Test: Human Physiology: Respiratory System - 2 - NEET MCQ

Respiration is a physiological process that is a combination of both physical and chemical changes in all organisms that modulate their respiration. In the simplest of organisms that can respire, bacteria, they depend upon the physical principle of diffusion to supply O2 to their respiratory machinery which are associated with their plasma membrane. If the diffusion of O2 from the environment is restricted they turn their metabolism to anaerobic which is a chemical process but is modulated by the physical access to O2 diffusion supply. Higher metazoans do not depend upon simple diffusion but often have a physical respiratory apparatus such as a tidal lung of terrestrial vertebrates controlled by muscular breathing, or in insects with a tracheolar system controlled by physically controlled spiracular valves to allow diffusion of O2 in and CO2 out of the insect body without losing too much water vapor. Respiration in all organisms thus has both a physical and a chemical component.

It connects the inferior part of the pharynx (hypopharynx) with the trachea. The laryngeal skeleton consists of six cartilages: three single (epiglottic, thyroid and cricoid) and three paired (arytenoid, corniculate, and cuneiform).

The diaphragm functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, thus enlarging the volume of the thoracic cavity (the external intercostal muscles also participate in this enlargement). This reduces intra-thoracic pressure.

• Approximately 3% of oxygen dissolves in the blood plasma. Remaining 97% oxygen combines with haemoglobin to form oxyhaemoglobin.
• Oxygen can bind with Hb in a reversible mannner to form oxyhaemoglobin.

Every 100 ml deoxygenated blood delivers around 4 ml carbon dioxide to alveoli, whereas every 100 ml oxygenated blood can deliver around 5 ml of oxygen to tissues under physiological conditions.

In response of bicarbonate ion, chloride ions diffuse from plasma into the erythrocyte to maintain the ionic balance. Thus, electrochemical neutrality is maintained. This is called chloride shift or Hamburger phenomenon.

Simple squamous epithelium lines the air sacs, or alveoli, of the lungs. The alveoli are sites where the air is exchanged in the lungs.
Simple squamous epithelial cells in the alveoli allow oxygen from the air to enter the blood in the capillaries of the lung. 
Carbon dioxide, a waste product, passes across the epithelium of the alveoli to be removed from the body. Striated, columnar and cuboidal epithelium is absent in the lines of alveoli. 
Therefore, the correct answer is option A.

So, the correct answer is option B.
Inhalation occurs when the pressure inside the lungs is lower than the atmospheric pressure, creating a vacuum that draws air in.

• Chloride shift occurs in response to HCO₃^-.
• In response of bicarbonate ion, chloride ions diffuse from plasma into the erythrocyte to maintain the ionic balance.
• Thus, electrochemical neutrality is maintained.
• This is called chloride shift or Hamburger phenomenon.

Blood supplies approximately 25% of oxygen to the tissues in one circulation as the partial pressure of oxygen in arterial blood is 75-95mmHg.

Answer:
The opening to the trachea is covered by a small flap of tissues called the epiglottis.
The epiglottis is located at the base of the tongue and acts as a valve to prevent food and drink from entering the trachea during swallowing. It covers the glottis, which is the opening to the trachea, and directs food and liquid towards the esophagus.
Here is a detailed explanation of each option:
- Glottis: The glottis is the opening to the trachea that consists of the vocal cords and the space between them. It is not a flap of tissues that covers the trachea opening but rather a structure within the trachea.
- Trachea: The trachea, also known as the windpipe, is a tube that connects the larynx to the bronchi of the lungs. It is responsible for conducting air to and from the lungs and does not cover its own opening.
- Epiglottis: As mentioned earlier, the epiglottis is the correct answer. It is a flap of tissues that covers the opening to the trachea during swallowing, preventing food and liquid from entering the airway.
- Larynx: The larynx, commonly known as the voice box, is located at the top of the trachea. It contains the vocal cords and is responsible for producing sound. While the larynx is involved in the opening and closing of the glottis, it does not cover the trachea opening itself.
In conclusion, the correct answer is C: Epiglottis.

The primary factor that causes oxygen to bind with haemoglobin is the partial pressure of oxygen in the surrounding environment. When the partial pressure of oxygen is higher, such as in the lungs, haemoglobin binds with oxygen, forming oxyhaemoglobin. This binding is crucial for transporting oxygen from the lungs to the tissues.

Blood is the medium of transport for oxygen and carbon dioxide. About 97 per cent of oxygen is transported by RBCs in the blood. The remaining 3 per cent of oxygen is carried in a dissolved state through the plasma. Nearly 20-25 per cent of carbon dioxide is transported by RBCs whereas 70 per cent of it is carried as bicarbonate. About 7 per cent of carbon dioxide is carried in a dissolved state through plasma. Every 100 ml of deoxygenated blood delivers approximately 4 ml of CO₂ to the alveoli.
Therefore, the correct answer is option A.

Oxyhaemoglobin is an acidic compound and thus releases H⁺ ions. Those ions combine with the bicarbonate ions to release the CO₂ associated with them. This is known as Haldane effect.

Answer:
The correct answer is C: Total lung capacity.
Detailed solution:
The maximum volume of air contained in the lung by a full forced inhalation is known as the total lung capacity. It represents the maximum amount of air that can be inhaled into the lungs after a maximum exhalation.
To understand the different lung capacities, let's break them down:
1. Vital capacity: It is the maximum volume of air that can be exhaled after a maximum inhalation. Vital capacity is the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
2. Tidal volume: It is the volume of air that is inhaled or exhaled during normal breathing.
3. Total lung capacity: It is the sum of all the lung volumes, including tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. Total lung capacity represents the maximum volume of air that the lungs can hold.
4. Inspiratory capacity: It is the maximum volume of air that can be inhaled after a normal exhalation. Inspiratory capacity is the sum of tidal volume and inspiratory reserve volume.
Therefore, the maximum volume of air contained in the lung by a full forced inhalation is called the total lung capacity.

Functional Residual Capacity (FRC) is the volume of air that will remain in the lungs after a normal expiration. This includes expiratory reserve volume i.e. 1100ml plus 1200ml or 2300ml. 

Carbon dioxide is transported in the blood in three ways: 10% is dissolved in plasma, 20% is carried on haemoglobin bound to globins, and 70% exists as bicarbonate, an important buffer of blood pH.

Bohr's effect because christian bohr told firstly about haemoglobin's binding efficiency with o2 which is inversely proportional to acidity and concentration of co2.

• Nearly 70% carbon dioxide is transported by plasma as sodium bicarbonate. Approximately, 5-7% of carbon dioxide is transported in dissolves form in plasma.
• About 20-25% carbon dioxide react with the amine group of haemoglobin and form carbamino-haemoglobin.

• About 20-25% carbon dioxide react with the amine group of haemoglobin and form carbamino-haemoglobin.
• Approximately 5-7% of carbon dioxide is transported in dissolves form in plasma.

After a human breathes in Earth's air (roughly 78 percent nitrogen and 21 percent oxygen), he or she exhales a mixture of compounds similar to the air inhaled: 78 percent nitrogen, 16 percent oxygen, 0.09 percent argon, and four percent carbon dioxide.

Asthma is difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles. Because of this air passage becomes narrow also it produces extra mucous which lastly leads into difficulty in breathing.

Chloride shift, also known as the Hamburger phenomenon is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate (HCO₃−) and chloride (Cl−) across the membrane of red blood cells.

Carbon dioxide is produced in tissues as a byproduct of normal metabolism. It dissolves in the solution of blood plasma and into RBC, where carbonic anhydrase catalyzes its hydration to carbonic acid (H₂CO₃). Carbonic acid then spontaneously dissociates to form bicarbonate Ions (HCO₃−) and a hydrogen ion (H+) in response to the decrease in intracellular partial pressure of CO₂, more CO₂ passively diffuses into the cell.

Hence, the chloride shift is essential for the transport of Carbon dioxide.

So, the correct  option is 'CO₂'.

Gas exchange between the air within the alveoli and the pulmonary capillaries occurs by diffusion. The oxygen must first dissolve before passing through the respiratory epithelium. Gas moves from a region of high partial pressure to a region of low partial pressure, down a partial pressure gradient.

The hindbrain comprises pons, cerebellum and medulla oblongata. The Pneumotaxic centre is present in the upper part of the pons. The function of the pneumotaxic center is to control rate and pattern of breathing. Hence pneumotaxic center is present in pons region of the brain.

The diaphragm is the membranous structure in the abdomen. The muscles of the diaphragm contracts during inspiration. Muscle contraction allows the diaphragm to become flat which helps to increase the volume of the thoracic cage. This allows the air to be taken in the lungs.
During the process of expiration, the diaphragm becomes dome shaped and the muscles relax. This reduces the volume of the thoracic cage and helps to pump the CO2 out from the lungs. 
Thus, the correct answer is option A.

Emphysema is chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. This is one of the causes of cigarette smoking.

a) Aortic arch and carotid artery receptors

Explanation: Receptors associated with the aortic arch and carotid artery can recognize changes in CO2 and H+ concentration. These receptors play a vital role in sending necessary signals to the respiratory rhythm centre for adjustments in the respiratory process based on these changes.

The structure of the lung maximizes its surface area to increase gas diffusion. Because of the enormous number of alveoli (approximately 300 million in each human lung), the surface area of the lung is very large (75 m²).

• During expiration, the contracted intercostal muscles and diaphragm tend to relax.
• The lungs can contract by themselves like a deflating balloon. Therefore, when the muscles that expand the thorax are relaxed, the lungs contract under their own elastic recoil forces so that the breath is expired.

 

So the answer is- relaxation of the diaphragm and intercostal muscles.