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Questions and Answers

Initiation of the action potential usually occurs ______ of the neuron.

  • on the axon
  • at the axon initial segment (correct)
  • on the dendrites
  • in the cell body

    • Which statement about an animal's nervous system is true?

  • Action potential signals degrade over distance.
  • Signal transmission rate is relatively slow.
  • Neurotransmitter is released throughout the body via the blood.
  • Neurons form highly discrete lines of communication. (correct)

    • For a hormone to elicit a specific response from a cell, the cell must possess

  • dendrites specific to the hormone
  • receptor proteins specific to the hormone (correct)
  • a cell body
  • a synapse

    • Which statement about the startle response of the cockroach is true?

    <p>Vibrations of hairs generate nerve impulses in sensory neurons.</p> Signup and view all the answers

    At the metathoracic ganglion, the interneurons synaptically inhibit leg motor neurons.

    <p>True</p> Signup and view all the answers

    Which glial cells are found in the peripheral nervous system?

    <p>Schwann cells</p> Signup and view all the answers

    Which statement about glial cells is true?

    <p>They help supply metabolic substrates to neurons.</p> Signup and view all the answers

    The separation of positive and negative charges constitutes

    <p>a voltage.</p> Signup and view all the answers

    Which statement about membrane capacitance is true?

    <p>It is in series with membrane resistance.</p> Signup and view all the answers

    What is occurring at the membrane?

    <p>Depolarization</p> Signup and view all the answers

    In the lower panel, the difference between the dashed line and the solid red line is due to

    <p>the capacitive properties of the membrane.</p> Signup and view all the answers

    In the figure, the ______ decreases with distance.

    <p>graded potential</p> Signup and view all the answers

    Which statement offers the best explanation for the difference between the middle panel and the lower panel?

    <p>The membrane voltage measured in the lower panel is farther away from the current pulse.</p> Signup and view all the answers

    The properties shown in the figure can be measured in

    <p>neurons, pacemaker cells, and muscle cells</p> Signup and view all the answers

    Which variable does not contribute to the passive electrical properties of a cell?

    <p>The resting membrane current</p> Signup and view all the answers

    The figure shows that the membrane potential results from

    <p>movement of ions across the cell membrane.</p> Signup and view all the answers

    In the figure, ______ in the center of the cell.

    <p>the overall charge neutrality would be maintained independently of the membrane potential</p> Signup and view all the answers

    Which characteristic is not a factor in the Nernst Equation?

    <p>Capacitance</p> Signup and view all the answers

    In a cell, the difference in ion concentration between the intracellular and extracellular fluids results from

    <p>both active ion transport and passive diffusion of ions.</p> Signup and view all the answers

    According to the Nernst equation, which change will depolarize Vm, the membrane potential?

    <p>A decrease in the concentration of anions inside the membrane</p> Signup and view all the answers

    Which statement regarding the ions in intracellular and extracellular fluids in a standard animal cell is true?

    <p>K+ leaks out of the cell slowly because the electrochemical gradient is small.</p> Signup and view all the answers

    According to the Goldman equation, the contribution of each ion to the membrane potential depends most on

    <p>its membrane permeability.</p> Signup and view all the answers

    Which structure is most responsible for the all-or-none property of the action potential?

    <p>Voltage-gated Na⁺ channels</p> Signup and view all the answers

    Which arrow best represents the point where permeability to sodium is the highest?

    <p>I</p> Signup and view all the answers

    Which arrow best represents the point where the voltage-gated sodium channels are inactivated?

    <p>III and IV</p> Signup and view all the answers

    ______ channels are responsible for the undershoot at point D of the figure.

    <p>Voltage-gated potassium</p> Signup and view all the answers

    What occurs when the membrane is clamped at -100 mV?

    <p>Voltage-gated ion channels do not open at all.</p> Signup and view all the answers

    How many separate current pulses cause the membrane potential to reach the threshold?

    <p>3</p> Signup and view all the answers

    What would likely occur if stimulus 3 and 6 were performed simultaneously?

    <p>An action potential would likely not occur.</p> Signup and view all the answers

    If stimulating current pulse 9 (not shown) was both stronger and longer than stimulating current pulse 8, then

    <p>the train of action potentials would continue for the length of the stimulating current.</p> Signup and view all the answers

    For an axon at resting membrane potential, the K⁺ leak channel is ______, the voltage-gated Na⁺ channel is ______, and the voltage-gated K+ channel is ______.

    <p>open; closed; closed</p> Signup and view all the answers

    During the falling phase of an action potential, the K+ leak channel on the axon is ______, the voltage-gated Na⁺ channel is ______, and the voltage-gated K+ channel is ______.

    <p>open; inactivated; open</p> Signup and view all the answers

    Which technique was used to collect the data in the bottom panel?

    <p>Patch-clamp</p> Signup and view all the answers

    On the figure, I represents ______ currents through voltage-gated ______ channels.

    <p>inward; Na+</p> Signup and view all the answers

    Why do the channels at II on the figure stay open longer than those at I?

    <p>Channels at I become inactivated, whereas channels at II close due to membrane voltage.</p> Signup and view all the answers

    Which technique was used to collect the data shown in the figure?

    <p>Voltage-clamp</p> Signup and view all the answers

    The treatment difference between the membranes shown in the graphs is that the membrane on the left is being ______, while the membrane on the right is being ______.

    <p>hyperpolarized; depolarized</p> Signup and view all the answers

    How would the trace on the right look if the neuron was soaking in TEA?

    <p>The outward ionic current would disappear.</p> Signup and view all the answers

    Which statement about a voltage clamp of a neuron at 0 mV is true?

    <p>Voltage-gated potassium channels open.</p> Signup and view all the answers

    Which statement regarding the structure of the voltage-gated Na⁺ channels is false?

    <p>The channel protein changes its primary structure in response to membrane depolarization.</p> Signup and view all the answers

    A spiking neuron and a nonspiking neuron share which characteristic?

    <p>Neurotransmitter secretion based on a change in membrane potential</p> Signup and view all the answers

    How do nonspiking neurons function even though their depolarization signal significantly degrades with distance?

    <p>Voltage-gated K+ channels compensate for the lack of voltage-gated Na⁺ channels.</p> Signup and view all the answers

    The figure depicts a

    <p>cardiac action potential.</p> Signup and view all the answers

    What is the best explanation for the plateau shown in the figure?

    <p>Voltage-gated Ca2+ channels remain open.</p> Signup and view all the answers

    Which statement about ion permeability as shown in the figure is true?

    <p>Na+ permeability is at its highest very close to the membrane potential peak.</p> Signup and view all the answers

    The absolute refractory period of the action potential is best explained by

    <p>inactivated voltage-gated sodium channels.</p> Signup and view all the answers

    Which statement about a local circuit in an axon is false?

    <p>Anions migrate into the membrane interior.</p> Signup and view all the answers

    ______ prevents bidirectional propagation of action potentials.

    <p>The inactivation of Na+ channels</p> Signup and view all the answers

    Conduction velocity shows ______ axon diameter.

    <p>either a proportional relationship to, or a proportional relationship to the square root of</p> Signup and view all the answers

    Considering neurons in living systems, which variable affects conduction velocity the most?

    <p>Myelination</p> Signup and view all the answers

    Myelination by Schwann cells increases the velocity of action potential propagation by

    <p>increasing the resistance and decreasing the capacitance, allowing the action potential to &quot;jump&quot; over the myelinated area.</p> Signup and view all the answers

    Compare and contrast nervous systems and endocrine systems.

    <p>Nervous systems are faster and more precise in communication, while endocrine systems are slower and more widespread in their effects. Nervous systems control rapid responses and short-term changes, while endocrine systems regulate long-term processes.</p> Signup and view all the answers

    Describe the startle response in the cockroach.

    <p>The startle response is triggered when sensory neurons on the cockroach's cerci detect vibrations or air currents. This activates a chain of neurons that ultimately triggers the contraction of leg muscles, causing the cockroach to jump or run away from a perceived threat.</p> Signup and view all the answers

    What are glial cells and how do they aid in the function of the nervous system?

    <p>Glial cells provide support and protection to neurons, forming the myelin sheath around axons, which increases conduction velocity, and supplying nutrients and removing waste products. They also contribute to the blood brain barrier.</p> Signup and view all the answers

    Compare and contrast current and voltage with respect to the cell membrane.

    <p>Current is the flow of charge, while voltage is the difference in electric potential between two points. In the context of the cell membrane, current is the movement of ions across the membrane, and voltage is the electrical potential difference across the membrane.</p> Signup and view all the answers

    Since the bulk solutions that make up the intracellular and extracellular fluids maintain charge neutrality, how does the cell produce membrane potentials?

    <p>Membrane potentials are generated by the separation of a small number of ions across the membrane. This creates an electrochemical gradient, which creates a potential difference across the membrane. The movement of ions across the membrane is controlled by ion channels and pumps.</p> Signup and view all the answers

    Explain in mechanistic terms how the action potential is an all-or-none phenomenon.

    <p>The action potential is triggered only when the threshold potential is reached. This threshold is the point at which enough voltage-gated sodium channels open to allow a rapid influx of sodium ions, which causes a depolarization that is strong enough to trigger a positive feedback loop, leading to the propagation of the action potential.</p> Signup and view all the answers

    Compare and contrast the techniques of patch clamping and voltage clamping.

    <p>Patch clamping allows for the recording of currents through individual ion channels, while voltage clamping controls the membrane potential to measure the currents flowing through the membrane. Both techniques are valuable for studying the electrical properties and dynamics of neurons.</p> Signup and view all the answers

    What are the similarities and differences among the channels in the voltage-gated channel superfamily?

    <p>All voltage-gated ion channels are composed of subunits, each with its own transmembrane domains, that are structured to form a pore for the passage of ions. The pore is gated by changes in voltage, allowing for the controlled flow of ions across the membrane. There are different types of voltage-gated channels, such as sodium, potassium, and calcium channels, each with specific roles in neuronal signal transmission. While they share similarities in their fundamental structure, they are specialized for specific ions and have different kinetic properties.</p> Signup and view all the answers

    Explain in mechanistic terms why the action potential can travel a great distance along an axon without degrading.

    <p>The action potential is propagated by a positive feedback mechanism. When the membrane potential reaches the threshold, voltage-gated sodium channels open, causing a rapid influx of sodium ions. This depolarizes the membrane and triggers the opening of additional sodium channels nearby, further depolarizing the membrane and propagating the signal down the axon. As the signal moves, some of the depolarization is lost, but because the initial stimulus is strong enough to trigger the opening of additional channels, the action potential is able to travel a significant distance without significantly degrading.</p> Signup and view all the answers

    Describe the significance of myelination.

    <p>Myelination increases the speed of action potential propagation by insulating the axon and reducing capacitance, effectively allowing the action potential to propagate more efficiently. The process of saltatory conduction, where action potentials 'jump' between the nodes of Ranvier, also contributes to the increased conduction velocity.</p> Signup and view all the answers

    The neuron converts an electrical signal to a chemical signal in the

    <p>presynaptic terminal</p> Signup and view all the answers

    Neurons that relay sensory signals to integrative centers of the CNS are called

    <p>afferent neurons</p> Signup and view all the answers

    Which glial cells function as metabolic intermediaries between capillaries and neurons?

    <p>Astrocytes</p> Signup and view all the answers

    Which term best describes the movement of ions across a membrane?

    <p>Current</p> Signup and view all the answers

    A decrease in the absolute value of the membrane potential toward zero is called

    <p>depolarization</p> Signup and view all the answers

    Study Notes

    Multiple Choice Questions

    • Question 1: Action potentials usually begin at the axon initial segment.
    • Question 2: True statement about the nervous system: Neurons form discrete communication lines.
    • Question 3: For a hormone to trigger a specific cellular response, the cell must have receptor proteins specific to the hormone.
    • Question 4: The startle response in cockroaches involves nerve impulses triggered by hair vibrations, not sound, and the sensory neurons synapse with the dorsal spinal cord.

    Additional Questions

    • Question 5 (Page 2): Schwann cells are glial cells found in the peripheral nervous system.

    • Question 6 (Page 2): Glial cells provide metabolic support to neurons, they do not integrate membrane potentials.

    • Question 7 (Page 2): The separation of positive and negative charges creates voltage.

    • Question 8 (Page 2): Membrane capacitance is in series with membrane resistance.

    • Question 9 (Page 3): Depolarization is occurring at the membrane.

    • Question 10 (Page 3): The difference between the dashed and solid red lines in the figure represents capacitive properties of the membrane.

    • Question 11 (Page 4): Graded potentials decrease in strength over distance.

    • Question 12 (Page 4): The difference between the middle and lower panel figures is that the membrane voltage in the lower panel is further from the current pulse.

    • Question 13 (Page 4): Membrane properties (graded potentials, action potentials) can be measured in neurons, muscle cells and pacemaker cells.

    • Question 14 (Page 5): Resting membrane current does not contribute to passive electrical properties.

    • Question 15 (Page 5): The membrane potential is determined by the overall difference in ionic concentrations inside and outside the cell (intra- versus extra-cellular).

    • Question 16 (Page 5): The figure shows there would be a slight negative charge in the center of the cell. This is because of the unequal concentrations of charged ions across the membrane.

    • Question 17 (Page 6): Capacity is not a factor in the Nernst Equation.

    • Question 18 (Page 6): Ion concentration differences between intracellular and extracellular fluids happen by both active ion transport and passive diffusion.

    • Question 19 (Page 6): Decreasing the intracellular concentration of anions (negatively charged ions) depolarizes the neuronal membrane potential (Vm).

    • Question 20 (Page 6): Potassium ions (K⁺) leak out of the cell slowly because the electrochemical gradient is small.

    • Question 21 (Page 7): The Goldman equation's most important factor is the membrane's permeability to the various ions.

    • Question 22 (Page 7): Voltage-gated sodium (Na⁺) channels are primarily responsible for the all-or-none property of action potentials.

    • Question 23 (Page 8): Sodium permeability is highest during phase I of an action potential.

    • Question 24 (Page 8): Voltage-gated sodium channels become inactivated during phase III of an action potential.

    • Question 25 (Page 8): Voltage-gated potassium channels are responsible for the undershoot phase.

    • Question 26 (Page 8): Voltage-gated ion channels remain closed if the membrane is clamped at -100 mV.

    • Question 27 (Page 9): Three current pulses cause the membrane potential to reach the threshold.

    • Question 28 (Page 9): Simultaneous stimuli 3 and 6 are less likely to trigger an action potential.

    • Question 29 (Page 9): If stimulus 9 is stronger than 8, it will result in a greater and longer duration of stimulation causing a longer train of action potentials.

    • Question 30 (Page 9): K⁺ leak channel is open/inactivated/closed while the voltage-gated Na⁺ channel is open/inactivated/closed.

    • Question 31 (Page 10): During the falling phase, the voltage-gated K⁺ channel is open and the voltage-gated Na⁺ channel is inactivated/closed.

    • Question 32 (Page 11): The technique used to collect the data in the bottom panel is the patch clamp technique.

    • Question 33 (Page 11): I represents outward Na⁺ current.

    • Question 34 (Page 12): Channels at II stay open longer because they're less sensitive to voltage compared to channels at I, and channels at I become inactivated.

    • Question 35 (Page 12): Voltage clamping was used to collect data in the figure.

    • Question 36 (Page 12): The membrane on the left is hyperpolarized, and the one on the right is depolarized.

    • Question 37 (Page 13): The inward ionic current would disappear if the neuron was soaking in TEA.

    • Question 38 (Page 13): Apart from the initial current shift, no other current is produced, when a neuron is voltage-clamped at 0 mV.

    • Question 39 (Page 13): The voltage-gated Na⁺ channel protein changes primary structure in response to membrane depolarization.

    • Question 40 (Page 14): A spiking neuron and a nonspiking neuron share the characteristic of neurotransmitter secretion which is based on a change in membrane potential.

    • Question 41 (Page 14): Nonspiking neurons function with significant signal degradation because a large number of similarly charged ions are clustered within a small volume of the signal area.

    • Question 42 (Page 15): The figure depicts a cardiac action potential.

    • Question 43 (Page 15): Voltage-gated Ca²⁺ channels stay open during the plateau stage.

    • Question 44 (Page 15): Na⁺ permeability is at its highest very close to the peak membrane potential.

    • Question 45 (Page 15): Inactivated voltage-gated sodium channels explain the absolute refractory period.

    • Question 46 (Page 15): Anions migrating into the membrane interior is false regarding a local circuit.

    • Question 47 (Page 15): Inactivation of sodium channels prevents bidirectional propagation of action potentials.

    • Question 48 (Page 15): Conduction velocity has a proportional relationship with the square root of the axon diameter.

    • Question 49 (Page 16): Myelination most affects conduction velocity.

    • Question 50 (Page 16): Myelination increases conduction velocity by increasing resistance and decreasing capacitance, allowing the action potential to jump over the myelinated area.

    • Question 1 (Page 18): The neuron converts an electrical signal to a chemical signal at the presynaptic terminal.

    • Question 2 (Page 18): Afferent neurons relay sensory signals to the CNS.

    • Question 3 (Page 19): Astrocytes are the glial cells that serve as metabolic intermediaries between capillaries and neurons

    • Question 4 (Page 19): Current describes ion movement across a membrane

    • Question 5 (Page 19): A decrease in membrane potential toward zero is called depolarization

    • Question 6 (Page 19): Electrogenic ion pumps actively contribute to the membrane potential.

    • Question 7 (Page 19): Resistance and capacitance of the membrane determine time constant.

    • Question 8 (Page 20): The change in membrane potential decreases as the distance from the current pulse increases.

    • Question 9 (Page 20): Resting neuron plasma membrane is most permeable to potassium (K⁺) ions.

    • Question 10 (Page 20): If ouabain blocks Na⁺-K⁺-ATPase pumps, the membrane potential would change towards equilibrium for Na⁺.

    • Question 11 (Page 20): In neurons, chloride (Cl⁻) is typically in passive equilibrium across the cell membrane.

    • Question 12 (Page 20): A slightly negative depolarizing current to threshold will not produce an action potential.

    • Question 13 (Page 21): Ions flow in intracellular fluids which carry current to other parts of the membrane.

    • Question 14 (Page 21): Inactivation of voltage-gated Na⁺ channels underlies the absolute refractory period which is when a neuron cannot respond to a stimulus.

    • Question 15 (Page 21): In an extremely long axon, action potentials degrade over distance due to the leakiness of membrane.

    • Question 16 (Page 21): Voltage-gated potassium channels becoming inactivated is responsible for the membrane returning to a repolarized state.

    • Question 17 (Page 21): Cardiac pacemaker cells are modified neural tissue.

    • Question 18 (Page 22): Slow Calcium (Ca²⁺) channels extend the time of cardiac action potentials.

    • Question 19 (Page 22): Axon diameter is the least impactful variable compared to myelination, axon length and temperature on conduction velocity.

    • Question 20 (Page 22): In myelinated axons, action potentials only occur at the nodes of Ranvier.

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