respitory 2

Question 1

pulmonary ventilation

Answer 1

Definition: Pulmonary ventilation is the process of moving air in and out of the lungs.

Key Principle: Air always moves from high pressure → low pressure (down a pressure gradient).

When lung pressure is lower than atmospheric pressure, air flows into the lungs (inspiration).

When lung pressure is higher than atmospheric pressure, air flows out of the lungs (expiration).

Question 2

Respiratory Cycle

Answer 2

A respiratory cycle = 1 inspiration + 1 expiration.

Normal breathing is called eupnea (about 12–20 cycles per minute in adults at rest).

Question 3

Air flows into the lungs
(inspiration)

Answer 3

atmospheric pressure is greater
than intra-alveolar pressure,
and intra-alveolar pressure is
greater than intrapleural
pressure, air flows in

Question 4

Air flows out of the lungs
(Expiration)

Answer 4

during expiration based on the
same principle; pressure within
the lungs becomes greater than
the atmospheric pressure, air is
expelled

Question 5

in general, two muscle groups are used during normal inspiration:

Answer 5

diaphragm and the external intercostal muscles

Additional muscles can be used if a bigger breath is required

Question 6

When the diaphragm contracts, it moves inferiorly toward the
abdominal cavity, creating a larger thoracic cavity and more space
for the lungs
Contraction of the external intercostal muscles moves the ribs
upward and outward, causing the rib cage to expand, which
increases the volume of the thoracic cavity

Question 7

Q: What drives pulmonary ventilation?

Answer 7

A: Air flows down a pressure gradient (from high pressure to low pressure).

Question 8

What pressure relationship allows inhalation?

Answer 8

A: Atmospheric pressure > alveolar pressure.

Question 9

Normal inspiration uses two muscle groups:

Answer 9

Diaphragm: contracts downward, enlarging thoracic cavity.

External intercostals: lift ribs upward/outward.
Accessory muscles (neck, chest) assist when deeper breaths are needed

Question 10

Why is normal expiration passive?

Answer 10

It relies on elastic recoil of lungs, not muscle contraction.

Extra Note: Pressure increases in the thoracic cavity drive air out until it equals atmospheric pressure.

Question 11

Q: What is quiet breathing (eupnea)

Answer 11

A: Resting, automatic breathing that uses diaphragm + intercostals.

Extra Note: It does not require conscious effort; expiration is passive.

Question 12

What is the difference between diaphragmatic and costal breathing?

Answer 12

Diaphragmatic (deep): Uses diaphragm strongly (“belly breathing”).

Costal (shallow): Uses intercostal muscles (“chest breathing”)

Question 13

In forced inspiration (exercise, coughing, singing)

Answer 13

Diaphragm + intercostals contract strongly.

Accessory muscles (sternocleidomastoid, scalenes, pectoralis minor) lift the thoracic cage, expanding lung volume further.

Question 14

Forced expiration is active (exercise, blowing, coughing):

Answer 14

Abdominal muscles push diaphragm upward.

Internal intercostals compress rib cage.
This reduces thoracic volume more than passive expiration

Question 15

Q: What are respiratory volumes and capacities?

Answer 15

A: Volumes are specific amounts of air moved during breathing (e.g., tidal volume), while capacities are combinations of volumes (e.g., vital capacity).

Extra Note: These values are useful in clinical tests like spirometry to check lung health.

Question 16

There are four main lung volumes:

Answer 16

Tidal Volume (TV): normal resting breath.

Inspiratory Reserve Volume (IRV): extra air inhaled after a normal breath.

Expiratory Reserve Volume (ERV): extra air exhaled after a normal breath out.

Residual Volume (RV): air left after maximum exhalation.

Question 17

What is tidal volume?

Answer 17

The normal volume of air inhaled or exhaled at rest (~500 mL).

Question 18

What is inspiratory reserve volume (IRV)?

Answer 18

A: The extra air inhaled beyond a normal inspiration.

Question 19

What is expiratory reserve volume (ERV)?

Answer 19

A: The additional air that can be forcefully exhaled after a normal breath.

Question 20

Q: What is residual volume (RV)?

Answer 20

The air left in the lungs after maximum exhalation.

Question 21

: What is total lung capacity (TLC)?

Answer 21

A: The maximum amount of air lungs can hold (sum of all volumes)

Men ≈ 6000 mL

Women ≈ 4200 m

Question 22

What is vital capacity (VC)

Answer 22

The maximum air that can be exhaled after maximum inhalation.

Extra Note: VC is usually 3000–5000 mL and measures functional breathing ability.

Question 23

: What is inspiratory capacity (IC)?

Answer 23

A: The maximum air inhaled after a normal exhalation (TV + IRV).

Question 24

What is functional residual capacity (FRC)?

Answer 24

The volume of air remaining after a normal exhalation.

Question 25

What is anatomical dead space?

Answer 25

Air that fills the conducting airways (~150 mL) and never reaches alveoli for gas exchange.

Question 26

What is alveolar (physiological) dead space?

Answer 26

Air that reaches alveoli but doesn’t undergo gas exchange (due to disease or poor blood flow).

Question 27

otal dead space =

Answer 27

= anatomical + alveolar dead space. This is the total air volume in the respiratory system that is not being used in gas exchange. Normally ~150 mL, but can be higher with disease.

Question 28

Respiratory rate =

Answer 28

number of breaths per minute. It’s controlled by the respiratory center in the medulla oblongata. The medulla responds mostly to CO₂ and pH changes, and less directly to O₂.

Question 29

The DRG in the medulla sets the rhythm of quiet breathing

Answer 29

Active phase: stimulates diaphragm & external intercostals → inspiration. Inactive phase: stops firing → muscles relax → expiration (passive).

Question 30

The VRG is recruited during forced breathing (exercise, coughing, singing).

Answer 30

Stimulates accessory inspiratory muscles. Stimulates expiratory muscles.

Question 31

The pons

Answer 31

modifies medulla activity, helping smooth the transition between inhalation & exhalation. It mainly adjusts depth of inspiration.

Question 32

Q: How does DRG activity control quiet breathing

Answer 32

A: DRG active → inhalation; DRG silent → exhalation. Extra Note: Quiet breathing rate = about 12–20 breaths/min.

Question 33

What muscles are used in forceful breathing?

Answer 33

: Accessory inspiratory (SCM, scalenes, pec minor) and expiratory (internal intercostals, abdominals).

Question 34

The main drive to breathe

Answer 34

is CO₂, not O₂. Rising CO₂ increases H⁺ (lowers pH). Central chemoreceptors: brain/brainstem, sense pH changes. Peripheral chemoreceptors: carotid bodies & aortic arch, sense CO₂, O₂, and pH.

Question 35

If CO₂ rises:

Answer 35

pH drops (more H⁺). Chemoreceptors activated. Breathing rate & depth increase. More CO₂ exhaled → pH normalizes.

Question 36

If CO₂ is too low:

Answer 36

: Breathing slows and becomes shallow until CO₂ returns to normal. H rises (less H⁺). Chemoreceptor activity decreases. Breathing slows → CO₂ builds up again.

Question 37

Low O₂ as a Stimulus

Answer 37

O₂ only triggers breathing when levels are very low (<60 mmHg). Then, peripheral chemoreceptors (carotid & aortic bodies) fire, stimulating breathing even if CO₂ is normal.

Question 38

Hering–Breuer Reflex

Answer 38

Pulmonary stretch receptors in bronchi/bronchioles prevent overinflation: When lungs expand too much (TV > ~1500 mL), vagus nerve signals medulla → inhalation stops. Protects lung tissue during extreme effort.

Question 39

3 LAWS

Answer 39

Gas exchange in the lungs and tissues follows the laws of gas behavior. Beyond Boyle’s Law (pressure & volume), we also use Dalton’s Law (partial pressures) and Henry’s Law (gas solubility).

Question 40

Dalton’s Law:

Answer 40

In a gas mixture, each gas exerts its own pressure (partial pressure). The total pressure = sum of all partial pressures. his explains why oxygen and CO₂ diffuse independently in the lungs.

Question 41

Atmospheric Pressure

Answer 41

Gases in the atmosphere (mainly N₂, O₂, CO₂, H₂O) exert pressure on surfaces. Together, they make up atmospheric pressure (≈760 mmHg at sea level).

Question 42

Partial Pressure (PO₂, PCO₂)

Answer 42

Each gas in a mixture has its own partial pressure (Px). Gases move from higher → lower partial pressure until equilibrium.

Question 43

Diffusion of Gase

Answer 43

Gas exchange happens because of partial pressure gradients: O₂ moves from high PO₂ (alveoli 105 mmHg) → low PO₂ (blood 40 mmHg). CO₂ moves from high PCO₂ (blood 45 mmHg) → low PCO₂ (alveoli 40 mmHg).

Question 44

What does Henry’s Law state?

Answer 44

Gas concentration in a liquid depends on its partial pressure and solubility. Extra Note: CO₂ dissolves in blood more easily than O₂.

Question 45

Atmospheric vs. Alveolar Air

Answer 45

Alveolar air differs from atmospheric air: Less O₂, more CO₂ (due to gas exchange). More water vapor (air humidified in airways).

Question 46

Diffusion Distance & Surface Area

Answer 46

hin membrane → easy diffusion. Large surface area of alveoli → efficient exchange. Diseases like pneumonia increase diffusion distance, impairing gas exchang

Question 47

Ventilation vs. Perfusion

Answer 47

entilation: airflow into alveoli. Perfusion: blood flow in pulmonary capillaries. Both must match for optimal gas exchange.

Question 48

Local Regulation (Airways & Blood Vessels)

Answer 48

High alveolar CO₂ → bronchioles dilate (more airflow). Low alveolar O₂ → pulmonary arterioles constrict (reduce blood flow). This balances ventilation & perfusion

Question 49

Sites OF GAS EXTIONH

Answer 49

External respiration: alveoli ↔ blood. Internal respiration: blood ↔ tissues. Both rely on simple diffusion.

Question 50

Q: What gradients drive external respiration?

Answer 50

Alveolar PO₂ ≈ 105 mmHg → blood PO₂ ≈ 40 mmHg → O₂ enters blood. Alveolar PCO₂ ≈ 40 mmHg → blood PCO₂ ≈ 45 mmHg → CO₂ enters alveoli O₂ diffuses into blood, CO₂ diffuses into alveoli.

Question 51

External respiration = alveoli ↔ blood. Internal respiration = blood ↔ tissues. Both follow the same rule: gases diffuse down their partial pressure gradients.

Question 52

Breathing = air movement External respiration = gas swapping