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BIOL 415 Nerve cell mechanisms in behavior
Test 2 Tuesday April 3, 2018 ­p; Prof. Stark
All questions are short answer. 65 points total

For Questions 1-5, go here

1. Give a name, number or function of the cranial nerve indicated.

occulomotor, 3, eye movement, pupil, accomodation

2. Give the function (for both) or a name (for either) area of white matter indicated .

outgoing voluntary motor tract, cerebral peduncle, trapezoid body

3. What is this white area called?


4. Answer either (1) What is this structure called? Or (2) Say one of the things you would see if you removed that structure.

septum pellucidum, head of the caudate and lateral ventrical

5. What is this area called?

hypothalamus, third ventricle

For Questions 6 - 10, go here

6. What is this white matter called?

internal capsule

7. What is this large structure in the middle of the brain called?


8. What is this white matter called?

corpus callosum

9. What is the white matter on the outside of this structure called? (Alternatively, you could say one of the tracts on the midsagittal slice you see that are formed from these axons.)

fimbria, fornix, hippocampal commisure

10. What white matter is being ripped here?

internal capsule

For Questions 11 - 15, go here

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


12. What is this cross-over structure called?

optic chiasm

13. What is this large area of the brain called?


14. You definitely saw this huge nerve in your dissection (pointed to twice). Give a name or number. Hint: there are 3 branches coming in from touch sensation in the face.

trigeminal, 5

15. 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

16. Using a stereotaxic atlas of the rat brain and a stereotaxic apparatus, what do you measure from on the rat's head to find a defined brain location like the ventromedial nucleus of the hypothalamus?

bone sutures bregma and lambda

17. Why do they call part of the basal ganglia the "striatum?"

looks striated from branches of white matter off the internal capsule

18. The most obvious of the "membranes" (meninges) of an "un-peeled" brain is a very thick and tough one called the (what)?

dura mater

19. When you remove the cerebellum, you are looking at the floor of which ventricle?


20. Other than cerebral cortex, name a major component of the telencephalon.

basal ganglia, hippocampus, olfactory bulb, basal forebrain

21. 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

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

to the spinal motor neuron in the ventral horn

23. The afferent from a nociceptor has its cell body in the dorsal root ganglion. Where is the first synapse? (Answer both: location plus which side, using the appropriate term to answer which side.)

dorsal horn gray matter ipsilateral

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

fingertips, lips, tongue

25. The head of a neurosurgery patient is opened to expose the brain using only local anesthetic. Answer either: (1) How do they get away with that? Or (2) Why would they do it that way?

no pain receptors in the brain, to make certain they are not messing with a really critical function

26. Where does a sensory receptor for discriminative touch make its first synapse?

gracile or cuneate nucleus in lower medulla

27. "A hemisection of the spinal cord leads to a contralateral loss of spinothalamic input from below the injury." This is in contrast with what other loss of what other system?

ipsilateral of lemniscal

28. You were introduced to the term "neospinothalamic" whose input is from A-delta fibers. In comparison, answer either (1) What slower fibers have input for the more evolutionary ancient system? Or (2) What is this more ancient system called?

C fibers, paleospinothalamic

29. Histological autoradiography demonstrated that a radioactive amino acid was incorporated into those disks of the outer segment nearest to the inner segment. What eventually happened to this band of radioactivity?

over a few weeks, it moved up the outer segment until those disks were shed and phagocytosed by the RPE

30. 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

31. Why would you go blind with poorly controlled diabetes?


32. Everybody should get tested for glaucoma regularly. Answer either (1) What is being measured? Or (2) Why, if left untreated, would glaucoma lead to blindness?

pressure of the eyeball, ganglion cells die

33. The mechanism by which one gene (for long wavelength cones in New World monkeys) became the yellow-green cone rhodopsin pair (in Old World monkeys) is the general mechanism for the origin of the G protein coupled receptor superfamily. How did one gene become two?

unequal crossing over in meiosis

34. Why is there a "ring scotoma" (doughnut-shaped blind area) in people afflicted with retinitis pigmentosa?

rods go first, that is where they are prevalent

35. How come surgical manipulations of the cornea such as LASIK and RK can be so effective in correcting myopia?

because the curved cornea-air interface, with its huge difference in index of refraction, is a powerful lens and these surgeries change the shape of the cornea

36. Abnormal elongation of the eyeball is associated with what refractive error?


37. Dark spots moving against a light background cause some ganglion cells in the frog retina to fire. Explain why this was considered an important finding.

it shows feature detection of a biologically relevant stimulus, bug detectors

38. Specifically, what crossed the LGN (lateral geniculate nucleus) synaptic cleft to allow Hubel to see the ocular dominance columns using autoradiography?

3H labeled protein

39. A thin bar of light made the simple cell fire quickly. Why did a wider bar not do likewise?

because the wider bar also hit the inhibitory areas in the receptive field of that cell

40. While an electrode is advanced obliquely through the cat's visual cortex, first the left eye predominates, then the right eye. What else has been changing during that advancement?

preferred angle

41. What is the most obvious thing that happens between the pretectum and the Edinger-Westfall nucleus?

goes bilateral

42. If Hubel and Wiesel had looked for a grandmother cell instead of the cells they identified (e.g. simple cell), why wouldn't they have gotten a Nobel Prize?

their systematic approach was very productive, good thing they didn't start looking for a needle in a haystack

43. What is the relevance of the value 0.0002 dynes/cm2 in hearing?

that is the denominator, the pressure standard in defining dB

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

ordinate is threshold (or sensitivity) plotted in intensity, plotted logarythmically, abscissa is frequency in Hz where log plotting is for convenience

45. What causes the channels that mediate hearing to open?

mechanosensitive, would be membrane deformation, assisted by tip links

46. A figure was shown to you with hair cells and the axons they are connected to. On the basis of how that figure was labeled, it was stated that outer hair cells do not function as receptors. What was it about the axons connected to outer hair cells that raised this issue?

those axons were called efferent

47. Mutants of the whirler gene cause improper detection of head orientation. Why is it no surprise that the animals are also deaf?

affects stereocilia, and hair cells are used in hearing and balance

48. For what aspect of hearing is the speed of sound relevant?

auditory localization

49. While jogging, you trip and start to fall. Name a sensory organ or a spinal pathway involved in the elicited responses of your spinal motor neurons.

vestibular apparatus, vestibulospinal tract

50. "Three SNPs associated with PTC insensitivity: A49P, V262A, I296V." Translate either (1) SNP, (2) PTC or (3) A49P, V262A, I296V.

single nucleotide polymorphism (genetic change), a bitter chemical tastant for which there are tasters and non-tasters (based on a gene) in humans, the number is the amino acid position - the first letter is the normal amino acid, the second letter is what it is changed to

51. In olfactory transduction, cAMP is made by adenylate cyclase. What does this cAMP do?

gate channels

52. Bitter stimulation, or stimulation with amino acids, activates PLC (phospholipase C) to create IP3. In this example, the IP3 activates a different Ca2+ channel than the IP3 receptor of the endoplasmic reticulum. Give the name or location of this channel.

TRPM5 in plasmalemma

53. Relative to all the other G protein coupled receptors we have discussed in this course, what is unusual about the ones for sweet and umami?

they are dimers

54. Relative to visual and auditory receptor cells, what is the notable difference in the life expectancy of olfactory (and gustatory) receptor cells?

taste and smell receptor cells die and get replaced

55. 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

56. Taste projected near to where the tongue's somatosensory representation was on cortex. Relate this to the situation for olfaction.

smell, by contrast, projects to a deep, dark, mysterious assortment of places, the limbic system

57. Why do male moths have more elaborate antennae than females?

to detect sex attractant pheromones from female

58. "A hallmark of mature glomeruli is that they are innervated exclusively by axons from olfactory neurons expressing the same olfactory receptor." What kind of molecule is this receptor?

G protein coupled receptor

59. Consecutive muscle twitches that come close enough together in time fuse to a steady and stronger contraction. What is this called?


60. The numbers 13 vs 1730 were given for extraocular vs gastrocnemius muscles respectively (and explained in terms of muscles for fine vs gross movement respectively). 13 and 1730 what?

number of muscle cells (fibers) per motor unit (one spinal motor neuron)

61. What cells degenerate in ALS (amyotrophic lateral sclerosis, Lou Gehrig's disease)?

spinal motor neurons

62. How is it that, in the knee-jerk reflex, the flexor is inhibited from contracting?

through an inhibitory interneuron

63. "The motor loss from a half spinal cord lesion is more like the lemniscal sensory loss than it is like the spinothalamic sensory loss." Why?"

decussation in medulla, so ipsilateral

64. Where are the cells that form the lateral and medial tracts of the pyramidal motor system?

precentral gyrus

65. Name a brain location other than the motor cortex that sends a motor tract down the spinal cord.

reticular formation, vestibular nucleus, red nucleus, superior colliculus

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last revised 3/23/18