in enhancing oxygenation of the blood in the lungs and in the release of O₂ in the tissues.

CO₂ is transported in the human body in the following ways
(i) In dissolved form about 7%
(ii) As bicarbonate ions about 70%
(iii) As carbaminohaemoglobin about 20-25%

The lower part of the curve indicates dissociation of oxygen from haemoglobin while, the upper part of the curve indicate acceptance of oxygen by Hb.

Mammals use negative pressure to suck air in. The diaphragm contracts and move down, the intercostal muscles contract and move up and out. This causes the lungs to expand. The pressure inside the lungs drops.

(i) Thin squamous epithelium of alveoli.
(ii) Endothelium of alveolar capillaries.
(iii) Basement substance in between

Cigarette smoking causes damages to the alveolar walls and reduces elasticity of the lungs, which leads to decreased respiratory surface for exchange of gases.Thus, causing emphysema.

Asthma, emphysema, occupational lung disorders (e.g., silicosis and asbestosis)

The respiratory rhythm is under dual control, i.e. nervous and chemical.
 

The respiratory process is regulated by certainly specialised cebtres present is hindbrain.Amongst them, pneumotaxis centre is located in the dorsal part of pons varoli of the brain, can reduce the duration of inspiration and thus, alter the respiratory rate.

A person sleeping in such room gets carbon monoxide poisonong.CO combines with Hb more readily than oxygen forming carboxyhaemoglobin.This reduce the amount of free Hb available for carrying O₂ .Thus, the tissue is starved of O₂ .this is the reason why it is not advisable to sleep in closed rooms warmed with coals

Large number of chemoreceptors are located in the carotid bodies (lie bilaterally in the bifurcations of the common carotid arteries).
Their afferent nerve fibers pass through glossophatyngeal cranial nerve and thus to dorsal respiratory area of the medulla oblongta, sizeable number of chemoreceptors are also located in the aortic bodies (which lie along the arch of aorta)
Their afferent nerve fibres pass through the vagus cranial nerve and thus, to dorsal respiratory group of neurons

The foul air follows the route given below
Alveoli\(\rightarrow \)Alveolar ducts\(\rightarrow \)Bronchioles\(\rightarrow \)Bronchi\(\rightarrow \)Trachea\(\rightarrow \)Larynx\(\rightarrow \)Glottis\(\rightarrow \)Pharynx\(\rightarrow \)Internal nares\(\rightarrow \)Nasal chambers\(\rightarrow \)External nares\(\rightarrow \)Atmosphere.
The tidal volume increases 4-10 times during excitment and activity.

The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere. The pressure within the lungs is less than the atmospheric pressure so, there is a negative pressure in the lungs with respect to atmospheric pressure. The puncture in the chest affects this pressure gradient maintained by the lungs and thus, may cause cessation of breathing

Part (a): IRV vs ERV

Part (b): Inspiratory Capacity vs Expiratory Capacity

Part (c): Vital capacity vs Total lung capacity

Oxygen dissociation curve shows the relationship between percentage saturation of haemoglobin with oxygen and partial pressure of oxygen. Each haemoglobin can bind with 4 molecules of oxygen at the most. The first molecule of oxygen binds with he most difficulty. But each subsequent moleculeases the binding of nest oxygen molecule. This results in graph rising rapidly. When all the 4 oxygen molecules bind, no further binding is possible. The graph plateaus at this stage. This explains the sigmoid curve.

Tidal volume is the volume of air inspired or expired during normal respiration. It is about 6000 to 8000 mL of air per minute.
The hourly tidal volume for a healthy human can be calculated as:
Tidal volume = 6000 to 8000 mL/minute
Tidal volume in an hour = 6000 to 8000 mL × (60 min)
= 3.6 × 10⁵ mL to 4.8 × 10⁵ mL
Therefore, the hourly tidal volume for a healthy human is approximately 3.6 × 10⁵ mL to 4.8 × 10⁵ mL.