26/5 Breathing Rates & Mechanisms

Question 1

During inhalation, describe how the diaphragm and external intercostals move

Answer 1

Diaphragm: contracts, moves inferiorly

External intercostals: contract, moves ribs up and out

Question 2

What are the accessory muscles involved in forced inhalation

Answer 2

Scalenes
Sternocleidomastoids
Pectoralis minors

Question 3

During inhalation, how does the lung volume change

Answer 3

increases

Question 4

During inhalation, how do the intrapleural and intrapulmonary pressures change

Answer 4

Intrapleural: more subatmospheric/ negative
Intrapulmonary: becomes negative (relative to atmospheric pressure)

Question 5

How do the diaphragm and external intercostals move during exhalation

Answer 5

Diaphragm: Relaxes, moves superiorly

External intercostals: relax, rib cage descends due to recoil of costal cartilages

Question 6

What are the accessory muscles involved in forced exhalation

Answer 6

Abdominal wall muscles (transverse & oblique)

Internal intercostals

Question 7

How does the volume of the lungs change during exhalation

Answer 7

decreases

Question 8

During exhalation, how do the intrapleural and intrapulmonary pressures change?

Answer 8

Intrapleural: less subatmospheric (more positive)
Intrapulmonary: Becomes positive (relative to atmospheric pressure)

Question 9

Define respiratory rate

Answer 9

frequency of breathing

Question 10

Define Respiratory Minute Volume (VE) aka Minute Ventilation Rate and give its equation.

Answer 10

Amount of air moved via Tidal Ventilation each minute

VE= VT x f

Question 11

Define Alveolar Ventilation(VA) and give its equation

Answer 11

Amount of air reaching the alveoli each minute

VA = (VT - VD) x f

Question 12

What does tidal volume (VT) mean?

Answer 12

Volume of air inhaled / exhaled during 1 normal breath

Question 13

What does dead space (VD) mean?

Answer 13

Amount of air in the conudcting zone that does not take part in gas exhange/ transfer
-> there is always a small volume of air that will re-enter the alveoli

Question 14

Define Expiratory Reserve Volume (ERV)

Answer 14

Volume of additional air that can be expired after a normal quiet expiration-> beyond tidal volume

Question 15

Define Inspiratory Reserve Volume (IRV)

Answer 15

Volume of additional air that can be inspired after a normal quiet inhalation -> beyond tidal volume

Question 16

Define residual volume (RV)

Answer 16

Air left in lungs after maximum forced expiration

-> air that can’t be breathed out and cannot be measured by spirometer

Question 17

What is Inspiratory capacity (IC) and what is its equation

Answer 17

Volume of air that can be inspired after a normal quiet expiration
IC= VT + IRV

Question 18

Define Functional Residual capacity

Answer 18

Total air remaining after a normal quiet expiration

Question 19

Define Vital Capacity (VC) and give its equation

Answer 19

Max air moving into/ out of lungs.

-> VC = ERV + VT + IRV

Question 20

Define Total lung capacity )TLC) and give the equation

Answer 20

Total air in the lungs after a forced inspiration

TLC = RV + ERV + VT + IRV

Question 21

What are the 3 routes of CO2 to the lungs

Answer 21

1. dissolved in plasma
2. bound to Hb
3. Bicarbonate-ion form

Question 22

How does the majority of CO2 travel to the lungs

Answer 22

in the form of bicarbonate ions in the blood

Question 23

What enzyme changes CO2 to a bicarbonate ion and what is the other ion formed in the process? State the full equation

Answer 23

Carbonic anhydrase
H+
CO2 + H2O H2CO3 H+ + HCO3-

Question 24

What is the difference between ventilation (V) and perfusion (Q)

Answer 24

Ventilation: flow of air into and out of alveoli
Perfusion: flow of blood to alveolar capillaries

Question 25

Describe the three zones of Ventilation-Perfusion ratios in the regional pulmonary blood flow

Answer 25

Zone 1: capillary pressure never more than alveolar air pressure, no blood flow, V/Q ratio= infinity

Zone 2: capillary pressure > alveolar air pressure during systole, intermittent blood flow (flows during systolic), V/Q = normal

Zone 3: capillary pressure always > alveolar air pressure, constant blood flow, V/Q still normal but lower than zone 2