Neuroscience Chapter on Synapses and Neurotransmitters
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Questions and Answers

What is the primary function of electrical synapses in the nervous system?

  • To support the structure of neuron cell bodies
  • To release neurotransmitters into the synaptic cleft
  • To relay signals through gap junctions (correct)
  • To insulate axons with myelin sheaths

    • Which cell type is primarily responsible for producing the myelin sheath in the peripheral nervous system (PNS)?

  • Schwann Cells (correct)
  • Oligodendrocytes
  • Microglia
  • Astrocytes

    • What type of neurotransmitter is likely released at chemical synapses?

  • Neuropeptides (correct)
  • Myelin
  • Hormones
  • Electrical impulses

    • Which mechanism is involved in the release of neurotransmitters at chemical synapses?

    <p>Calcium-dependent exocytosis</p> Signup and view all the answers

    What is the primary means of communication between neurons?

    <p>Chemical signals through synapses</p> Signup and view all the answers

    Which neurotransmitter is considered the principal excitatory neurotransmitter in the central nervous system (CNS)?

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

    What is the primary mechanism by which neurotransmitters are released from presynaptic neurons?

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

    Which neurotransmitter is primarily involved in the function of the parasympathetic nervous system?

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

    What is required for a neurotransmitter to elicit a response in a target cell?

    <p>Sufficient quantity of release</p> Signup and view all the answers

    Which of the following statements about neurotransmitter synthesis is correct?

    <p>It usually occurs in the nerve terminal</p> Signup and view all the answers

    Which neurotransmitter serves as the principal inhibitory neurotransmitter in the CNS?

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

    What role do antagonists play concerning neurotransmitter action?

    <p>They prevent both endogenous and exogenous transmitter action</p> Signup and view all the answers

    What is one of the main requirements for effective neuron communication?

    <p>Release of enough transmitter for a response</p> Signup and view all the answers

    What is the primary function of efferent neurons?

    <p>Transmit motor signals from the CNS to the periphery</p> Signup and view all the answers

    Which structure in a neuron is primarily responsible for transmitting signals away from the cell body?

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

    What defines a pseudounipolar neuron?

    <p>Possessing only one axon and receiving input primarily through its dendrites</p> Signup and view all the answers

    What is a unique feature of neurons concerning their lifecycle?

    <p>They can live and function for a lifetime without dividing</p> Signup and view all the answers

    What component of neurons provides the structural support and is involved in protein synthesis?

    <p>Nissl bodies</p> Signup and view all the answers

    Which of the following statements about neuron communication is true?

    <p>Neurons use electrical impulses to transmit action potentials</p> Signup and view all the answers

    Which property of neurons necessitates a high metabolic rate?

    <p>Their requirement for abundant oxygen and glucose</p> Signup and view all the answers

    What is primarily found in the ganglia of the peripheral nervous system?

    <p>Clusters of neuronal cell bodies</p> Signup and view all the answers

    What is the significance of Schwann cells in the peripheral nervous system (PNS)?

    <p>They are responsible for the repair and regeneration of neuronal tissues.</p> Signup and view all the answers

    Which of the following best describes the primary function of myelination in nerves?

    <p>It enhances the ability of axons to transmit action potentials rapidly.</p> Signup and view all the answers

    Which type of synapse is characterized by direct cytoplasmic connections between two neurons?

    <p>Electrical synapse</p> Signup and view all the answers

    What type of matter in the brain is primarily associated with myelin?

    <p>White matter</p> Signup and view all the answers

    In what way does the structure of neurons contribute to their function in the nervous system?

    <p>Their varied structures enable specialized functions and communication.</p> Signup and view all the answers

    Which component is primarily responsible for processing sensory information within the central nervous system?

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

    What is the main role of the peripheral nervous system in relation to the central nervous system?

    <p>Transmitting information to and from the CNS</p> Signup and view all the answers

    What type of neuron is primarily involved in transmitting motor commands from the CNS to muscles?

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

    Which aspect of the nervous system is reflected when sensory information is modified into a response?

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

    What term is used to describe neurons that primarily carry messages towards the central nervous system?

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

    Which type of neuron is characterized by having a single dendrite and a single axon?

    <p>Bipolar neuron</p> Signup and view all the answers

    What type of glial cell is responsible for maintaining the chemical environment in the central nervous system?

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

    Which neuron class is predominantly found within the central nervous system and is characterized by multiple dendrites?

    <p>Multipolar neuron</p> Signup and view all the answers

    What defines a neuroglial cell within the central nervous system?

    <p>It's primarily supportive in function.</p> Signup and view all the answers

    Which type of glial cell is responsible for forming myelin in the peripheral nervous system?

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

    Which of the following statements best describes chemically gated ion channels?

    <p>They regulate the permeability of ions in response to neurotransmitters.</p> Signup and view all the answers

    What is a key feature of multipolar neurons that allows them to collect multiple inputs?

    <p>Multiple dendrites</p> Signup and view all the answers

    What is the predominant function of microglia in the central nervous system?

    <p>Remove cellular debris</p> Signup and view all the answers

    What is the primary mechanism by which neurotransmitters are removed from the synaptic cleft?

    <p>Active reuptake by glial cells</p> Signup and view all the answers

    Which statement best describes the process of exocytosis in neurotransmitter release?

    <p>Vesicles fuse with the membrane and release neurotransmitters into the synapse</p> Signup and view all the answers

    Which requirement is NOT essential for neurotransmitter function at synapses?

    <p>Method of synthesis in the postsynaptic target</p> Signup and view all the answers

    Which neurotransmitter is primarily associated with memory formation within the central nervous system?

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

    What is the principal effect of antagonists on neurotransmitter activity?

    <p>They inhibit the binding of neurotransmitters to receptors</p> Signup and view all the answers

    Which neurotransmitter is the principal inhibitory neurotransmitter in the central nervous system?

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

    What role does depolarization of the membrane play in neurotransmitter release?

    <p>It stimulates vesicles to undergo exocytosis</p> Signup and view all the answers

    Which neurotransmitter has a primary role in the sympathetic nervous system?

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

    What type of neuron is characterized by having a single axon that branches to connect to spinal cord or CNS neurons?

    <p>Pseudounipolar neuron</p> Signup and view all the answers

    Which of the following structures in a neuron transmits electrical signals towards the cell body?

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

    How do neurons primarily maintain their lifelong function despite not being capable of division?

    <p>By utilizing neural stem cells</p> Signup and view all the answers

    What primarily protects the neuronal cell bodies located within the central nervous system (CNS)?

    <p>Bone structure</p> Signup and view all the answers

    What role do chromatophilic bodies (Nissl bodies) play in neuronal cells?

    <p>Protein synthesis</p> Signup and view all the answers

    Which characteristic is primarily responsible for the high metabolic rate of neurons?

    <p>Requirement for oxygen and glucose</p> Signup and view all the answers

    What is the primary function of the axon in a neuron?

    <p>Transmitting action potentials away from the cell body</p> Signup and view all the answers

    What intrinsic quality distinguishes neurons from other cell types, particularly concerning their lifecycle?

    <p>Lifespan comparable to the host organism</p> Signup and view all the answers

    What effect does the influx of Ca2+ have during neurotransmitter release?

    <p>It causes the fusion of synaptic vesicles to the presynaptic terminal.</p> Signup and view all the answers

    Which mechanism is NOT involved in the recovery or degradation of neurotransmitters?

    <p>Capillary influx into the presynaptic neuron.</p> Signup and view all the answers

    Which type of receptor is characterized by its response being slower and often longer-lasting?

    <p>Metabotropic receptors.</p> Signup and view all the answers

    What is the primary action of ionotropic receptors when a ligand binds?

    <p>They undergo a conformational change leading to channel opening.</p> Signup and view all the answers

    What happens to neurotransmitters after they bind to postsynaptic receptors?

    <p>They may be either degraded or taken back into the presynaptic terminal.</p> Signup and view all the answers

    Which statement best describes the selectivity of ionotropic channels compared to voltage-gated channels?

    <p>Ionotropic channels are not as selective to ions as voltage-gated channels.</p> Signup and view all the answers

    Which neurotransmitter transporter is specifically mentioned for noradrenaline?

    <p>Noradrenaline transporter (NAT).</p> Signup and view all the answers

    Which of the following actions is directly facilitated by voltage-gated calcium channels?

    <p>Calcium influx inducing synaptic vesicle fusion.</p> Signup and view all the answers

    Study Notes

    Nervous System Lectures

    •  The nervous system lectures are scheduled for Tuesday, November 19th on cells and synaptic transmission; Wednesday, November 20th on membrane and action potentials; Tuesday, November 26th on the autonomic nervous system; and Wednesday, November 27th on graded potentials, neuromuscular junctions, and a recap exercise.

    Lecture Content - 1st Hour

    •  The first hour of the lecture covers an introduction to neurons and basic neuroanatomy along with an introduction to non-neuronal cells in the nervous system.
    •  Suggested reading is Silverthorn, Human Physiology: An Integrated Approach, 7th edition, Chapters 5, 8, and 11; and Rang et al., Rang and Dales Pharmacology, 8th edition, sections of chapters 4, 12, 13, and 14.

    Organisation of the NS

    •  The nervous system (NS) is organised into two main parts: - Central nervous system (CNS) — comprises of the brain and spinal cord - Peripheral nervous system (PNS) — comprises nerves outside of the CNS that extend to and from the brain and spinal cord.

    Functions of the Nervous System

    •  Sensory Function: afferent neurons transmit sensory information from the periphery to the CNS.
    •  Processing function: the CNS processes the incoming sensory information and initiates a response that modifies a process.
    •  Motor function: efferent neurons transmit motor signals that travel from the CNS to the periphery.

    Sensory & Motor Information Types

    •  PNS has two divisions    - Sensory (afferent) division includes:        - Somatic sensory (general): touch, pain, pressure, vibration, temperature, proprioception (body position) in skin, body walls, and limbs. (Special senses include: hearing, equilibrium, vision, smell)        - Visceral sensory (general): stretch, pain, temperature, chemical changes, and irritation of viscera (internal organs), such as nausea, hunger        - Special senses include: taste    - Motor (efferent) division includes:        - Somatic motor (voluntary motor): motor innervation to all skeletal muscles        - Visceral motor (involuntary): motor innervation to smooth muscle, cardiac muscle, and glands. This is equivalent to the autonomic nervous system (ANS).

    The Neuron

    •  Functional unit of the nervous system
    •  Estimated to contain 86 billion neurons in the human brain.
    •  Neurons can live and function for a lifetime.
    •  Foetal neurons lose their ability to undergo mitosis — neural stem cells are the exception.
    •  Require abundant glucose and oxygen.

    The Neuron - Structure

    •  Cell body (biosynthetic center and receptive region): contains nucleus, organelles plus other structures, chromatophilic bodies (Nissl bodies), clusters of rough ER and ribosomes; located within the CNS
    •  Dendrites: extensive branching from the cell body, transmit electrical signals towards the cell body.
    •  Axon: nerve fiber, impulse generator and conductor; transmits action potentials away from the cell body
    •  Axon Terminal: secretory component

    The Neuron - Structure

    •  Myelin sheath: protective covering around some axons, enables saltatory conduction. Increases the speed of transmission.
    •  Synapse: region where axons transmit to target cells, via neurotransmitters.
    •  Ganglia: clusters of cell bodies in the PNS.

    Neuron Classes

    •  Unipolar: Single axon, sensory neurons
    •  Bipolar: Single dendrite, single axon, found as sensory neurons in ear, eye, and nose.
    •  Pseudounipolar: Single axon branches to connect to spinal cord or CNS neurons; found as sensory neurons
    •  Multipolar: Single axon, multiple dendrites, most common type of neuron; found as interneurons (within CNS) and motor neurons

    Glial Cells

    •  Support cells of the nervous system.
    •  6 types: - CNS Neuroglial cells: astrocytes (chemical environment), microglia (phagocytic), ependymal (CSF), oligodendrocytes (myelin)
    •  PNS Non-neuroglial cells: Schwann cells (myelin), satellite cells (chemical environment)

    Schwann Cells

    •  Produce the myelin sheath in the PNS.
    •  Protect axons and insulate them. 
    •  Myelinated axons conduct action potentials more quickly.
    •  Maintains microenvironment, assists neural repair, enables saltatory conduction.

    Summary - 1st Hour

    •  Neurons have common structural features but can be classified on anatomical features.
    •  The nervous system contains additional non-neuronal cells with diverse functions.

    Lecture Content - 2nd Hour

    •  Introduction to electrical synapses
    •  Introduction to chemical synaptic transmission
    •  Suggested reading: Silverthorn, Human Physiology: An Integrated Approach, 7th edition, chapters 5, 8, and 11; and Rang et al., Rang and Dales Pharmacology, 8th edition, sections of chapters 4, 12, 13, and 14.

    The Synapse

    •  Synapse: the connection between a neuron and another cell
    •  Chemical Synapse:    - synaptic cleft [20-50 nm]—space between two communicating cells    - presynaptic density – axon terminal    - synaptic vesicles containing neurotransmitter molecules    - postsynaptic density – dendrite or cell body

    The Synapse - Electrical

    •  Direct transfer of ionic current from one cell to the next.
    •  Gap junction formed by connexons — channels formed by six connexions.
    •  Cell membranes connected by connexons.
    •  allow ions to pass from one cell to another.
    •  found in smooth muscle and the heart.

    The Synapse - Chemical

    •  presynaptic neuron releases neurotransmitter into synaptic cleft.
    •  neurotransmitter binds to receptors on postsynaptic cell
    •  causes a response in the postsynaptic cell

    Neurotransmitters

    •  Substances released by a neuron, affecting transmission of information to a post-synaptic target.
    •  Criteria: method of synthesis, storage, mechanism of release, mechanism of removal

    Neurotransmitters - More

    •  Nerve stimulation must result in release of sufficient transmitter to elicit observed response.
    •  Response must be mimicked when applied exogenously.
    •  Antagonists must block both endogenous and exogenous transmitters.

    Neurotransmitter Classes

    •  Major Neurotransmitters in the CNS:
    •  glutamate (principle excitatory), GABA (principle inhibitory)
    •  Acetylcholine — parasympathetic function, memory
    •  Noradrenaline — sympathetic function

    Neurotransmitter Release

    •  Exocytosis: Process by which vesicles release their contents.

    The Chemical Synapse - steps

    •  Neurotransmitter synthesis
    •  Neurotransmitter loaded into synaptic vesicles
    •  Action potential causes membrane depolarization
    •  Voltage-gated Ca2+ channels open
    •  Ca2+ triggers fusion of synaptic vesicles to presynaptic terminal
    •  Neurotransmitter is released into the synaptic cleft by exocytosis
    •  Neurotransmitter crosses the cleft and binds to postsynaptic receptors
    •  Biochemical or electrical response elicited in postsynaptic cell.
    •  Neurotransmitter removed.

    The Chemical Synapse - Postsynaptic Receptors

    •  Ionotropic    - Ligand-gated ion channels    - Ligand binding causes a conformational change that leads to the opening of channels.
    •  Metabotropic    - G protein-coupled receptors    - Trigger slower, often longer-lasting actions.

    Summary - 2nd Hour

    •  Description of electrical and chemical synapses.
    •  Neurotransmitter synthesis, storage, release, signal generation, and removal.

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    Lecture - Cells of the NS - Synaptic Transmission - 19Nov2024 PDF

    Description

    Test your knowledge on the functions of electrical synapses, the production of myelin sheaths, and the roles of various neurotransmitters in the nervous system. This quiz covers key concepts around neurotransmitter release mechanisms, communication between neurons, and the excitatory and inhibitory roles of these chemicals. Perfect for students studying neuroscience or biological psychology.

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