- Globin protein bound to a heme molecule containing iron

- Usually within blood cells

- Appears red when oxygenated

- Four protein subunits: 2 alphas, 2 betas

- Myoglobin is a type of hemoglobin found in muscles

1. Vertebrates

2. Nematodes

3. Some annelids

4. Some crustaceans

5. Some insects

- Each protein contains two coppers and bind to one oxygen molecule

- Usually dissolved in hemolymph and not located in blood cells

- Appears blue when oxygenated

- Very large multisubunit protein consisting up to 48 individual subunits

1. Arthropods (crustaceans, arachnids, centipedes)

2. Molluscs (gastropods, bivalves, cephalopods)

- Contains iron directly bound to protein

- Trimeric or octomeric and 2 irons per subunit

- Usually found inside coelomic cells (blood cells of the coelom)

- Appears violet-pink when oxygenated

Volume of air inhaled over and above resting tidal volume

Max amount of air that can be moved in and out of the lungs with one breath

VC = V_T + IRV + ERV

1. Anatomical dead space

- volume of trachea and bronchi

2. Alveolar dead space

- volume of alveoli that are not perfused

Volume of fresh air that enters alveoli with each respiratory cycle

V_A = V_{T -} V_D

Volume of fresh air that enters alveoli each minute

`V_A = f(V_T - V_D)

where f = breathing rate in breaths per minute

1. Hemoglobins

2. Hemocyanins

3. Hemerythrins

Airway diameter affects resistance to air flow

- As diameter increases, resistance decreases

- Scarring of lung tissue (e.g. asbestos, coal dust)

- Reduced lung compliance, therefore inspiration difficult

- Shallow breathing

- Must breath more rapidly to obtain sufficient oxygen

- e.g. smoking

- Lung is more compliant but less elastic

- Airways tend to collapse

- Lung is easily inflated but must expend more energy to expire

- Reduce surface tension by disrupting the cohesive forces bewteen water molecules

- Reduces tendency of alveolar walls and small airways to stick together

- Less force required to expand alveoli in lungs

- Allows you to breath more easily

1. Motor neuron stimlates inspiratory muscles

2. Contraction of external intercostals and diaphragm

3. Ribs move outward, diaphragm moves downward

4. Volume of thorax increases, intrathoracic pressure decreases

5. Decrease in intrapleural pressure

6. Increase in transpulmonary pressure gradient

7. Lungs expand, decreases alveolar pressure and air is pulled in

1. Nerve stimulation of inspiratory muscles stops

2. Muscles relax

3. Ribs and diaphragm return to resting positions

4. Interpleural pressure increases

5. Volume of thorax decreases, Intrathoracic pressure increases

6. Passive recoil of lungs decreases lung volume, which increases alveoli pressure and results in air flowing out of lungs

- Surrounds each mammalian lung

- Two layers of cells with small space between them: pleural cavity

- Pleural cavity contains small volume of pleural fluid

- Interpleural pressure is subatomic which keeps lungs expanded

1. Upper respiratory tract

- mouth, nasal cavity, pharynx, trachea

2. Lower respiratory tract

- Bronchi and alveoli

Site of gas exchange

Type I: Gas exchange

Type II: secrete surfactant

- outer surface are covered in capillaries

Unidirection:

1. Crosscurrent

2. Countercurrent

- Lungs are stiff and change little in volume

- Lungs are in between a series of air sacs that act as bellows (posterior and anterior sacs)

1. Expansion of chest, fresh air flows through bronchi into posterior air sacs

2. Compression of chest pushes fresh air to lungs

3. Expansion of chest causes stale air to flow to anterior air sacs

4. Compression of chest pushes stale air out via trachea

NOTE: Two cyles of inhalation and exhalation

- Generally rely on aspiration pumps (may be supplemented with buccal pump)

- Separation of feeding and respiratory muscles

- Two phases: inspiration and expiration

- Several mechanisms change volume of chest cavity

Inhalation: ribs move forward and outward, thorax expands

Exhalation: ribs move backward and inward, thorax compresses

1. Cutaneous respiration

2. Simple bilobed lungs (more complex in terrestrial frogs and toads)

1. Air enters pocked of buccal cavity

2. Glottis opens, elastic recoil of lungs and compression of chest wall reduces lung volume. Air forced out of lungs and out nares

3. Nares close, floor of buccal cavity rises, air is pushed into lungs

4. Glottis closes, gas exchange occurs in lungs

Extensive tracheal system

- air-filled tubes called tracheae

- Opens to outside via spiracle

- tracheae branch to form trachioles

- contract abdominal muscles or thorax for air flow

- Gases diffuse in and out

- Do not use circulatory system to deliver gases

- Reinforced gills that do not collapse in air

- Highly vascularized mouth or pharyngeal cavity

- Highly vascularized stomach

- Specialized pockets of gut

- Lungs

1. Mouth opens, buccal cavity expands, air enters BC

2. Mouth closes, BC compresses, air enters anterior chamber of air breathing organ

3. Mouth closed, anteriod chamber closed, posterior chamber contracts, spent air exhaled from posterior chamber, air exits via operculum

4. Mouth closed, anterior chamber opens and contracts, air flows into posterior chamber, gas exchange occurs

1. Mouth open, opercular valve closed, buccal and opercular cavities expand

2. Pressure decreases and sucks water in through mouth

3. Mouth closes

4. Floor of buccal cavity raises and operculum expands

5. Pressure pushes water into opercular cavity

6. Opercular valve opens and water leaves through the opercular slit

1. Expand buccal cavity

2. Increased volume sucks water into BC via mouth and spiracles

3. Mouth and spiracles close

4. Muscles around buccal cavity contract, focing water past gills and out the gill slits

Gills = ctenidia

1. Snails and clams

- Cilia on gills move water across gills uniderectionally

2. Cephalopods

- Muscular contractions of mantle propel water unidirectionally past gills and into mantle cavity

dQ/dt = D x A x (dC/dx)

where...

dQ/dt = rate of diffusion

D = diffusion coefficient

A = membrane area

dC/dx = gradient 

t = x² / 4D = time

- Seen in combination with diffusion in larger organisms

- Consists of ventilation and circulation

1. Circulating the external medium through the body

- sponges, cnidarians, insects

2. Diffusion of gases across the body surface accompanied by circulatory transport

- most aquatic invertebrates, some amphibians

3. Diffusion of gases across a specialized respiratory surface accompanied by circulatory transport

- gills, lungs

1. Nondirectional

- medium flows past the respiratory surface in an unpredictable pattern

2. Tidal

- medium moves in and out of the chamber

3. Unidirectional

- Medium enters the chamber at one point and exits at another

1. Concurrent flow

- flow of medium and blood move in same direction

2. Countercurrent flow

- flow of medium moves in opposite direction of blood flow

3. Crosscurrent flow

- Blood flow crosses over respiratory surface and the flow of the medium

Decrease in pH or increase in P_CO2 reduces oxygen affinity and causes a right shift

- P₅₀ is increased

Increases in temperature decrease oxygen affinity; right shift

- P₅₀ increased

- Promotes oxygen delivery to warm muscles during exercise

Increases in these modulators decrease oxygen affinity; right shift

- Helps oxygen unloading at tissues

- Anemia and high altitudes stimulate 2, 3-DPG synthesis

1. Small amounts of CO₂ gas are transported in the plsma

- CO₂ is more soluble in body fluids than O₂

2. Some CO₂ binds to proteins

- e.g. carbaminohemoglobin

3. Most CO₂ is transported as bicarbonate (HCO₃^-)

- CO₂ + H₂O <--> H₂CO₃ <--> HCO₃^- + H⁺

- carbonic anhydrase catalyzes the formation of HCO₃^-

- Red blood cells

- Therefore, reactions to synthesize HCO₃^- occur in the RBCs

- HCO₃^- is exchanged for Cl^- in the plasma

As total CO₂ in the blood increases, P_CO2 increases

- Deoxygenated blood can carry more CO₂ than oxygenated blood (Haldane effect)

At respiratory surface, CO₂ diffuses out of the blood

- Carbaminohemoglobin releases CO₂

- Bicarbonate reaction goes to the left

- As P_CO2 increases, [HCO₃^-] increases and pH decreases (due to increased [H⁺]) --> reaction shifts to the right

 - As P_CO2 decreases, [HCO₃^-] decreases and pH increases (due to decreased [H⁺]) --> reaction shifts to the left

- Hyperventilation causes P_CO2 to decrease = increased pH

- Hypoventilation causes P_CO2 to increase = decreased pH