Neuron Classes and Nervous System Structure
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Questions and Answers

What are the 3 general classes of neurons?

  • Sensory (afferent) Neurons (correct)
  • Interneurons (correct)
  • Motor (efferent) Neurons (correct)
  • Glial Cells

    • What specialized function do sensory (afferent) neurons serve?

    They detect changes in the environment called stimuli.

    Where do interneurons lie and what is their function?

    They lie within the CNS and receive signals from other neurons to carry out integrative functions.

    What is the primary function of motor (efferent) neurons?

    <p>They send signals to muscle and gland cells to carry out the body's responses to stimuli.</p> Signup and view all the answers

    What does the Central Nervous System (CNS) consist of?

    <p>The brain and spinal cord.</p> Signup and view all the answers

    What does the Peripheral Nervous System (PNS) consist of?

    <p>The nerves leading to and from the CNS.</p> Signup and view all the answers

    What does the somatic nervous system innervate?

    <p>Skeletal muscle.</p> Signup and view all the answers

    What function does the autonomic nervous system control?

    <p>It innervates cardiac and smooth muscle to control body function.</p> Signup and view all the answers

    What is the soma of a neuron?

    <p>The control center of the neuron containing the nucleus and organelles.</p> Signup and view all the answers

    What are dendrites?

    <p>Cellular extensions from the cell body that have receptors for neurotransmitters.</p> Signup and view all the answers

    What does the axon hillock do?

    <p>It gives rise to the axon.</p> Signup and view all the answers

    What are multipolar neurons?

    <p>Neurons with one axon and several dendrites.</p> Signup and view all the answers

    What is the defining characteristic of bipolar neurons?

    <p>They have one axon and one dendrite.</p> Signup and view all the answers

    What is unique about unipolar neurons?

    <p>They have only a single process leading away from the soma.</p> Signup and view all the answers

    What are anaxonic neurons?

    <p>Neurons with multiple dendrites but no axon.</p> Signup and view all the answers

    What is axonal transport?

    <p>The two-way transport of materials along an axon.</p> Signup and view all the answers

    What is anterograde transport?

    <p>Movement away from the soma.</p> Signup and view all the answers

    What is retrograde transport?

    <p>Movement toward the soma.</p> Signup and view all the answers

    What is neuroglia?

    <p>Helper cells in nervous tissue that provide support and bind neurons together.</p> Signup and view all the answers

    What do oligodendrocytes do?

    <p>They form discontinuous myelin sheaths in the CNS.</p> Signup and view all the answers

    What are abundant astrocytes?

    <p>Star-shaped cells found in the CNS.</p> Signup and view all the answers

    What role do protoplasmic astrocytes have?

    <p>They help form the blood-brain barrier.</p> Signup and view all the answers

    What do fibrous astrocytes provide?

    <p>A physically supportive framework for the CNS.</p> Signup and view all the answers

    What is the function of ependymal cells?

    <p>They produce and circulate cerebrospinal fluid.</p> Signup and view all the answers

    What are microglia?

    <p>Small macrophages that develop from monocytes.</p> Signup and view all the answers

    What do Schwann cells do in the PNS?

    <p>They form a neurilemma and myelin sheaths around neuron fibers.</p> Signup and view all the answers

    What are satellite cells responsible for?

    <p>They surround cell bodies in the PNS.</p> Signup and view all the answers

    All axons in the PNS have a sheath of ______ cells around them.

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

    What is myelin?

    <p>A sheath composed of Schwann cells that insulates axons.</p> Signup and view all the answers

    How does the speed of nerve signal travel depend?

    <p>On the diameter of the nerve fiber and presence of myelin.</p> Signup and view all the answers

    What is necessary for the regeneration of peripheral nerve fibers?

    <p>The soma must not be damaged, and some neurilemma must remain intact.</p> Signup and view all the answers

    What is an electrical potential?

    <p>Difference in the concentration of charged particles between one point and another.</p> Signup and view all the answers

    What does it mean when cells are polarized?

    <p>When living cells have electrical potential.</p> Signup and view all the answers

    What is the resting membrane potential of neurons?

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

    What characterizes a local potential?

    <p>A small deviation in the resting membrane potential caused by stimulation.</p> Signup and view all the answers

    What generates an action potential?

    <p>Adequate density of voltage-gated ion channels.</p> Signup and view all the answers

    What does the refractory period signify?

    <p>The time during which a new action potential cannot be initiated.</p> Signup and view all the answers

    What characterizes signal conduction in unmyelinated fibers?

    <p>Voltage-gated sodium ion channels are distributed along their length.</p> Signup and view all the answers

    What did Otto Loewi discover about neurotransmitter communication?

    <p>Neurons communicate through synapses and not just electrical connections.</p> Signup and view all the answers

    What roles do presynaptic neurons play?

    <p>They house vesicles filled with neurotransmitters.</p> Signup and view all the answers

    What characterizes postsynaptic neurons?

    <p>They contain proteins that function as receptors and ion gates.</p> Signup and view all the answers

    What is synaptic transmission?

    <p>The process of neurotransmitter release and reception between neurons.</p> Signup and view all the answers

    What happens during cessation of the signal?

    <p>ACh binds to receptors briefly and is then removed by diffusion or enzymatic degradation.</p> Signup and view all the answers

    What are neuromodulators?

    <p>Hormones and peptides that modify synaptic transmission.</p> Signup and view all the answers

    What is neural integration?

    <p>The information-processing and decision-making mechanisms of neurons.</p> Signup and view all the answers

    What is excitatory postsynaptic potential (EPSP)?

    <p>The likelihood of the postsynaptic cell reaching action potential.</p> Signup and view all the answers

    What is inhibitory postsynaptic potential (IPSP)?

    <p>When a neurotransmitter makes the postsynaptic membrane hyperpolarized.</p> Signup and view all the answers

    What is the nature of glutamic and aspartic acid?

    <p>They are excitatory and tend to produce EPSPs.</p> Signup and view all the answers

    What role does glycine play in neurotransmission?

    <p>It is inhibitory and generally produces IPSPs.</p> Signup and view all the answers

    What is summation in neural physiology?

    <p>The process of adding up incoming information and responding to its net effect.</p> Signup and view all the answers

    What is facilitation in neural activity?

    <p>One neuron enhances the effect of another.</p> Signup and view all the answers

    What is presynaptic inhibition?

    <p>A mechanism where one presynaptic neuron suppresses another.</p> Signup and view all the answers

    What is neural coding?

    <p>The way the nervous system converts information to action potentials.</p> Signup and view all the answers

    What are neuronal pools?

    <p>Groups of thousands to millions of interneurons functioning together.</p> Signup and view all the answers

    What is a neuronal circuit?

    <p>The connection pathway among a series of neurons.</p> Signup and view all the answers

    What is the basis of memory in neuroscience?

    <p>The memory trace (engram) where new synapses form or existing ones are modified.</p> Signup and view all the answers

    Study Notes

    Neuron Classes

    • Sensory (afferent) Neurons: Detect environmental changes (stimuli).
    • Interneurons: Integrate signals within the CNS, facilitating communication between neurons.
    • Motor (efferent) Neurons: Transmit signals to muscles and glands for bodily responses.

    Nervous System Structure

    • Central Nervous System (CNS): Comprises the brain and spinal cord, consisting of gray matter and white matter.
    • Peripheral Nervous System (PNS): Includes nerves extending to and from the CNS.

    Nervous System Divisions

    • Somatic Nervous System: Controls skeletal muscle movements.
    • Autonomic Nervous System: Regulates cardiac and smooth muscle functions.

    Neuron Anatomy

    • Soma: Neuron's control center containing the nucleus and organelles.
    • Dendrites: Extensions that receive signals via neurotransmitter receptors.
    • Axon Hillock: Site of action potential initiation.

    Types of Neurons

    • Multipolar Neurons: Most common, with one axon and multiple dendrites.
    • Bipolar Neurons: One axon and one dendrite, primarily found in sensory organs.
    • Unipolar Neurons: Contain a single process from the soma.
    • Anaxonic Neurons: Multiple dendrites but no distinct axon.

    Axonal Transport

    • Axonal Transport: Two-way movement of materials along the axon.
    • Anterograde Transport: Movement away from the soma via kinesin protein.
    • Retrograde Transport: Movement toward the soma.

    Glial Cells

    • Neuroglia: Supportive cells in the nervous system, with six distinct types.
    • Oligodendrocytes: Form myelin sheaths around CNS neurons.
    • Astrocytes: Star-shaped, assist in forming the blood-brain barrier and provide structural support.
    • Ependymal Cells: Produce and circulate cerebrospinal fluid.
    • Microglia: Immune cells in the CNS, act as macrophages.
    • Schwann Cells: Create myelin sheaths in the PNS, aiding in neuron regeneration.
    • Satellite Cells: Surround PNS neuron cell bodies; function is less understood.

    Myelin and Nerve Fibers

    • Myelin Sheath: Composed of Schwann cells, enhancing signal conduction speed.
    • Unmyelinated Fibers: Associated with Schwann cells, but signal travels slower.
    • Regeneration: Possible in PNS if the neurilemma and soma are intact.

    Electrical Potentials

    • Resting Membrane Potential (RMP): Neurons are polarized at -70 mV; maintained primarily by the sodium-potassium pump.
    • Local Potentials: Small, graded deviations in RMP that can be excitatory or inhibitory.

    Action Potentials

    • Action Potential Generation: Requires sufficient depolarization at the axonal hillock.
    • Phase Changes: Rapid depolarization followed by repolarization; involves sodium and potassium ion channels.
    • Refractory Period: Includes absolute and relative stages, defining the neuron's responsiveness following an action potential.

    Signal Conduction

    • Unmyelinated Fibers: Impulses travel at slower speeds (up to 2 m/sec).
    • Saltatory Conduction: In myelinated fibers, action potentials jump between nodes of Ranvier, increasing speed (up to 120 m/sec).

    Neurotransmission

    • Discovery: Communication through synapses, first identified by Otto Loewi, with acetylcholine as the first neurotransmitter.
    • Synaptic Transmission: Involves release of neurotransmitters, receptor binding, and generation of postsynaptic potentials (PSP).
    • Neuromodulators: Substances modifying synaptic transmission and receptor expression.

    Neural Processing

    • Neuronal Integration: Mechanisms of information processing and memory based on neurotransmitter effects.
    • Facilitation and Inhibition: Processes that enhance or suppress synaptic transmission.

    Memory and Plasticity

    • Memory Trace (Engram): Pathways formed by new or modified synapses.
    • Types of Memory: Immediate, short-term, and long-term memory, with declarative and procedural categories.

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    Description

    This quiz covers the different classes of neurons, including sensory, interneurons, and motor neurons. It also explores the structure of the nervous system, including the central and peripheral nervous systems, and the components that make up each type of neuron. Test your knowledge on the organization and function of neurons and their role in the nervous system.

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