The document discusses the respiratory system and contains questions about muscles involved in breathing, changes during exercise and disease, lung volumes and pressures, and mechanisms of increased intracranial pressure. It defines terms like compliance and describes the processes of normal inspiration and expiration as well as forced inspiration and expiration. Finally, it reviews these concepts and provides explanations for different conditions involving airway obstruction.

1. Respiratory
System IRS
Dr. Dinesh Veera
(MBBS, MSc Medical Physiology)
AIMST University

2. 1. A healthy, 45-year-old man is reading the newspaper. Which of the
following muscles are used for quiet breathing?
A) Diaphragm and external intercostals
B) Diaphragm and internal intercostals
C) Diaphragm only
D) Internal intercostals and abdominal recti
E) Scaleni
F) Sternocleidomastoid muscles

3. 2. A healthy, 25-year-old medical student participates in a 10-km
charity run for the American Heart Association. Which of the following
muscles does the student use (contract) during expiration?
A) Diaphragm and external intercostals
B) Diaphragm and internal intercostals
C) Diaphragm only
D) Internal intercostals and abdominal recti
E) Scaleni
F) Sternocleidomastoid muscles

4. 3. The pleural pressure of a normal 56-year-old woman is
approximately −5 cm H2O during resting conditions immediately before
inspiration (i.e., at functional residual capacity). What is the pleural
pressure (in cm H2O) during inspiration?
• A) +1
• B) +4
• C) 0
• D) −3
• E) −7

5. 4. A 34-year-old male sustains a bullet wound to the chest that causes
a pneumothorax. Which of the following best describes the changes in
lung volume and thoracic volume in this man, compared to normal?

6. 5. The resistance of the pulmonary tree is so low that a 1 cm of water
pressure gradient is sufficient to cause normal air flow during resting
conditions. Which of the following often has a substantial resistance
during pulmonary disease states that can limit alveolar ventilation?
• A) Alveoli
• B) Bronchioles
• C) Large bronchi
• D) Small bronchi
• E) Trachea

7. The larger bronchi near to the trachea have the greatest
resistance to airflow in the healthy lung.
However, in disease conditions, the smaller bronchioles often
have a far greater role in determining resistance because :
(a) they are easily occluded because of their small size
(b) they have an abundance of smooth muscle in their walls and
therefore constrict easily

9. Compliance (C) is the change in lung volume (ΔV) that occurs for a
given change in the transpulmonary pressure (ΔP), that is, C = ΔV/ΔP.
Because compliance is equal to the slope of the volume–pressure
relationship
curve S represents the highest compliance
curve U represents the lowest compliance

10. 7. By which mechanism can hypercapnia increase intracranial pressure?
a. Prolonged elevation of Paco2 produces arterial hypertension.
b. Elevated Paco2 causes cerebrovascular vasodilatation.
c. Elevated Paco2 decreases oxygenation of brain tissue.
d. Elevated Paco2 decreases reabsorption of CSF.

11. • Hypercapnia directly and indirectly (through alteration of CSF pH)
dilates the cerebral vasculature, and hypercapnia can cause
intracranial hypertension.

13. According to these results, which is the most likely explanation of the
patient’s underlying condition?
a. Unilateral mainstem bronchus obstruction
b. Variable intrathoracic upper airway obstruction
c. Variable extrathoracic upper airway obstruction
d. Fixed upper airway obstruction

14. Quick Review

15. Normal Inspiration Normal Expiration
Active Process Passive Process
Diaphragm contracts and flattened Diaphragm relaxed and dome shaped
Increase in volume of thoracic cavity and
lungs
Decrease in volume of thoracic cavity and
lungs
Decrease in intra-thoracic pressure and
intrapulmonary/alveolar pressure.
Alveolar pressure is lower than
atmospheric pressure.
Increase in intra-thoracic pressure and
intrapulmonary/alveolar pressure.
Alveolar pressure is greater than
atmospheric pressure.
Air moves from atmosphere into lungs
due to the pressure gradient
Air moves from the lungs to the
atmosphere due to the pressure gradient

16. Forceful Inspiration Forceful Expiration
Active Process Active Process
Diaphragm contracts and flattened.
External intercostal contracts along with
accessory muscle.
Diaphragm relaxed and dome shaped.
Abdominal muscles contract.
Internal intercostal muscle contract.
Rib cage move outwards and upwards
(Elevation).
Increase in antero-posterior and lateral
diameter of rib cage.
Further increase in volume of thoracic
cavity and lungs.
Rib cage move inwards and downwards
(Depression).
Decrease in antero-posterior and lateral
diameter of rib cage.
Further decrease in volume of thoracic
cavity and lungs.
Futher decrease in intra-thoracic pressure
and intrapulmonary/alveolar pressure.
Alveolar pressure is lower than
atmospheric pressure.
Futher increase in intra-thoracic pressure
and intrapulmonary/alveolar pressure.
Alveolar pressure is greater than
atmospheric pressure.
More air moves from atmosphere into
lungs due to the pressure gradient.
More air moves from the lungs to the
atmosphere due to the pressure gradient.

21. Thank You