Espiratory Physiology

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Respiratory Physiology

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Respiration

Ventilation:Action of breathing with muscles and lungs.

Gas exchange:Between air and capillaries in the lungs.

Between systemic capillaries and tissues of thebody.

02 utilization:Cellular respiration in mitochondria.

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Ventilation

Mechanical process thatmoves air in and out of thelungs.

Diffusion of

O2: air to blood.

C02: blood to air.

Rapid:large surface area

small diffusion distance.

Insert 16.1

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Respiratory structures

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Conducting Zone

Conducting zone:

All the structures air

passes throughbefore reaching therespiratory zone.

Mouth,nose, pharynx,trachea, glottis,larynx, bronchi.

Insert fig. 16.5

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Conducting Zone

Conducting zone

Warms and humidifies until inspired air becomes:37 degrees

Saturated with water vapor

Filters and cleans:M

ucus secreted to trap particlesMucus/particles moved by cilia to be expectorated.

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Respiratory Zone

Respiratory zone

Region of gas exchange between air andblood.

- bronchioles- alveoli

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Respiratory Zone

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Respiratory Zone

Alveoli

Air sacs

Honeycomb-like clusters

~ 300 million.Large surface area (6080 m2).

Each alveolus: only 1 thin cell layer.

Total air barrier is 2 cells across (2 Qm) (alveolarcell and capillary endothelial cell).

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Respiratory Zone

Alveolar cells:

Alveolar type I: structural cells.

Alveolar type II: secrete surfactant.

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Mechanics of breathing

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Thoracic Cavity

Diaphragm:Sheets of striated muscle divides anterior body

cavity into 2 parts.

Above diaphragm: thoracic cavity:Contains heart, large blood vessels, trachea,

esophagus, thymus, and lungs.

Below diaphragm: abdominopelvic cavity:Contains liver, pancreas, GI tract, spleen, and

genitourinary tract.

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Gas: the more volume, the less pressure (Boyles law).

Inspiration:

lung volume increase ->

decrease in intrapulmonary pressure, to just belowatmospheric pressure ->

air goes in!

Expiration: viceversa

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Intrapleural space:Space between visceral and parietal

pleurae.

Visceral and parietal pleurae (membranes) areflush against each other.

Lungs normally remain in contact with the chestwalls.

Lungs expand and contract along with thethoracic cavity.

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Pleura

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Compliance: lungs can stretch when under tension.

Elasticity: they recoil (to original shape).

- elastin

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Inspiration

Inspiration

Diaphragm contracts -> increased thoracic volumevertically.

Intercostals contract, expanding rib cage ->increased thoracic volume laterally.

Active

More volume -> lowered pressure -> air in.

Negative pressure breathing.

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Expiration

Expiration

Due to recoil of elastic lungs.Passive.

Less volume -> pressure within alveoli is just aboveatmospheric pressure -> air leaves lungs.

Note: Residual volume of air is always left behind, soalveoli do not collapse.

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Quiet breath: +/- 3 mmHgintrapulmonary pressure.

Forced breath:

Extra muscles, including abs

+/- 20-30 mm Hg intrapulmonary pressure

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Problems

Pneumothorax: a hole in chest can causeone lung to collapse.

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Surface tension

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Surface Tension

Very thin film of fluid in alveoli.

Absorb: Na+ active transport.Secrete: Cl- active transport.

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Surface Tension

Surface tension:

H20 molecules at the surface are attracted toother H20 molecules rather than to air.

Surface tension-> hard to expand the

alveoli.Small alveoli, more resistance to expansion.

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Surface tension

Surfactant

produced by alveolar type II cells.

Interspersed among water molecules.

Lowers surface tension.

RDS, respiratory distress syndrome, in preemies.

First breath: big effort to inflate lungs!

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Surface tension

Insert fig. 16.12

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Measuring pulmonary function

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Pulmonary Function

Spirometry:

Breathe into a closed system, with air,water, moveable bell

Insert fig. 16.16

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Lung volumes

Inspiratory reserve volume (IRV): extra (beyondTV) in with forced inspiration.

Expiratory reserve volume (ERV): extra (beyond TV)out with forced expiration.

Residual volume: always left in lungs, even with forced

expiration.Not measured with spirometer

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Lung capacities

Vital capacity (VC): the most you can actuallyever expire, with forced inspiration andexpiration.

VC= IRV + TV + ERV

Total lung capacity: VC plus residual volume

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Pulmonary disorders

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Pulmonary disorders Stop

Restrictive disorder:

Vital capacity is reduced.

Less air in lungs.

Obstructive disorder:

Rate of expiration is reduced.

Lungs are fine, but bronchi are obstructed.

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Pulmonary Disorders

COPD (chronic obstructive pulmonarydisease):Asthma

Emphysema

Chronic bronchitis

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Disorders

Obstructive disorder:

FEV= forced expiratory

volume.

FEV1 = % of vital capacityexpired in 1st second.

Disorder if FEV1 is < 80%

Note: same total amountexpired.

Insert fig. 16.17

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Disorders

Asthma:Obstructive

Inflammation, mucus secretion, bronchialconstriction.

Provoked by: allergic, exercise, cold and dry air

Anti-inflammatories, including inhaled epenephrine(specific for non-heart adrenergic receptors),anti-leukotrienes, anti-histamines.

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Disorders

Emphysema:

Alveolar tissue is destroyed.

Chronic progressive condition

Cigarette smoking stimulates macrophages and WBCto secrete enzymes which digest proteins.

Or: genetic inability to stop trypsin (which digestsproteins).

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Blood gases

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Blood gases

Barometers use mercury (Hg) asconvenience to measure total atmosphericpressure.

Sea level: 760 mm Hg (torr)

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Blood gases

Total pressure of a gas mixture is = to the sum of theindependent, partial pressures of each gas (Daltons

Law).

In sea level atmosphere:

PATM= 760 mm Hg = PN2 +P02 + PC02 +PH20

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Blood gases

Partial pressures: % of that gas x total pressure.

In atmosphere:02 is 21%, so (.21 x 760) = 159 mm Hg = P02

Note: atmospheric P02 decreases on a mountain,increases as one dives into the ocean.

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Blood gases

But inside you, the air is saturated with water vapor.PH20 = 47 mm Hg at 37 degrees

So, inside you, there is less P02:P02 = 105 mm Hg in alveoli.

In constrast, alveolar air is enriched in CO2, ascompared to inspired air.

PCO2 = 40 mm Hg in alveoli.

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Blood gases

Insert fig. 16.20

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Blood gases

Gas and fluid in contact:

[Gas] dissolved in a fluid depends directly on its partialpressure in the gas mixture.

With a set solubility, non changing temp.

(Henrys law)

So

P02 in alveolar air ~ = P02 in blood.

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Blood gases

O2 electrodes can measure dissolved O2 in a fluid.(also CO2 electrodes.)

Good index of lung function.

Arterial P02 is only slightly below alveolar P02

Arterial P02 = 100 mm HgAlveolar P02 = 105 mm Hg

P02 level in the systemic veins is about 40 mm Hg.45



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Blood gases

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Copyright The McGraw Hill Companies, Inc. Permission required for reproduction or display.

Blood gases

Most O2 is in hemoglobin

.3 ml dissolved in plasma +

19.7 ml in hemoglobin20 ml O2 in 100 mls blood!

But: O2 in hemoglobin-> dissolved -> tissues.

Breathing pure O2 increases only the dissolvedportion.

- insignificant effect on total O2- increased O2 delivery to tissues

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Pulmonary Circulation

L ventricle pumps to entire body, R ventricleonly to lungs.

Both ventricles pump 5.5 L/min!

Pulmonary circulation: various adaptations.as a mellow river, doesnt spill over the banks

low pressure, low resistance.

prevents pulmonary edema.

pulmonary arteries dilate if P02 is low (opposite of systemic)

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Neural control

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py g p , q p p y

Neural control

Respiratory centers

In hindbrain

- medulla oblongata

- pons

automatic breathing

Insert fig. 16.25

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py g p q p p y

Neural control

I neurons = inspiration

E neurons = expiration

I neurons -> spinal motor neurons ->respiratory muscles.

E neurons inhibit I neurons.

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Neural control

Ondines curse: only voluntary breathing.

Ondine: water nymph, punished by gods, must stay awake in orderto breath.

Or: she so cursed her philandering husband, after she gave upimmortality to join him, and he promised to love her with everywaking breath

http://www.silentpartners.org/sleep/sinfo/miscl/ondine.htm

Gene mutation in fetus:http://news.bbc.co.uk/1/hi/health/2996791.stm

Description:

http://www.medterms.com/script/main/art.asp?articlekey=9634

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Chemoreceptors

Oxygen: large reservoir attached to hemoglobin.

So chemoreceptors are more sensitive to changes in

PC02 (as sensed through changes in pH).

Ventilation is adjusted to maintain arterial PC02 of 40mm Hg.

Chemoreceptors are located throughout the body (inbrain and arteries).

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chemoreceptors

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Hemoglobin

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Hemoglobin

Each hemoglobin has 4 polypeptide chains (2 alpha,

2 beta) and 4 hemes (colored pigments).

In the center of each heme group is 1 atom of ironthat can combine with 1 molecule 02.

(so there are four 02 molecules per hemoglobinmolecule.)

280 million hemoglobin molecules per RBC!57



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Hemoglobin

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Hemoglobin

Oxyhemoglobin:

Ferrous iron (Fe2+) plus 02.

Deoxyhemoglobin:

Still ferrous iron (reduced).

No 02.

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Hemoglobin

Carboxyhemoglobin:carbon monoxide (CO) binds to heme insteadof 02

- smokers

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Hemoglobin

Can tell % of types of hemoglobin by color!

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Hemoglobin

Loading/unloading depends on:

- P02

- Affinity between hemoglobin and 02- pH

- temperature

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Hemoglobin

Dissociation curve: % oxyhemoglobinsaturation at different values of P02.

Describes effect of P02 on loading/unloading.Sigmoidal

At low P02 small changes produce large

differences in % saturation and unloading.Exercise: P02 drops, much more unloading from veins.

At high P02 slow to change.

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Oxyhemoglobin DissociationCurve

Insert fig.16.34

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Hemoglobin

Affinity between hemoglobin and 02:

- pH falls -> less affinity -> more unloading(and viceversa if pH increases)

- temp rises -> less affinity -> more unloading

exercise, fever

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Hemoglobin

Arteries: 97% saturated (i.e. oxyhemoglobin)

Veins: 75% saturated.

Arteries: 20 ml 02/100 ml blood.

Veins: ~ 5 ml less

Only 22% was unloaded!Reservoir of oxygen in case:

- dont breathe for ~5 min

- exercise (can unload up to 80%!)68



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Hemoglobin

Fetal hemoglobin (F):

- gamma chains (instead of beta)

- more affinity than adult (A) hemoglobin

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Anemias

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Hemoglobin

Anemia:

[Hemoglobin] below normal.

Polycythemia:

[Hemoglobin] above normal.

Altitude adjustment.

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Disorders

Sickle-cell anemia:fragile, inflexible RBC

inherited change: one base pair in DNA -> one aa inbeta chains

hemoglobin S

protects vs. malaria; african-americans

Thalassemia:

defects in hemoglobin

type of anemia

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Disorders

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RBC

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RBC

RBC

no nucleus

no mitochondria

Cannot use the 02 they carry!!!

Respire glucose, anaerobically.

(note: androgens stimulate erythropoiesis)

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Transport of CO2

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C02 Transport

H20+C02

carbonic acid bicarbonate

H2C03 H+ +HC03

-

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C02 transported in the blood:

- most as bicarbonate ion (HC03-)

- dissolved C02- C02 attached to hemoglobin

(Carbaminohemoglobin)

C02 Transport

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C02 Transport

Carbonic anhydrase in RBC promotes usefulchanges in blood PC02

H20+C02 ->H2C03-> HC03-

high PC02

CA

H20+C02


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C02 Transport

Chloride shift:

Chloride ions help maintain electroneutrality.

HC03- from RBC diffuses out into plasma.

RBC becomes more +.Cl- attracted in (Cl- shift).

H+ released buffered by combining withdeoxyhemoglobin.

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Acid-base balance

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Acid-Base Balance

Ventilation is normally adjusted to keep pacewith metabolic rate, so homeostasis of bloodpH is maintained.

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Acid-Base Balance

Hyperventilation -> PC02 down -> pH of CSF up ->vasoconstriction -> dizziness.

If hyperventilating, should you breath into paperbag? Yes! It increases PC02!

Metabolic acidosis can trigger hyperventilation.

Diarrhea -> acidosis.

Vomit -> alkalosis.

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Adaptations

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Exercise

During exercise, breathing becomes deeper and more rapid.

Yet blood gas levels instantly stay about the same. Huh?!

Neurogenic: sensory response from muscles?

Humoral: homones?

Local differences we cant sense in a lab?

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Adaptations

Frequent exercise, or high altitudes ->

series of changes in oxygenconsumption, or [hemoglobin], etc.

Espiratory Physiology

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