Neurotransmitters and Their Functions
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Neurotransmitters and Their Functions

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Questions and Answers

Which neurotransmitter is primarily responsible for inhibitory signaling in the central nervous system?

  • Aspartate
  • Glutamate
  • Acetylcholine
  • Glycine (correct)

    • What is the primary excitatory neurotransmitter in the central nervous system?

  • Serotonin
  • Glycine
  • GABA
  • Glutamate (correct)

    • Which category of neurotransmitters does GABA belong to?

  • Peptides
  • Trace Amines
  • Purines
  • Amino Acids (correct)

    • Which neurotransmitter category includes molecules like serotonin and dopamine?

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

    What role does aspartate play in neurotransmission?

    <p>Excitatory, but less widespread than glutamate</p> Signup and view all the answers

    What occurs when there is an action potential in a neuron?

    <p>Potassium ions leave the cell.</p> Signup and view all the answers

    What type of ion is associated with excitatory synapses?

    <p>Sodium ion</p> Signup and view all the answers

    What triggers the opening of voltage-gated sodium channels?

    <p>Sufficient diffusion of sodium ions to the axon hillock</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with inhibitory synapses?

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

    What happens when ligand-gated sodium channels are activated?

    <p>Sodium ions enter and diffuse through the cytoplasm.</p> Signup and view all the answers

    What is the primary function of the synaptic terminal?

    <p>Store neurotransmitters</p> Signup and view all the answers

    Which of the following statements accurately describes dendrites?

    <p>They act as the main receptive surfaces of the neuron.</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with excitatory postsynaptic potentials in the CNS?

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

    What describes the process by which an action potential is generated in neurons?

    <p>It requires summation of excitatory signals.</p> Signup and view all the answers

    Which component is primarily responsible for transmitting action potentials to other cells?

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

    What is the primary role of neurotransmitters?

    <p>To act as chemical messengers at synapses</p> Signup and view all the answers

    What is the relationship between the synaptic cleft and synaptic transmission?

    <p>Neurotransmitters cross the synaptic cleft during transmission.</p> Signup and view all the answers

    Which of the following statements about synaptic vesicles is correct?

    <p>They contain chemical messengers released upon an action potential.</p> Signup and view all the answers

    What initiates an action potential in the post-synaptic cell?

    <p>Influx of sodium ions</p> Signup and view all the answers

    For another action potential to be generated after an initial one, what is required?

    <p>An influx of positively charged ions</p> Signup and view all the answers

    What type of ion channels must be activated to generate another action potential?

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

    What results from the summation at the synaptic connections to the postsynaptic cell?

    <p>Increased likelihood of action potential generation</p> Signup and view all the answers

    What role do dendrites play in relation to action potentials?

    <p>They receive signals that can lead to action potentials</p> Signup and view all the answers

    Which of the following ions primarily facilitates the creation of an action potential?

    <p>Sodium ions</p> Signup and view all the answers

    What is the primary effect of positively charged ions influx on the neuron?

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

    Which statement about action potentials is accurate?

    <p>They depend on the influx of sodium ions for initiation</p> Signup and view all the answers

    What is the threshold membrane potential necessary to generate an action potential?

    <p>-55</p> Signup and view all the answers

    Which process occurs immediately after depolarization reaches the threshold?

    <p>2.45</p> Signup and view all the answers

    What is the main role of inhibitory postsynaptic potentials (IPSPs) in neuronal activity?

    <p>1.55</p> Signup and view all the answers

    What triggers the opening of voltage-gated sodium channels during the action potential initiation?

    <p>1</p> Signup and view all the answers

    During the repolarization phase of an action potential, which ion primarily leaves the neuron?

    <p>2.22</p> Signup and view all the answers

    What happens to the inactivation gate of sodium channels once the action potential is generated?

    <p>0.1</p> Signup and view all the answers

    What is the primary function of the Na+/K+ pump in the context of action potentials?

    <p>2</p> Signup and view all the answers

    Which ion does NOT have an inactivation gate during action potential changes?

    <p>0.4</p> Signup and view all the answers

    What occurs during hyperpolarization of a neuron?

    <p>-90</p> Signup and view all the answers

    Which of the following statements about action potentials is correct?

    <p>1.4</p> Signup and view all the answers

    What is the resting membrane potential of a typical neuron?

    <p>70</p> Signup and view all the answers

    What primarily drives the movement of sodium ions into the neuron during depolarization?

    <p>1.6</p> Signup and view all the answers

    Which of the following best describes the state of voltage-gated sodium channels during repolarization?

    <p>1.7</p> Signup and view all the answers

    What is the effect of EPSPs on a neuron's membrane potential?

    <p>1</p> Signup and view all the answers

    What term describes the diffusion of positively charged sodium ions into a postsynaptic cell?

    <p>Excitatory postsynaptic potential</p> Signup and view all the answers

    Which of the following statements is true regarding synapses on the soma compared to those on dendrites?

    <p>Synapses on soma have a larger effect.</p> Signup and view all the answers

    What triggers the opening of voltage-gated sodium channels in the context of postsynaptic responses?

    <p>Changes in membrane potential</p> Signup and view all the answers

    Which of the following best describes the impact of local excitatory postsynaptic potentials (ePSPs) on neuronal activity?

    <p>They can spread through the soma and promote action potentials.</p> Signup and view all the answers

    In which phase of neuronal transmission do voltage-gated sodium channels primarily play a pivotal role?

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

    What happens to potassium ions when potassium channels open in a neuron?

    <p>They leave the cell.</p> Signup and view all the answers

    What is the primary factor that influences the movement of ions across the membrane?

    <p>Ionic charge and concentration gradient</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between electrical potential and ion movement?

    <p>Positively charged ions are repelled by positive electrical potentials.</p> Signup and view all the answers

    How does the membrane potential change when potassium ions leave the cell?

    <p>It becomes more negative.</p> Signup and view all the answers

    What occurs when there is a decreased potential difference across the membrane?

    <p>The membrane is primed for depolarization.</p> Signup and view all the answers

    What is the primary reason that the resting membrane potential is measured as a negative value?

    <p>Higher concentration of negatively charged ions inside the cell</p> Signup and view all the answers

    Which of the following describe gaseous neurotransmitters?

    <p>Produced on demand without storage</p> Signup and view all the answers

    How are neurotransmitter precursors made available for synthesis in neurons?

    <p>Acquired by selective transporters or as by-products of cellular processes</p> Signup and view all the answers

    What is the typical resting potential value of a neuron?

    <p>-70</p> Signup and view all the answers

    Which neurotransmitter is considered a trace amine?

    <p>Beta-phenylethylamine (PEA)</p> Signup and view all the answers

    What primarily affects the difference in charge across a neuron's membrane at rest?

    <p>Presence of negatively charged organic anions inside the cell</p> Signup and view all the answers

    Where are the enzymes necessary for neurotransmitter synthesis typically produced?

    <p>In the cell body and transported to the terminal</p> Signup and view all the answers

    Which gas is not considered a gaseous neurotransmitter?

    <p>Ammonia (NH3)</p> Signup and view all the answers

    What is the primary function of autoreceptors in neuronal communication?

    <p>To sense and regulate the concentration of neurotransmitters</p> Signup and view all the answers

    How are neurotransmitters typically removed from the synaptic cleft?

    <p>Through specific transporter proteins and degradation by enzymes</p> Signup and view all the answers

    What mechanism do transporter proteins utilize to move neurotransmitters across the presynaptic membrane?

    <p>Symport combining sodium ions and neurotransmitters</p> Signup and view all the answers

    What role do glial cells play in neurotransmitter management?

    <p>They participate in reuptake and degradation processes</p> Signup and view all the answers

    Which statement about neurotransmitter degradation is accurate?

    <p>Specific enzymes are responsible for breaking down certain neurotransmitters</p> Signup and view all the answers

    What is a common misbelief about the transporters of neurotransmitters?

    <p>They are highly selective and vary for different neurotransmitters</p> Signup and view all the answers

    What may occur if neurotransmitter reuptake is impaired?

    <p>Increased frequency of synaptic events due to prolonged neurotransmitter action</p> Signup and view all the answers

    What is not a method used to deactivate neurotransmitters in the synaptic cleft?

    <p>Absorption directly by postsynaptic membranes</p> Signup and view all the answers

    What is the result of the influx of negatively charged chloride ions in the postsynaptic cell?

    <p>It creates an inhibitory postsynaptic potential.</p> Signup and view all the answers

    What prevents voltage-gated sodium ion channels from opening in the postsynaptic cell?

    <p>The presence of chloride ions leading to hyperpolarization.</p> Signup and view all the answers

    What phenomenon describes the summation of multiple synaptic events required to reach action potential threshold?

    <p>Spatial summation</p> Signup and view all the answers

    What must occur for a postsynaptic neuron to generate an action potential after receiving excitatory input?

    <p>The excitatory postsynaptic potentials must exceed inhibitory influences.</p> Signup and view all the answers

    How is an inhibitory postsynaptic potential (IPSP) characterized in terms of membrane potential?

    <p>It results in a more negative membrane potential.</p> Signup and view all the answers

    Which action describes what occurs during synaptic transmission in relation to a presynaptic neuron?

    <p>Neurotransmitters are released into the synaptic cleft upon activation.</p> Signup and view all the answers

    Which factors influence the likelihood of postsynaptic action potential initiation?

    <p>The rate of action potentials fired by presynaptic neurons.</p> Signup and view all the answers

    What is the effect of the postsynaptic cell receiving insufficient excitatory signals?

    <p>It may remain at resting potential.</p> Signup and view all the answers

    How can multiple simultaneous presynaptic neuron activations impact a postsynaptic neuron?

    <p>They can collectively increase the chances of generating an action potential.</p> Signup and view all the answers

    What role do ligand-gated chloride channels play during neurotransmission?

    <p>They allow chloride ions to enter, influencing the postsynaptic membrane potential.</p> Signup and view all the answers

    What is the significance of the summation of synaptic events in the context of action potentials?

    <p>It allows for the integration of numerous excitatory and inhibitory signals.</p> Signup and view all the answers

    What buffering mechanism exists to prevent excessive action potential generation in the postsynaptic cell?

    <p>Inhibition through increased chloride permeability.</p> Signup and view all the answers

    What occurs when a single excitatory postsynaptic potential (ePSP) is insufficient?

    <p>It fails to reach the action potential threshold on its own.</p> Signup and view all the answers

    Which condition must be met for a postsynaptic neuron's action potential to be considered likely?

    <p>Accumulated excitatory signals must reach a critical threshold.</p> Signup and view all the answers

    Study Notes

    Gaseous Neurotransmitters

    • Gaseous neurotransmitters are unique because they are not stored in synaptic vesicles and are produced on demand.
    • Examples of gaseous neurotransmitters include Nitric Oxide (NO), Carbon Monoxide (CO), and Hydrogen Sulphide (H2S).

    Trace Amines

    • Trace amines are related to classic monoamines but are found in the brain at much lower levels.
    • Examples of trace amines include Beta-phenylethylamine (PEA), Tyramine, Tryptamine, and Octopamine.

    Neurotransmitter Synthesis

    • Neurotransmitters are synthesized locally within the axon terminal.
    • Precursors necessary for synthesis are either taken up by selective transporters on the membrane of the terminal or readily available byproducts of cellular processes that take place within the neuron itself.
    • Enzymes for synthesizing neurotransmitters are usually produced in the cell body and transported to the terminal by slow axonal transport.

    The Membrane Potential

    • The resting potential is measured as a negative value because of the higher concentration of negatively charged ions (anions) inside the cell.
    • The membrane potential measures the difference in charges between the inside of the cell and the outside.
    • At rest, the inside of the cell is much more negatively charged than the outside, around -70mV, although this value varies between neurons.

    The Resting Potential

    • The resting potential refers to the membrane potential when the cell is at rest.
    • The difference in voltage inside compared to outside is -70mv (this is called potential difference).
    • This difference is due to the concentration of anions (like organic anions and PO4) inside the cell and a higher concentration of Sodium ions outside the cell.

    The Resting Potential

    • Positively charged ions are attracted to the side of the membrane with a more negative electrical potential.
    • Ion concentration gradients and ion charge gradients create an electrochemical gradient across the membrane.
    • This electrochemical gradient contributes to the membrane potential.

    Membrane Potential and Ion Movement

    • The potential difference across the membrane can be influenced by the opening and closing of ion channels.
    • Opening potassium channels will increase the membrane potential (making it more negative), as potassium ions will leave the cell, decreasing the positive charge inside the cell.

    Autoreceptor

    • Autoreceptors are sensitive to higher concentrations of the same neurotransmitter.

    Neurotransmitter Deactivation

    • The action of neurotransmitters must be terminated after release.
    • There are several mechanisms for neurotransmitter deactivation:
      • Taken up by the presynaptic neuron via a transporter protein
      • Inactivated/degraded by enzymes in the synaptic cleft
      • Taken up by glial cells
      • Diffuses away into the periphery.

    Neurotransmitter Reuptake

    • Specific transporter proteins remove most small-molecule neurotransmitters (or their metabolites) from the synaptic cleft, delivering them back to the presynaptic terminal for reuse.
    • These transporters are highly specific.
    • Reuptake also occurs at glial cells.

    Neurotransmitter Reuptake Mechanism

    • Transporters usually utilize symport to transport neurotransmitters across the membrane of the presynaptic neuron.
    • The neurotransmitter binds to sodium ions, and sodium ions flow down their concentration and electrical gradient, pulling the neurotransmitter into the cell against its own gradient.

    Neurotransmitter Degradation

    • After a neurotransmitter has been secreted into the synaptic cleft, it must be removed to enable the postsynaptic cell to produce another synaptic event.
    • Neurotransmitters can undergo degradation by specific enzymes.

    Excitatory Postsynaptic Potential (EPSP)

    • The influx of positively charged sodium ions into the postsynaptic cell is called an excitatory postsynaptic potential.
    • These ions can spread through the soma.
    • Synapses on the soma have a larger effect than those on dendrites.

    Inhibitory Postsynaptic Potential (IPSP)

    • The influx of negatively charged chloride ions into the postsynaptic cell is called an inhibitory postsynaptic potential.
    • These ions cause a more negative membrane potential, preventing voltage-gated sodium ion channels from opening.
    • This can prevent an action potential from being initiated in the postsynaptic cell.

    Summation

    • A single EPSP is usually unable to bring a postsynaptic neuron to the action potential threshold.
    • Postsynaptic responses result from the summation of many synaptic events from many incoming neurons.
    • The probability of initiating an action potential is higher when multiple presynaptic neurons are firing action potentials simultaneously.

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