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BIOL 415 Nerve cell mechanisms in behavior
Test 2 Tuesday March 29, 2016 ­p; Prof. Stark
All questions are short answer. 65 points total

For questions 1-4, go here

1. What kind of information is being carried by this tract?


2. State ONE of the functions of this nerve seen coming out of the cerebral peduncles.

eye movements, eyelid movements (somatic motor), pupil constriction, accomodation (autonomic)

3. These fibers, hidden as they pass under the pons, form what tract?

corticospinal, pyramidal

4. Here it is called the pons. What do you call these fibers, on the "other side," in the dissection of the 3 components of the cerebellar peduncle?

brachium pontis or middle cerebellar peduncle

For questions 5-8 go here

5. The brains provided for your dissection still had this white "membrane" (called what?) that you were required to remove before proceeding.

dura mater

6. You removed the gray matter of what major structure to reveal this tract?


7. Answer EITHER (1) What is the name of this structure? OR (2) If you removed it, name ONE of the things you would see.

septum pellucidum, lateral ventricle or head of caudate

8. If you removed this structure, what major subdivision of the diencephalon would you be looking at?


For 9-12, go here

9. What is this structure?


10. The postsynaptic cells in this area receive their input from cells that are located where?

retina (ganglion cells)

11. What is the name associated with the gray matter you needed to scrape away (from the mid-sagittal plane) to reveal this tract?

massa intermedia, thalamus

12. What is the name of the ventricle you see here?


For 13-16, go here

13. For this figure, ANSWER EITHER (1) What is it called when the entire white matter under the cortical gray matter is exposed? OR (2) What is the term used for these particular axons?

corona radiata, arcuate fibers

14. What is this structure?

superior colliculus (lamina quadrigemina)

15. What is this structure?


16. ANSWER EITHER (A) Using a tract name, what is the white matter that is being ripped? OR (B) Using a tract name, why is the outside of this structure white?

internal capsule, the fimbria covers the hippocampus

17. In the corticospinal tract, motor cells in the precentral gyrus make their first synapse (where?).

to the spinal motor neuron in the ventral horn

18. You have a rat brain atlas and your anesthetized rat (in an approved protocol) is mounted in a stereotactic device with the skull exposed. Say something about what you need to do to get the tip of an electrode into the ventromedial nucleus of the hypothalamus.

measure from the bone sutures*, drill a hole, lower the electrode to the correct depth*, *=requires consulting the atlas

19. How did Pruisinger propose that a protein (without DNA or RNA) can be infectious and alter the proteins in the victim, making those proteins infectious.

protein in scrapie configuration converts protein in control configuration into the scrapie form

20. Using the terminology (5 compartments from Telencephalon to Myelencephalon), say where you find the third ventricle


21. Which one of the three cranial nerves that control eye movements via extraocular muscles also has other motor controls relevant to the eye?

3 oculomotor

22. With your "orange stick," you scrape all the gray matter out of one sulcus. Answer either (1) How can you tell what direction the myelinated axons run? or (2) Where do the first axons you find come from and go to?

stick glides in axon direction and scrapes across the grain, from and to the adjacent gyri

23. What is missing from this list of gray matter components of the telencephalon: Cerebral cortex, Basal ganglia, Olfactory bulb, Basal forebrain?


24. For (1) striatum OR (2) lenticular nucleus, explain how the body got its name.

striated because of branches of internal capsule, shaped like a convex lens in horizontal section

25. Stimulation of 9 square mm of skin affects one Merkl disk; by contrast, stimulation of 60 square mm of skin affects one Ruffini end organ. Thus the Ruffini has a larger (what is the expression?) than the Merkl.

receptive field

26. Group IA sensory afferent neurons ANSWER EITHER (1) come in from what receptors? OR (2) have their cell bodies where?

muscle spindles, dorsal root ganglion

27. Capsaicin stimulates the VR-1 receptor. ANSWER EITHER (1) What would be the "normal" (biologically relevant) stimulus? (2) What related Drosophila mutant was discovered much earlier? OR (3) Say something about the molecular structure of this receptor.

heat, transient receptor potential, channel

28. The gracile nucleus is ANSWER EITHER (1) located where? OR (2) is in a branch of the somatosensory system called what?

caudal medulla, lemniscal system

29. "In the Brown-Sequard syndrome, you have an ipsilateral loss of touch as mediated by the lemniscal system." ANSWER EITHER (1) What is the nature of the lesion? OR (2) What and where is the alternative sensory loss?

lesion halfway across the spinal cord, contralateral loss of anterolateral system

30. Your text has a picture of dermatomes. Why was the face not included in that picture?

face input is via trigeminal, not spinal segments

31. The anterolateral system is for pain. There is a notable exception (in terms of spinal tract location). ANSWER EITHER (1) What type of pain is carried in this exceptional tract? OR (2) Where in the spinal cord is it carried?

viceral, dorsal columns at midline

32. In contrast with the input via the dorsal root of the spinal cord, where does somatosensory information from the face come in?


33. Tell me a place where the 2-point discrimination threshold for fine touch is less than 5 mm.

fingertips, lips, tongue

34. A human rod is very sensitive. Why is it theoretically impossible for it to be more sensitive?

it is stimulated by a single photon, the smallest quantum of light

35. Say something about why vision, as we know it, would not work for wavelengths far below or above "visible wavelengths."

too short is ionizing (also cut off by ozone layer), just right excites electrons, too long vibrates molecules (heat is waste)

36. A person who had had emmetropia (normal vision) developed hyperopia. Another person who had had emmetropia developed presbyopia. Answer either (1) What kind of corrective lens would help in both situations? Or (2) What is the difference in these two disorders?

convex lens, hyperopia is far sightedness person would always wear glasses, presbyopia is loss of accomodation, person would need reading glasses

37. "You would be able to see a letter that is 5 minutes." What is the more conventional way of saying that?

you have 20:20 vision

38. The ciliary muscle is contracted. ANSWER EITHER (1) What nerve innervates this muscle? OR (2) What type of vision is this good for?

3-oculomotor, near vision

39. What disorder leads to tunnel vision and why?

retinitis pigmentosa b/c of mid periphery rod loss

40. A radioactive amino acid allowed the rod outer segment disks closest to the inner segment to be labeled. On the basis of this methodology, what fundamental finding ensued?

that new outer segment is continuously made, the outer segment turns over, old outer segment is phagocytosed by the retinal pigment epithelium

41. A paper published in 1942 demonstrated that a rod can respond to a single photon of light. Say something about the methodology in this study.

human subject answered if he could see carefully calibrated 500 nm light; 6-14 quanta were absorbed by a 500 rod area (psychophysics)

42. "You can walk through the forest with nothing but star light, but you cannot run." Why not?

phototransduction is slow

43. In terms of cGMP levels, explain why the rod hyperpolarizes in response to light.

with the cation channel continuously gated by cGMP in the dark, the cell is depolarized, and when PDE is activated in phototransduction, the channel closes because cGMP has been turned into 5' GMP

44. Unequal crossing over leading to gene duplication explains what phenomenon in the visual system?

evolution of two long wavelength cone opsins such as old world monkeys, apes and humans have from one such as new world monkeys have

45. How was the horseshoe crab Limulus used to show how contrast detection was enhanced by feature detection?

neural input from ommatidia at a light-dark boundry show a more accentuated gradient of activity

46. A stroke wipes out the connection of the pretectum to the contralateral Edinger-Westphal nucleus but not to the ipsilateral one. How could you infer this with a very simple non-invasive vision test on a cooperative subject?

there would still be a pupillary reflex but not in the contralateral eye

47. On the way to the thalamus, what is different about axons from the nasal vs the temporal retina at the optic chiasm?

temporal stays ipsilateral, nasal crosses to contralateral

48. Regarding feature detection, what and where is a "bug detector?"

in the frog retina, ganglion cells respond to small dark moving dots

49. Simple cells respond to a line at an angle. These cells presumably receive inputs from an organized subset of lateral geniculate neurons whose receptive field organization is (what?).


50. What aspect of visual development prompted me to draw a parallel to imprinting of mother's image in precocial geese?

the 2 & 1/2 month sensitive (critical) period after birth required for binocular vision in the development of normal binocular cortical connectivity

51. As an electrode is advanced obliquely, the ocular dominance changes. What else changes?

the orientation preference

52. Injection into one eye followed by a specialized histological technique demonstrated a zebra-stripe pattern of ocular dominance columns in the visual cortex. ANSWER EITHER (1) What was injected in the eye? OR (2) What technique was used for the visualization in the cortex?

a radioactive amino acid, audioradiography

53. The human audibility curve plots Y as a function of X. Answer either what is on the Y OR X axes.

ordinate is threshold plotted in intensity, plotted logarithmically, abscissa is frequency in Hz where log plotting is for convenience

54. Given the data on how stimulation by sound causes vibrations in the basilar membrane, why is it astounding that you can tell the difference of stimuli that differ by just a few Hz?

because localization is crude, there is tremendous overlap in part of basilar membrane stimulated

55. Tip links assist channels (ANSWER EITHER) (1) for what ion? Or (2) located on what specific subcellular component?

K+, stereocilium

56. Where is the first place in the auditory projection that receives bilateral input?

superior olive (mid-pons)

57. How do insectivorous bats use sound to catch their prey?

echolocation (sonar)

58. Name (OR give the number for) an efferent cranial nerve that would mediate eye movements controlled through the vestibular system.

occulomotor III, abducens VI (also trochlear IV)

59. In addition to the semicircular canals, what are the two organs that detect head movement?

utricle, saccule

60. How many alleles of the PTC taster gene are there in most of the human population?

just taster and non-taster

61. T1R3 is a G protein-linked receptor used to mediate sweet and umami tastes. What is unique about its interactions with other membrane proteins relative to any other G protein-coupled receptor we have covered in this course?

dimerizes with T1R2 (sweet) and T1R1 (amino acids)

62. In addition to the 5 primaries for taste stimulation, with input via cranial nerves VII, IX an X, it is argued that stimulants like capsaicin contribute to our overall appreciation of gustation. Answer either (1) Which cranial nerve is used? Or (2) What is the term for the receptor type?

5 trigeminal, polymodal nociceptive

63. A male moth is excited by a female's sex attractant pheromone at a concentration of one molecule per cubic foot. How does he know which way to fly?

up wind

64. For cAMP in olfactory receptor cells, answer either (1) What enzyme makes it? Or (2) What does it do?

adenylate cyclase, gates a sodium-calcium channel

65. For mammalian olfaction, say something about EITHER (1) the domain structure of each protein molecule OR (2) the intron-exon structure of each gene.

seven trans-membrane domains, no introns

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