The diaphragm and intercostal muscles are used in normal respiration to draw air into the lungs. The diaphragm flattens and descends, and the intercostal muscles move the rib cage outward to increase chest volume. These actions increase the chest volume during passive inspiration (contraction) and decrease the chest volume during passive expiration (relaxation). An increase in chest volume with result in a negative pressure in the lung that acts to pull air into lungs. Paralysis of these muscles would lead to an inability to create a negative pressure in the lungs and would inhibit inspiration.

Tidal volume is determined by the total volume of air moved with each passive breath. It is the sum of inspired air and expired air. If inspiration is inhibited, this value will decrease. Inspiratory reserve volume is the additional volume that can be drawn in by forced inspiration, via voluntary contraction of the diaphragm. This value would also decrease with paralysis of the diaphragm.

The diaphragm contracts during inspiration and relaxes during expiration. External intercostals are used for inspiration, and internal intercostals are used for expiration only if it is forced expiration. Usually expiration is a passive process, unless someone is forcefully exhaling, such as during strenuous exercise.

Contraction of the diaphragm increases the volume of the thoracic cavity, decreasing the pressure. When the pressure in the lungs is less than the atmospheric pressure, air will be drawn into the lungs. When the diaphragm relaxes (passively), the thoracic cavity shrinks and air is expelled.

Duchenne Muscular Dystrophy is a muscular disorder, so cause of death will be related to muscle weakening. Two main muscles are essential to maintaining the body: the heart and the diaphragm. As the disease progresses to these muscles, causing weakening of the heart and diaphragm, the body begins to deteriorate and cause of death is usually heart failure or respiratory failure when these muscles give out.

Contraction of the diaphragm allows air to enter the lungs. A weaker contraction means less air flow, and eventually leads to respiratory failure.

As inspiration takes place, the diaphragm and the external intercostal muscles contract. This increases the volume of the thorax, which results in a decrease in pressure in the lungs.

As inspiration continues, the addition of air to the alveoli results in an increase in pressure. When alveolar pressure equals atmospheric pressure, inspiration stops.

When whales dive to great depths, they are unable to replenish oxygen from the water's surface. Several adaptive characteristics allow for the whales to maintain adequate oxygen supply to their tissues: large lung capacity (to absorb a greater amount of oxygen when breathing), selective arterial constriction (to restrict blood flow to non-essential tissues and thus prevent inefficient oxygen consumption), high cellular tolerance for carbon dioxide (CO₂ will build up over time without gas exchange), and large muscle myoglobin concentrations (to replenish oxygen supply to muscles as necessary).

A high basal metabolic rate, however, would increase the demand for oxygen and thus would not be an adaptive characteristic for whales in order to maintain themselves at great, watery depths without an external supply of oxygen.

The individual's blood pH level will decrease (become more acidic). The increase in CO₂ will cause the carbonic anhydrase reaction to shift to the right, increasing the concentration of protons (H⁺) in the blood. The individual can raise their pH level back to normal by breathing out all of the excess CO₂. This accounts, in part, for increased respiration rates during exercise (along with the increased demand for oxygen).

Slightly increased levels, or partial pressures, of carbon dioxide (CO₂) would signal for an increase in breathing rate. As CO₂ levels in the blood rise due to the breathing of such air as described in the passage, a breathing mechanism in the brain is triggered to increase ventilation (hyperventilation) to remove as much CO₂ through the lungs as possible. A decrease in breathing rate would build up CO₂ to even higher levels, causing respiratory acidosis. There would be no changes to blood pressure because slight increases of CO₂ has no significant effect on this property.

It is important to know that the medulla oblongata in the brainstem is the site of breathing rate control. pH receptors at the medulla sense the hydrogen concentration in the blood, and increase or decrease the rate of breathing to alter bicarbonate levels in the blood, maintaining healthy pH levels.

The cerebellum is involved in balance and coordination, while the frontal cortex and occipital lobe are both regions of the cerebrum, involved in higher thinking, processing, and voluntary actions.

The total lung capacity is the maximum amount of air that can fill the lungs.

The vital capacity is the amount of air that can be exhaled after fully inhaling.

The tidal volume is the amount of air inhaled during normal, relaxed breathing.

The expiratory reserve volume is the amount of air that can be forcibly exhaled after a normal exhalation.

The inspiratory reserve volume is the amount of air that can be forcibly inhaled after a normal inhalation.

The residual volume is the amount of air still remaining in the lungs after the expiratory reserve volume is exhaled.

By adding the residual volume and vital capacity, you can obtain a value for the total lung capacity.

Epinephrine binds to the beta-2 receptor. The binding of epinephrine to the beta-2 receptor causes bronchodilation by relaxing the smooth muscles surrounding the airway. The relaxation of the smooth muscles around the airway increases the airway diameter and therefore allows the patient to breathe easier.