Phys 1

Question 1

Muscles of Inspiration

Answer 1

Diaphragm (pulls down abdomen)
External intercostals (raise ribs) 
Scalene (raise 1st and 2nd ribs)
Sternomastoids (raise sternum)
Additional muscles of head and neck

Question 2

Why skeletal muscles?

Answer 2

Because we want to be able to control them, and to change respiratory rate when we need more air
-Allows rapid, uniform action and ability to respond to changes

Question 3

Why is skeletal muscle not great always?

Answer 3

• if you injure the brain/SC they can stop working

- length-tension curve (you can have increased lung size–> stretched muscles)

Question 4

Under normal conditions, the lungs and muscle/ribs are…

Answer 4

NOT physically connected to one another

-separated by pleural cavity, which is filled with fluid

Question 5

What is on either side of the intrapleural space?

Answer 5

Visceral plura (by the lungs) and parietal pleura (by the muscle) 
-they have fluid in-between them

Question 6

Intrapleural Pressure

Answer 6

• at rest: -5cmH2O (negative because of the lung’s elastic coil–the lungs want to be smaller, and the ribs want to pull away/be bigger)
• with inspiration: decreases (-8; reached at end of inspiration)

Question 7

Alveolar Pressure

Answer 7

• as the lungs increase in size, the AP decreases
• rest: 0 cm H2O (matches atm pressure)
• inspiration: -1 cm H2O (below atm pressure, so air flows in)
• end of inspiration: returns to 0, and air stops coming in

Question 8

Tidal Volume

Answer 8

amount of air inhaled in a given breath (Vt)

-in a typical breath, Vt is about 500mL

Question 9

Muscles of Expiration

Answer 9

• abdominal muscles (push diaphragm upwards)
• intercostal muscles (decrease AP diameter of the thorax)
• accessory muscles (indicated difficulty breathing)

Question 10

When do we use muscles of expiration?

Answer 10

in pathology–>typically we do not use them in a normal breath because expiration is passive because the lungs have elastic recoil (want to be smaller)
-basically, once the inspiratory muscles relax, air flows out and we reset

Question 11

As expiration continues, the volume of air ____ and the alveolar pressure ___.

Answer 11

1. decreases

2. increases (back to 0)

Question 12

Peak negative value at inspiration of Intrapleural vs. alveolar

Answer 12

1. End of inspiration

2. Mid inspiration

Question 13

Minute Ventilation

Answer 13

how much air is inhaled every minute

Vdot=Vt x frequency

Question 14

Anatomic Dead Space

Answer 14

no alveoli; cannot participate in gas exchange

-typically equals the same number as their weight

Question 15

Minute Alveolar Ventilation

Answer 15

Valv=Vt - Vds

VdotA=Valv x f

Question 16

When does air flow reach maximum L/sec?

Answer 16

halfway because as alveolar pressure starts to return back to 0 cmH2O, airflow begins to decrease as well

Question 17

Transpulmonary Pressure

Answer 17

=Palv-Pip

-when positive, it means that the lungs are “open”

Question 18

PAO2 vs. PaO2 vs. PvO2

Answer 18

1. Alveolar gas
2. Arterial gas
3. Venous blood