Discussion Questions — Part B 181 



13. One method of studying visual systems is to "drive" the eye with a 

 flashing light. Describe the ability to follow as a function of frequency of: 

 the retinal potentials; the potentials in the optic nerve; the nerve potentials in 

 the midbrain; and the cortical potentials. 



14. Sketch the anatomical features of the visual system of limulus. Describe 

 in more detail the type of experiment summarized in Figure 4 of Chapter 7. 

 Include descriptions of the light source, light-intensity measurements, 

 preparation of nerve fibers, measuring equipment, and conclusions reached. 



15. The electrical potentials of the eyeball are sometimes referred to as 

 electroretinograms. Describe the magnitude of the potentials obtained and 

 their time dependence. Illustrate their use with a detailed description of one 

 experiment depending on electroretinograms. 



16. The experiments of Land on color vision in a heterochromatic field are 

 reviewed briefly in Chapter 7. Expand this discussion, emphasizing its 

 significance for theories of color vision. * 



17. Ramsey has used single muscle fibers for studies of their mechanical 

 properties. How does he prepare these fibers? Compare his results with 

 those for whole, excised muscles. 



18. The various types of heat produced during muscular contraction are 

 described briefly in Chapter 8. Expand on this description; include equip- 

 ment necessary to make the measurements, the type of raw data obtained, and 

 their interpretation. 



19. Contrast the resting and action potentials of various forms of skeletal 

 muscle, cardiac muscle, of nerves, and of the alga Nitella. Include magnitude 

 of the potentials, time course of the spike, and dependence on ionic con- 

 centrations. 



20. Illustrate the changes in the thick and thin filaments during muscular 

 contraction in terms of the model of A. F. Huxley. Show what type of 

 electron-microscope pictures would be expected for longitudinal sections, for 

 transverse sections at various points along the myofibrillar unit, and for 

 several oblique sections. 



21. Ballistocardiography consists of measuring the reaction of the body to 

 the thrust of the heart on the blood. How are ballistocardiographs con- 

 structed? What does a typical record look like? How is it related to the 

 electrocardiogram ? 



22. The heart rate is controlled by two sets of nerves. These in turn are 

 activated by centers in the central nervous system in response to impulses 

 from certain pressure-sensitive and 2 /C0 2 -sensitive organs. Fill in the 

 anatomical details to the extent they are known. Represent the over-all 

 system, in block diagram form, as interlocking negative feedback loops. 



23. Abnormalities in the electrocardiogram are used to diagnose many 



