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TEST BANK for TETS BANK FOR Principles of Neurobiology 2nd Edition PRINCIPLES OF NEUROBIOLOGY 2 EDITION BY LIQUN LUO Liqun Luo A E E C ND

NSWERS ARE AT THE

ND OF

ACH

HAPTER

Nature and Nurture in Brain Function and Behavior 1–1

Twin studies found the following correlation coefficients (r) for monozygotic (MZ) vs. dizygotic (DZ) twins: rMZ rDZ Alcoholism (males) 0.4 0.21 Autism 0.65 0.1 Reading disability 0.75 0.45 Schizophrenia 0.5 0.19 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. 1–2

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

1–3

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?

1–4

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.

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(e)

naive adults fitted with prisms are able to adjust their auditory maps in small increments.

How Is the Nervous System Organized? 1–5

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

1–6

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

A. ____________ B. ____________ C. ____________ D. ____________

Figure Q1–6

1–7

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

1–8

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?

1–9

Indicate whether each of the following characteristics is generally true for invertebrate nervous systems, vertebrate nervous systems, or both. A. Dendrites receive information via postsynaptic specializations. B. Axons often project to targets located far from the cell body. C. Neurons are unipolar, with one process bifurcating to form dendritic vs. axonal branches. D. The brain and spinal cord are located in the dorsal part of the body. E. Motor information generally flows from the CNS to the periphery.

1–10

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

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postsynaptic neuron, while _____________ inputs make it less likely. _____________ neurons do not fire action potentials at all. all-or-none chemical continuous electrical excitatory

graded inhibitory non-spiking receptor synaptic

1–11

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

1–12

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

1–13

In the simple knee-jerk reflex circuit (Figure Q1–13):

Figure Q1–13

(a) (b) (c) (d) (e)

sensory neuron connectivity exemplifies divergent excitation. sensory neuron axons terminate directly on the extensor muscles to stimulate contraction. sensory neurons form monosynaptic connections with the flexor motor neurons. sensory neuron excitation stimulates contraction of the flexor muscle. All of the above

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1–14

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. B. C. D. E.

1–15

In the vertebrate retina, afferent neurons excite inhibitory interneurons that project onto the targets of their neighbors. Sensory neurons relay somatosensory stimuli to the primary somatosensory cortex via nuclei in the brainstem and thalamus. A class of cerebral cortical neurons inhibits other classes of inhibitory neurons in the brain, indirectly increasing the activity of final targets. In the insect olfactory system, excitatory projection neuron axons project to two different brain structures, the mushroom body and the lateral horn. In the vertebrate knee-jerk reflex, two parallel excitatory pathways inhibit each other via inhibitory neuron intermediates.

Figure Q1–15 shows the sensory and motor cortical homunculi in humans. In both cases:

Figure Q1–15

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(a) (b) (c) (d) (e) 1–16

the topographic map is distorted, with overrepresentation of heavily innervated body parts such as the hand and mouth. each side of the brain processes information corresponding to the opposite side of the body. the order of representation along the mediolateral axis roughly corresponds to that of the rostrocaudal body axis (reversed). the functions of specific regions were defined using electrical stimulation of epilepsy patients. All of the above

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 1–17

To understand which parts of the human nervous system are specialized for which specific functions, we can perform three basic classes of experiments: correlation, which tells us whether that part is active during performance of the function; loss of function, which tells us whether activity in that part is necessary for a function; and gain of function, which tells us whether activity in that part is sufficient for a function. Give a specific example of each of the following classes of experiments. A. Loss of function B. Gain of function C. Correlation

ANSWERS 1–1

Heritability is calculated as the difference between the correlation of monozygotic and dizygotic twins, multiplied by two. This method attempts to control for the effects due to shared environment rather than shared genetics. The smallest difference between monozygotic and dizygotic twins shown here is seen for alcoholism in males, suggesting a relatively low contribution from genetics.

1–2

(e) These factors are not directly inherited from the parents' DNA and would be expected to affect identical and non-identical pairs of twins to the same degree.

1–3

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 crossfostered 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.

1–4

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

1–5

midbrain, pons, medulla, cervical spine, thoracic spine, lumbar spine, sacral spine

1–6 A. Dendrite

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B. Cell body (soma) C. Axon D. Myelin sheath E. Presynaptic terminal 1–7 A. CNS (oligodendrocytes are the glia that provide myelin sheaths in the CNS) B. PNS (Schwann cells are the glia that provide myelin sheaths in the PNS) C. Both (neurons are found in both the PNS and CNS) D. CNS (astrocytes regulate neuronal development and communication in the gray matter of the CNS) E. CNS (microglia are the resident immune cells of the CNS, while macrophages patrol the PNS) 1–8

Multiple lines of evidence provided support for the neuron doctrine, in which the nervous system is generated by communication between many individual cells. Staining methods (developed by Golgi!) allowed visualization of single neurons and their processes. Later, electron microscopy methods allowed visualization of gaps separating neurons from their targets and synaptic vesicles in axon terminals. Eventually, tissue culture techniques allowed real-time visualization of individual neurons and axon outgrowth.

1–9 A. both B. both C. invertebrate D. vertebrate E. both 1–10

An action potential is a(n) all-or-none transient change in neuronal membrane potential. Another important form of intraneuronal communication is a(n) graded (or local) potential, referring to continuous changes in membrane potential. One type is a(n) synaptic potential, which is produced in response to neurotransmitter release by presynaptic partners. The other type is a(n) receptor potential, which can be induced at peripheral nerve endings by sensory stimuli. Regardless of the source, inputs can be either excitatory or inhibitory. Excitatory inputs facilitate action potential production by the postsynaptic neuron, while inhibitory inputs make it less likely. Non-spiking neurons do not fire action potentials at all.

1–11

(d) An action potential is a discontinuous event of fixed shape and amplitude, with stimulus intensity reflected by an increase in frequency. However, neurons can also exhibit continuous changes in membrane potential in which stimulus intensity is reflected by amplitude.

1–12

(d) Action potentials allow information to be transmitted along the process of a particular neuron, not between neurons.

1–13

(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.

1–14 A. Lateral inhibition

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