THE RESPIRATORY SYSTEM

Many respiratory diseases affect pulmonary function by altering the ability of alveoli to participate in gas exchange. What physical change would most greatly reduce the degree to which a particular alveolus is ventilated?

Increased alveolar elastic recoil

Septic shock is a serious condition resulting from the body's response to systemic bacterial infections, which may impair oxygen uptake and delivery. What physiological change may result from septic shock which would decrease the ability of hemoglobin in the alveolar capillaries to become fully saturated with oxygen?

Increased capillary blood flow

If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?

Alveolar pressure is greater than the pressure of atmospheric air

In a situation where the respiratory bronchioles become inflamed and narrowed, such as is seen in asthma, which aspect of respiration would be most mechanically impaired?

Forced expiration

Which of the following is the most likely value of an asthmatic FEV/FVC ratio during an asthma attack compared to normal? A. Equal to the predicted value B. Less than the predicted value C. More than the predicted value D. May be more or less than the predicted value, depending on the trigger that caused the attack

B; Asthma is a disease of hyperresponsive smooth muscle of the bronchioles (they are over-constricted). Therefore, asthmatics have a more difficult time getting air out of their lungs in the first second of breathing. The FEV1/FVC ratio should be less than normal because the FEV1 will be less while the FVC is roughly normal (choice B is correct, and choices A and C are wrong). The trigger that causes asthma does not change the overall lung reaction, which is hyperresponsive smooth muscle constriction (choice D is wrong).

The partial pressures of carbon dioxide (pCO_2) and oxygen (pO_2) in the atmosphere at sea level are 0.3 mmHg and 160 mmHg respectively, but the partial pressures of these gases in blood leaving the lungs are 40 mmHg (pCO_2)and 95 mmHg (pO_2). What factor most likely accounts for this difference?

CO_2 is more soluble in the blood than O_2

How might central and peripheral chemoreceptors compare with regard to their role in the detection of respiratory gases resulting from a prolonged period of hypoventilation?

Central chemoreceptors and peripheral chemoreceptors may both respond to the resultant increase in pCO_2 chemoreceptors could respond to the decrease in pO_2

Which of the following medications are used to treat asthma? Salbutamol (short acting β-agonist) 1. Prednisolone (glucocorticoid) 2. Cromolyn sodium (mast cell stabilizer) 3. Propranolol (long acting β-antagonist) A. I only B. II, III, and IV only C. I and II only D. I, II, and III only

D; Many medications have been used to combat asthma over the years. Item I is true: The passage describes the use of β-agonists as smooth muscle relaxants. β-Agonists will stimulate the receptors of the sympathetic system on smooth muscles of bronchioles to cause dilation (choice B can be eliminated). Note that if Item I is true, then Item IV must be false: a β-antagonist would have the opposite effect as a β-agonist. Item II is true: The passage mentions that inflammation of the airways is a major cause of chronic asthma, and steroids can be used to reduce inflammation (choice A can be eliminated). Item III is true: The passage mentions that allergens are often triggers to asthma. Mast cells will degranulate when stimulated by IgE and release histamine, causing a local inflammatory response and mucous production. Cromolyn sodium can stabilize this process and help reduce this inflammatory response (choice C can be eliminated and choice D is correct).

Which of the following is a true statement about the diaphragm? A. It contains both skeletal and smooth muscle cells. B. Its effector neurotransmitters are norepinephrine and acetylcholine. C. It is innervated by the phrenic nerve and autonomic nervous system. D. It receives neural signals from the cerebral cortex and the brain stem.

D; The diaphragm is purely skeletal muscle (choice A is false) and as such, ACh is the only neurotransmitter used (choice B is false). It's innervated only by the phrenic nerve, not autonomic nerves (choice C is false). The phrenic nerve originates both in the cerebral cortex, for voluntary breathing, and in the brain stem for involuntary control (choice D is correct).

Interstitial lung disease (ILD) refers to a set of conditions which affect the pulmonary interstitium-- the area of tissue and space which lies between the alveoli and alveolar capillaries. What factor in the setting of severe ILD, would NOT decrease the extent to which oxygen passes from the air sacs of the lungs into the blood?

Decreased interstitial thickness

What produces the force which drives normal exhalation, and is the process active or passive?

Elastic force, passive

Bronchodilators are a class of drug often used in the treatment of asthma and COPD, which act on β-adrenergic receptors of the airways to induce smooth muscle relaxation. The anatomic distribution of these receptors is closely correlated to the function of each structural component of the lungs. What structural component(s) of the airway would be most affected by the use of a bronchodilator, and in what functional zone(s) are they found?

Lobar bronchi, which are found in the conducting zone

What is the pressure of gas within the alveoli at the peak of inspiration, just before expiration, relative to that of atmospheric air?

The same as atmospheric air