Test Bank For Principles of Neurobiology 2nd Edition by Liqun Luo by welldoneassistant

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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B. Feedforward excitation C. Disinhibition D. Divergent excitation E. Recurrent (cross) inhibition 1–15

(e) All of the above.

1–16

The human nervous system relies on massive parallel processing, while computers perform operations as serial processes. The nervous system, but not the computer, utilizes input convergence, integrating up to thousands of analog (as opposed to digital) inputs. The nervous system can also change the strengths of synaptic transmission between presynaptic and postsynaptic partners in response to activity and experience, making it much more flexible and adaptable in function.

1–17 A. Analysis of behavior in patients with brain lesions. B. Analysis of behavior in patients upon electrical stimulation of specific areas of the brain. C. Monitoring of changes in blood flow with PET or fMRI techniques.

What is the transcription unit? (a) The part of the gene that serves as a template for RNA synthesis (b) The part of RNA that serves as a template for protein synthesis (c) The part of the gene that serves as a template for protein synthesis (d) The unit of RNA that is made from a particular gene

2–2

Proteins that function in the cytoplasm and nucleus are synthesized in/on which organelle? (a) Free ribosomes (b) Endoplasmic reticulum (c) Golgi apparatus (d) Nucleus

2–3

Proteins that are destined for export from the cell or that are inserted into the lipid bilayer are synthesized in/on which organelle? (a) Free ribosomes (b) Endoplasmic reticulum (c) Golgi apparatus

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(d) Nucleus

2–4

What is the function of exocytosis? Choose all that are correct. (a) To take proteins to the plasma membrane (b) To take proteins away from the plasma membrane (c) Potential degradation of proteins (d) To secrete proteins from the cell

2–5

What is the function of endocytosis? Choose all that are correct. (a) To take proteins to the plasma membrane (b) To take proteins away from the plasma membrane (c) Potential degradation of proteins (d) To secrete proteins from the cell

2–6

What does ‗local protein translation‘ mean in neurons? (a) Proteins are synthesized only in the nucleus. (b) Proteins are synthesized only in the cell body. (c) Proteins can be synthesized in dendrites. (d) Proteins can be synthesized by a neighboring neuron.

2–7

What kinds of organelles have been localized to dendrites? (a) Polyribosomes (b) ER (c) Golgi (d) All of the above (e) None of these are located in dendrites.

2–8

List in order of size: neurofilaments, microtubules, microfilaments.

2–9

The brains of patients with Alzheimer‘s disease show degradation of microtubule function, in part from over-phosphorylation of the microtubule-associated protein, tau. What might happen to neurons when microtubule function is disrupted?

2–10 Figure Q2–10 shows an interpretive drawing of a microtubule moving rightward on a glass slide to which a substance purified from squid axoplasm had been immobilized, in the presence of ATP.

Figure Q2–10

A. What is the substance that was purified that allows movement of the microtubule? B. What would happen if a non-hydrolyzable form of ATP was added to the solution?

2–11 In transportation within neurons, which direction is retrograde? Which direction is anterograde? 2–12 Which membrane proteins require ATP to move ions across the membrane? Choose all that apply.

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(a) Symporters (b) Pumps (c) Antiporters (d) Ion channels

2–13 Which membrane proteins use the electrochemical gradient to move ions across the membrane? Choose all that apply. (a) Symporters (b) Pumps (c) Antiporters (d) Ion channels

2–14 Label depolarization, repolarization, and hyperpolarization in Figure Q2–14.

Figure Q2–14

2–15 What helps maintain the ion concentration across the membrane of neurons? (a) The driving force for any ion (b) Na+/K+ ATPase (c) Leak K+ channels (d) Leak Na+ channels

2–16 Which equation is used to determine the equilibrium potential of any ion? (a) Ohm‘s law (b) The driving force (c) The Nernst potential (d) The Goldman–Hodgkin–Katz equation

2–17 The equilibrium potential for any ion is the point at which two forces/gradients balance each other. What are the two forces/gradients? 2–18 In the cochlea of the ear sounds waves are turned into electrical signals through special cells called hair cells. When a wave travels through the cochlea it moves the ‗hairs‘ and opens ion channels that are permeable to K+ and Ca2+. These ‗hairs‘ are in a fluid that has a very high K+ concentration compared to the inside of the cell. A. When the ion channels open, in what direction do K+ ions flow and why? B. Based on this relative concentration difference of K+, what do you predict the equilibrium potential for K+ will be: positive, negative or zero?

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2–19 According to the Goldman–Hodgkin–Katz equation, if the membrane were more permeable to Na+ at rest, instead of K+, what would the approximate resting membrane potential be? (a) –70 mV (b) +50mV (c) –79 mV (d) +100mV

2–20 Changes in ion conductance or ion concentration can alter the resting membrane potential of a cell. For each of the following, write in the letter indicating whether each condition would cause hyperpolarization (H), depolarization (D), or very little change (LC) in the resting membrane potential, and the reason for this change. Condition

Increase in [K+]O Increase in [Na+]O Increase in K+ permeability Increase in Na+ permeability

Membrane potential change

Reason

_______ _______

________________________________________ ________________________________________

_______

________________________________________

_______

________________________________________

2–21 A. If there is a large voltage across a membrane and a low resistance, is the current going to be larger or small? B. In order to have a large current, if there is a large resistance what should the voltage difference be?

2–22 What best describes current? (a) Resistance (b) Movement of charge (c) Potential difference (d) Storage of charge

2–23 What is the ‗driving force‘? (a) The concentration gradient (b) The conductance of an ion (c) The equilibrium potential for an ion (d) The difference between the membrane potential and equilibrium potential

2–24 Match each representative electrical component with its equivalent in a neuron. A. Resistor ____ membrane B. Capacitor ____ ion channel C. Battery ____ movement of ions D. Current ____ concentration gradient 2–25 What is the function of the ‗capacitor‘ in a neuron? Choose all that apply.

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(a) Storage of charge across the membrane (b) To allow the movement of ions across the membrane (c) To provide the ability to integrate signals (d) To provide a delay in changes in voltage across the membrane

2–26 What is an RC circuit? Choose all that apply. (a) A circuit with a resistor and capacitor (b) An electronic representation of a biological membrane (c) An electronic representation of voltage dependent ion channels (d) A circuit with ions and voltage

2–27 Invertebrates and vertebrates have evolved different strategies to change the length/space constant (λ) of a neuron. For each strategy, say whether this increases or decreases the length constant and what property in the following equation it influences. A. Invertebrates increased the diameter of the axon. B. Vertebrates use myelination of the axon.

2–28 If myelin makes action conduction velocity faster, why are axons not completely covered with myelin? That is, what would happen to the electrical signal if the axon was completely covered in myelin and had no Nodes of Ranvier? 2–29 A. Label Figure Q2–29 with the following terms: action potential threshold, action potential, subthreshold stimulus, suprathreshold stimulus.

Figure Q2–29

B. In Figure Q2–29, stimulus 4 is of larger amplitude than stimulus 3. What happened to the action potential when a larger stimulus was provided and why? C. In Figure Q2–29, what do you predict would happen if you increased the duration of stimulus 4?

How Do Electrical Signals Propagate from the Neuronal Cell Body to Its Axon Terminals? 2–30 In order to test the hypothesis that the rising phase of the action potential is caused by Na+ influx, researchers recorded the magnitude of the action potential when in a normal solution (like sea water) and then again after increasing the extracellular Na+

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concentration. What do you predict will happen to the action potential with the increased extracellular Na+ concentration and why? Draw the action potential on Figure Q2–30.

Figure Q2–30

2–31 In order to understand how currents move during an axon potential Hodgkin and Huxley used the voltage clamp technique. Why was this technique so important? Choose all that apply. (a) It allowed the investigators to measure ions moving across single channels. (b) It prevented the change in membrane potential associated with ions flowing across the membrane. (c) It allowed them to calculate the conductance of the individual ions. (d) It showed that currents vary with voltage and time.

2–32 Using the voltage clamp technique, Hodgkin and Huxley found an early inward current and a later outer current (Figure Q2–32, recorded current). What would happen to the current if you would apply tetrodotoxin to the bath before changing the voltage across the membrane? Please select between currents A and B and explain your answer.

Figure Q2–32

2–33 Why does the Na+ conductance decrease after a short time? (a) The channels close. (b) The cell reaches ENa. (c) The Na+ channels inactivate. (d) The K+ channels start to open.

2–34 For each labeled point (A–D) on the action potential shown in Figure Q2–34, state whether the conductance through voltage-dependent Na+ and K+ channels is low, high, or no conductance. Explain. [Note: For this answer, ignore conductance through leak channels.]

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Figure Q2–34

2–35 Why are action potentials usually generated at the axon hillock in vertebrate neurons? (a) There is a high concentration of Na+ channels. (b) There is a high concentration of K+ channels. (c) This is the point at which most synaptic contacts are made. (d) It is located at the beginning of the axon.

2–36 Why do action potentials usually travel unidirectionally down an axon? (a) Delayed activation of K+ channels (b) Inactivation of Na+ channels (c) Myelin prevents travel in the opposite direction. (d) Action potentials are all-or-none.

2–37 Figure Q2–37 shows a whole-cell sodium current (bottom trace) elicited by stepping the membrane potential from –70 mV to 0 mV (top trace). The dashed line is 0 nA. Upon depolarizing the membrane, there is an inward current. This whole-cell current is a reflection of the cumulative activity of many individual ion channels. What is the probable state of an individual sodium channel at each point (A, B, and C)?

Figure Q2–37

2–38 Figure Q2–38 shows the response of a single Na+ channel patch clamp recording. Which individual ion channel state best describes the current in A, B, and C?

Figure Q2–38

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2–39 You are in a lab and conduct a patch clamp experiment (Figure Q2–39) in which you change the voltage across the membrane by +20 mV (top trace). You record the resulting single channel current (lower three traces). Based on these single channel currents, what do you think the whole-cell current would look like?

Figure Q2–39

2–40 What is the size of the primary structure of K+ channels compared to Na+ channels? (a) It is twice the size. (b) It is half the size. (c) It is one quarter the size. (d) It is four times the size.

2–41 How do Na+ and K+ ion channel structures allow them to detect changes in voltage across the membrane? Note: Questions 2–42 and 2–43 refer to the data in Figure Q2–42. These questions may be used independently or as a group. 2–42 Figure Q2–42 shows a patch clamp recording from the Shaker channel (ShB). What is the presumed molecular mechanism for inactivation of the channel?

Figure Q2–42

(a) Several positively charged amino acids in S4 (b) Several negatively charge amino acids in S4 (c) The N-terminal ‗ball-and-chain‘ (d) A block by Na+ ions

2–43 In Figure Q2–42, amino acids 6–46 were removed from the ShB channel through mutagenesis. A. What happened to the single channel response?

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B. When the ShB peptide (the first 20 amino acids of the ShB protein) was added to the ShBΔ6– 46 protein, what happened to the single channel response and what does that tell you about the function of the first 20 amino acids?

2–44 The structure of the selectivity filter is known. A. Why are the electronegative carbonyl groups important for K+ to move across the filter? B. How do electrostatic forces of K+ ions help move K+ across the filter?

2–45 Reconstruct an action potential starting with the resting potential and ending with the voltage across the membrane coming back to rest after the action potential. Describe single channel behavior, whole cell current and/or conductance, and changes in voltage with respect to the equilibrium potential for each ion.

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ANSWERS 2–1

(a)

2–2

(a)

2–3

(b)

2–4

(d) Exocytosis does not take proteins to the plasma membrane, as that is a form of transportation.

2–5

(b) Endocytosis takes proteins from the extracellular space and the membrane into the cell.

2–6

(c) In neurons proteins can be synthesized in dendrites because the molecular machinery to make proteins is located there.

2–7

(d)

2–8

Microfilaments < neurofilaments < microtubules

2–9

Axon transportation would cease, as proteins could not be transported down microtubules. After a short time, the neuron would not function and then would eventually die.

2–10 A. Kinesin (although dynein would not be a bad answer). This is from Box 2–1. B. The microtubule would not move as you need ATP to provide energy for the kinesin.

2–11 Retrograde refers to movement toward the cell body. Anterograde refers to movement down an axon, away from the cell body. 2–12 (b) Pumps require ATP. The other choices use electrochemical gradients as the energy to move ions across the membrane. 2–13 (a), (c), and (d). All these types of transport use electrochemical gradients to move ions across the membrane. For symporters the electrochemical gradient of one ion is used to drive another ion in the same direction, up its electrochemical gradient. For antiporters, the electrochemical gradient of one ion is used to drive another ion in the opposite direction, up its electrochemical gradient. 2–14 See Figure A2–14. Hyperpolarization is more negative and depolarization is more positive. The first hyperpolarization and second depolarization could also be considered ‗repolarization‘ as the voltage across the membrane is repolarizing back to rest.

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