Basic Structure And Function Of The Nervous System! Trivia Quiz

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Basic Structure And Function Of The Nervous System! Trivia Quiz - Quiz

The trivia quiz is on the basic structure and function of the nervous system! The nervous system is tasked with communication between the brain and all the organs in the body. Do you know the different nerves in the boy, and what task they accomplish? Do take up the quiz and get to find out for sure. All the best!


Questions and Answers
  • 1. 

    Which of the following is/are functions of the human nervous system?

    • A.

      A. receiving, storing, and processing information on the internal and external environments

    • B.

      B. bringing about changes in physiology and/or behavior to ensure optimal functions of homeostatic mechanisms

    • C.

      C. secretion of hormones

    • D.

      D. coordination of movement

    • E.

      E. All of the choices are correct.

    Correct Answer
    E. E. All of the choices are correct.
    Explanation
    The human nervous system is responsible for receiving, storing, and processing information from both the internal and external environments. It also plays a crucial role in bringing about changes in physiology and behavior to maintain homeostasis. Additionally, the nervous system coordinates movement and is involved in the secretion of hormones. Therefore, all of the given choices accurately describe the functions of the human nervous system.

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  • 2. 

    Which is not true of myelin?

    • A.

      A. It is a fatty membranous sheath.

    • B.

      B. It is formed by glial cells.

    • C.

      C. It influences the velocity of conduction of an electrical signal down an axon.

    • D.

      D. It covers all parts of the neuron, including the axon, cell body, and dendrites.

    Correct Answer
    D. D. It covers all parts of the neuron, including the axon, cell body, and dendrites.
    Explanation
    Myelin is a fatty membranous sheath that is formed by glial cells. It influences the velocity of conduction of an electrical signal down an axon. However, it does not cover all parts of the neuron, including the axon, cell body, and dendrites. Myelin primarily covers the axon, forming a protective layer that allows for faster transmission of electrical signals. The cell body and dendrites of a neuron are not covered by myelin.

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  • 3. 

    Which of the following is not true about axon transport?

    • A.

      A. It refers to the passage of materials from the cell body of a neuron to the axon terminals.

    • B.

      B. It refers to the passage of materials from axon terminals to the cell body of a neuron.

    • C.

      C. It refers to the transport of materials from the inside to the outside across the axonal membrane.

    • D.

      D. It is especially important for maintaining the integrity of neurons with long axons.

    Correct Answer
    C. C. It refers to the transport of materials from the inside to the outside across the axonal membrane.
    Explanation
    Axon transport refers to the passage of materials from the cell body of a neuron to the axon terminals. This process is crucial for maintaining the integrity of neurons with long axons. However, it does not involve the transport of materials from the inside to the outside across the axonal membrane.

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  • 4. 

    Which is FALSE about neurons?

    • A.

      A. A given neuron can be either a presynaptic neuron or a postsynaptic neuron.

    • B.

      B. An individual neuron can receive information from multiple other neurons.

    • C.

      C. An individual neuron can transmit information to multiple other neurons.

    • D.

      D. A neuron can simultaneously release more than one type of neurotransmitter.

    • E.

      E. A neuron receives information on its axons and delivers it to other neurons through its dendrites.

    Correct Answer
    E. E. A neuron receives information on its axons and delivers it to other neurons through its dendrites.
  • 5. 

    Which of the following is not true of glial cells?

    • A.

      A. They form the myelin for axons.

    • B.

      B. Neurons outnumber glial cells 10 to 1 in the nervous system.

    • C.

      C. They deliver fuel molecules to neurons and remove the waste products of metabolism.

    • D.

      D. They are important for the growth and development of the nervous system.

    • E.

      E. They regulate the composition of the extracellular fluid in the CNS.

    Correct Answer
    B. B. Neurons outnumber glial cells 10 to 1 in the nervous system.
    Explanation
    Glial cells are non-neuronal cells that support and protect neurons. Option B is not true because glial cells actually outnumber neurons in the nervous system. There are about 10 times more glial cells than neurons. Therefore, option B is the correct answer as it contradicts the actual ratio of neurons to glial cells in the nervous system.

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  • 6. 

    The difference in electrical charge between two points:

    • A.

      A. is called the potential difference between those points.

    • B.

      B. is called the diffusion potential between those points.

    • C.

      C. is called the the current, and is expressed in the units of millimoles.

    • D.

      D. is the same for all ions.

    Correct Answer
    A. A. is called the potential difference between those points.
    Explanation
    The difference in electrical charge between two points is referred to as the potential difference between those points. This potential difference is a measure of the electrical potential energy per unit charge, and it is commonly measured in volts. It represents the work done per unit charge in moving a positive test charge from one point to another in an electric field. The potential difference is an important concept in understanding electrical circuits and the flow of electric current.

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  • 7. 

    According to the equation expressed as Ohm's law, which of these would cause the greatest increase in current?

    • A.

      A. doubling both voltage and resistance

    • B.

      B. reducing both voltage and resistance by half

    • C.

      C. doubling voltage and reducing resistance by half

    • D.

      D. reducing voltage by half and doubling resistance

    • E.

      E. quadrupling both voltage and resistance

    Correct Answer
    C. C. doubling voltage and reducing resistance by half
    Explanation
    According to Ohm's law, the current (I) is directly proportional to the voltage (V) and inversely proportional to the resistance (R). Therefore, doubling the voltage will double the current, and reducing the resistance by half will also double the current. Hence, doubling the voltage and reducing the resistance by half will cause the greatest increase in current.

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  • 8. 

    Compartments A and B are separated by a membrane that is permeable to K+ but not to Na+ or Cl-. At time zero, a solution of KCl is poured into compartment A and an equally concentrated solution of NaCl is poured into compartment B. Which would be true once equilibrium is reached?

    • A.

      A. The concentration of Na+ in A will be higher than it was at time zero.

    • B.

      B. Diffusion of K+ from A to B will be greater than the diffusion of K+ from B to A.

    • C.

      C. There will be a potential difference across the membrane, with side B negative relative to side A.

    • D.

      D. The electrical and diffusion potentials for K+ will be equal in magnitude and opposite in direction.

    • E.

      E. The concentration of Cl- will be higher in B than it was at time zero.

    Correct Answer
    D. D. The electrical and diffusion potentials for K+ will be equal in magnitude and opposite in direction.
    Explanation
    Since the membrane is permeable to K+ but not to Na+ or Cl-, K+ will diffuse from compartment A to compartment B until equilibrium is reached. As K+ diffuses, it will create a concentration gradient, causing a diffusion potential. At the same time, the movement of K+ will also create an electrical potential due to the charge of K+. At equilibrium, the electrical and diffusion potentials for K+ will be equal in magnitude but opposite in direction, resulting in no net movement of K+. Therefore, option D is correct.

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  • 9. 

    Which is TRUE about the resting membrane potential?

    • A.

      A. It requires very few ions to be distributed unevenly.

    • B.

      B. It has the same value in all cells.

    • C.

      C. It is oriented so that the cell's interior is positive with respect to the extracellular fluid.

    • D.

      D. Only nerve and muscle cells have a potential difference across the membrane at rest.

    • E.

      E. It is not altered by changing concentration gradients of permeating ions.

    Correct Answer
    A. A. It requires very few ions to be distributed unevenly.
    Explanation
    The resting membrane potential is the electrical potential difference across the plasma membrane of a cell when it is at rest. It is maintained by the uneven distribution of ions across the membrane. Option A is true because the resting membrane potential is established by the unequal distribution of a few key ions, such as potassium (K+) and sodium (Na+), across the membrane. These ions are actively pumped in and out of the cell by ion channels, creating a charge imbalance and resulting in a negative internal charge compared to the external environment.

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  • 10. 

    Which is TRUE about typical, resting neurons?

    • A.

      A. The plasma membrane is most permeable to sodium ions.

    • B.

      B. The concentration of sodium ion is greater inside the cell than outside.

    • C.

      C. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions.

    • D.

      D. The plasma membrane is completely impermeable to sodium ions.

    • E.

      E. The plasma membrane is completely impermeable to potassium ions.

    Correct Answer
    C. C. The permeability of the plasma membrane to potassium ions is much greater than its permeability to sodium ions.
    Explanation
    The correct answer is C because resting neurons have a higher permeability to potassium ions compared to sodium ions. This is due to the presence of leak channels in the plasma membrane that allow potassium ions to pass through more easily. The concentration of sodium ions is actually higher outside the cell, creating an electrochemical gradient that drives sodium ions into the cell when channels are open. The plasma membrane is not completely impermeable to sodium ions, as they can still enter the cell through other channels such as voltage-gated channels. Similarly, the plasma membrane is not completely impermeable to potassium ions, as they can also exit the cell through other channels.

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  • 11. 

    The membrane potential of most neurons at rest is:

    • A.

      A. equal to the equilibrium potential for potassium.

    • B.

      B. equal to the equilibrium potential for sodium.

    • C.

      C. slightly more negative than the equilibrium potential of potassium ion.

    • D.

      D. more positive than the equilibrium potential for potassium.

    • E.

      E. more positive than the equilibrium potential for sodium.

    Correct Answer
    D. D. more positive than the equilibrium potential for potassium.
    Explanation
    The resting membrane potential of most neurons is more positive than the equilibrium potential for potassium because the cell membrane is more permeable to potassium ions at rest. This means that there is a higher concentration of potassium ions inside the cell compared to outside, creating an electrochemical gradient that drives potassium ions out of the cell. As a result, the inside of the cell becomes more negative relative to the outside, leading to a resting membrane potential that is more positive than the equilibrium potential for potassium.

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  • 12. 

    The diffusion potential due to the concentration gradient for Na+ across a nerve cell membrane:

    • A.

      A. favors its movement into the cell at the resting membrane potential.

    • B.

      B. favors its movement out of the cell at the resting membrane potential.

    • C.

      C. is equal and opposite to the electrical potential acting on Na+ at the resting membrane potential.

    • D.

      D. Is in the same direction as the diffusion potential due to the concentration gradient for K+.

    • E.

      E. favors movement of Na+ in the opposite direction as the electrical potential acting on Na+ at the resting membrane potential.

    Correct Answer
    A. A. favors its movement into the cell at the resting membrane potential.
    Explanation
    The correct answer is A because the concentration gradient for Na+ is higher outside the cell compared to inside the cell. This means that there is a higher concentration of Na+ outside the cell, creating a diffusion potential that favors the movement of Na+ into the cell. At the resting membrane potential, the electrical potential acting on Na+ is not strong enough to overcome the concentration gradient, so Na+ tends to move into the cell.

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  • 13. 

    Which would result from an increase in the extracellular concentration of K+ above normal?

    • A.

      A. depolarization of resting nerve cells

    • B.

      B. hyperpolarization of resting nerve cells

    • C.

      C. The potassium equilibrium potential of nerve cells would become more negative.

    • D.

      D. The sodium equilibrium potential would become less positive.

    Correct Answer
    A. A. depolarization of resting nerve cells
    Explanation
    An increase in the extracellular concentration of K+ above normal would result in depolarization of resting nerve cells. This is because K+ plays a crucial role in maintaining the resting membrane potential of nerve cells. An increase in extracellular K+ concentration would disrupt the balance between intracellular and extracellular K+ concentrations, leading to a higher influx of K+ ions into the cell. This influx of positive charge would cause the membrane potential to become less negative, resulting in depolarization of the cell.

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  • 14. 

    Which is TRUE about the Na+, K+ ATPase pump in neurons?

    • A.

      A. It generates a small electrical potential such that the inside is made negative with respect to the outside.

    • B.

      B. It maintains a concentration gradient for K+ such that diffusion forces favor movement of K+ into the cell.

    • C.

      C. It maintains an electrical gradient at the equilibrium potential of K+.

    • D.

      D. It transports equal numbers of sodium and potassium ions with each pump cycle.

    • E.

      E. It pumps 3 Na+ ions into the cell for every 2 K+ ions it pumps out.

    Correct Answer
    A. A. It generates a small electrical potential such that the inside is made negative with respect to the outside.
    Explanation
    The Na+, K+ ATPase pump in neurons generates a small electrical potential that makes the inside of the cell negative compared to the outside. This is known as the resting membrane potential and is essential for the proper functioning of neurons. This electrical potential is created by the pump actively transporting 3 sodium ions out of the cell for every 2 potassium ions it pumps into the cell. This creates an imbalance of positive and negative charges across the cell membrane, resulting in a negative interior. Therefore, option A is the correct answer.

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  • 15. 

    Which of these would occur if the concentration of ATP were depleted in a typical nerve cell?

    • A.

      A. Resting membrane potential would become more negative.

    • B.

      B. Resting membrane potential would become less negative.

    • C.

      C. The concentration gradient for Na+ would remain the same.

    • D.

      D. The resting membrane potential would eventually become positive inside with respect to outside.

    • E.

      E. There would be no change in the resting membrane potential.

    Correct Answer
    B. B. Resting membrane potential would become less negative.
    Explanation
    If the concentration of ATP were depleted in a typical nerve cell, the correct answer is B. Resting membrane potential would become less negative. ATP is required for active transport mechanisms, such as the sodium-potassium pump, which maintains the resting membrane potential by pumping sodium out of the cell and potassium into the cell. Without ATP, the sodium-potassium pump would not be able to function properly, leading to a decrease in the concentration gradient of ions and a less negative resting membrane potential.

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  • 16. 

    Which is FALSE about the equilibrium potential of a given ion across a membrane?

    • A.

      A. It is a function of the concentration of that ion on both sides of the membrane.

    • B.

      B. It is the potential at which there is no net movement of that ion across the membrane.

    • C.

      C. It is the potential difference across the membrane at which an electric force favoring movement of the ion in one direction is equal in magnitude and opposite in direction to the diffusion force provided by the concentration difference of the ion across the membrane.

    • D.

      D. A permeable ion will move in the direction that will tend to bring the membrane potential toward that ion's equilibrium potential.

    • E.

      E. An anion that is in higher concentration inside the cell than outside the cell will have a negative eqilibrium potential.

    Correct Answer
    E. E. An anion that is in higher concentration inside the cell than outside the cell will have a negative eqilibrium potential.
    Explanation
    The equilibrium potential of an ion is determined by the concentration gradient of that ion across the membrane. If an anion is in higher concentration inside the cell than outside, it means that there is a higher concentration of negatively charged ions inside the cell. Since the equilibrium potential is the potential at which there is no net movement of the ion across the membrane, the negative charge inside the cell will create a negative equilibrium potential to balance the diffusion force provided by the concentration difference. Therefore, the statement is true.

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  • 17. 

    The equilibrium potential of K+ ions in nerve cells is about -90 mV. The membrane potential of typical nerve cells at rest is -70 mV. Therefore

    • A.

      A. Increasing the permeability of a resting neuronal membrane to K+ will make the membrane potential more negative inside with respect to outside.

    • B.

      B. In resting neurons, there is a net diffusion of K+ into the cell.

    • C.

      C. changing the resting membrane potential of a neuron to -80 mV would increase K+ diffusion rate out of the cell.

    • D.

      D. potassium is the only permanent ion at rest.

    • E.

      E. there must be another permanent ion with an equilibrium potential more negative than -90 mV.

    Correct Answer
    A. A. Increasing the permeability of a resting neuronal membrane to K+ will make the membrane potential more negative inside with respect to outside.
    Explanation
    Increasing the permeability of a resting neuronal membrane to K+ ions means that more K+ ions will be able to move across the membrane. Since the equilibrium potential of K+ ions is -90 mV, this means that the K+ ions will move out of the cell, making the inside of the membrane more negative with respect to the outside. Therefore, the correct answer is A.

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  • 18. 

    Which of the following statements concerning the permeability of a typical neuron membrane at rest is true?

    • A.

      A. The permeability to Na+ is much greater than the permeability to K+.

    • B.

      B. All of the K+ channels in the membrane are open.

    • C.

      C. The voltage-gated Na+ channels are in the inactivated state.

    • D.

      D. Most of the voltage-gated Na+ channels are in the closed state.

    • E.

      E. There is equal permeability to Na+ and K+.

    Correct Answer
    D. D. Most of the voltage-gated Na+ channels are in the closed state.
    Explanation
    At rest, the neuron membrane has a higher permeability to K+ ions than Na+ ions. This is because most of the voltage-gated Na+ channels are in the closed state, preventing the influx of Na+ ions. On the other hand, the K+ channels are mostly open, allowing K+ ions to flow out of the cell. This difference in permeability contributes to the resting membrane potential of the neuron.

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  • 19. 

    Which is NOT an example of a graded potential?

    • A.

      A. a receptor potential in a sensory receptor cell

    • B.

      B. a depolarizing excitatory postsynaptic potential (EPSP)

    • C.

      C. a hyperpolarizing inhibitory postsynaptic potential (IPSP)

    • D.

      D. a depolarizing pacemaker potential

    • E.

      E. a depolarizing action potential

    Correct Answer
    E. E. a depolarizing action potential
    Explanation
    A depolarizing action potential is not an example of a graded potential because it is an all-or-nothing event that does not vary in magnitude. Graded potentials, on the other hand, are variable in magnitude and can be either depolarizing or hyperpolarizing. Examples of graded potentials include receptor potentials in sensory receptor cells, depolarizing excitatory postsynaptic potentials (EPSPs), hyperpolarizing inhibitory postsynaptic potentials (IPSPs), and depolarizing pacemaker potentials.

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  • 20. 

    An action potential in a neuronal membrane differs from a graded potential in that:

    • A.

      A. an action potential requires the opening of Ca2+ channels, whereas a graded potential does not.

    • B.

      B. an action potential is propagated without decrement, whereas a graded potential decrements with distance.

    • C.

      C. an action potential has a threshold, whereas a graded potential is an all-or-none phenomenon.

    • D.

      D. movement of Na+ and K+ across cell membranes mediate action potentials, while graded potentials do not involve movement of Na+ and K+.

    • E.

      E. action potentials vary in size with the size of a stimulus, while graded potentials do not.

    Correct Answer
    B. B. an action potential is propagated without decrement, whereas a graded potential decrements with distance.
    Explanation
    An action potential in a neuronal membrane is different from a graded potential because it is propagated without decrement, meaning it maintains its strength as it travels along the membrane. In contrast, a graded potential decrements with distance, meaning it becomes weaker the further it travels. This difference in propagation allows action potentials to carry information over long distances in the nervous system, while graded potentials are limited to short distances.

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  • 21. 

    A threshold stimulus applied to an excitable membrane is one that is just sufficient to:

    • A.

      A. trigger an excitatory postsynaptic potential.

    • B.

      B. cause a change in membrane potential.

    • C.

      C. trigger an action potential.

    • D.

      D. be conducted to the axon hillock.

    • E.

      E. depolarize a dendrite.

    Correct Answer
    C. C. trigger an action potential.
    Explanation
    A threshold stimulus is the minimum level of stimulation required to generate an action potential in an excitable membrane. When this threshold is reached, the excitable membrane undergoes a rapid change in membrane potential, resulting in the generation of an action potential. This action potential is a brief electrical impulse that travels along the membrane, allowing for the transmission of signals between neurons. Therefore, the correct answer is C. trigger an action potential.

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  • 22. 

    Which must happen in order for an action potential to begin?

    • A.

      A. The membrane potential must be at the Na+ equilibrium potential.

    • B.

      B. Na+ influx must exceed K+ efflux.

    • C.

      C. The membrane must be out of the relative refractory period.

    • D.

      D. Na+ channels must all be inactivated.

    • E.

      E. Multiple inhibitory postsynaptic potentials (IPSPs) must summate.

    Correct Answer
    B. B. Na+ influx must exceed K+ efflux.
    Explanation
    For an action potential to begin, the influx of sodium ions (Na+) into the cell must exceed the efflux of potassium ions (K+). This is because the opening of voltage-gated Na+ channels causes depolarization of the cell membrane, leading to the initiation of an action potential. The influx of Na+ ions causes the membrane potential to become more positive, while the efflux of K+ ions helps to repolarize the membrane after the action potential is generated. Therefore, option B is the correct answer.

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  • 23. 

    Which describes the response of the voltage-gated channels when an axon is stimulated to threshold?

    • A.

      A. K+ channels open before the Na+ channels.

    • B.

      B. Na+ channels are activated and then inactivated.

    • C.

      C. K+ channels open at the same time as the Na+ channels.

    • D.

      D. K+ channels are opened when Na+ binds to the channel.

    • E.

      E. K+ influx causes Na+ channels to inactivate.

    Correct Answer
    B. B. Na+ channels are activated and then inactivated.
    Explanation
    When an axon is stimulated to threshold, the correct answer B states that Na+ channels are activated and then inactivated. This is because when the axon reaches threshold, the voltage-gated Na+ channels open, allowing Na+ ions to rush into the axon, which causes depolarization and the generation of an action potential. However, shortly after opening, these Na+ channels become inactivated, preventing further influx of Na+ ions. This inactivation is important for the proper propagation of the action potential along the axon.

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  • 24. 

    During the rising (depolarizing) phase of a neuronal action potential

    • A.

      A. PK+ becomes much greater than PNa+.

    • B.

      B. PNa+ becomes much greater than PK+.

    • C.

      C. PK+ is the same as PNa+.

    • D.

      D. Na+ efflux (flow out of the cell) occurs.

    • E.

      E. K+ flows rapidly into the cell.

    Correct Answer
    B. B. PNa+ becomes much greater than PK+.
    Explanation
    During the rising (depolarizing) phase of a neuronal action potential, the correct answer is B. PNa+ becomes much greater than PK+. This is because during this phase, there is a rapid influx of sodium ions (Na+) into the cell through voltage-gated sodium channels. This influx of sodium ions causes the membrane potential to become more positive, leading to depolarization. At the same time, the efflux of potassium ions (K+) is relatively slower compared to the influx of sodium ions, resulting in a greater permeability of sodium ions compared to potassium ions.

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  • 25. 

    Which is true about neuronal membrane electrical and concentration gradients at the peak of the action potential?

    • A.

      A. The electrical gradient is in a direction that would tend to move K+ out of the cell.

    • B.

      B. The concentration gradient for K+ is in a direction that would tend to move it into the cell.

    • C.

      C. The concentration gradient for K+ greatly increases compared to at rest.

    • D.

      D. The concentration gradient for Na+ is in a direction that would tend to move it out of the cell.

    • E.

      E. The electrical gradient for Na+ is in a direction that would tend to move it into the cell.

    Correct Answer
    A. A. The electrical gradient is in a direction that would tend to move K+ out of the cell.
    Explanation
    At the peak of the action potential, the neuronal membrane is depolarized, meaning that the inside of the cell becomes positively charged compared to the outside. This creates an electrical gradient that would tend to move positively charged ions, such as K+, out of the cell. Therefore, option A is correct.

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  • 26. 

    Which is most directly responsible for the falling (repolarizing) phase of the action potential?

    • A.

      A. Voltage-gated Na+ channels are opened.

    • B.

      B. The Na+, K+ pump restores the ions to their original locations inside and outside of the cell.

    • C.

      C. The permeability to Na+ increases greatly.

    • D.

      D. ATPase destroys the energy supply that was maintaining the action potential at its peak.

    • E.

      E. The permeability to K+ increases greatly while that to Na+ decreases.

    Correct Answer
    E. E. The permeability to K+ increases greatly while that to Na+ decreases.
    Explanation
    During the falling (repolarizing) phase of the action potential, the permeability to K+ increases greatly while that to Na+ decreases. This allows K+ ions to flow out of the cell, repolarizing the membrane potential and restoring it to its resting state. At the same time, the decreased permeability to Na+ prevents further influx of Na+ ions, helping to bring the membrane potential back to its resting level. This change in permeability is crucial for the repolarization of the action potential.

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  • 27. 

    Why are action potentials sometimes described as being "all-or-none" in character?

    • A.

      A. The rate of propagation of an action potential down an axon is independent of stimulus strength.

    • B.

      B. They are associated with an absolute refractory period.

    • C.

      C. A supra-threshold stimulus is required to stimulate an action potential during the relative refractory period.

    • D.

      D. An action potential occurs whenever a suprathreshold stimulus occurs, and its amplitude does not vary with the size of a stimulus.

    • E.

      E. Action potentials are always the same size, even when ion gradients vary in size.

    Correct Answer
    D. D. An action potential occurs whenever a suprathreshold stimulus occurs, and its amplitude does not vary with the size of a stimulus.
    Explanation
    Action potentials are described as "all-or-none" because they either occur fully or not at all in response to a suprathreshold stimulus. Once the threshold is reached, an action potential is generated and its amplitude remains constant regardless of the strength of the stimulus. This means that a stronger stimulus will not result in a larger action potential. Therefore, the size of the stimulus does not affect the amplitude of the action potential, leading to the "all-or-none" characteristic.

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  • 28. 

    Which of the following statements about the phases of a neuronal action potential is true?

    • A.

      A. During the after-hyperpolarization phase, the permeability of the membrane to sodium ions is greater than its permeability to potassium ions.

    • B.

      B. During the after-hyperpolarization phase, the permeability of the membrane to potassium ions is greater than its permeability at rest.

    • C.

      C. During the repolarizing phase, the permeability of the membrane to sodium ions is greater than its permeability to potassium ions.

    • D.

      D. Potassium channels inactivate during the depolarization phase.

    • E.

      E. Repolarizing to negative membrane potentials causes the sodium channels to inactivate.

    Correct Answer
    B. B. During the after-hyperpolarization phase, the permeability of the membrane to potassium ions is greater than its permeability at rest.
    Explanation
    During the after-hyperpolarization phase, the permeability of the membrane to potassium ions is greater than its permeability at rest. This is because after an action potential, the membrane potential becomes more negative than the resting potential, known as hyperpolarization. During this phase, potassium channels remain open, allowing potassium ions to flow out of the cell, which increases the permeability of the membrane to potassium ions. This increased permeability to potassium ions contributes to the restoration of the resting membrane potential.

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  • 29. 

    Which of the following statements about the refractory period of a membrane is true?

    • A.

      A. The absolute refractory period refers to the period of time during which another action potential cannot be initiated in that part of the membrane that is undergoing an action potential, no matter how great the strength of the stimulus.

    • B.

      B. The relative refractory period refers to the period of time during which another action potential can be initiated in that part of the membrane that has just undergone an action potential if a stronger than normal stimulus is applied.

    • C.

      C. The refractory period prevents the action potential from spreading back over the part of the membrane that just underwent an action potential.

    • D.

      D. The refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials.

    • E.

      E. All of the above choices are correct.

    Correct Answer
    E. E. All of the above choices are correct.
    Explanation
    The correct answer is E. All of the above choices are correct.

    The refractory period of a membrane refers to the period of time during which the membrane is unable to generate another action potential. The absolute refractory period (A) is the period during which another action potential cannot be initiated, regardless of the strength of the stimulus. The relative refractory period (B) is the period during which another action potential can be initiated if a stronger than normal stimulus is applied. The refractory period also prevents the action potential from spreading back over the part of the membrane that just underwent an action potential (C). Finally, the refractory period places an upper limit on the frequency with which a nerve cell can conduct action potentials (D). Therefore, all of the statements are true.

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  • 30. 

    The relative refractory period of an axon coincides with the period of

    • A.

      A. activation and inactivation of voltage-dependent Na+ channels.

    • B.

      B. Na+ permeability that is greater than that during the depolarization phase.

    • C.

      C. increased K+ flux into the cell.

    • D.

      D. increased K+ permeability of the cell.

    • E.

      E. Increased Na+ flux through K+ channels.

    Correct Answer
    D. D. increased K+ permeability of the cell.
    Explanation
    The relative refractory period of an axon refers to the period of time following an action potential where it is possible for another action potential to be generated, but with a higher threshold. This is due to the increased K+ permeability of the cell, which causes an efflux of potassium ions, leading to hyperpolarization of the cell membrane. This hyperpolarization makes it more difficult for the cell to reach the threshold for generating another action potential. Therefore, option D, increased K+ permeability of the cell, is the correct answer as it accurately describes the mechanism behind the relative refractory period.

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  • 31. 

    Neuronal axons typically have abundant

    • A.

      A. voltage-gated channels for Na+ that open in response to depolarization.

    • B.

      B. voltage-gated channels for K+ that open in response to hyperpolarization.

    • C.

      C. receptor-mediated channels for Na+.

    • D.

      D. receptor-mediated channels for K+.

    • E.

      E. voltage-gated channels for Ca2+.

    Correct Answer
    A. A. voltage-gated channels for Na+ that open in response to depolarization.
    Explanation
    Neuronal axons typically have abundant voltage-gated channels for Na+ that open in response to depolarization. This is because during an action potential, the axon membrane depolarizes, meaning the inside of the axon becomes more positive. The opening of these Na+ channels allows Na+ ions to flow into the axon, further depolarizing the membrane and propagating the action potential along the axon. Therefore, the presence of these voltage-gated Na+ channels is crucial for the transmission of electrical signals in neurons.

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  • 32. 

    Which of the following statements regarding action potentials generated in a neuronal membrane is not true?

    • A.

      A. Action potentials travel decrementally down the membrane.

    • B.

      B. An action potential generates a new action potential in an adjacent area of membrane.

    • C.

      C. An action potential generates a local current that depolarizes adjacent membrane to threshold potential.

    • D.

      D. Action potentials are usually initiated at the initial segment of a neuron.

    • E.

      E. An action potential generated by a threshold stimulus is the same size as one generated by a suprathreshold stimulus.

    Correct Answer
    A. A. Action potentials travel decrementally down the membrane.
    Explanation
    Action potentials do not travel decrementally down the membrane. Instead, they propagate in an all-or-nothing manner, meaning that once initiated, they travel along the membrane at a constant amplitude and speed.

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  • 33. 

    Which of the following statements concerning the properties of action potentials is true?

    • A.

      A. The rate of propagation of an action potential down an axon is independent of stimulus strength.

    • B.

      B. Action potentials can undergo summation.

    • C.

      C. A supra-threshold stimulus can stimulate an action potential during the absolute refractory period.

    • D.

      D. Action potentials generally propagate from the axon terminal toward the initial segment.

    • E.

      E. Increasing the size of a stimulus will increase the amplitude of an action potential.

    Correct Answer
    A. A. The rate of propagation of an action potential down an axon is independent of stimulus strength.
    Explanation
    The rate of propagation of an action potential down an axon is independent of stimulus strength. This means that once an action potential is initiated, it will travel down the axon at a constant speed regardless of the strength of the stimulus that initiated it. The strength of the stimulus only determines whether or not an action potential will be generated in the first place, but it does not affect the speed at which it travels.

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  • 34. 

    How is the strength of a stimulus encoded by neurons?

    • A.

      A. by the size of action potentials

    • B.

      B. by the frequency of action potentials

    • C.

      C. by the duration of action potentials

    • D.

      D. by whether the action potential peak is positive or negative

    Correct Answer
    B. B. by the frequency of action potentials
    Explanation
    The strength of a stimulus is encoded by neurons through the frequency of action potentials. When a stimulus is stronger, it causes the neurons to fire action potentials at a higher frequency. This increased frequency of action potentials allows for more information about the strength of the stimulus to be transmitted to the brain. Therefore, the frequency of action potentials is a key factor in encoding the strength of a stimulus.

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  • 35. 

    Which of the following statements concerning the rate of action potential propagation is true?

    • A.

      A. It is faster in small-diameter axons than in large-diameter axons.

    • B.

      B. It is faster for a strong stimulus than for a weak one.

    • C.

      C. It is faster in myelinated axons than in nonmyelinated axons.

    • D.

      D. It is faster in the dendrites than in the axon.

    • E.

      E. It occurs at the same rate in all axons, regardless of their diameter.

    Correct Answer
    C. C. It is faster in myelinated axons than in nonmyelinated axons.
    Explanation
    The correct answer is C. It is faster in myelinated axons than in nonmyelinated axons. This is because myelin acts as an insulating sheath around the axon, allowing for faster propagation of the action potential. In nonmyelinated axons, the action potential must travel continuously along the entire length of the axon, which is slower compared to myelinated axons where the action potential "jumps" from one node of Ranvier to the next, known as saltatory conduction. This allows for faster and more efficient transmission of the action potential.

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  • 36. 

    An action potential does not re-stimulate the adjacent membrane that was previously depolarized because

    • A.

      A. stimulation is inhibited by the myelin sheath.

    • B.

      B. it is impossible for an action potential to be propagated along an axon toward the nerve cell body.

    • C.

      C. the resting membrane potential of the axon is too positive.

    • D.

      D. the resting membrane potential of the axon is too negative.

    • E.

      E. that area of the membrane is in the absolutely refractory period.

    Correct Answer
    E. E. that area of the membrane is in the absolutely refractory period.
    Explanation
    An action potential does not re-stimulate the adjacent membrane that was previously depolarized because that area of the membrane is in the absolutely refractory period. During this period, the voltage-gated sodium channels responsible for generating an action potential are inactivated and cannot be reopened until the membrane potential returns to its resting state. This prevents the action potential from propagating backward and ensures that the signal moves in one direction along the axon.

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  • 37. 

    The regions of axon membrane that lie between regions of myelin are the

    • A.

      A. islets of Langerhans.

    • B.

      B. nodes of Ranvier.

    • C.

      C. synaptic membranes.

    • D.

      D. glial cells.

    • E.

      E. dens of iniquities.

    Correct Answer
    B. B. nodes of Ranvier.
    Explanation
    The regions of axon membrane that lie between regions of myelin are called nodes of Ranvier. These nodes are small gaps in the myelin sheath where the axon is exposed. They play a crucial role in the conduction of nerve impulses by allowing the electrical signals to jump from one node to another, which speeds up the transmission of the signal along the axon.

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  • 38. 

    Which is FALSE about interneurons?

    • A.

      A. They receive synaptic input from other other neurons in the CNS.

    • B.

      B. They sum excitatory and inhibitory synaptic inputs.

    • C.

      C. They deliver synaptic input on other neurons.

    • D.

      D. They make synapses on effector organs in the PNS.

    • E.

      E. They can transmit information between afferent neurons and efferent neurons.

    Correct Answer
    D. D. They make synapses on effector organs in the PNS.
    Explanation
    Interneurons are a type of neuron that are found entirely within the central nervous system (CNS). They receive synaptic input from other neurons in the CNS (A), summing both excitatory and inhibitory inputs (B), and deliver synaptic input to other neurons (C). However, they do not make synapses on effector organs in the peripheral nervous system (PNS) (D). Instead, interneurons primarily function in transmitting information between afferent neurons (sensory neurons) and efferent neurons (motor neurons) (E).

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  • 39. 

    Exocytosis of neurotransmitter into the synaptic cleft is triggered by an influx of ______ in response to the arrival of an action potential in the axon terminal.

    • A.

      A. K+

    • B.

      B. Na+

    • C.

      C. Ca2+

    • D.

      D. ATP

    • E.

      E. Cl-

    Correct Answer
    C. C. Ca2+
    Explanation
    Exocytosis is the process by which neurotransmitters are released from the axon terminal into the synaptic cleft. This release is triggered by an influx of calcium ions (Ca2+) in response to the arrival of an action potential. Calcium ions play a crucial role in the fusion of synaptic vesicles containing neurotransmitters with the cell membrane, allowing the neurotransmitters to be released into the synaptic cleft and bind to receptors on the postsynaptic neuron. Therefore, the correct answer is C. Ca2+.

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  • 40. 

    The main role of calcium ions at chemical synapses is to

    • A.

      A. depolarize the axon terminal of the presynaptic cell.

    • B.

      B. bind to neurotransmitter receptors on the postsynaptic cell.

    • C.

      C. cause fusion of synaptic vesicles with the plasma membrane of the axon terminal.

    • D.

      D. interfere with IPSPs in the postsynaptic cell.

    • E.

      E. diffuse across the synaptic space and enter the postsynaptic cell.

    Correct Answer
    C. C. cause fusion of synaptic vesicles with the plasma membrane of the axon terminal.
    Explanation
    Calcium ions play a crucial role in the process of neurotransmission at chemical synapses. When an action potential reaches the axon terminal of the presynaptic cell, it causes voltage-gated calcium channels to open. This allows calcium ions to enter the axon terminal. The influx of calcium ions then triggers the fusion of synaptic vesicles, which contain neurotransmitters, with the plasma membrane of the axon terminal. This fusion leads to the release of neurotransmitters into the synaptic cleft, allowing them to bind to neurotransmitter receptors on the postsynaptic cell and initiate a response. Therefore, the main role of calcium ions at chemical synapses is to cause fusion of synaptic vesicles with the plasma membrane of the axon terminal.

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  • 41. 

    At an excitatory chemical synapse between two neurons,

    • A.

      A. there is increased permeability of the postsynaptic cell to both Na+ and K+.

    • B.

      B. a small hyperpolarization of the postsynaptic membrane occurs when the synapse is activated.

    • C.

      C. an action potential in the presynaptic neuron always causes an action potential in the postsynaptic neuron.

    • D.

      D. excitation occurs because K+ enters the postsynaptic cell.

    • E.

      E. action potentials spread through gap junctions between cells.

    Correct Answer
    A. A. there is increased permeability of the postsynaptic cell to both Na+ and K+.
    Explanation
    At an excitatory chemical synapse between two neurons, there is increased permeability of the postsynaptic cell to both Na+ and K+. This allows both Na+ and K+ ions to flow into the postsynaptic cell, causing depolarization and making it more likely for an action potential to be generated. This increased permeability is due to the opening of specific ion channels in the postsynaptic membrane in response to the release of neurotransmitters from the presynaptic neuron. This influx of positive ions contributes to the excitatory nature of the synapse.

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  • 42. 

    An inhibitory postsynaptic potential:

    • A.

      A. is produced by simultaneous increases in permeability to both Na+ and K+.

    • B.

      B. occurs when a ligand-gated ion channel increases its permeability to K+.

    • C.

      C. is a small depolarization in a postsynaptic cell.

    • D.

      D. can be summed with other IPSPs to trigger an action potential in the postsynaptic cell.

    • E.

      E. is produced by an increase in permeability to only Na+.

    Correct Answer
    B. B. occurs when a ligand-gated ion channel increases its permeability to K+.
    Explanation
    An inhibitory postsynaptic potential (IPSP) is a small hyperpolarization in a postsynaptic cell, not a depolarization as mentioned in option C. It is caused by the opening of ligand-gated ion channels that increase the permeability to K+ ions, leading to an efflux of positive ions and making the cell more negative inside. This hyperpolarization makes it less likely for an action potential to be generated in the postsynaptic cell. Thus, option B correctly describes an IPSP.

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  • 43. 

    Which of the following statements about EPSPs is false?

    • A.

      A. They are produced by the opening of chemically-gated sodium channels.

    • B.

      B. They transmit signals over relatively short distances.

    • C.

      C. They depolarize postsynaptic cell membranes.

    • D.

      D. They are able to summate.

    • E.

      E. They are always the same amplitude.

    Correct Answer
    E. E. They are always the same amplitude.
    Explanation
    EPSPs, or excitatory postsynaptic potentials, are graded potentials that occur in the postsynaptic membrane of a neuron. These potentials are produced by the opening of chemically-gated sodium channels (A), which allow sodium ions to enter the cell and depolarize the membrane (C). EPSPs are able to summate (D), meaning that multiple EPSPs can add together to reach the threshold for an action potential. However, EPSPs do not always have the same amplitude (E). The amplitude of an EPSP can vary depending on factors such as the strength of the stimulus and the number of synapses activated.

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  • 44. 

    An EPSP:

    • A.

      A. is a direct result of the opening of ligand-gated channels permeable to both Na+ and K+ ions.

    • B.

      B. is a direct result of the opening of voltage-gated channels permeable to both Na+ and K+ ions.

    • C.

      C. stabilizes the membrane to remain at its resting potential.

    • D.

      D. opens voltage-gated Ca2+ channels in the presynaptic membrane.

    • E.

      E. occurs when voltage-gated Cl- channels open in a postsynaptic cell membrane.

    Correct Answer
    A. A. is a direct result of the opening of ligand-gated channels permeable to both Na+ and K+ ions.
    Explanation
    An EPSP (excitatory postsynaptic potential) is a depolarization of the postsynaptic membrane potential that brings the neuron closer to its threshold for firing an action potential. This depolarization is caused by the opening of ligand-gated channels, which are permeable to both Na+ and K+ ions. When these channels open, Na+ ions enter the cell and K+ ions exit the cell, leading to a net positive charge inside the cell and depolarization. Therefore, option A is the correct answer.

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  • 45. 

    Which best describes temporal summation?

    • A.

      A. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated.

    • B.

      B. It only refers to addition of EPSPs.

    • C.

      C. Two synapses on different regions of a cell are stimulated at the same time.

    • D.

      D. It always brings a postsynaptic cell to threshold.

    • E.

      E. The size of an EPSP depends on the size of the stimulus.

    Correct Answer
    A. A. A synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated.
    Explanation
    Temporal summation refers to the phenomenon where a synapse is stimulated a second time before the effect of a first stimulus at the synapse has terminated. This means that the second stimulus is added to the residual effect of the first stimulus, resulting in a cumulative effect on the postsynaptic cell. This process can lead to the generation of an action potential if the cumulative effect reaches the threshold for firing. It is important to note that temporal summation can occur with both excitatory and inhibitory inputs.

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  • 46. 

    A postsynaptic neuron has three presynaptic inputs - from neurons X, Y, and Z. Stimulation of neuron X causes the postsynaptic neuron to depolarize by 0.5 mV. When X and Y are stimulated simultaneously, the postsynaptic neuron depolarizes by 1 mV. When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. What is most likely true about presynaptic neurons Y and Z?

    • A.

      A. They are both excitatory.

    • B.

      B. They are both inhibitory

    • C.

      C. Y is excitatory and Z is inhibitory.

    • D.

      D. Z is excitatory and Y is inhibitory.

    Correct Answer
    C. C. Y is excitatory and Z is inhibitory.
    Explanation
    The postsynaptic neuron depolarizes when neuron X is stimulated, indicating that neuron X is excitatory. When both X and Y are stimulated, the postsynaptic neuron depolarizes even more, suggesting that neuron Y is also excitatory. However, when both X and Z are stimulated, there is no change in the membrane potential, indicating that neuron Z is inhibitory. Therefore, it is most likely true that presynaptic neuron Y is excitatory and presynaptic neuron Z is inhibitory.

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  • 47. 

    A postsynaptic neuron has three presynaptic inputs - from neurons X, Y, and Z. When X and Y are stimulated simultaneously and repeatedly, the postsynaptic neuron reaches threshold and undergoes an action potential. When X and Z are stimulated simultaneously, however, there is no change in the membrane potential of the postsynaptic neuron. The simultaneous stimulation of X and Y is an example of

    • A.

      A. temporal summation.

    • B.

      B. presynaptic inhibition.

    • C.

      C. spatial summation.

    • D.

      D. neuronal divergence.

    • E.

      E. presynaptic facilitation.

    Correct Answer
    C. C. spatial summation.
    Explanation
    Spatial summation refers to the process by which the postsynaptic neuron integrates signals from multiple presynaptic inputs that are spatially separated. In this scenario, when neurons X and Y are stimulated simultaneously and repeatedly, their signals are combined at the postsynaptic neuron, reaching threshold and resulting in an action potential. This demonstrates spatial summation because the signals from X and Y, which are spatially separated inputs, are combined to generate an action potential. On the other hand, when X and Z are stimulated simultaneously, there is no change in the membrane potential of the postsynaptic neuron, indicating that the signals from these inputs do not summate and do not reach threshold. Therefore, the correct answer is C. spatial summation.

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  • 48. 

    Which is TRUE about the initial segment of an axon?

    • A.

      A. Its threshold potential is more positive than that of the cell body and dendrites.

    • B.

      B. Its threshold potential is more negative than that of the cell body and dendrites.

    • C.

      C. Synapses far from the initial segment are more effective in influencing whether an action potential will be generated in the axon than are synapses close to the initial segment.

    • D.

      D. It is the region where neurotransmitter vesicles are docked and ready to be released by exocytosis.

    • E.

      E. It can only conduct graded potentials because it lacks voltage-gated Na+ channels.

    Correct Answer
    B. B. Its threshold potential is more negative than that of the cell body and dendrites.
    Explanation
    The initial segment of an axon is the region where the action potential is initiated. It contains a high density of voltage-gated sodium channels, which are responsible for depolarizing the membrane and generating an action potential. The threshold potential is the membrane potential at which an action potential is triggered. In order for an action potential to be generated, the membrane potential at the initial segment must reach a certain level, which is more negative than the threshold potential of the cell body and dendrites. Therefore, option B is the correct answer.

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  • 49. 

    A presynaptic synapse:

    • A.

      A. is a synapse between an axon terminal and a dendrite that can be either excitatory or inhibitory.

    • B.

      B. is a synapse between an axon terminal and another axon's terminal that can be either excitatory or inhibitory.

    • C.

      C. is any synapse onto a cell body, and they can be either stimulatory or inhibitory.

    • D.

      D. is a synapse between an axon terminal and a dendrite of the same cell, which is always inhibitory.

    • E.

      E. is a synapse between an axon terminal and another axon terminal that is always inhibitory.

    Correct Answer
    B. B. is a synapse between an axon terminal and another axon's terminal that can be either excitatory or inhibitory.
    Explanation
    A presynaptic synapse refers to a synapse where the signal transmission occurs from the axon terminal of one neuron to the terminal of another neuron. Option B correctly states that a presynaptic synapse is between an axon terminal and another axon's terminal. It also mentions that this type of synapse can be either excitatory or inhibitory, which is accurate as the release of neurotransmitters at the synapse can either increase or decrease the likelihood of an action potential in the postsynaptic neuron.

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  • 50. 

    Neuron X makes inhibitory axon-axon synaptic contact with neuron Y at the synapse of Y and neuron Z. Which will occur when action potentials are stimulated in neuron X?

    • A.

      A. Neuron Y will be inhibited from reaching the threshold to fire an action potential.

    • B.

      B. The release of neurotransmitter by neuron Y will be inhibited.

    • C.

      C. The synapse between neurons Y and Z will be changed from an excitatory synapse to an inhibitory one.

    • D.

      D. Neurons Y and Z will both be more likely to reach threshold and fire an action potential.

    • E.

      E. Neurons Y and Z will both be less likely to reach threshold and fire an action potential.

    Correct Answer
    B. B. The release of neurotransmitter by neuron Y will be inhibited.
    Explanation
    When action potentials are stimulated in neuron X, it will make inhibitory axon-axon synaptic contact with neuron Y at the synapse of Y and neuron Z. This means that the release of neurotransmitter by neuron Y will be inhibited. Inhibitory synapses prevent the postsynaptic neuron from firing an action potential by hyperpolarizing the postsynaptic membrane or decreasing its excitability. Therefore, in this scenario, the release of neurotransmitter by neuron Y will be inhibited, preventing it from transmitting signals to neuron Z.

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  • Mar 22, 2023
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