L23. Neuroscience - Cytology of Neurons & Glia
41 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which type of synapse is typically classified as inhibitory and formed between local circuit neurons?

  • Axodendritic synapse
  • Axospinous synapse
  • Axoaxonic synapse (correct)
  • Axosomatic synapse

What characterizes intrinsic neurons in the context of local circuit neurons?

  • They only form excitatory synapses.
  • They are primarily found in the white matter of the brain.
  • They are smaller and remain within the nucleus of origin. (correct)
  • They have long axons projecting out of the nucleus.

Which of the following statements is NOT true regarding local circuit neurons?

  • All local circuit neurons project their axons outside the nucleus. (correct)
  • Golgi cells are examples of local circuit neurons with localized intrinsic axons.
  • Most local circuit neuron synapses are inhibitory.
  • Local circuit neurons can have axonal morphology in their dendrites.

Which synapse type is generally considered excitatory?

<p>Axospinous synapse (B)</p> Signup and view all the answers

Where are examples of intrinsic neurons typically found?

<p>Cerebellum and olfactory bulb. (D)</p> Signup and view all the answers

Which type of neuron is characterized by having only one process that functions as both an axon and a dendrite?

<p>Unipolar (pseudo-unipolar) neuron (D)</p> Signup and view all the answers

What is the primary role of astrocytes in the central nervous system?

<p>Support and maintain neuronal function (D)</p> Signup and view all the answers

Which type of glial cell is responsible for myelinating neurons in the central nervous system?

<p>Oligodendrocytes (D)</p> Signup and view all the answers

Dendrites are primarily specialized for which of the following functions?

<p>Receiving synaptic contacts from other neurons (A)</p> Signup and view all the answers

Which of the following statements is true regarding the axons of neurons?

<p>The axon usually originates from the cell body (D)</p> Signup and view all the answers

What distinguishes oligodendrocytes from Schwann cells in terms of myelination?

<p>Oligodendrocytes myelinate multiple axons while Schwann cells myelinate a single axon (A)</p> Signup and view all the answers

Which characteristic of neurons is primarily responsible for their ability to respond to stimuli and transmit information?

<p>Their electrical excitability (C)</p> Signup and view all the answers

What primarily composes the tissue found in the central nervous system (CNS)?

<p>Gray and white matter (A)</p> Signup and view all the answers

Which structures in the white matter of the CNS are defined by their shared origin, destination, and function?

<p>Fasciculi and tracts (C)</p> Signup and view all the answers

Which type of membrane specialization is characterized by distinct pre- and postsynaptic membrane thickenings?

<p>Synapses (B)</p> Signup and view all the answers

How do cell bodies of neurons typically vary in size?

<p>They can be as small as 4μm or as large as 50μm (D)</p> Signup and view all the answers

What is the primary role of the integral membrane proteins in the neuronal plasma membrane?

<p>To function as receptors and channels for neurotransmitters and ions (C)</p> Signup and view all the answers

Which type of junction acts as an electrical synapse for ultra-rapid communication in neurons?

<p>Gap junction (C)</p> Signup and view all the answers

What is a defining characteristic of gray matter in the CNS?

<p>Rich in neuronal cell bodies and dendrites (C)</p> Signup and view all the answers

What provides the structural organization of axons in the white matter of the CNS?

<p>The arrangement into tracts and columns (A)</p> Signup and view all the answers

Which of the following adhesion molecules is found in the plasma membrane of neurons?

<p>Cadherins (D)</p> Signup and view all the answers

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

<p>Acts as the initiation site for action potentials due to voltage-gated Na+ channels (A)</p> Signup and view all the answers

Which statement about myelinated axons is true?

<p>Nodes of Ranvier serve to increase the speed of nerve impulse conduction via saltatory conduction (D)</p> Signup and view all the answers

What distinguishes unmyelinated axons from myelinated ones in terms of structure?

<p>Unmyelinated axons lack organized myelin sheaths (A)</p> Signup and view all the answers

What term describes the branching of an axon at angles to its parent branch?

<p>Axon Collaterals (A)</p> Signup and view all the answers

What role do voltage-gated Na+ channels in the initial segment of the axon play?

<p>They allow for the initiation of action potentials (C)</p> Signup and view all the answers

In terms of action potential propagation speed, which factor is most influential?

<p>The diameter and myelination of the axon (C)</p> Signup and view all the answers

Which type of neuron is most likely to have no axon?

<p>Retinal amacrine cell (B)</p> Signup and view all the answers

What aspect of axon structure is critical for saltatory conduction?

<p>Regular interval of nodes of Ranvier (A)</p> Signup and view all the answers

What cellular component is directly involved in the formation of myelin sheaths around axons?

<p>Oligodendrocytes (A)</p> Signup and view all the answers

What is the significance of postsynaptic membrane densities in neuronal communication?

<p>They anchor neurotransmitter receptors and scaffold proteins (B)</p> Signup and view all the answers

What is the role of Schwann cells concerning myelination of axons?

<p>They myelinate axons with diameters larger than 0.6 microns. (B)</p> Signup and view all the answers

How do unmyelinated axons in the CNS differ from those in the PNS?

<p>Unmyelinated axons in the CNS are ensheathed by astrocytes. (B)</p> Signup and view all the answers

What structures do varicosities contain within the axonal tree?

<p>Mitochondria and synaptic vesicles. (A)</p> Signup and view all the answers

What characterizes the synaptic cleft in a typical synapse?

<p>It fluctuates between 20-30 nm in width. (D)</p> Signup and view all the answers

Which type of fibers are categorized as C fibers?

<p>Unmyelinated fibers associated with autonomic and pain sensation. (B)</p> Signup and view all the answers

What is the maximum number of troughs a single Schwann cell can provide to unmyelinated axons?

<p>12-20 troughs. (D)</p> Signup and view all the answers

Which elements are present in the presynaptic membrane at a synapse?

<p>Membrane density and synaptic vesicles. (B)</p> Signup and view all the answers

What function does the presynaptic membrane density serve?

<p>It facilitates the release of neurotransmitters. (A)</p> Signup and view all the answers

What distinguishes the conduction velocity of C fibers?

<p>They exhibit very slow conduction velocities. (A)</p> Signup and view all the answers

What is an essential feature of the axonal tree's structure?

<p>It forms a highly branched structure called telodendria. (B)</p> Signup and view all the answers

Flashcards

What is the CNS?

The part of the nervous system that includes the brain and spinal cord.

What is the PNS?

The part of the nervous system that includes the nerves outside of the brain and spinal cord.

What are neurons?

Neurons are specialized cells designed for communication in the nervous system. They receive, integrate, and transmit information using electrical signals.

What is the soma or perikaryon?

The cell body of a neuron, containing the nucleus and most of the cell's organelles.

Signup and view all the flashcards

What are dendrites?

Processes that extend from the soma, specialized for receiving signals from other neurons.

Signup and view all the flashcards

What is the axon?

A long, slender process that extends from the soma, specialized for transmitting signals to other neurons.

Signup and view all the flashcards

What are presynaptic terminals?

Specialized junctions where neurons communicate with each other or with other cells.

Signup and view all the flashcards

What is the Central Nervous System (CNS)?

The part of the nervous system that includes the brain and spinal cord. Controls complex functions like thinking, feeling, and movement.

Signup and view all the flashcards

What is the Peripheral Nervous System (PNS)?

The part of the nervous system that connects the CNS to the rest of the body. Carries signals to and from the brain and spinal cord.

Signup and view all the flashcards

What is gray matter?

The dark-colored tissue in the CNS composed of neuron cell bodies, dendrites, and supporting cells (glia).

Signup and view all the flashcards

What is white matter?

The lighter-colored tissue in the CNS composed of bundles of axons (both myelinated and unmyelinated), and supporting cells.

Signup and view all the flashcards

What are the components of a neuron's plasma membrane?

The plasma membrane of a neuron contains various proteins, including receptors for neurotransmitters, ion channels, pumps, and adhesion molecules.

Signup and view all the flashcards

What is a synapse?

A specialized junction between two neurons where signals are transmitted. It has a pre-synaptic thickening and a post-synaptic thickening.

Signup and view all the flashcards

What is a gap junction?

A type of cell junction that acts as an electrical synapse, allowing rapid communication between cells. It's rare in mature mammalian brains but common during development.

Signup and view all the flashcards

What is a punctum adherens?

A type of cell junction that connects adjacent cells in tissues. It's analogous to the zonula adherens found in epithelial tissues.

Signup and view all the flashcards

What is a neuron's cell body?

The central part of a neuron that contains the nucleus and other organelles. It's responsible for the neuron's metabolic activities.

Signup and view all the flashcards

Axodendritic Synapse

Synapses formed between the axon of one neuron and the dendrite of another neuron. They can be either excitatory or inhibitory.

Signup and view all the flashcards

Axosomatic Synapse

Synapses formed between the axon of one neuron and the cell body (soma) of another neuron. They can be both excitatory and inhibitory.

Signup and view all the flashcards

Axoaxonic Synapse

Synapses formed between the axon of one neuron and the axon of another neuron. They are usually inhibitory and can modulate the strength of signals.

Signup and view all the flashcards

Axospinous Synapse

Synapses formed between the axon of one neuron and the dendritic spines of another neuron. They are usually excitatory and play a crucial role in learning and memory.

Signup and view all the flashcards

Local Circuit Neuron

Neurons that remain within a specific nucleus of origin and connect to other neurons in the same region. They play a vital role in local circuit functions.

Signup and view all the flashcards

Axon Hillock

The part of the axon where an action potential is initiated, located at the junction of the soma and axon.

Signup and view all the flashcards

Initial Segment

The beginning segment of the axon, immediately after the hillock, where the action potential first propagates.

Signup and view all the flashcards

Voltage-gated Na+ Channels

Specialized channels that open in response to changes in membrane potential, allowing sodium ions to flow into the neuron and depolarize the membrane.

Signup and view all the flashcards

Threshold for Action Potential

The lowest level of depolarization needed to trigger an action potential in the initial segment.

Signup and view all the flashcards

Axon Collaterals

Axons that branch off from the main axon, allowing a single neuron to communicate with multiple targets.

Signup and view all the flashcards

Oligodendrocytes

A type of glial cell that wraps around axons, forming a myelin sheath that insulates the axon and speeds up signal transmission.

Signup and view all the flashcards

Nodes of Ranvier

Gaps in the myelin sheath along the axon, where the axon membrane is exposed.

Signup and view all the flashcards

Saltatory Conduction

The process of nerve impulse conduction along myelinated axons, where the signal jumps from one node of Ranvier to the next, increasing the speed of transmission.

Signup and view all the flashcards

Axonal Transport

The movement of molecules and organelles along the axon, including both anterograde (soma to terminal) and retrograde (terminal to soma) transport.

Signup and view all the flashcards

Presynaptic Terminals

Specialized structures at the end of an axon where the signal is transmitted to another neuron or target cell.

Signup and view all the flashcards

Myelinating Schwann cell

A type of Schwann cell that wraps around a peripheral nerve axon, forming a myelin sheath.

Signup and view all the flashcards

Non-myelinating Schwann cell

A type of Schwann cell that forms cytoplasmic troughs, which contain unmyelinated axons.

Signup and view all the flashcards

C fiber

A type of peripheral nervous system axon that is not myelinated, typically found in pain and autonomic fibers.

Signup and view all the flashcards

Axonal tree (telodendria)

The distal branching structure of an axon, containing varicosities filled with synaptic vesicles.

Signup and view all the flashcards

Varicosities

Small swellings on the axonal tree that contain mitochondria and synaptic vesicles.

Signup and view all the flashcards

Synapse

The specialized junction between the presynaptic terminal of one neuron and the dendrites, cell body, or axon hillock of another neuron.

Signup and view all the flashcards

Presynaptic membrane density

The part of the presynaptic terminal membrane, which contains proteins that bind to synaptic vesicles.

Signup and view all the flashcards

Synaptic vesicles

Small, spherical sacs within the presynaptic terminal, containing neurotransmitters and/or modulatory peptides.

Signup and view all the flashcards

Postsynaptic membrane density

The part of the target cell membrane, which contains receptors for neurotransmitters.

Signup and view all the flashcards

Synaptic cleft

The narrow space between the presynaptic terminal and the postsynaptic membrane.

Signup and view all the flashcards

Study Notes

Neurocytology Lecture Objectives

  • Neuronal Features in CNS and PNS:

    • Contrast differences between the peripheral nervous system (PNS) and central nervous system (CNS).
    • Detail the plasma membrane of neurons, including the characteristics of the cell body (soma).
    • Outline the morphology of dendrites and axons, and their myelin sheaths
    • Summarize the presynaptic terminals of neurons.
    • Classify local circuit neurons (interneurons).

  • Neuroglia in CNS and PNS:

    • Provide a summary of glial cells' general characteristics.
    • List the morphology and function of astrocytes.
    • Detail the morphology and function of oligodendrocytes and their role in myelination
    • Detail the morphology and function of microglia
    • Detail the morphology and function of ependymal and tanycytic cells.
    • Discuss the differences between oligodendrocytes and Schwann cells in myelination.

Neuronal Features

  • Neuron Structure:

    • Neurons are long-lived, electrically excitable cells specialized for receiving, integrating, and transmitting information to other target cells.
    • Neuron morphology consists of a cell body (soma, perikaryon) with branching processes (dendrites, axon).
    • Different types of neurons exist based on the number of processes originating from the cell body (bipolar, unipolar, multipolar).
    • Dendrites receive signals; the axon transmits signals. The axon usually originates from the axon hillock.

  • Plasma Membrane:

    • The plasma membrane of neurons is a phospholipid bilayer with integral proteins (receptors, ion channels, pumps, adhesion molecules).
    • Synapses (junctions between neurons) are characterized by thickening of pre- and postsynaptic membranes.
    • Junctions (adhesion, gap and punctum adherens) exist to facilitate neural transmission.

Cell Body Features

  • Cell body:
    • The cell body (soma or perikaryon) contains cytoplasm and nucleus.
    • Nissl bodies are aggregates of rough endoplasmic reticulum, crucial for protein synthesis.
    • Smooth endoplasmic reticulum helps in ion sequestration and synthesis of membrane-bound vesicles.
    • Mitochondria provide energy (ATP) for neuronal function.
    • Other organelles essential for cellular function (lysosomes, microtubules, neurofilaments) are present inside the neuron.
    • Lipofuscin pigment accumulates with aging.

Dendrites

  • Dendrites
    • Dendrites taper and branch extensively, increasing receptive surface area.
    • Membranes of dendrites contain receptors for neurotransmitters promoting excitatory or inhibitory activity.
    • Dendritic spines (appendages) enhance the number of receptive sites.
    • They contain microtubules and neurofilaments necessary for their structure and maintenance.

Axons/Myelin

  • Axons:
    • Axons conduct nerve impulses away from the cell body.
    • Axon hillock is the initial segment where the action potential originates.
    • The Axon varies in diameter (0.7-25 microns)
    • Myelination speeds up the rate of impulse conduction.

Axons and Myelin

  • Myelination:
    • Myelinated axons are faster than unmyelinated axons.
    • PNS myelination involves Schwann cells, forming a single segment of myelin on the axon.
    • CNS myelination involves oligodendrocytes which create myelin segments on multiple axons.
    • Nodes of Ranvier are important for saltatory conduction.

Presynaptic Terminals

  • Synaptic Terminals:
    • Axon terminals branch forming axonal tree (telodendria or arborization).
    • Varicosities (swellings) contain mitochondria and synaptic vesicles.
    • The presynaptic membrane density is part of the axon varicosity membrane.

Neuroglia

  • Types of neuroglia:

    • Astrocytes, oligodendrocytes, & microglia are the most abundant Glia in CNS.
    • Ependymal, & tanycytes are neural supporting cells present in CNS.
    • Schwann cells are found in PNS. They can form a myelin sheath around axons.
    • Satellite cells are found in the PNS associated with neuronal cell bodies.

  • Neuroglia Functions:

    • Provide structural support, insulation, and nutritional support to neurons. They help compartmentalize and isolate neuronal units.
    • Buffer potassium, help regulate the extracellular potassium concentration and thus maintenance of transmembrane potential, and maintain the blood-brain barrier.
    • Involved in neuronal repair, removing cellular debris, and maintaining the microenvironment.
    • Support nutrient delivery to neurons, through blood-brain barrier maintenance.
    • Glia can have roles in synaptic plasticity and neurogenesis.

Interneurons

  • Interneurons:
    • Interneurons (local circuit neurons, LCN) have axons that remain within the nuclei of origin (or intrinsic neurons); different morphology according to the role.
    • Several anatomical locations with varying degrees of axon localization.
    • Their synapses are often inhibitory

Dendritic Morphology

  • Dendrites:
    • Dendrites have receptive surfaces with numerous synapses and specific receptors.
    • They contain microtubules and neurofilaments, crucial for their morphology.
    • Spine-like structures on the dendrites help to improve the surface area to form synapses.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Neurocytology Lecture Objectives PDF

Description

Test your knowledge on neuronal features and neuroglia within the CNS and PNS. This quiz covers the morphology, functions, and characteristics of neurons and glial cells, highlighting their differences and roles in the nervous system. Perfect for students studying neuroanatomy and neurophysiology.

Use Quizgecko on...
Browser
Open
Browser
Browser