1

2 Lecture 14 Outline (Ch. 49) I.Overview II.Respiration in different organism III. Methods – bulk flow vs. diffusion IV.Gas exchange and partial pressures V.Inhalation/exhalation VI.Brain control VII.Respiratory problems

3 If you are an athlete who trains at high elevations, what happens if you compete at a lower elevation? Thought Question:

4 Living things process energy They need oxygen for this - Why? Overview

5 Cellular respiration uses O 2 and produces CO 2 C 6 H 12 O 6 + O 2  CO 2 + H 2 O + ATP energy Breathing – respiration supports this process by exchanging gasses Overview Cell

6 Exchanging gasses Moist surface –Gasses dissolve in water to move in/out of cells Thin Large surface area Gas Exchange Systems

7 Who needs a respiratory system? I don’t! Moist environment Small (or thin) Low energy demand I do! Dryer environment Large or thick-bodied High energy demand Gas Exchange Systems

8 Respiratory systems enable gas exchange Bulk flow –Fluids move in bulk –Air/water move to respiratory surface –Blood moves through vessels Diffusion –Individual molecules move down concentration gradients –Gas exchange across respiratory surface –Gas exchange in tissues Gas Exchange Systems

9 Gills Aquatic gas exchange Gas Exchange Systems Elaborately folded (  surface area) Contain capillary beds Gill size inversely related to [O 2 ] Large gills = low [O 2 ]

10 Fish Efficiency Dissolved O 2 is < 1% of water (21% of air) Countercurrent exchange increases efficiency Gas Exchange Systems

11 Terrestrial respiration Internal –Stay moist & supported Insects have tracheae –Air enters/exits through spiracles –Branching channels (trachioles) allow gas exchange with cells Gas Exchange Systems

12 Vertebrate respiration Terrestrial use of lungs –Evolved from accessory respiratory organs of freshwater fish Amphibians are weird –Remain tied to water –Larval gills to adult lungs –Moist skin transfers gasses Gas Exchange Systems

13 Reptiles & Mammals use lungs exclusively Lack permeable skin Lungs are more efficient –Especially birds! Gas Exchange Systems

14 Human Respiration Air enters through nose and mouth to pharynx Travels through larynx (voice box) Epiglottis directs travel Mammals

15 On to the lungs Trachea  Bronchi  Bronchioles  Alveoli Human Respiration Air is warmed & cleaned Dust & bacteria trapped by mucus Swept up and out by cilia Microscopic chambers provide enormous surface area Surfactant keeps surface moist Association with capillaries –Diffusion of gasses

16 Diffusion Blood arrives from pulmonary artery Low in O 2 –Higher concentration in air diffuses into blood High in CO 2 –Higher concentration in blood diffuses into air Lungs

17 Human Respiration Gas exchange is driven by differences in pressures Blood from body with low O2, has a partial oxygen pressure (P O2 ) of ~40 mm Hg By contrast, the P O2 in the alveoli is about 105 mm Hg Blood leaving lungs, thus, normally contains a P O2 of ~100 mm

18 CO 2 Transport CO 2 binds hemoglobin loosely Dissolved in plasma Combines with H 2 0 to form bicarbonate (HCO 3 - ) –More CO 2 = lower pH Transport of gasses The Bohr Effect: Hemoglobin binds more tightly to O 2 when pH is increased and loosely when pH is decreased

19 O 2 Transport Binds to hemoglobin –Removes O 2 from plasma solution –Increases concentration gradient; favors diffusion from air Transport of gasses CO binds more tightly to hemoglobin than O 2 Prevents O 2 transport

Outside lung covered by the visceral pleural membrane Inner wall of thoracic cavity lined with parietal pleural membrane Space between called the pleural cavity –Thin space w fluid –Causes 2 membranes to adhere –Lungs move with thoracic cavity 20 Breathing Mechanisms

21 Breathing Mechanisms Inhalation: Contraction of intercostal muscles expands rib cage Contraction of diaphragm expands the volume of thorax and lungs Thoracic cavity expands, produces negative pressure which draws air into the lungs

22 Breathing is involuntary Breathing Mechanisms Controlled by respiratory center of the brain Adjusts breath rate & volume based on sensory input –Maintain a constant concentration of CO 2

23 Asthma Smooth muscle in bronchioles becomes irritated and constricts or spasms Increased mucus Can lead to collapse Linked to air quality and allergies Respiratory Problems Chronic obstructive pulmonary disease (COPD) –Refers to any disorder that obstructs airflow on a long-term basis

24 Emphysema Reduces surface area available for gas exchange Labored and difficult breathing 80-90% of deaths linked with smoking Respiratory Problems Alveoli rupture or become brittle creating larger but fewer alveoli

25 Bronchitis & Pneumonia Inflammations of respiratory passages & lungs Increase in mucus production, decrease in cilia Reduces air flow to alveoli Causes include bacteria, viruses, fungi, & parasites Respiratory Problems Jim Henson, creator of the Muppets, died at age 53 from pneumonia

26 Tuberculosis Bacteria attack and cause lesions on lung tissue Respiratory Problems

different toxins! –Includes tar, carbon monoxide, formaldehyde Smoking Lung cancer accounts for more deaths than any other form of cancer Caused mainly by cigarette smoking 3 of the Marlboro men died from lung cancer Lung cancer metastasizes rapidly – usually cancer has spread to other tissues before detected Chance of recovery poor: only 3% of patients survive > 5 yrs

Lecture 14 Summary 1. Respiration Overview (Ch. 49) -Diffusion -Insects -Gills -Birds, reptiles, mammals 2. Airway Route & gas exchange (Ch. 49) -Hemoglobin -Partial pressures 3. Control (Ch. 49) -Inhalation/exhalation -Brain control 4. Respiratory Problems (Ch. 49) -Asthma, emphysema, lung cancer, bronchitis, pneumonia, tuberculosis