1. 4-18-05 Monday Blood Gas Continued Structure of the Brain

2. The low solubility of oxygen in water is a fundamental problem for animals that rely on the circulatory systems for oxygen delivery (gill) –For example, a person exercising consumes almost 2 L of O 2 per minute, but at normal body temperature and air pressure, only 4.5 mL of O 2 can dissolve in a liter of blood plasma (blood without RBCs) in the lungs. –If 80% of the dissolved O 2 were delivered to the tissues (an unrealistically high percentage), the heart would need to pump 500 L of blood per minute - a ton every 2 minutes (impossible). Respiratory pigments transport gases and help buffer the blood Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

3. In fact, most animals transport most of the O 2 bound to special proteins called respiratory pigments instead of dissolved in solution. –Respiratory pigments, often contained within specialized cells, circulate with the blood. –The presence of respiratory pigments increases the amount of oxygen in the blood to about 200 mL of O 2 per liter of blood (normal output= 5.25liter/min. –Exercising person output is 5 times normal. –For our exercising individual, the cardiac output would need to be a manageable 20-25 L of blood per minute to meet the oxygen demands of the systemic system. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

4. Oxygen Transport Pigments Pigments load oxygen in lung or gill and carry it to the capillaries where it is unloaded for cell Hemoglobin--(tetrameric molecule inside cell) Associated 4 iron molecules bind 4 molecular oxygens. Hemocyanin--large molecule (10 6 Daltons) containing many copper atoms colors hemolymph blue found in crustaceans and molluscs. Chlorocruorin--large iron containing molecule found in polychaete.

5. Physiologists Study Oxygen Transport with Oxygen Binding Curves Expose deoxygenated blood to increasing amounts of air and measure the partial pressure of oxygen in the blood with an oxygen electrode. Plot partial pressure of oxygen in mixtures of air versus partial pressure of oxygen in the blood.

6. Cooperative oxygen binding and release is evident in the dissociation curve for hemoglobin. Where the dissociation curve has a steep slope, even a slight change in P O2 causes hemoglobin to load or unload a substantial amount of O 2. This steep part corresponds to the range of partial pressures found in body tissues. Hemoglobin can release an O 2 reserve to tissues with high metabolism. Fig. 42.28a

7. Like all respiratory pigments, hemoglobin must bind oxygen reversibly, loading oxygen at the lungs or gills and unloading it in other parts of the body. –Loading and unloading depends on cooperation among the subunits of the hemoglobin molecule. –The binding of O 2 to one subunit induces the remaining subunits to change their shape slightly such that their affinity for oxygen increases. –When one subunit releases O 2, the other three quickly follow suit as a conformational change lowers their affinity for oxygen. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

8. As with all proteins, hemoglobin’s conformation is sensitive to a variety of factors. For example, a drop in pH lowers the affinity of hemo- globin for O 2, an effect called the Bohr shift. Because CO 2 reacts with water to form carbonic acid, an active tissue will lower the pH of its surroundings and induce hemoglobin to release more oxygen. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.28b

9. Figure 42.28 Oxygen dissociation curves for hemoglobin Partial pressure of oxygen in Air is 160 mm Hg P 50 is partial pressure at which blood pigment is 50% saturated P 50

10. Bohr Effect Lower pH shifts oxygen binding curve to the right. That means that the oxygen is unloaded more easily at the tissues because of the lower pH. At the lungs the pH rises because the carbon dioxide is “blown off” and curve shifts to left making it easier to load oxygen.

11. Overhead of equilibrium curves with myoglobin and cytochrome Oxygen passed from hemoglobin to myoglobin (in cell) to cytochrome in mitochrondia

12. Figure 42.27 Loading and unloading of respiratory gases

13. Arterial Blood O 2 saturation and O 2 content 0 20 40 60 Arterial blood % O2 saturation PO 2 (mm Hg) O Content (vol. %) (= mL O 2 per 100mL blood) 2 80 100 306090 0 10 20 5 15

14. Overhead of oxygen content curve Correlation between habitat and amount of oxygen that is carried in the blood. Can only be observed with an oxygen content curve.

15. Figure 42.29 Carbon dioxide transport in the blood Carbonic anhydrase converts CO 2 + water to bicarbonate Most CO 2 transported as bicarbonate in plasma

16. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.29, continued

17. In addition to oxygen transport, hemoglobin also helps transport carbon dioxide and assists in buffering blood pH. –About 7% of the CO 2 released by respiring cells is transported in solution. –Another 23% binds to amino groups of hemoglobin. –About 70% is transported as bicarbonate ions. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

18. When an air-breathing animal swims underwater, it lacks access to the normal respiratory medium. –Most humans can only hold their breath for 2 to 3 minutes and swim to depths of 20 m or so. –However, a variety of seals, sea turtles, and whales can stay submerged for much longer times and reach much greater depths.(Weddell –700m) Deep-diving air-breathers stockpile oxygen and deplete it slowly Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.30

19. Figure 42.30 The Weddell seal, Leptonychotes weddelli, a deep-diving mammal

20. Unnumbered Figure (page 899) Dissociation curves for two hemoglobins Fetal hemoglobin Organophosphates displace Oxygen from hemoglobin

21. One adaptation of these deep-divers, such as the Weddell seal, is an ability to store large amounts of O 2 in the tissues. –Compared to a human, a seal can store about twice as much O 2 per kilogram of body weight, mostly in the blood and muscles. –About 36% of our total O 2 is in our lungs and 51% in our blood. –In contrast, the Weddell seal holds only about 5% of its O 2 in its small lungs (small because they exhale before they dive and their lungs collapse so they can avoid the bends) and stockpiles 70% in the blood. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

22. Several adaptations create these physiological differences between the seal and other deep- divers in comparison to humans. –First, the seal has about twice the volume of blood per kilogram of body weight as a human. –Second, the seal can store a large quantity of oxygenated blood in its huge spleen, releasing this blood after the dive begins. –Third, diving mammals have a high concentration of an oxygen-storing protein called myoglobin in their muscles (meat is reddish black in color). This enables a Weddell seal to store about 25% of its O 2 in muscle, compared to only 13% in humans. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

23. Diving vertebrates not only start a dive with a relatively large O 2 stockpile, but they also have adaptations that conserve O 2. –They swim with little muscular effort and often use buoyancy changes to glide passively downward. –Their heart rate and O 2 consumption rate decreases during the dive (bradycardia) and most blood is routed to the brain, spinal cord, eyes, adrenal glands, and placenta (in pregnant seals). –Blood supply is restricted or even shut off to the muscles, and the muscles can continue to derive ATP from fermentation after their internal O 2 stores are depleted (none to the kidneys—our kidneys would “die”). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

24. Nervous System

25. CHAPTER 48 NERVOUS SYSTEMS Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings An Overview Of Nervous Systems 1. Nervous systems perform the three overlapping functions of sensory input, integration, and motor output 2. Networks of neurons with intricate connections form nervous systems

26. Peripheral nervous system (PNS). –Sensory receptors are responsive to external and internal stimuli. Such sensory input is conveyed to integration centers. –Where the input is interpreted an associated with a response. Nervous systems perform the three overlapping functions of sensory input, integration, and motor output

27. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.1

28. Motor output is the conduction of signals from integration centers to effector cells. –Effector cells carry out the body’s response to a stimulus. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

29. The central nervous system (CNS) is responsible for integration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

30. The signals of the nervous system are conducted by nerves. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

31. Neuron Structure and Synapses. –The neuron is the structural and functional unit of the nervous system. Nerve impulses are conducted along a neuron. –Dentrite  cell body  axon hillock  axon –Some axons are insulated by a myelin sheath. Networks of neurons with intricate connections form nervous systems

32. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.2

33. A Simple Nerve Circuit – the Reflex Arc. –A reflex is an autonomic response. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.3

34. A ganglion is a cluster of nerve cell bodies within the PNS. A nucleus is a cluster of nerve cell bodies within the CNS. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

35. Schwann cells are found within the PNS. –Form a myelin sheath by insulating axons. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.5 Degradation of Myelin Sheath=Multiple Sclerosis

36. The ability of cells to respond to the environment has evolved over billions of years

37. Nerve nets. Nervous systems show diverse patterns of organization Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.15a, b

38. With cephalization come more complex nervous systems. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.15c-h

39. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Vertebrate Nervous Systems 1. Vertebrate nervous systems have central and peripheral components 2. The divisions of the peripheral nervous system interact in maintaining homeostasis 3. Embryonic development of the vertebrate brain reflects its evolution from three anterior bulges of the neural tube 4. Evolutionarily older structures of the vertebrate brain regulate essential autonomic and integrative functions

40. 1. Vertebrate nervous systems have central and peripheral components Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Central nervous system (CNS). –Brain and spinal cord. Both contain fluid-filled spaces which contain cerebrospinal fluid (CSF). –The central canal of the spinal cord is continuous with the ventricles of the brain. –White matter is composed of bundles of myelinated axons –Gray matter consists of unmyelinated axons, nuclei, and dendrites. Peripheral nervous system. –Everything outside the CNS.

41. Structural composition of the PNS. –Paired cranial nerves that originate in the brain and innervate the head and upper body. –Paired spinal nerves that originate in the spinal cord and innervate the entire body. –Ganglia associated with the cranial and spinal nerves. The divisions of the peripheral nervous system interact in maintaining homeostasis Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

42. Functional composition of the PNS. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.17

43. A closer look at the (often antagonistic) divisions of the autonomic nervous system (ANS). Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 48.18