Lecture 2

Question 1

The Main purpose of Pulmonary Ventilation

Answer 1

The main purpose of ventilation is to maintain an

optimal composition of alveolar gas

Question 2

Phrenic nerve (C 3,4,5) Does what?

Answer 2

transmits motor stimulation to diaphragm

Question 3

Intercostal nerves (T 1-11) does what?

Answer 3

sends signal external intercostal muscles

Question 4

The act of inhaling is?

Answer 4

Negative pressure ventilation

Question 5

Diaghram responsible for how much inspiratory effort?

Answer 5

Responsible for 75% of inspiratory effort.

Question 6

Movement during During contraction of diaphragm

Answer 6

• Abdominal contents forced downward & forward causing increase in vertical dimension of chest cavity
• Rib margins are lifted & moved outward causing increase in the transverse diameter of thorax

-Diaphragm moves down 1cm during normal inspiration
During forced inspiration diaphragm can move down 10cm

Question 7

Paradoxical movement of diaphragm when paralyzed does what?

Answer 7

• Upward movement with inspiratory drop of intrathoracic pressure
• Occurs when the diaphragm muscle is denervated

Question 8

External Intercostal Muscles

Answer 8

Responsible for 25% of inspiratory effort.

Contraction of EIM pulls ribs upward & forward

Thorax diameters increase in both lateral & anteroposterior directions

Ribs move outward in “bucket-handle” fashion

Intercostals nerves from spinal cord roots innervate EIMs

These originate from the ventral rami of T1 to T11

Question 9

Scalenes & Sternocleidomastoid Muscles

do what?

Answer 9

assist with forced inspiration

Question 10

Scalene Muscle

Answer 10

Attach cervical spine to apical rib

Elevate the first two ribs during forced inspiration.

Question 11

Sternocleidomastoid Muscle

Answer 11

Attach base of skull (mastoid process) to top of sternum and clavicle medially

Raise the sternum during forced inspiration