Neuroscience Quiz: Action Potentials and Cells
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Neuroscience Quiz: Action Potentials and Cells

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Questions and Answers

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

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

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

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

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

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

    • 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

    <p>leg motor neurons</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>the six pairs of ions sitting on the 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>Both nervous and endocrine systems serve as methods for communication within the body. The nervous system is distinguished by its rapid speed and precision in delivering signals, making it ideal for controlling fine-grained and prompt responses, whereas endocrine systems work more broadly and over longer time scales by releasing hormones into the bloodstream, affecting a wide range of target cells and tissues. The nervous system allows for finely tuned control of specific responses while the endocrine system manages large-scale and long-term processes.</p> Signup and view all the answers

    Describe the startle response in the cockroach.

    <p>The cockroach startle response is a reflex triggered by sensory stimulation. When sound waves or vibrations stimulate the filiform hair receptors on the cockroach’s antennae, sensory neurons are activated. These neurons transmit the signal to giant interneurons, which, in turn, activate the leg motor neurons. This rapid sequence of events triggers the characteristic leg movements of the startle response.</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 are supporting cells found in the nervous system. They play a vital role in maintaining the health and function of neurons. One key function is providing insulation around neurons in the form of myelin, which significantly increases the speed of action potential conduction. Glial cells also maintain the blood-brain barrier, provide metabolic support for neurons, and remove cellular debris.</p> Signup and view all the answers

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

    <p>Current represents the flow of electrical charge through a conductor, which, in the context of the cell membrane, is the movement of ions through the membrane channels. Voltage, on the other hand, is the measure of the potential difference between two points, indicating the separation of charges across the membrane. The current is a dynamic aspect, reflecting the movement of charge, while the voltage is a static measure of the potential energy 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 a highly localized separation of charges across the cell membrane. Despite the overall charge neutrality of the intracellular and extracellular fluids, specific ion gradients are established. To maintain these gradients, the cell expends energy to pump ions across the membrane. The resulting difference in charge distribution across the membrane creates an electrical potential difference, leading the membrane potential.</p> Signup and view all the answers

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

    <p>An action potential is triggered when a sufficiently strong depolarization is reached near the axon hillock. When this threshold is surpassed, voltage-gated sodium channels open, allowing sodium ions to rush into the neuron. This inflow of sodium further depolarizes the membrane, positively feeding back into the process, creating a positive loop of sodium entry that amplifies the potential and causes its rapid rise. If the threshold depolarization is not reached, the sodium channels do not open sufficiently, and the potential does not reach the threshold necessary to trigger the cycle, which explains the all-or-none nature of the action potential.</p> Signup and view all the answers

    Study Notes

    Multiple Choice Questions

    • Question 1: The initiation of an action potential typically occurs at the axon initial segment of a neuron.
    • Question 2: A true statement about an animal's nervous system is that neurons form discrete communication lines.
    • Question 3: For a hormone to trigger a specific cellular response, the target cell must possess receptor proteins that are specific to that hormone.
    • Question 4: The startle response in a cockroach involves sensory neurons receiving impulses from hairs, which stimulate the dorsal spinal cord.

    Additional Questions

    • Question 5: Schwann cells are glial cells found in the peripheral nervous system.
    • Question 6: Glial cells assist neurons by providing metabolic support.
    • Question 7: A voltage is the separation of positive and negative charges, representing an electrical potential difference.
    • Question 8: Membrane capacitance is measured in farads or its reciprocal.
    • Question 9: Depolarization occurs at the membrane.
    • Question 10: The difference between dashed and solid red lines in the figure is due to differing capacitance properties.
    • Question 11: In the figure, the graded potential decreases with distance.
    • Question 12: In the lower panel, the voltage is farther away from the current pulse.
    • Question 13: Neurons, pacemaker cells, and muscle cells demonstrate the properties measured by the figure.
    • Question 14: The resting membrane current does not contribute to passive electrical properties in a cell.
    • Question 15: The membrane potential results from the overall difference in intracellular and extracellular ion concentrations.
    • Question 16: In the center of the cell, there would be a slight negative charge.
    • Question 17: Capacitance is not a factor in the Nernst equation. The equation accounts for the temperature, valence of the ion, and concentrations inside and outside of the membrane.
    • Question 18: Differences in ion concentration are due to passive diffusion and active ion transport, in a typical cell.
    • Question 19: A decreased ion concentration inside the membrane depolarizes the membrane potential, according to the Nernst equation.
    • Question 20: Potassium ions (K⁺) leak out of cells more slowly than sodium ions (Na⁺) due to the smaller electrochemical gradient.
    • Question 21: Membrane permeability is the most important factor in the contribution to membrane potential as per the Goldman equation.
    • Question 22: Voltage-gated sodium channels (Na⁺) are primarily responsible for the all-or-none property of an action potential.
    • Question 23: The arrow representing the highest permeability to sodium is labeled I.
    • Question 24: Voltage-gated sodium channels are inactivated at the time point labeled III and IV.
    • Question 25: Voltage-gated potassium channels are responsible for the undershoot.
    • Question 26: If the membrane is clamped at -100 mV, voltage-gated ion channels don't typically open.
    • Question 27: Three current pulses are needed to reach the threshold.
    • Question 28: Simultaneous stimuli 3 and 6 will usually not produce an action potential.
    • Question 29: If the stimulating current from pulse 9 is stronger than pulse 8, the action potentials will increase in frequency.
    • Question 30: At resting membrane potential, the K⁺ leak channel is open, the voltage-gated Na⁺ channel is inactivated, and the voltage-gated K⁺ channel is closed.
    • Question 31: During the falling phase of an action potential, the K⁺ leak channel is open, the voltage-gated Na⁺ channel is inactivated, and the voltage-gated K⁺ channel is open.
    • Question 32: The technique used in the bottom panel is patch clamping.
    • Question 33: I represents outward Na⁺ flow.
    • Question 34: Channels at II (in the figure) stay open longer due to inactivation of the Na⁺ channels and not responding to a repolarization at I.
    • Question 35: The technique used to collect the data is voltage clamping.
    • Question 36: The membrane on the left is hyperpolarized, while the membrane on the right is depolarized.
    • Question 37: If the neuron is exposed to TEA, the inward ionic current will disappear.
    • Question 38: In voltage clamping of a neuron at 0mV, voltage-gated potassium channels open.
    • Question 39: Channels are not changing their structure in response to changes in membrane depolarization during an action potential.
    • Question 40: A critical characteristic shared by spiking neurons and nonspiking neurons is neurotransmitter secretion.
    • Question 41: Nonspiking neurons use other mechanisms to maintain signal integrity over long distances.
    • Question 42: The figure depicts a cardiac action potential.
    • Question 43: The plateau phase is due to voltage-gated calcium channels remaining open.
    • Question 44: Sodium permeability is highest closest to the peak of the membrane potential.
    • Question 45: The absolute refractory period is caused by inactivated voltage-gated sodium channels.
    • Question 46: It is false that anions migrate into the membrane interior during a local circuit.
    • Question 47: Inactivation of sodium channels prevents bidirectional propagation of action potentials.
    • Question 48: Conduction velocity is related exponentially to the square root of axon diameter.
    • Question 49: Myelination greatly affects conduction velocity.
    • Question 50: Myelination increases action potential velocity by increasing membrane resistance and decreasing membrane capacitance, allowing the action potential to "jump" between Nodes of Ranvier.
    • Question 1: In a typical neuron, the neuron converts an electrical signal into a chemical signal in the presynaptic terminal.
    • Question 2: Neurons that relay sensory signals are called afferent neurons.
    • Question 3: Astrocytes function as metabolic intermediaries.
    • Question 4: Current describes the flow of ions.
    • Question 5: Depolarization describes a decrease in membrane potential toward zero.
    • Question 6: The overall resistance of the membrane and the presence of electrogenic pumps actively contribute to the cell's membrane potential.
    • Question 7: The time constant depends on resistance and capacitance.
    • Question 8: If a current pulse generates a passive potential, the change in membrane potential decreases as the distance from the current pulse increases.
    • Question 9: In a resting neuron, the plasma membrane is most permeable to potassium (K+).
    • Question 10: If ouabain blocks Na+/K+ pumps, sodium (Na+) will equilibrate across the membrane.
    • Question 11: Chloride (Cl-) is in passive equilibrium in a typical neuron.
    • Question 12: A slight depolarizing current that is just below threshold will not produce an action potential.

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    Test your knowledge on the fundamentals of neuroscience, focusing on action potentials, neurons, and glial cells. This quiz covers essential concepts related to the nervous system, including hormone-receptor interactions and the physiological mechanisms behind neuronal communication.

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