Chapter 37 Respiratory System

Respiratory System (Breathing) (Cellular) RespirationBreathing 1.Chemical Process Food is oxidized by enzymes & converted to ATP (most ATP from mitochondria) 1.Mechanical or Physical Exchange of O2 & CO2 (inhalation and exhalation) 2.Cellular Process Occurs in every cell of the body 2. Usually occurs in Specialized Organs/ body surface (In simpler organisms thru skin/ cell membrane)

Respiration vs Breathing

Variations in Breathing Structures (represents evolutionary trends) 1.Cell membrane  in unicellular organisms Ex: Cnidaria, Porifera 2.Moist skin  mucus secreting cells maintain moisture Ex: Worm phyla 3.Tracheae  air enters spiracles (opening along abdomen) which leads into tracheal tubes to small air sacs surrounded by body fluid w/in sinus Ex: Insects (grasshopper)

4. Gills  thin filamentous structures composed of capillaries and flat squamous epithelial cells Ex: Fishes, immature amphibians, crayfish, skin gills on starfish, mollusks (clam)

Cont. Variations in Breathing Structures Oops!!! Forgot this slide! 5. Lungs  * mature amphibian, reptiles, birds, & mammals (possess diaphragm) (*) skin 6. Stoma  Opening on underside of leaf- gas exchange 7.Lenticels  openings in stem when leaf drops (Roots possess root hairs- gases diffuse across into root)

Breathing Organs Overview 1.Earthworm  moist skin 2.Starfish  skin gills 3.Clams  gills (squid) 4.Grasshopper  tracheae 5.Crayfish  gills 6.Perch  gills 7.Human  lungs

Human Respiratory System 1.Nasal Cavity  ciliated columnar epithelium- secrete mucus 2.Pharynx  back of throat 3.Epiglottis  flap of tissue over glottis 4.Glottis  opening to trachea 5.Larynx  voice box 6.Trachea  windpipe 7.Left and right bronchus(i)  bronchial tubes that leads to bronchioles 8.Bronchiole  smaller branches w/in lungs 9.Alveolus (i)  microscopic air sac 10.Capillary bed around alveoli  site of gas exchange (oxyhemoglobin H 6 + 4O 2 = H 6 O) 11. Venules  small veins 12. Pulmonary veins to left atrium- part of the pulmonary circuit of the circ system 13. Pulmonary artery to lungs (fr right ventricle)

Breathing Muscles 1.Diaphragm  sheet of voluntary muscle found between the thoracic and abdominal cavities in mammals 2.Intercostal (rib muscles)  muscles b/t rib bones (internal & external layers)

Breathing Mechanism A.Inhalation- intake of air due to contraction of: 1. Diaphragm- when diaphragm contracts it straightens 2. External intercostal- when contracted these muscles lift rib cage up and out 3. Thoracic cavity enlarges & air rushes into inflate lungs (Intrathoracic pressure low- low pressure on lungs) - Result: Inhalation occurs B.Exhalation 1. Muscles relax, volume decreases, pressure increases and exhalation occurs

Negative Pressure Breathing

Nerves Controlling Breathing (Medulla) 1.Phrenic Nerve Motor nerve from medulla which causes contraction of diaphragm and intercostal muscles [*Motor nerves  transmit impulses AWAY from CNS to effectors] RESULT: Inhalation 2. Vagus Nerve Mixed nerve (both sensory & motor) sensory fibers transmit impulses to brain indicating that diaphragm & intercostals muscles are contracted - Signals inhibits further stimulation by phrenic nerve RESULT: Exhalation

3. BLOOD pH = CO 2 conc of blood is the factor which regulates breathing rate (blood pH) CO 2 + H 2 O ← ↕ → H 2 CO 3 ↔ H + + HCO 3 - RBC (lungs) carbonic anhydrase carbonic acid(plasma 90%) Carbonic Anhydrase  enzyme in RBC which converts CO 2 & H 2 O to H 2 CO 3 & H + (also reverses this rxn at the lungs) - Lowers blood pH (below 7.4)  stimulates medulla to increase breathing rate via phrenic nerves

4. Hyperventilation Rapid breathing (over breathing- inhaling too much O 2 ) reduces the CO 2 levels in the blood Less CO 2 causes dilation of arteries – blood pressure lowers (carotid arteries to the brain) brain receives less blood  dizzy, light- headed, & weak (vasoconstriction)

CO2 Transfer from Body Tissues to Blood and Lungs 1.CO2 leaves cells and enters tissue spaces 2.CO2 enter capillaries 3.CO2 reacts with H2O (RBC)  H2CO3 4.H2CO3  dissociates into H+ and HCO3- (bicarbonate ion) 5.HCO3- leave RBC and enter plasma 6.Blood travels to lungs and enters lung capillaries 7.HCO3- reenters RBC 8.HCO3- + H+  H2CO3 9.H2CO3 + carbonic anhydrase (enzyme)  H2O +CO2 10.W/in RBC, CO2 enters plasma 11.CO2 leaves lung capillary and enters alveolar space (result:CO2 exits out of mouth)

O 2 Transfer from Blood to Body Tissues 1.RBC enters lung capillary 2.O2 from alveolar space enters lung capillary plasma 3.O2 enters RBC from plasma; combines with hemoglobin (Hb) = oxyhemoglobin 4.RBC carry oxyhemoglobin out of lung to body tissues 5.O2 laden RBC enter tissue capillary 6.Oxyhemoglobin breaks down, releasing O2 into plasma 7.O2 leaves plasma and enters tissue space 8.O2 enters tissue cells from tissue space 9.RBC returns to lungs via circulatory system

CO 2 conc in metabolically active cells is much greater than in capillaries, so CO 2 diffuses from the cells into the capillaries ~ 7% of the CO 2 directly dissolves in the plasma ~23% binds to the amino groups in hemoglobin ~70% is transported in the blood as bicarbonate ion - H 2 O in the blood combines with CO 2 to form bicarbonate ions (via carbonic anhydrase) - This removes the CO 2 from the blood so diffusion of even more CO 2 from the cells into the capillaries continues yet still manages to "package" the CO 2 for eventual passage out of the body

- In the alveoli capillaries, bicarbonate combines with a hydrogen ion (proton) to form carbonic acid, which breaks down into carbon dioxide and water (via carbonic anhydrase) - CO 2 then diffuses into the alveoli and out of the body with the next exhalation