Deck 1: An Invitation to Neurobiology

Question 1

Both male insects (such as fruit flies and crickets) and songbirds (such as canaries) produce species-specific songs in order to attract mates. What sorts of experiments could be used to determine whether these courtship behaviors are learned vs. innate?

Answer 1

Males could be isolated from birth and then presented to females as adults in order to see whether they sing and how closely their song matches that of a typical male. They could also be cross-fostered with (or exposed to the songs of) males of a different species to see whether that experience alters the song that they sing when presented to females as adults.

Question 2

In the simple knee-jerk reflex circuit (Figure Q1-13): Figure Q1-13
(a) sensory neuron connectivity exemplifies divergent excitation.
(b) sensory neuron axons terminate directly on the extensor muscles to stimulate contraction.
(c) sensory neurons form monosynaptic connections with the flexor motor neurons.
(d) sensory neuron excitation stimulates contraction of the flexor muscle.
(e) All of the above

Answer 2

(A)
Sensory neuron axons bifurcate so that their activity excites the extensor motor neurons (not the extensor muscles directly) and simultaneously excites inhibitory interneurons that project onto the flexor motor neurons, stimulating relaxation. Meanwhile, the extensor muscle is stimulated to contract by the extensor motor neurons.

Question 3

Experiments in which juvenile or adult barn owls are fitted with prisms that cause a mismatch between auditory and visual stimuli demonstrate that:
(a) owls that learned a task as juveniles can relearn it as adults, and novel tasks can still be learned in adulthood as long as training is more gradual.
(b) neural plasticity-in this case, the ability to adjust the auditory map-is completely lost by the time the owls reach maturity.
(c) owls that adjusted their auditory maps to large mismatches with the visual field as juveniles can still do so if fitted with prisms as adults.
(d) naive adults fitted with prisms are able to adjust their auditory maps to large mismatches with the visual field.
(e) naive adults fitted with prisms are able to adjust their auditory maps in small increments.

Answer 3

(A)
The statements from c and e are both correct and are combined and paraphrased in a.

Question 4

Fill in each of the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once.
An action potential is a(n) ______________ transient change in neuronal membrane potential. Another important form of intraneuronal communication is a(n) _____________ (or local) potential, referring to ____________ changes in membrane potential. One type is a(n) _____________ potential, which is produced in response to neurotransmitter release by presynaptic partners. The other type is a(n) _____________ potential, which can be induced at peripheral nerve endings by sensory stimuli. Regardless of the source, inputs can be either excitatory or inhibitory. _____________ inputs facilitate action potential production by the postsynaptic neuron, while _____________ inputs make it less likely. _____________ neurons do not fire action potentials at all.
all-or-none graded
chemical inhibitory
continuous non-spiking
electrical receptor
excitatory synaptic

Question 5

The human nervous system is often compared to a computer, but the analogy breaks down upon closer examination of the organization and function of both systems. What are some key differences between the nervous systems we evolved and the early computers we designed and built?
General Methodology

Question 6

Indicate whether each of the following types of cells can be found in the central nervous system (CNS), peripheral nervous system (PNS), or both.
A. Oligodendrocytes
B. Schwann cells
C. Neurons
D. Astrocytes
E. Microglia

Question 7

In twin studies, 'environmental factors' are any factors not inherited from parents' DNA. These would include:
(a) methylation of fetal DNA due to smoking during pregnancy.
(b) random mutation during early embryonic development.
(c) availability of folic acid during pregnancy.
(d) viral infection during pregnancy.
(e) All of the above

Question 8

Arrange the following structures from the vertebrate CNS in order from anterior (rostral) to posterior (caudal):
pons, cervical spine, lumbar spine, medulla, sacral spine, midbrain, thoracic spine

Question 9

Figure Q1-15 shows the sensory and motor cortical homunculi in humans. In both cases: Figure Q1-15
(a) the topographic map is distorted, with overrepresentation of heavily innervated body parts such as the hand and mouth.
(b) each side of the brain processes information corresponding to the opposite side of the body.
(c) the order of representation along the mediolateral axis roughly corresponds to that of the rostrocaudal body axis (reversed).
(d) the functions of specific regions were defined using electrical stimulation of epilepsy patients.
(e) All of the above

Question 10

Twin studies found the following correlation coefficients (r) for monozygotic (MZ) vs. dizygotic (DZ) twins: Data from Plomin R, Owen MJ & McGuffin P (1994) Science 264:1733-1739.
Which mental trait has the lowest heritability (contribution of genetic differences to trait differences)? Briefly explain your reasoning.

Question 11

Indicate the name of the structure found at each location in Figure Q1-6.

Question 12

The intensity of a stimulus can be encoded by:
(a) the amplitude of action potentials in a neuron.
(b) the frequency of action potentials in a neuron.
(c) the amplitude of graded potentials in a neuron.
(d) b and c
(e) All of the above

Question 13

Figure Q1-14 shows commonly used circuit motifs. Identify the type of circuit motif featured in each of the following examples. Figure Q1-14
A. In the vertebrate retina, afferent neurons excite inhibitory interneurons that project onto the targets of their neighbors.
B. Sensory neurons relay somatosensory stimuli to the primary somatosensory cortex via nuclei in the brainstem and thalamus.
C. A class of cerebral cortical neurons inhibits other classes of inhibitory neurons in the brain, indirectly increasing the activity of final targets.
D. In the insect olfactory system, excitatory projection neuron axons project to two different brain structures, the mushroom body and the lateral horn.
E. In the vertebrate knee-jerk reflex, two parallel excitatory pathways inhibit each other via inhibitory neuron intermediates.

Question 14

Information is transmitted between neurons by:
(a) vesicular release, diffusion, and reception of molecules called neurotransmitters.
(b) ion flow across gap junctions.
(c) action potentials.
(d) a and b
(e) All of the above

Question 16

Early neuroscientists Camillo Golgi and Santiago Ramón y Cajal famously espoused two opposing theories regarding the organization of the nervous system. Golgi believed in the reticular theory, in which nerve cells were physically linked by their processes to form a giant net. What experimental evidence supported the neuron doctrine instead?