Neurotransmitter Receptors Quiz
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Questions and Answers

What occurs when neurotransmitters are removed from their receptors?

  • They produce continuous postsynaptic effects.
  • They degrade only in the synaptic cleft.
  • They bind to a different type of receptor.
  • They might be reabsorbed by astrocytes or presynaptic terminals. (correct)
  • Which synaptic potential is characterized by transient depolarization of the postsynaptic membrane?

  • Inhibitory postsynaptic potential (IPSP)
  • Both EPSP and IPSP cause depolarization.
  • Excitatory postsynaptic potential (EPSP) (correct)
  • Synaptic delay influences EPSP generation.
  • What role do GABA and glycine play in neural signaling?

  • They primarily cause excitatory postsynaptic potentials.
  • They are responsible for synaptic delays.
  • They contribute to transient hyperpolarization. (correct)
  • They serve only in the peripheral nervous system.
  • Which of the following receptors are classified as ionotropic receptors?

    <p>Nicotinic ACh receptors</p> Signup and view all the answers

    What is the significance of synaptic integration in neural computation?

    <p>It combines multiple synaptic potentials in one neuron.</p> Signup and view all the answers

    Which types of G proteins do M1, M3, and M5 metabotropic receptors couple to?

    <p>Pertussis toxin-insensitive G proteins</p> Signup and view all the answers

    What is the primary role of NMDA-gated channels in the brain?

    <p>Influencing calcium ion concentration and learning functions</p> Signup and view all the answers

    Which of the following is true about AMPA receptors?

    <p>They are found in most excitatory synapses and mediate fast excitation</p> Signup and view all the answers

    Which neurotransmitter is predominantly associated with inhibitory synapses in the brain?

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

    What type of receptors do benzodiazepines and barbiturates specifically target?

    <p>GABAA receptors</p> Signup and view all the answers

    What distinguishes the different groups of metabotropic glutamate receptors?

    <p>Their subunit composition and pharmacological properties</p> Signup and view all the answers

    How does the probability of ionotropic GABA and glycine channels opening relate to neurotransmitter concentration?

    <p>It is directly proportional</p> Signup and view all the answers

    Which process primarily utilizes the glutamate-glutamine cycle?

    <p>Synthesis and recycling of glutamate</p> Signup and view all the answers

    What effect does glycine binding to its receptors have on the postsynaptic neuron?

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

    Which statement accurately describes the GABAB receptor?

    <p>It activates K+ channels through a metabotropic mechanism.</p> Signup and view all the answers

    What role does glycine play in NMDA receptor activation?

    <p>It acts as a co-agonist with glutamate.</p> Signup and view all the answers

    Which neurotransmitter is synthesized from the amino acid serine?

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

    Barbiturates enhance the activity of which type of receptor?

    <p>GABAA receptors</p> Signup and view all the answers

    What effect does the activation of K+ channels through GABAB receptors have on the postsynaptic cell?

    <p>Leads to hyperpolarization</p> Signup and view all the answers

    Which neurotransmitter is considered a biogenic amine and is derived from tyrosine?

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

    What is the primary function of glycine in the central nervous system?

    <p>Providing inhibitory control</p> Signup and view all the answers

    Study Notes

    Metabotropic Receptors

    • Metabotropic receptors are coupled to different G proteins and can thus have distinct effects on the cell
    • M1, M3, and M5 are coupled to pertussis toxin-insensitive G proteins
    • M2 and M4 are coupled to pertussis toxin-sensitive G proteins
    • Each set of G proteins is coupled to different enzymes and second messenger pathways

    Glutamate

    • Glutamate is the major excitatory neurotransmitter in the central nervous system
    • Glutamate has both ionotropic and metabotropic receptors
    • Ionotropic receptors subtypes are AMPA, Kainate and NMDA

    AMPA Receptors

    • AMPA-gated channels are found in most excitatory synapses in the brain
    • AMPA receptors mediate fast excitation

    NMDA Receptors

    • NMDA-gated channels have more complex behavior
    • NMDA channels are permeable to Na+, K+, and Ca2+
    • Ca2+ permeability allows NMDA receptors to influence intracellular Ca2+ levels
    • Ca2+ can activate many enzymes, regulate the opening of a variety of channels, and affect the expression of genes
    • Excess Ca2+ can precipitate the death of a cell
    • NMDA-gated channels coexist with AMPA-gated channels in many synapses of the brain

    Metabotropic Glutamate Receptors

    • Eight genes coding for metabotropic glutamate receptors have been identified and classified into three groups
    • Group I receptors are found mainly postsynaptically
    • Groups II and III are found mainly presynaptically

    Inhibitory Amino Acid Receptors: GABA and Glycine

    • Both glycine and GABA (GABAA and GABAC) have ionotropic receptors
    • Each of these receptors has a Cl- channel

    Glycine

    • Glycine-mediated inhibitory synapses predominate in the spinal cord
    • Glycine receptors are ionotropic receptors (ligand-gated chloride channels)
    • Glycine also serves as a co-agonist with glutamate at NMDA receptors in the CNS

    GABA

    • GABAergic synapses make up the majority of inhibitory synapses in the brain
    • GABAA receptors are the targets of two major classes of drugs: benzodiazepines and barbiturates
    • GABAB receptor is a metabotropic receptor

    Termination of Neurotransmitter Effects

    • Neurotransmitter bound to a postsynaptic neuron produces a continuous postsynaptic effect
    • Neurotransmitter must be removed from its receptor
    • Removal of neurotransmitters occurs when they are degraded by enzymes, reabsorbed by astrocytes or the presynaptic terminals, or diffuse from the synaptic cleft

    Synaptic Delay

    • Neurotransmitter must be released, diffuse across the synapse, and bind to receptor
    • Synaptic delay – time needed for this process (0.3-5.0 ms)
    • Synaptic delay is the rate-limiting step of neural transmission

    Postsynaptic Potentials

    • EPSP: Transient postsynaptic membrane depolarization by presynaptic release of neurotransmitter
    • EPSPs are caused by Ach- and glutamate-gated channels
    • IPSP: Transient hyperpolarization of postsynaptic membrane potential caused by presynaptic release of neurotransmitter
    • IPSPs are caused by glycine- and GABA-gated channels

    Synaptic Integration

    • The combining of excitatory and inhibitory signals acting on adjacent membrane regions of a neuron
    • In order for an action potential to occur, the sum of excitatory and inhibitory postsynaptic potentials (local responses) must be greater than a threshold value

    Acetylcholine (ACh)

    • Released from all preganglionic and most postganglionic neurons in the parasympathetic nervous system and from all preganglionic neurons in the sympathetic nervous system
    • Ach is the transmitter at neuromuscular junction and also within the CNS

    Nicotinic ACh receptors

    • Ionotrophic; nonselective cationic channel

    Muscarinic ACh receptors

    • There are five known muscarinic subtypes of ACh receptors (M1 to M5)

    Biogenic Amines

    • Dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), serotonin (5-hydroxytryptamine [5-HT]) are biogenic amines that act as neurotransmitters
    • Dopamine, norepinephrine, and epinephrine are catecholamines, and they share a common biosynthetic pathway that starts with the amino acid tyrosine

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    Synaptic Transmission PDF

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    Test your knowledge on metabotropic and ionotropic receptors, focusing on glutamate and its major receptor subtypes like AMPA and NMDA. Understand how these receptors influence neuronal signaling and their distinct roles within the central nervous system.

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