Respiratory System Flashcards Preview

Physiology > Respiratory System > Flashcards

Flashcards in Respiratory System Deck (26):

3 processes in the exchange of air

1. pulmonary ventilation
- inspiration and expiration
2. external respiration
3. internal respiration


pulmonary ventilation

exchange of air between the lungs and the atmosphere. Due to pressure gradients made by changing thoracic volume


boyle's law

V and P have an inverse relationship if the number of molecules remain the same


Pulmonary ventilation (pressures involved)

Patm = 760 mmhg

pressure in the lungs
Ppul = Patm in between breaths

pressure in the pleural cavity
Pip = ~ 4 mmhg less than Patm = 756 mmHg
always smaller than Ppul

Pip makes sure that the lungs expand and the thoracic wall goes in.


Pulmonary Ventilation (quiet inspiration)

active process
diaphragm and the external intercostals contract increasing thoracic volume. Lungs want to collapse so the Pip decreases further to 754 mmhg causing the pressure gradient to increase between the Ppul. So Ppul goes down to 758 mmHg. Lungs then expand and air goes in until Ppul = Patm = 760 mmHg.


Pulmonary Ventilation (forced inspiration)

active process
diaphragm, external intercostals, sterncelidomastoids, scalenes, and pectoralis minors contract.
increase thoracic volume. Greater P gradient and therefor more air in.


Pulmonary Ventilation (quiet expiration)

passive process
diaphragm and external intercostals relax
decrease thoracic volume increase Pip to 756 mmHg and Ppul goes up from 760 to 762 mmHg.


Pulmonary Ventilation (forced expiration)

active process
diaphragm and the external intercostals relax
internal intercostals and the abdominals contract making the thoracic cavity even smaller. More air pushed out. Ppul increases.


stretch in lungs determined by...

compliance = how much effort needed to expand the lungs. low compliance = less effort
recoil = going back to resting shape after expanding

both result of elastic CT and surfactant.


Lungs collapse is prevented by...

1. Pip being less than Ppul all the time.
pneumothorax = Pip = Ppul = Patm, lungs collapse and thoracic wall expands. (air in the pleural cavity)

2. Surfactant
- lipoprotein/phospholipid mixture
- lowerse compliance, watery film surrounds the alveoli, less surface tension, lets the lungs expand easier.
respiratory distress syndrome
- newborns less than 7 months gestation, not enough surfactant, alveoli collapse, compliance high = death, exhaustion.


Air Flow

F = P/R
-P is the difference between Patm and Ppul
-R is the resistance of air moving through the bronchi and bronchioles.
- increased R with Emphysema, asthma, bronchitis.
- SNS dilates the bronchioles and PSNS contracts them,


respiratory volumes are measured using...



respiratory volumes (TIDAL VOLUME)

the amount of air during quiet inspiration or expiration.


respiratory volumes (IRV)

inspiratory reserve volume
excess air over TV, the amount of air inhaled on max inspiration.
3000 mL


respiratory volumes (ERV)

expiratory reserve volume
excess air over TV, the amount of air exhaled on max expiration.
1200 mL


respiratory volumes (RV)

residual volume
the remaining amount of air left in the lungs after maximal expiration
1200 mL


respiratory volumes (MRV)

Minute respiratory volume
the amount of air moved in a minute.
TV x # of breath/min
6L/min avg.


respiratory volumes (Forced Expiratory Volume in 1 Second)

the amount of air forcibly pushed out in one second following max inspiration.


respiratory capacities

consists of 2 volumes or more

IC: inspiratory capacity

VC: vital capacity: largest vol in and out of lungs

TLC: total lung capacity, the max amount of air the lungs can hold


Clinical application of FEV1

FEV1 is used while measuring VC to make up for body size. FEV1 as a percent of VC, usually 80%

1. obstructive disorders
- too hard to breath out
- emphysema, asthma, cystic fibrosis
- decrease in VC, increase in RV, FEV1 < 80% but still greater than normal.

2. restrictive disorders
- to hard to inspire
- pneumothorax, scoliosis
- decrease in VC, decrease in IC, decrease FEV1, FEV1 = 80%


external respiration

O2 from lungs to blood
CO2 from blood to lungs

aided by
1. Large surface area of alveoli and capillaries
2. Thin surface membrane (2 cells + basement membrane)
3. blood velocity is slow compared to gas diffusion


internal respiration

O2 from blood to cells
Co2 from cells to blood


Oxygen transport

2 ways
plasma 1.5%
hemoglobin 98.5 %

1. in the lungs (external resp)
- alveolar O2pressure 105mmHg, moves down into the capillary which has PO2 of 40 mmHg. blood in capillary becomes 105 mmHg in the venous blood going to the heart.
2. in the tissues (internal resp)
- systemic arterial PO2 = 95 mmHg
- systemic resting venous is 40 mmHg
- ISF is 40 mmHg
- ICF is <40 mmHg

1. Hb binds to 4O2 molecules.
- O2 + deoxyHb --> oxyHb

O2-Hb Dissociation curve
- plateau: range of O2 in the lungs. 60-100 mmHg of PO2 = max saturation for Hb.
- steep: range of O2 in the tissues. used to measure how much O2 was unloaded from Hb.
ex: at rest PO2 in tissues is 40 mmHg = 75%saturation
97-75 = 22% of O2 unloaded.
at exercise the amount unloaded increases.

shift of the curve to the right, unloads more easily and loads less easily
occurs when ...
increase in CO2, temp, and a decrease in pH meaning more H (which binds to the Hb instead of O2 to bind (bohr effect)
all occur when there is an increase in metaboism

shift of the curve to the left, unloads harder and loads easier.
occurs when decrease in CO2, increase in pH, and temp decreases
all occur in the conditions of the lung.


CO2 Transport

3 ways
1. plasma 8%
2. hemoglobin 20%
3. bicarbonate 72%

1. in lungs (ext. resp)
alveolar PCO2 = 40 mmHg
arterial pulmonary PCO2 = 45 mmHg
venous pulm PCO2 = 40 mmHg

2. in the tissues (int. resp)
systemic art PCO2 = 40 mmHg
systemic venous PCO2 = 45 mmHg
ISF = 45 mmHg
ICF = >45 mmHg

- CO2 binds to hemoglobin = carbaminoglobin.
CO2 binds to deoxy hemoglobin better than O2 at the tissues.

H2O + CO2 --> carbonic anhydrase --> H2CO3 -->H + HCO3-

Hb + H --> HbH

remove HCO3- so we can make more
chloride shift.

(i) O2 binds to deoxyHb better than CO2 (haldane effect) therefore CO2 and H are released

(ii) H + HCO3 --> H2CO3 --> H2O + CO2
reverse chloride shift because there was a decrease in the amount of HCO3 in the RBC, so HCO3 from plasma goes down the concentration gradient and into the RBC.


Control of respiration

1. respiratory centres in the medulla
- 2 GROUPS of neurons
(a) VRG (ventral respiratory group) --> control rate
(i) inspiratory neurons
- phrenic nerve (diaphragm)
- thoracic nerve (external intercostals)
(ii) expiratory neurons --> inhibit insp neurons.
(b) DRG (dorsal respiratory group) --> receive input from chemoreceptors and then send signal to modify output of VRG.

2. pontine respiratory system
- works with the resp systems in the medulla and makes sure breathing is smooth and even.
- damage = irregular and gasping.

3. other
(a) stretch receptors (hering-breuer reflex)
- overstretch lungs in smooth muscle of bronchi and bronchioles --> stretch receptors --> inhibit insp. neurons --> muscle relax and expiration occurs.
(b) voluntary control
- primary motor cortex to skel muscle (corticospinal pathway) overrides bypass medulla
- hold breath, when CO2 is too high medulla overrides the voluntary control and we expire.
(c) chemical control
(i) peripheral chemoreceptors
- in carotid and aortic bodies
- sensitive to H in the blood. Increase in H = increase in ventilation. but blood is buffered alot so it must take a large change in H.
- also detect changes in O2 when it is in the emergency zone of 50-60 mmHg on the curve.
(ii) central chemoreceptors
- in medulla oblongata (dominant)
- responds indirectly to PCO2 (arterial)
- highly sensitive to H. in the CSF because CO2 passes the BBB but not H and HCO3.
- CSF is not buffered well.
(d) other factors
increase temp = increase vent
decrease temp = decrease vent
increase emotion = increase
increase proprioreceptors = increase
sudden increase in bp = decrease
sudden decrease in bp = increase
pain sudden = stops temp
chronic pain = increase
cold sudden = stops temp
stretch anal sphincter = increase


Clinical applications

hyperventilation = too little CO2 --> vasoconstriction in the brain and therefore not enough O2 gets to the brain --> dizziness

hypoventilation = too much CO2 --> acidosis --> confuses CNS

CO poisoning = incomplete burning of gas
- 210x likely to bind to fe than O2
- forms carboxyHb
- decrease in O2
- blood gases remain the same, no change in ventilation.