Nervous System Architecture Overview
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Questions and Answers

Which statements correctly describe the function of myelination in the peripheral nervous system?

  • Myelination is essential for the regeneration of axons in the central nervous system.
  • Myelination increases the speed of action potential transmission along the axon. (correct)
  • Myelination occurs solely through oligodendrocytes wrapping multiple axons.
  • Myelination decreases electrical resistance in nerve fibers.

What role do perineuronal satellite cells play in the nervous system?

  • They act as immune cells responding to pathogens in the neural tissue.
  • They assist in neurotransmitter release at synaptic junctions.
  • They provide electrical insulation and metabolic support surrounding nerve cell bodies. (correct)
  • They form the myelin sheath around multiple axons.

How are unmyelinated axons in the PNS structurally different from myelinated axons?

  • Unmyelinated axons are fully embedded in the processes of glial cells.
  • Unmyelinated axons consist of multiple oligodendrocytes surrounding them.
  • Unmyelinated axons are tightly abutted within grooves of Schwann cells without nodes. (correct)
  • Unmyelinated axons are surrounded by Schwann cells, forming nodes of Ranvier.

Which of the following best describes the function of microglia?

<p>They perform immune surveillance and phagocytosis within neural tissue. (B)</p> Signup and view all the answers

What initiates the process of myelination by Schwann cells?

<p>The surrounding of the axon by Schwann cell processes or mesaxon. (C)</p> Signup and view all the answers

What characteristic distinguishes pseudounipolar neurons from unipolar neurons?

<p>Pseudounipolar neurons have a single process that bifurcates. (D)</p> Signup and view all the answers

Where are the neural cell bodies of sensory neurons typically located?

<p>In the dorsal root ganglia or cranial nerve ganglia. (C)</p> Signup and view all the answers

Which type of neuron has a very long axon and collects stimuli via a long dendrite?

<p>Bipolar neuron. (A)</p> Signup and view all the answers

What is a key feature of multipolar neurons?

<p>They usually have many dendrites and one long axon. (A)</p> Signup and view all the answers

What role does the axon hillock play in neuron function?

<p>It is involved in the generation of the action potential. (B)</p> Signup and view all the answers

Which part of a neuron is primarily responsible for propagating electrical impulses away from the soma?

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

What distinguishes bipolar neurons in terms of their structural morphology?

<p>They have two long processes—one dendrite and one axon. (D)</p> Signup and view all the answers

What type of axon structure may not contain elements such as Golgi apparatus or free ribosomes?

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

What type of neuron primarily sends signals away from the cell body to effectors?

<p>Multipolar neurons (C)</p> Signup and view all the answers

Which neuron type primarily participates in sensory functions by detecting stimuli?

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

What is the primary function of interneurons?

<p>Integrate and transmit information between neurons (C)</p> Signup and view all the answers

In the motor neuron system, which type of neuron is responsible for the initial signal transmission to target muscles?

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

Which type of neuron is primarily responsible for transmitting signals from sensory receptors to the central nervous system?

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

What is the primary role of interneurons within the nervous system?

<p>Connect sensory and motor pathways (A)</p> Signup and view all the answers

What is the characteristic feature of multipolar neurons?

<p>Single long axon with multiple dendrites (D)</p> Signup and view all the answers

What type of synapse primarily relies on neurotransmitter diffusion between neurons?

<p>Chemical synapse (C)</p> Signup and view all the answers

Which glial cell type is primarily responsible for maintaining the blood-brain barrier?

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

Which components of neurons are directly involved in synaptic integration?

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

What aspect of axonal transport primarily moves substances from the axon terminal back to the cell body?

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

What is the main function of oligodendrocytes in the central nervous system?

<p>Myelinate axons (C)</p> Signup and view all the answers

Which type of synapse is characterized by direct transfer of electrical signals through gap junctions?

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

Which characteristic is most commonly associated with the excitability of neurons?

<p>Capability to respond to stimuli (A)</p> Signup and view all the answers

What process declines in neurons as they mature and cannot divide?

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

What type of glial cell is responsible for immune defense in the central nervous system?

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

What is the typical structure found at the presynaptic terminal of a chemical synapse?

<p>Synaptic vesicles containing neurotransmitters (D)</p> Signup and view all the answers

Which part of the neuron is primarily responsible for processing and integrating incoming signals?

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

What feature differentiates myelinated axons from unmyelinated ones?

<p>Presence of the myelin sheath (C)</p> Signup and view all the answers

Which part of the nervous system contains both the spinal cord and the brain?

<p>Central Nervous System (C)</p> Signup and view all the answers

Which type of astrocyte is predominantly found in white matter?

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

What is a primary function of astrocytes in the nervous system?

<p>Maintenance of the blood-brain barrier (C)</p> Signup and view all the answers

Which of the following statements about glial cells is TRUE?

<p>Glial cells have a larger population than neurons in the nervous system. (D)</p> Signup and view all the answers

What type of cell is primarily responsible for the formation of the myelin sheath in the peripheral nervous system?

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

Which type of astrocyte has thicker, highly branched processes and is mainly found in gray matter?

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

What role do astrocytes play during injury responses in the nervous system?

<p>Phagocytize neuronal debris (C)</p> Signup and view all the answers

How do astrocytes contribute to maintaining electrolyte balance in the extracellular environment?

<p>By buffering K+ and neurotransmitters (B)</p> Signup and view all the answers

Which of these cells is considered the main immune defense in the central nervous system?

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

What potential consequence is linked to the proliferation of glial cells?

<p>Formation of brain tumors (A)</p> Signup and view all the answers

Which statement accurately describes the recovery function of astrocytes?

<p>Astrocytes repair and maintain the blood-brain barrier. (B)</p> Signup and view all the answers

Flashcards

Soma (Cell Body)

The central region of a neuron containing the nucleus and other organelles responsible for protein synthesis.

Dendrites

Branched extensions of the soma that receive signals from other neurons and the external environment.

Axon

A single, long, slender extension of the soma that transmits electrical impulses away from the soma.

Axoplasm

The cytoplasm within the axon that lacks large organelles like Golgi apparatus and free ribosomes.

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Axon Hillock

The conical-shaped zone of transition between the soma and axon.

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Pseudounipolar Neuron

A neuron with one axon and one dendrite fused together, forming a single process.

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Bipolar Neuron

A neuron with one very long dendrite and one very long axon.

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Multipolar Neuron

A neuron with one long axon and many dendrites that form a large field to collect stimuli.

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Sensory Neurons

Specialized neurons that detect stimuli, such as light, sound, or touch, and transmit this information to the central nervous system.

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Motor Neurons

Neurons that carry signals from the central nervous system to muscles and glands, causing them to contract or secrete.

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Interneuron

A type of neuron that processes information within the central nervous system, connecting other neurons together.

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Axonal Transport

The process of transporting materials within a neuron, essential for maintaining its structure and function.

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Chemical Synapse

A type of synapse where chemical signals are used to transmit information between neurons.

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Electrical Synapse

A type of synapse where electrical signals are directly transmitted through gap junctions between neurons.

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Synapse

The junction between two neurons, where information is transmitted.

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Synaptic Transmission

The process of transmitting information from the presynaptic neuron to the postsynaptic neuron at a synapse.

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Presynaptic Terminal

The specialized structure at the end of an axon that releases neurotransmitters.

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What makes up the CNS?

The central nervous system (CNS) consists of the brain and spinal cord, which integrate and process information.

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What is the PNS?

The peripheral nervous system (PNS) encompasses all nerve fibres and ganglia outside the brain and spinal cord, extending to the body's extremities and organs.

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What does the SNS control?

The somatic nervous system (SNS) enables voluntary control over skeletal muscles, allowing conscious movement.

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What does the ANS control?

The autonomic nervous system (ANS) regulates involuntary functions like heart rate, digestion, and glandular secretions.

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What are neurons?

Neurons are the fundamental units of the nervous system, responsible for processing and transmitting information via electrochemical signals.

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What are glial cells?

Glial cells, also known as neuroglial cells, provide support and structure to neurons, ensuring their proper function.

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What is grey matter?

Grey matter is composed of neuron cell bodies, unmyelinated axons, dendrites, glial cells, and capillaries, forming the site for information processing and integration.

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What is white matter?

White matter is composed of glial cells and myelinated axons, facilitating rapid signal transmission throughout the nervous system.

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What are ganglia?

Ganglia are clusters of nerve cell bodies located outside the CNS, serving as relay points for information.

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What are nerves?

Nerves are bundles of myelinated and/or unmyelinated axons with supporting cells, transmitting information between the CNS and the rest of the body.

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Glial cells

Specialized cells in the nervous system responsible for supporting and protecting neurons, providing structural and metabolic functions.

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Astrocytes

The largest type of glial cell in the CNS, characterized by numerous branches and involvement in diverse functions.

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Fibrous astrocytes

Type of astrocyte found predominantly in white matter, featuring long, unbranched processes.

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Protoplasmic astrocytes

Type of astrocyte found mainly in gray matter, featuring shorter, thicker, and highly branched processes.

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Oligodendrocytes

A type of glial cell in the CNS that forms the myelin sheath around axons, providing insulation and speeding up nerve impulse conduction.

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Microglia

Immune cells of the CNS, acting as macrophages to engulf debris and pathogens.

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Ependymal cells

Ependymal cells line the cavities of the brain and spinal cord, contributing to the production and circulation of cerebrospinal fluid.

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Schwann cells

Supporting cells of the PNS, responsible for forming the myelin sheath around axons, providing insulation and speeding up nerve impulse conduction.

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Astrogliosis

The process of astrocytes responding to injury by phagocytizing debris, filling space, and reducing inflammation.

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Blood-brain barrier (BBB)

The protective barrier formed by astrocyte processes that regulate the passage of substances between the blood and the brain.

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Myelin Sheath

A layered structure formed by specialized glial cells that surrounds and protects axons, facilitating the faster transmission of action potentials. It also assists in axon regeneration in the peripheral nervous system.

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Nodes of Ranvier

Gaps between myelin sheaths where the axon membrane is exposed. They play a crucial role in allowing the action potential to jump between these nodes, speeding up signal transmission.

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Saltatory Conduction

The type of conduction that occurs along myelinated axons, where the action potential jumps from one node of Ranvier to the next, increasing the speed of transmission.

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Perineuronal Satellite Cells

Glial cells that reside within ganglia, surrounding nerve cell bodies. They regulate the microenvironment, provide electrical insulation, facilitate metabolic exchange, and offer protection. They are similar to Schwann cells but do not form myelin.

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Study Notes

Nervous System Architecture

  • The nervous system receives, processes, integrates, and responds to information.
  • It enables perception and cognition.
  • It controls somatic and visceral system activities.

Central Nervous System (CNS)

  • Comprised of the brain and spinal cord.
  • Contains nerve fibers and ganglia outside of brain and spinal cord.

Peripheral Nervous System (PNS)

  • Includes nerve fibers and ganglia outside of the brain and spinal cord.
  • Contains special nerve endings.

Functional Divisions of the Nervous System

  • Somatic Nervous System (SNS): Voluntary, conscious control of body activities. Provides motor and sensory innervation to all parts of the body (excluding internal organs, smooth muscles, and glands).
  • Autonomic Nervous System (ANS): Controls cardiac muscles, smooth muscles, and glands. Provides sensory innervation to internal organs.

Nervous Tissue: Basic Components

  • Neurons (Nerve cells): Process and integrate information.
  • Glial cells (Neuroglial cells): Support and glue neural cells. They make up 90% of the nervous system.

Glial Cells

  • Differentiated and developed from Neural Stem Cells (neuroepithelial cells), which are multipotent.
  • In the CNS, neuroepithelial cells can develop into all types of neuroglial cells and neurons.
  • Grey matter: Neuronal cell bodies, neuropil (unmyelinated axons and dendrites), glial cells, and capillaries. Involved in synaptic integration, information processing, motor control, and sensory perception.

Structures of Nerve Fibers

  • Axon and myelin sheath
  • Endoneurium
  • Nerve fascicle
  • Perineurium
  • Nerve trunk
  • Epineurium

Neuron Structure

  • Cytoplasm: Contains nucleus, rough endoplasmic reticulum (rough ER; Nissl bodies), smooth endoplasmic reticulum (smooth ER), nucleus, and organelles.
  • Dendrites: Propagate electrochemical stimulation to the soma. Branched extensions of cytoplasm from the soma. They receive signals from other neurons, forming a large dendritic field for wider detection of stimuli.
  • Axon: Conducts electrical impulses away from the soma, usually long and slender. Myelinated or unmyelinated

Neuron Morphology and Classification

  • Unipolar, Pseudounipolar, Bipolar, and Multipolar: Depending on the number of processes (extensions) arising from the cell body.
  • Pseudounipolar: Looks like a unipolar neuron but actually has two processes. The peripheral axon carries signals to the soma from receptors, and the central axon carries impulses to the CNS. Found in sensory neurons.
  • Bipolar: One dendrite and one axon. Found in special sense organs (e.g., olfactory and retina).
  • Multipolar: Many dendrites and one axon. Most common type, including motor and interneurons.

Interneurons (Interneurons)

  • Found in the brain's motor cortex.
  • Collect signals from one neuron then sends signals to other.
  • Involved in integration of information, process, store, retrieve, and make decisions.
  • Small neurons form networks with unmyelinated axons.

Synapse Classification

  • Chemical synapse: Chemical signals (ions) are transferred to chemical signals (then back to electrical signals). Neurotransmitters are released from the presynaptic neuron to carry signals across the synaptic cleft.
  • Electrical synapse: Electrical signals (ions) move directly between synapses. Common in smooth muscle cells, cardiac muscle cells, and retinal cells.

Axonal Transport

  • Newly synthesized protein molecules are transported to distant locations within neurons.
  • Antrograde transport: Moves materials from the cell body to axon terminals.
  • Retrograde transport: Moves materials from axon terminals to the cell body.

Postsynaptic Terminal & Membrane

  • Contain membrane receptors and ion gates to receive chemical signals.
  • A synaptic cleft separates the pre- and postsynaptic membranes (20-30nm of space).

Types of Neuroglia: Central Nervous System

  • Astrocytes: Largest glial cells with many branches(both fibrous and protoplasmic). Provide structural support, maintain and repair BBB, and participate in the injury response.
  • Oligodendrocytes: Form myelin sheaths around CNS axons, accelerating signal transmission.
  • Microglia: Smallest neuroglia, immune surveillance cells.
  • Ependymal cells: Epithelial-like cells lining ventricles of the brain and involved in CSF production.

Types of Neuroglia: Peripheral Nervous System

  • Schwann cells: Form myelin sheaths around PNS axons. Allow for fast signal transmission and axon regeneration when injury occurs.
  • Satellite cells: Surround neuron cell bodies in ganglia. Provide metabolic support and protection.

Nerve Injury and Regeneration

  • CNS: Regeneration is slower or blocked by inhibitory factors and glial scar formation.
  • PNS: Regeneration is possible, with Schwann cells promoting axon regrowth.

Saltatory Conduction

  • Action potentials jump between myelinated regions (nodes of Ranvier) on axons, increasing conduction velocity.

Unmyelinated Axons

  • Schwann cells tightly cover the axon.
  • Nodes of Ranvier do not form.
  • Axons fit into grooves of schwann cells.

Antigen-Presenting Cells

  • Activated during injury, they become enlarged, amoeboid shaped
  • Involved in phagocytosis and surveillance.
  • Present antigens with other cells.

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Description

This quiz covers the architecture of the nervous system, including the central and peripheral nervous systems. It explores functional divisions like the somatic and autonomic nervous systems and the basic components such as neurons. Test your knowledge on how the nervous system operates and its various functions.

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