Lecture 12 Notes
Animal Circulation and Respiration
| I. Circulatory System
A. Main functions: circulation of heat (yes heat!), nutrients, hormones, and gases B. Two major types 1. Open a. insects have open circulation - blood not all in vessels, but sloshes around body cavity b. works okay for small organisms, but is inefficient for distributing materials, especially oxygen, in large organisms 2. Closed a. all higher animals have closed systems, including earthworms b. more efficient C. We'll concentrate on closed systems D. See handout on how heart works to circulate blood in humans E. Terminology 1. Arteries - blood vessels that carry blood away from heart 2. Veins - vessels that carry blood to heart 3. Capillaries - very small blood vessels where most gas exchange occurs 4. Atria - chambers in heart that accept blood from veins 5. Ventricles - chambers that push blood out of heart F. Evolution of Circulatory Systems 1. Fish - two chambered heart 2. Amphibians and Reptiles - three chambered heart 3. Humans and Birds - four chambered heart G. Heart Function in Humans 1. Two phases for each heartbeat (normal heart beat takes 0.8 sec) a. systolic - when heart contracts i. takes 0.1 sec for atrium to contract ii. takes 0.3 sec for ventricle to contract iii. total systolic time is 0.4 sec b. diastolic - when heart is relaxed between beats i. 0.7 sec for atria to fill back up (starts right after contraction) ii. 0.4 sec for ventricles to fill back up c. typical heartrate is 75 beats/min, but can vary greatly depending on level of activity 2. Valves help control flow of blood into and out of heart a. atrioventricular - keeps blood from flowing back into atria when ventricles contract - located between atria and ventricles b. semilunar - keeps blood from going back into ventricles when heart is diastolic, located at exit of ventricles c. sinoatrial node - electrical nerve center -sends electrical signal that induces heart muscle to contract 3. Cardiac Output - example for average person a. 75 beats/min b. 70 mls/beat c. 5.25 liters/min - about entire blood supply circulated once a minute 4. Heartrate inversely proportional to body size -slowest in elephants, fastest in hummingbirds 5. Heartrate in humans depends on temperature (goes up with temp), and on hormones (adrenaline stimulates heartrate), and carbon dioxide in blood (too much lowers pH, carbonic acid, and heart rate picks up) 6. Blood flows fastest right out of heart, slowest in capillaries. Blood pressure highest at exit from heart, lowest in veins II. Respiration A. Primitive organisms can "breathe" through their skin - but must be small and flat to get enough surface area to do this. Also, skin needs to be moist, or exchange is too slow B. Other organisms use gills or lungs 1. Fish - use gills. Work well in water, but would be hard to keep intact in dry air (wind, dessication, etc.) 2. Terrestrial organisms use lungs, although insects do not have lungs 3. Insects have trachea (tubes that go all through their body). Openings on their body are called spiracles, which let oxygen in and carbon dioxide out 4. In mammals, as chest expands, it draws out the lungs, creating negative pressure, and air rushes into lungs. We do not "push" air into our lungs, but frogs do 5. Air enters trachea (windpipe) and goes into large tubes called bronchi. 6. Bronchi branch into bronchioles, smaller tubes, and eventually end at the alveoli, small sacs where gas exchange occurs in lungs 7. Mucus and cilia line the bronchi and bronchioles - keep dust particles out 8. Each breath brings in about 500 ml (1/2 liter) of air 9. Stretch sensors in lungs determine when a breath ends 10. Breathing rate - controlled by blood pH (too low, more rapid breathing) 11. Exchange of gases in lungs i. partial pressure of oxygen is greatest in atmosphere (21%, or 210,000 ppm) ii. is much lower in lungs, hence oxygen diffuses into lungs iii. partial pressure of carbon dioxide is much higher in lungs than in atmosphere (20,000 ppm vs 365 ppm) and hence carbon dioxide diffuses out of lungs, not in! 12. Hemoglobin is used to facilitate movement of oxygen in blood. Each molecule can bind 4 oxygens 13. Each hemoglobin molecule contains 4 iron molecules, which are where the oxygen molecules bind 14. Some insects have hemocyanin, which has copper instead of iron - makes their blood bluish instead of reddish C. Smoking 1. smokers 70% more likely to die of heart disease 2. smoke particles damage lungs - paralyze cilia and destroy mucus - this is why smokers have smoker's cough 3. aveoli are destroyed by smoke - permanently, reducing lung capacity 4. loss of alveoli leads to emphysema, a debilitating lung disease 5. smoke contains carbon monoxide (CO), which binds 200x more easily to hemoglobin than oxygen - this results in oxygen deficit for smokers and contributes to heart disease 6. smoking also lowers a person's immune system, and smokers have more colds than non-smokers 7. women who smoke and take the pill run a higher risk of stroke 8. Conclusion - its stupid to smoke D. Lung Diseases 1. Asthma - involuntary constrictions of the bronchioles, leading to breathing distress. Is on the rise among urban children, for reasons unknown 2. Asthma treated by giving sprays with histamines - causes tubes to relax and open (epinephrine for example) 3. Black Lung - accumulation of coal dust in lungs - common among coal miners but not as prevalent today as in the past. Devastating disease 4. Particulate inhalation a major concern today - diesel engine particles from |