1. Ventilation (atmosphere) - O₂ in, CO₂ out.
2. Gas exchange (alveoli) - O₂ out, CO₂ in?
3. Gas transport (pulmonary circulation) of oxygenated blood to the left heart.
4. Gas exchange (systemic circulation)
5. Cellular respiration - O₂ in, CO₂ out.

(diagram on p6 of outline) - confusing

About 2400 ml.

Amount of air remaining in lungs

after a tidal volume (TV) expiration.

RV +

About 3600 ml.

Amount of air that can be inspired

after a tidal volume (TV) expiration.

TV + IRV = IC

(500 ml + 3100 ml = 3600 ml)

1. Inspiratory Capacity (IC)
2. Functional Residual Capacity (FRC)
3. Vital Capacity (VC)
4. Total Lung Capacity (TLC)

Generate respiratory rate. (Remember: DIVE) (why?)*

1. Ventral Respiratory Group (VRG) MOST IMPORTANT: Depolarizn of neuronal cell bodies in this ctr generate resp rhythm (sets rate). Discharge mainly associated w/ expiration.
2. Dorsal Respiratory Group (DRG): Simply influences VRG, doesn't do much else. Receives input from chemoreceptors, etc., modifies VRG which then simulate inspiration. Generate rhythm by pattern of neuronal depolarizatn.

Volume of air in and out of alveoli in one minute. (p. 824)

V_A = (TV - dead space) x frequency (b/min)

V_A = (500 - 150) x 12 b/min

V_A = 4200 ml/min or 4/2 L/min

Anatomical dead space (150 ml)

Note: If some alveoli cease to act in gas exchange

(ie, due to alveolar collapse or obstruction)

alveolar dead space is added to anatomical dead space,

and the sum of that is total dead space.

(p. 824?)

Law of relationship btw pressure/volume of gases.(p 827)

At constant temp, pressure of gas varies inversely w/its volume.

P₁V₁ = P₂V₂

Initial pressure (P₁) and initial volume (V₁) of gas equals

resulting pressure (P₂) and resulting volume (V₂) of gas.

In a large volume, gas pressure will be low; inversely,

in a small volume, gas pressure will be high. (3)(2) = (2)(3)

Ex: ↑ vol from 2 to 3 → ↓ pressure from 3 to 2.

Calculate P_O2 using Dalton's Law: P_O2 = P_t x F_O2

Atmosphere = 760 mmHg x 0.21      Alveolar = 760 mmHg x 0.14

                 = 160 mmHg                           = 160 mmHg (104)

(p. 828)

The total pressure exerted by a mixture of gases

is sum of pressures exerted independentlly by each gas in mixture.

Thus, pressure exerted by each gas (its partial pressure)

is directly proportional to its percentage in total gas mixture.

P_x = P_t x F_x: Partial pressure of gas (P_x) equals sum of partial pressures in all gases in mixture [total atmospheric pressure (P_t)] times fractional concentration of gas in the mixture (F_x).

Ex: F_O2 = 21%; P_t of air 760 mmHg;

→ P_O2 = 760 mmHg x 0.21 = 160 mmHg

Located in ventral medulla, respond to chgs in H⁺ (pH).

↑ CO₂ → ↑ H⁺; ↑ CO₂ + H₂O → ↑ H₂CO₂ → H⁺ + HCO₃

CO₂ reacts with water to form H⁺and bicarbonate.

As pH decreases (H⁺ increases), ventilation is ____________.

Hypercapnia - ↑ P_CO2 levels. Hypocapnia - ↓ P_CO2 levels.

(see also hyperventilation leads to fainting)

Shift Right on chart:

Hb has lower affinity for O2 (exercise), more O2 available for tissues. ↑ H+ (↓ pH); ↑ temp; ↑ PCO2

Shift Left on chart:

Hb has higher affinitiy for O2 (relaxed), less O2 available for tissues.

↓ H+ (↑ pH); ↓ temp; ↓ PCO2

Scalenes, sternocleidomastoid mucles of neck, pectoralis minor muscles of chest - may be used during vigorous exercise or obstructive pulmonary disease.

1. Specific - directed against identified enemy.
2. Involves B&T lymphocytes.
3. Memory - recognizes enemies previously encountered. (measles)
4. Systemic - can act anywhere in body. (Army always on patrol)

       Atmospheric   Alveolar

O₂        21%            14%             (oxygen)

N₂        79%            75%             (nitrogen)

CO₂      .04%             5%             (carbon dioxide)

                               6% H₂O

Liquid film that coats the

alveolar walls,

composed primarily of water.

1. Type I - simple squamous epithelium
2. Macrophages - removes debris/microbes
3. Type II - secretes surfactant which decreases surface tension and prevents alveoli from collapsing.

Yes.

Protein molecules, called antibodies, bind antigens.

These antibodies,

which play an important role in destroying pathogens,

are secreted by the clonal descendents of B cells,

called plasma cells.

Collapse of lungs,

could be due to airway obstruction,

lung tumor, aspirated object or pneumothorax. (p. 820)

1. Boyle's Law (pressure/volume relationship)
2. Dalton's Law (partial pressures)
3. Henry's Law (solubility)

Blue-staining granules.

Least abundant leukocyte.

Release histamine and other antinflam. chemicals.

The pressure of a gas is

inversely proportional to

volume of its container.

Increasing volume decreases pressure;

decreasing volume increases pressure.

trachea - main bronchi - lobular bronchi -

segmental bronchi -terminal bronchioles

Cartilage keeps airways open from trachea thru bronchi.

Bronchioles do not contain cartilage but

contain smooth muscle which allows for regulation of airflow.

Branching network of airways

(main bronchi to terminal bronchioles)

that conducts air within each lung.

60-70% (most) of CO₂ transported in form of HCO₃, bicarbonate ions.

 [RBCs contain carbonic anhydrase (enzyme*)]

CO₂+ H₂O ↔* H₂CO₃ ↔ H+ + HCO₃

therefore ↑ CO₂ →  ↑ H+

Can't be transferred by transferring body fluids.

Involves T cells, which directly attack other cells of our own body

(cancer cells, virus-invaded cells,

cells with bacteria in their extracellular fluid, and

cells transplanted from other people.

• ACh (acetylcholine) and histamine cause contraction of bronchial smooth mucle, reduce diameter of airways.
• Epi and Atropine (bee stings) relax bronchial smooth muscle, cause airway dilation.

When bicarbonate ions diffuse out of RBC,

chloride ions diffuse in

to counterbalance the negative charge.

Airways from nasal cavity through terminal bronchioles.

Function: moisten/warm the air.

No gas exchange.

• warm/humidify the air
• NO gas exchange
• constitute anatomical dead space (150 ml)

in descending order:

• Trachea
• Left/Right bronchi, 2 branches (primary)
• Lobar bronchi, 4 branches (secondary)
• Segmental bronchi, 8 branches (tertiary)
• Bronchioles, 16 branches (little bronchi)
• Terminal Bronchi, 32 to 6x10⁴ (last of conducting zone)

1. Medullary Centers
2. Pontine Respiratory Group (PRG)
3. Higher Brain Regions

1. Hypothalamic controls - emotions/pain will modulate respiratory ctrs.
2. Cerebral motor cortex - allows us to exert voluntary control over resp muscles.

Centers in pontine can influence and modify (alter) activity of medullary center neurons (formerly apneustic/pneumotaxic areas).

(fig Outline p. 13)

Deep Insp:

• diaphragm
• external intercostal muscles
• sternocleidomastoid & scalenes

Deep Exp:

• internal intercostal muscles
• abdominal & oblique muscles

The diaphragm is the main muscle of respiratory inspiration.  It is dome-shaped, rests on floor of thoracic cavity.

With contraction, the dome flattens and:

↑ volume of thoracic cavity, ↑ lung volume, ↓ intrapulmonary pressure

Bilobed nucleus,

red-staining granules contain enzymes,

defend against parasites (worms)

by releasing digestive enzymes onto them.

Also play a role in asthma.

Passive process in which

diaphragm moves up, relaxing/external intercostal muscles relax,

elastic lungs recoil inward, and

thoracic wall recoils inward.

Decreased volume in lungs means

increased pressure in thoracic cavity.

These are some of the muscles of respiration, particularly inspiration.  Contraction pulls sternum out/ribs up.

They are important during forceful respiration.

1. Partial pressures and solubilities in pulmonary blood/alveoli
2. Thickness of respiratory membrane
3. Surface area for gas exchange
4. Ventilation-Perfusion coupling

(Not to be confused with FVC)

Amount of air expelled during specific time interval of the FVC test

(Ex: in 1 second, FEV₁)

(not to be confused with FEV)

Amount of air expelled

when subject takes deep breath

and forcefully exhales

maximally and rapidly as possible.

O₂ diffuses from alveoli into pulmonary blood

CO₂ diffuses from pulmonary blood to the alveoli

Henry's Law: Tho large diff in partial pressures of O₂/CO₂

equal amounts are exchanged

because CO₂ is 20x more soluble than O₂.

Increases perfusion of bases of lungs,

leaving apices (tops) relatively under-perfused.

Amount of CO2 carrid in blood

is influenced by amt of O2 carried in blood.

↓ O2 → ↑ CO2

(Bohr was opposite: O2 inflenced by CO2.)

Remember: BO CH  (Bohr Oxygen/Carbon Dioxide Haldane)

Two factors determine how gas will dissolve in a liquid:

Partial pressure (P_x) and solubility (K_x).

C_x = K_x x P_x

Inflation reflex as a result of

lung hyperinflation on inspiration.

(PSRs) Stretch receptors stimulated

resulting in inhibition of inspiration.

Branch of Adaptive Immunity that can be transferred via body fluids and involves B cells and the antibodies they ultimately produce.

Humoral immunity is directed against extracellular pathogens.

Body fluids.

Humors can be transferred from one person to another, transferring immunity.

↑ H⁺ levels leads to vasodilation of cerebral vessels,

so hyperventilation lowers CO₂  → ↓ H⁺

thus vasoconstriction of cerebral blood vessels (↓ O₂)

leads to fainting.

P_CO2 decreases

pH increases

Inadequate O2 delivery to tissues.

• Anemic hypoxia - ↓ RBC or hemoglobin
• Ischemic hypoxia - ↓ blood flow → ↓ O2 → death (congestive heart failure), ↓ circulation
• Histotoxic hypoxia - cells unable to use O2 (cyanide)
• Hypoxemic hypoxia - CO poison (garage suicide). Affinity of Hb for CO is 200x > for O2. CO will bind rather than O2.

Specialized immune cells (ie, leukocytes)

Lymphoid organs and tissues

(bone marrow, lymph nodes, spleen, thymus, etc)

Decreased surfactant

will cause surface tension forces to collapse alveol,

more energy will be needed to inflate alveoli.

• Efferent - Phrenic nerve exits spinal cord at cervical level, innervates diaphragm. Carries info from receptors to lung.
• Afferent? - Vagus (cranial) nerve carries info from lungs to medulla oblongata (respiratory centers) and other brainstem areas.

Diaphragm flattens, moves down (contracts),

external intercostal muscles elevate rib cage,

elastic lungs expand outward, and

thoracic wall expands outward.

Increased volume in lungs means

decreased pressure in thoracic cavity.

Pressure within the pleural cavity (balloon).

Always negative, it acts like a suction to keep lungs inflated.

Pleural cavity is filled with pleural fluid.

Negative pressues is due to:

• surface tension of alveolar fluid
• elasticity of lungs
• elasticity of thoracic wall

It is most negative during inspiration.

As thoracic wall moves outward,

intrapleural pressure gets more negative.

As thoracic wall recoils during expiration,

pressure returns to

-4 mm Hg or 756 mm Hg.

Pressure within pleural cavity (negative pressure)

Always less than atmospheric pressure (4 mmHg less) -- subatmospheric.

This plus surface tension holds parietal/visceral pleura together.

(a/k/a intra-alveolar pressure)

Pressure within the lungs.

Btwn breaths it equals atmospheric pressure (760 mm Hg)

a/k/a pulmonary pressure of 0.

Intrapulmonary pressure decreases during inspiration

(as lung volume increases - Boyle's law)

and increases during expiration

(lung volume decreases).

Located in airways.

Stimulated by dust, smoke, fumes.

Protective reflexes: coughing, sneezing

Electrochemical attraction

that molecules in liquid have for one another

tends to hold them closely together.

Because of this, alveoli tend to decrease their radius. 

(A/k/a surface tension.)

in the larynx, obvious externally as Adam's Apple

1. provides open airway
2. acts as switching mechanism to route air into trachea, food into esophagus
3. houses vocal cords (voice production)

• laryngeal prominence
• glottis
• epiglottis

(Never let monkeys eat bananas)

This is the order from most common to least.

1. Cells of the immune system are called leukocytes when traveling in the blood.
2. Originate in bone marrow.
3. Migrate to tissues or circulate thru blood/lymphatic system, entering tissues when needed.
4. Classified by shape of nucleus and colors of granules when stained.

Stretchiness.

The more lung expands with ↑ pressure,

the greater its compliance.

Factors that decrease compliance:

• scar tissue from TB (fibrosis)
• congestion from pneumonia or chronic bronchitis

Surface tension.

Electrochemical attraction that molecules in liquid have for one another tends to hold them closely together. Because of this, alveoli tend to decrease their radius (LAPLACE'S LAW).

PSR (stretch receptors) will be stimulated.

Result: inhibits inspiration

This inflation reflex is called Hering-Breuer Reflex.

Round nucleus, no granules

Include B & T cells

Amount of air that flows into or out of respiratory tract in 1 minute.

V_E = TV x frequency

V_E = TV x breaths/minute

V_E = 500 x 12 breaths/min

V_E = 6000 ml/min or 6 L/min

Large U-shaped nucleus,

no granules.

Become macrophages in tissues.

In a normal, healthy, resting person expiration is a passive process, depending mostly on elastic recoil of lungs.

• Abdominal muscles (oblique/transverse) - contraction pushes viscera (abd organs) up against diaphragm and depress rib cage, decreasing volume of thoracic cavity.
• Internal inercostal muscles - also help depress rib cage, decreasing volume pulls ribs in and down.

• air conduit
• continuous with nasal cavity
• extends to soft pallet
• contains uvula

Multi-lobed nucleus.

Pale-staining granules.

Phagocytize pathogens.

• warms/moistens air
• cleans/filters inspired air
• olfactory receptors

Partial pressures and solubilities in pulmonary blood/alveoli:

↑ O₂       PO₂ pulm. blood =  40 mmHg

             PO₂ alveoli        = 104 mmHg

↓ CO₂     PCO₂ pulmonary blood = 45 mmHg

             PCO₂ alveoli              = 40 mmHg

• extends from soft palate to epiglottis (within pharynx)
• provides passage for food/air
• contains palatine and lingual tonsils

• lighten skull
• warms/moistens air
• resonance chambers (speech)

The surface of a pathogen is studded with large molecules

called antigens.

The 3D shapes of antigens constitute their

antigenic determinants. 

(Antigens can be proteins, carbohydrates, or nucleic acids.)

in throat, extends from base of skull to level of C6,

connects nasal cavity/mouth to larynx/esophagus

1. Nasopharynx and uvula
2. Oropharynx
3. Laryngopharynx

Clonal descendents of B cells. 

They secrete antibodies (protein molecules)

which play an important role in destroying pathogens.

Pleurae are the serous membranes of the lungs.

1. Parietal pleura (outer) lines thoracic wall/mediastinum,diaphragm.
2. Pleural cavity (btwn) (intrapleural space) filled w/ pleural fluid to reduce surface tension, lubricant (prevents separation of lungs from thoracic wall).
3. Visceral pleura (inner) covers surface of lungs.

Lungs like a fist inside a balloon (pleurae).

• Inflammation of pleura (often results from pneumonia)
• Membranes produce excessive pleural fluid
• Pleural surfaces become dry/rough
• Pain with each breath

Presence of air in intrapleural space (intrapleural pressure).

Ex. thoracic wall puncture

Presence of air in intrapleural space;

reversed by closing the "hole" and

drawing air out of the intrapleural space with chest tubes.

This allows lung to reinflate and

resume its normal function.

As air enters pleural cavity (ie, after puncture)

it moves from HIGH pressure to Low pressure - pneumothorax.

Pressure diff btw intraPULMONARY and intraPLEURAL pressures

(transpulmonary pressure)

creates the suction to keep lungs inflated.

Dependent on cross-sectional area.

Most of the resistance is in the nasopharynx and upper bronchi (medium-sized bronchi)

Movement of chest wall outward away from lungs.

Lung tissue tends to collapse due to:

1. Elastic fibers
2. 3D meshwork of non-elastic fibers act as elastic fibers as they stretch and recoil (ie, nylon stocking)
3. Surface tension (LARGEST COMPONENT OF LUNG RECOIL). Electrochemical attraction that molecules in liquid have for one another tends to hold them closely together. Because of this, alveoli tend to decrease their radius (LAPLACE'S LAW).

Recoil of lungs is inward, recoil of chest wall is outward.

This produces subatmospheric pressure in intrapleural space;

keeps lungs inflated.

There is resistance when tissues move across each other,

normally very low.

Air moves in/out lungs due to pressure gradient.

1. Respiratory muscle contraction
2. Elastic recoil of lungs/chest wall
3. Airway resistance
4. Tissue resistance

Contraction of muscle changes volume of thoracic cavity

to produce changes in intrapulmonary pressure.

contraction → ↑ volume → ↓ pressure (more negative)

Air moves inside on pressure gradient,

lungs expand,

approximately 500 ml of air enters lungs (tidal volume).

This is where gas exchange takes place.

They surround the alveoli.

A low pressure/low resistance vasculature which supplies blood to lungs that is available for gas exchange with inspired air.

• pulmonary trunk
• pulmonary arteries
• pulm capillaries
• pulm veins

Note: Gravity increases perfusion of bases of lungs, leaving the apices relatively underperfused.

In congestive heart failure,

there is accumulaton of interstitial fluid in the lungs.

It increases the thickness of the

respiratory membrane

which results in less gas exchange.

Substance that reduces surface tension,

a detergent-like lipoprotein produced by Type II alveolar cells.

Decreased surfactant will cause surface tension forces to collapse alveoli and more energy will be needed to inflate alveoli.

(Infant respiratory distress syndrome)

Dense networks of blood vessels surrounding each alveolus.

They EXCHANGE GASES with the alveoli.

Oxygen and CO2 are exchanged btw

air in alveoli and blod in pulmonary capillaries.

Spirometer used to measure respiratory volumes:

1. Minute ventilation (V_E) or Minute Respiratory Volume (MRV)
2. Alveolar Ventilation Rate (V_A) or AVR)
3. Forced Vital Capacity (FVC) and Forced Expiratory Volume (FEV)

Oxygenated blood leaves the lungs via the pulmonary veins

and returns to the heart.

As air flows into lungs, gas molecules encounter resistance when they strike walls of airway. Therefore, DIAMETER of airway affects resistance. When diameter decreases, resistance INCREASES.

IOW, if bronchiole constricts,

resistance increases and airflow decreases.

Effect change in size/volume of thoracic cavity.

↑ cavity volume →  ↓ pressure,

           and inversely

↓ cavity volume →  ↑ pressure

As air moves in/out of lungs

it travels from HIGH PRESSURE regions

to Low Pressure regions.

Sum of all lung volumes at end of maximal inspiration.

(about 5800-6000 ml)

TLC = VC + RV (4800+1200)

and

TLC = IRV + TV + ERV + RV

(3100+500+1200+1200)

Total amount of exchangeable air;

amount of air that can be expired after maximum inspiratory effort

(about 4800 ml; about 80% of TLC)

IRV + TV + ERV = VC

(3100 ml + 500 ml + 1200 ml = 4800 ml)

Basic rhythm of breathing.

Rhythm is modified in response to

sensory receptors input and

from other regions in the brain.

1. diaphragm (main muscle)
2. external intercostals
3. accessory muscles (scalenes, sternocleidomastoid of neck, pectoralis minor of chest)

Thin membrane across which gas exchange occurs in lungs;

composed of:

1. simple squamous epithelium of alveoli,
2. basement membrane of alveoli,
3. basement membrane of capillaries,
4. simple squamous epithelium of capillaries.
   

Respiratory membrane avgs .5 μm width.

In many regions there is no interstitial fluid.

O2/CO2 easily diffuse across it.

1. Alveoli - single layer simple squamous epithelium Type I cells.
2. Type II cells - cuboidal epithelium, secrete surfactant to decrease surface tension.
3. Alveolar macrophages - scavenger cells.
4. Pulmonary capilary networks - surround alveoli.

• heat loss
• metabolic reactions (Angiotensin I to Ang II)
• acid-base regulation (short term)
• speech

Exchange of gases

(supply body with O₂ and remove CO₂)

• Respiratory Membrane - alveolar and capillary walls and their fused basal laminae.
• Pleura - thin, double-layered serosa which produces pleural fluid

Anatomical Dead Space - 150 ml (Conducting Zone)

Respiratory Zone - 3,000 ml (3L)

Inspiratory reserve volume - 3100 ml

Tidal volume - 500 ml

Expiratory reserve volume 1200 ml

Residual volume - 1200 ml

in descending order:

• Respiratory bronchioles
• Alveolar ducts
• Alveolar sacs

Gas IS exchanged here.

Begins after terminal bronchioles (Conducting Zone).

Thickness influences exchg of O₂/CO₂

anything that thickens the membrane (ie, edema, pneumonia)

will ↓ gas exchange

• nose/nasal cavity
• parnasal sinuses
• pharynx
• larynx
• trachea
• bronchi
• lungs (contain alveoli)

About 1200 ml,

amount of air remaining in lungs

after a strenuous expiration.

RV helps prevent lung collapse.

1. Tidal Volume (TV)
2. Inspiratory Reserve Volume (IRV)
3. Expiratory Reserve Volume (ERV)
4. Residual Volume (RV)

About 1200 ml,

amount of air that can be expired forcefully

after a tidal volume expiration.

About 3100 ml,

amount of air that can be inspired forcefully

beyond tidal volume inspiration.

About 500 ml of air, moved in/out lungs

during normal respiration at rest.

1. Central chemoreceptors
2. Peripheral chemoreceptors
3. Lung receptors

Leukocytes are normally found in the blood, tho sometimes migrate thru tissues.

Non-leukocytes found in tissue:

• Phagocytes (neutrophils in blood/macrophages in tissues) engulf/destroy pathoges, dead cells, debris.
• Antigen-presenting cells (APCs) process/present antigens to Tcells. These are dentritic cells (in tissue), macrophages (in tisues), B-cells (in blood). All three commonly found in lymphoid organs and tissues.
• Effector Cells of Adaptive Immunity - B&T cells (both in blood)
• Other - leukocytes and non-l's (ie, mast cells found in tissues).

Instrument used to measure reapiratory volumes.

Wet - measures inspiration/expiration.

Consisted of a hollow bell inverted over water. As patient exhaled into connecting mouthpiece, bell went up, pen down, marking a moving chart. Useful for evalating losses in resp function following disease.

Dry - measures only expirations.

↑ surface area → ↑ gas exchange

(Ex: emphysema ↓ surface area)

Force of attraction btw water molecules

at an air-water surface,

which draws water molecules closer together.

Mixture of phospholipids and lipoproteins

which coats the alveolar surface and

lowers surface tension of the

alveolar fluid.

Secreted by cuboidal cell (type II) found within alveolus.

Without surfactant,

alveoli would have to be completely reinflated between breaths.

Air in conducting areas (passageways)

where no gas is exchanged.

Anatomical dead space (150 ml)

If some alveoli cease to act in gas exchange

(ie, due to alveolar collapse or obstruction)

alveolar dead space is added to anatomical dead space,

and the sum of that is total dead space.

1. Small amt (7-10%) dissolved in plasma
2. 20-30% bound to globin (Hb) "carbaminohemoglobin"
3. Most 60-70% transported in form of bicarbonate ions (HCO3)
4. Chloride shift
5. Haldane effect (opposite of Bohr)

• contains adenoids (pharyngeal tonsils)
• in nasopharynx

1. Resistance (within airways)
2. Lung compliance

• pressures
• pressure gradient
• lung compliance
• respiratory volumes/capacities
• total dead space

Normally, amount of air that enters respiratory system

is matched with proportionate amount of blood.

Thus, when ventilation increases,

blood flow to the alveolar capillaries increases.

↑ ventilation (O₂) → ↑ blood flow in lungs (vasodilation)

RV or Residual Volume -

Air remaining in lungs even after a strenuous expiration.

In the pharynx, posterior to epiglottis,

extends to the larynx

They do this by contracting/relaxing the smooth muscle

in the airway walls, esp bronchioles.

Airflow = pressure/resistance

• Histamine constricts bronchioles (increase resistance, decrease airflow)
• Epinephrine dilates bronchioles (decrease resistance, increase airflow)

Histamine will contract bronchioles

increase resistance

decrease airflow (hard to breathe).

Histamine is released during allergic reactions.

(released by adrenal medulla, ie during exercise)

dilates bronchioles,

descrease airway resistance,

greatly increases airflow, ensuring adequate gas exchange.

Airflow = pressure/resistance

Parasympathetic neurons release this neurotransmitter,

constricts bronchioles,

increases airway resistance,

decreases air flow.

(PNS restores conserves/restores energy.)

The ease with which lungs expand,

determined by 2 factors:

1. Stretchability of elastic fibers in lungs
2. surface tension w/in alveoli

Healthy lungs have high compliance due to

abundant elastic connective tissue.

Low lung compliance occurs with fibrosis,

making it difficult to inflate lungs.

Low lung compliance occurs with fibrosis,

making it difficult to inflate lungs.

Without enough surfactant

(produced by cell secretion)

alveoli have high surface tension and tend to collapse.

Respiratory distress syndrome of newborn.

Surfactant lowers surface tension and increases lung compliance.

Changes in the thoracic cavity volume

(due to muscle activity).

This allows air to move from

high pressure to low pressure regions.

Normally low,

but nervous stimulation and chemical factors

can change the diameter of bronchioles,

thereby altering resistance and airflow.

Normally high

due to lungs abundant elastic tissue and

surfactant's ablity to lower

surface tension of alveolar fluid.

Oxygen = O2 = 20.9%

Carbon dioxide = CO2 = .04%

Nitrogen = N2 = 78.6%

Water = H20 = .46%

O2 20.9% x 760 mmHg = 159 mmHg Po2

            O2 20.9% x 747 mmHg = 156 mmHg Po2

CO2 .04% x 760 mmHg = .3 Co2

            CO2 .04% x 747 mmHg = .3 mmHg PCo2

N2 78.6% x 760 mmHg = 597

             N2 78.6% x 747 mmHg = 587 mmHg PN2

H20 .46% x 760 mmHg = 3.5 mmHg

             H20 .46% x 747 mmHg = 3.4 mmHg PH20

In a mixture of gases,

the total pressure equals the

sum of the partial pressures

exerted by each gas.

O2 = 20.9% x 440 mmHg = Po2 92 mmHg

Amount of gas which dissolves in a liquid

is proportional to

• partial pressure of the gas
• solubility of the gas

CO2 is more soluble in liquid than O2

(see Henry's Law)

External Respiration:

• CO2 diffuses from pulmonary capillaries into alveoli
• O2 diffuse from alveoli into pulm. caps.

Internal Respiration:

• O2 diffuses from sytemic capillaries into cells
• CO2 diffuses from cells into systemic capillaries.

1. Surface area and structure of respiratory membrane.
2. Partial pressure gradients.
3. Matching alveolar ariflow to pulmonary capillary blood flow.

3 factors cause partial pressures of gases in alveoli

to differ fro pressure in atmosphere:

1. humidification of inhaled air
2. gas exch btwn alveoli/pulmonary capillaries
3. mixing of old/new air

Facilitates efficient gas exchange

by maintaining alveolar airlfow that is

proportional to the pulmonary capillary blood flow.

Local arterioles vasoconstrict,

blood redirected to other alveoli with

higher airflow and more O2 available

to be picked up by blood.

When airflow thru bronchiole is lower than normal,

the Pco2 rises.

Bronchioles respond by dilating,

thereby eliminating excess CO2 from alveoli.

1. Available surface area, which varies in different tissues
2. partial pressure gradients
3. rate of blood flow varies