Nervous Tissue Quiz
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Questions and Answers

What describes the axons that are covered by a myelin sheath?

  • Sensory neurons
  • Myelinated axons (correct)
  • Gray matter
  • Unmyelinated axons

    • What is the primary function of the myelin sheath?

  • To connect neurons to muscle fibers
  • To insulate the axon and speed up impulse transmission (correct)
  • To increase the size of the axon
  • To form synapses between neurons

    • Which part of the neuron sends the impulse to the synapse?

  • Presynaptic neuron (correct)
  • Dendrite
  • Postsynaptic neuron
  • Synaptic cleft

    • What are the gaps called that are found in myelinated axons?

    <p>Nodes of Ranvier</p> Signup and view all the answers

    Which type of neuron is primarily involved in carrying sensory information to the brain?

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

    What characterizes a bipolar neuron?

    <p>Two extended processes, one dendrite and one axon</p> Signup and view all the answers

    Where are interneurons primarily located?

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

    What do synaptic vesicles contain?

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

    What type of neuron conducts nerve impulses from the brain or spinal cord to the effector organ?

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

    Which type of neuroglia helps form the blood-brain barrier?

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

    What is the primary role of microglial cells?

    <p>Providing immune protection</p> Signup and view all the answers

    The Central Nervous System (CNS) comprises which of the following structures?

    <p>Brain and spinal cord</p> Signup and view all the answers

    Which division of the nervous system is involved in voluntary muscle contractions?

    <p>Somatic Nervous System</p> Signup and view all the answers

    How many pairs of spinal nerves are present in the human body?

    <p>31 pairs</p> Signup and view all the answers

    What is the function of ependymal cells in the nervous system?

    <p>Form a porous layer for substance diffusion</p> Signup and view all the answers

    What are the two main components of the Peripheral Nervous System (PNS)?

    <p>Cranial nerves and spinal nerves</p> Signup and view all the answers

    What are the three major functions of the nervous system?

    <p>Sensory input, Integration, Motor output</p> Signup and view all the answers

    What distinguishes the responses of the nervous system from the endocrine system?

    <p>Nervous system responses are immediate but short-lived.</p> Signup and view all the answers

    Which type of cells compose nerve tissue?

    <p>Neurons and neuroglial cells</p> Signup and view all the answers

    What role do dendrites play in a neuron?

    <p>They conduct nerve impulses toward the soma.</p> Signup and view all the answers

    What is unique about the axon structure in neurons?

    <p>All neurons contain only one axon.</p> Signup and view all the answers

    What is the function of the myelin sheath in neurons?

    <p>To increase the speed of action potential propagation.</p> Signup and view all the answers

    Why don't neurons undergo mitosis?

    <p>They are specialized cells that do not regenerate.</p> Signup and view all the answers

    What function do interneurons serve in the nervous system?

    <p>They process and interpret messages from sensory neurons.</p> Signup and view all the answers

    What type of conduction occurs in myelinated axons that significantly increases the rate of impulse transmission?

    <p>Saltatory conduction</p> Signup and view all the answers

    In the classification of neurons by structure, which type is characterized by a single nerve fiber extending from the soma that divides into a dendrite and an axon?

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

    Which part of a synapse is responsible for receiving neurotransmitters from the presynaptic neuron?

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

    What is the gap between two neurons at a synapse called?

    <p>Synaptic cleft</p> Signup and view all the answers

    What type of neuron primarily relays nerve impulses from sensory neurons to motor neurons?

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

    What type of motor neurons increases activity in the effector organ?

    <p>Accelerator motor neurons</p> Signup and view all the answers

    Which of the following neuroglial cells are primarily involved in immune protection within the nervous system?

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

    Which category do sensory neurons that conduct nerve impulses towards the brain belong to?

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

    What is the main function of astrocytes in the nervous system?

    <p>Regulate blood flow and nutrient transport</p> Signup and view all the answers

    In the context of synaptic transmission, what role do synaptic vesicles play?

    <p>They store neurotransmitters</p> Signup and view all the answers

    Which division of the nervous system includes the cranial and spinal nerves?

    <p>Peripheral Nervous System (PNS)</p> Signup and view all the answers

    What is a characteristic feature of bipolar neurons?

    <p>Two distinct processes: a dendrite and an axon</p> Signup and view all the answers

    The ependymal cells serve primarily to:

    <p>Facilitate diffusion between interstitial fluid and cerebrospinal fluid</p> Signup and view all the answers

    Which classification of neuron is primarily unipolar and functions as a sensory receptor?

    <p>Sensory or afferent neurons</p> Signup and view all the answers

    What is the primary role of the somatic nervous system?

    <p>Regulate voluntary muscle contractions</p> Signup and view all the answers

    In the structure of a synapse, what are synaptic knobs?

    <p>The endings of the axon that house synaptic vesicles</p> Signup and view all the answers

    Which type of neuron primarily conducts nerve impulses toward the central nervous system?

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

    What characterizes oligodendrocytes in the nervous system?

    <p>They produce myelin sheath within the CNS</p> Signup and view all the answers

    The autonomic nervous system regulates functions of which muscle types?

    <p>Smooth, cardiac muscles and glands</p> Signup and view all the answers

    What is the primary difference in the response time between the nervous system and the endocrine system?

    <p>The nervous system produces immediate but short-lived responses.</p> Signup and view all the answers

    Which type of neuron typically has the highest number of dendrites?

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

    What function do Schwann cells serve in relation to the neurons?

    <p>They produce the myelin sheath around axons.</p> Signup and view all the answers

    What is a key structural feature of all neurons regarding their axons?

    <p>Neurons have only one axon.</p> Signup and view all the answers

    What is the main function of the 'node of Ranvier' in myelinated axons?

    <p>To facilitate voltage-gated channel interaction for action potentials.</p> Signup and view all the answers

    What distinguishes interneurons from sensory and motor neurons in the nervous system?

    <p>Interneurons are primarily involved in integrating and processing information.</p> Signup and view all the answers

    Which of the following best describes the role of neuroglial cells in nerve tissue?

    <p>They fill spaces and provide support for neurons.</p> Signup and view all the answers

    What is the primary reason neurons cannot regenerate after injury?

    <p>Neurons lack the ability to undergo mitosis.</p> Signup and view all the answers

    How are sensory (afferent) neurons primarily characterized?

    <p>They detect stimuli from the internal or external environment.</p> Signup and view all the answers

    Study Notes

    Nervous System Functions

    • The nervous system and endocrine system are the primary control centers for maintaining body homeostasis.
    • The nervous system uses electrical signals (nerve impulses) for immediate but short-lived responses, while the endocrine system uses chemical signals (hormones) for slower but longer-lasting responses.
    • The nervous system has three major functions:
      • Sensory Input: Sensory or afferent neurons detect internal or external changes (stimuli) and transmit the message to the brain or spinal cord.
      • Integration: Interneurons in the brain or spinal cord process and interpret the message from sensory neurons and relay the message back to body parts.
      • Motor Output: Motor or efferent neurons receive the message from interneurons and produce a response at the effector organ (muscle or gland).

    Nerve Tissue

    • Nerve tissue is composed of two main types of cells:
      • Neurons: Nerve cells specialized for detecting and reacting to stimuli by generating and conducting nerve impulses.
      • Neuroglial cells: Accessory cells that provide support and fill spaces around neurons.
    • Microscopic anatomy of neurons:
      • All neurons have a cell body called soma containing a nucleus, organelles, and a modified endoplasmic reticulum called Nissl body.
      • Despite containing DNA, neurons lack the ability to reproduce or regenerate.
      • Extensions from the soma form nerve fibers:
        • Dendrites: Conduct nerve impulses toward the soma.
        • Axon: Conduct nerve impulses away from the soma (to another neuron or effector organ).
      • The number of dendrites varies (from 1 in unipolar and bipolar neurons to thousands in multipolar neurons).
      • All neurons only have one axon.
      • Longer axons are enclosed by a lipoprotein substance called the myelin sheath, produced by Schwann cells.

    Myelin Sheath

    • The myelin sheath insulates the axon against depolarization, forcing action potentials to occur in the gaps between the myelin sheath (nodes of Ranvier).
    • Axons enclosed by the myelin sheath are called myelinated axons, comprising the white matter in the nervous system.
    • Axons without a myelin sheath are called unmyelinated axons, comprising the gray matter in the nervous system.

    Saltatory Conduction

    • The myelin sheath insulates the axon, leaving only narrow gaps called nodes of Ranvier where action potentials can occur.
    • This type of nerve impulse propagation, where action potentials jump from one gap to the next, is called saltatory conduction, significantly increasing the rate of impulse transmission.

    Synapse

    • A synapse is the junction between two neurons or between a neuron and an effector organ (muscle or gland).
    • Each synapse consists of:
      • Presynaptic neuron: Sends an impulse to the synapse.
      • Axon: The nerve fiber extending from the presynaptic neuron that propagates the impulse to the synapse.
      • Synaptic knobs: Round endings of the axon.
      • Synaptic vesicles: Membranous sacs containing a neurotransmitter (e.g. acetylcholine, norepinephrine, dopamine) located in the synaptic knobs.
      • Synaptic cleft: Gap between the two neurons in the synapse.
      • Dendrite: Nerve fiber that continues to propagate the nerve impulse to the second neuron (postsynaptic neuron). Receptors on this dendrite receive the neurotransmitter from the axon.
      • Postsynaptic neuron: Neuron receiving the nerve impulse from the presynaptic neuron through the synapse.

    Neuron Classification (Structure)

    • Unipolar neuron: A single nerve fiber extends from the soma, dividing into a dendrite and an axon (sensory neurons conducting reflexes or detecting various stimuli).
    • Bipolar neuron: A dendrite and an axon extend independently from the soma (sensory neurons involved in special senses such as vision, olfaction, and hearing).
    • Multipolar neuron: One axon and many dendrites extend from the soma (interneurons located inside the brain and spinal cord).

    Neuron Classification (Function)

    • Sensory (Afferent) neuron:
      • Conducts nerve impulses from the body to the brain or spinal cord.
      • Endings of its dendrite may be modified to become nerve receptors.
      • Usually unipolar in structure.
    • Interneuron:
      • Relays nerve impulses from sensory neurons to motor neurons.
      • Located entirely inside the tissues of the brain or spinal cord.
      • Involved in processing and integration within the nervous system.
      • Usually multipolar in structure.
    • Motor (Efferent) neuron:
      • Conducts nerve impulses from the brain or spinal cord to the effector organ (muscles or glands).
      • Usually multipolar in structure.
      • Accelerator motor neurons: Increase activity in the effector organ.
      • Inhibitory motor neurons: Decrease activity in the effector organ.

    Neuroglia Classification

    • Neuroglia: Supporting cells of the nervous system.
      • Astrocytes: Star-shaped cells found between neurons and blood vessels.
        • Most abundant glial cells.
        • Help form the blood-brain barrier.
        • Functions: structural support, transport of substances between blood vessels and neurons, mop up excess ions (K+) and neurotransmitters.
      • Microglial cells: Small ovoid cells.
        • Function: structural support and phagocytosis (immune protection).
      • Ependymal cells: Cuboidal or columnar shaped cells.
        • Function: Form a porous layer through which substances diffuse between the interstitial fluid and the cerebrospinal fluid.
      • Oligodendrocytes: Resemble astrocytes but have fewer processes and are arranged in rows along nerve fibers.
        • Function: Produce myelin sheaths within the brain and spinal cord.

    Nervous System Divisions

    • The human nervous system consists of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
    • CNS: Composed of the brain (located in the cranial cavity) and the spinal cord (located in the vertebral cavity).
    • The CNS serves as the main control center for all body activities.
    • PNS: Composed of nerves derived from the brain and spinal cord (12 pairs of cranial nerves and 31 pairs of spinal nerves).
    • The PNS serves as a linkage between the CNS and the body.
    • The PNS can be subdivided into:
      • Sensory (Afferent) nerves: Send nerve impulses from the body to the CNS.
      • Motor (Efferent) nerves: Send nerve impulses from the CNS to effector organs.
    • Motor nerves: Divided into:
      • Somatic Nervous System (SNS): Regulates voluntary contraction of skeletal muscles.
      • Autonomic Nervous System (ANS): Regulates involuntary control of smooth muscles, cardiac muscles, and glands.

    Nervous System Functions

    • The nervous system, along with the endocrine system, maintains body homeostasis.
    • The nervous system transmits information rapidly using electrical signals, resulting in immediate but short-lived responses.
    • The endocrine system utilizes chemical signals (hormones) for slower but longer-lasting responses.
    • The nervous system is responsible for three primary functions:
      • Sensory input: Sensory (afferent) neurons detect internal and external stimuli, transmitting this information to the brain or spinal cord.
      • Integration: Interneurons in the brain or spinal cord process and interpret sensory information, then send signals back to the appropriate body parts.
      • Motor output: Motor (efferent) neurons receive signals from interneurons and initiate a response in effector organs (muscles or glands).

    Nerve Tissue

    • Nerve tissue is composed of two main cell types:
      • Neurons: Specialized cells that detect and react to stimuli by generating and conducting nerve impulses.
      • Neuroglial cells: Accessory cells that provide support and fill spaces around neurons.

    Neuron Anatomy

    • All neurons have a cell body (soma) containing a nucleus, organelles, and Nissl bodies (modified endoplasmic reticulum).
    • Neurons lack the ability to undergo DNA replication and mitosis, preventing them from reproducing or regenerating.
    • Extensions from the soma form nerve fibers:
      • Dendrites: Conduct nerve impulses towards the soma.
      • Axon: Conducts nerve impulses away from the soma, towards another neuron or an effector organ.
    • The number of dendrites varies, with unipolar and bipolar neurons having one or two, while multipolar neurons can have thousands.
    • All neurons have only one axon.
    • Longer axons are wrapped in a myelin sheath, a lipoprotein substance produced by Schwann cells (a type of neuroglial cell).

    Myelin Sheath

    • The myelin sheath insulates the axon, preventing depolarization and forcing action potentials to occur only at the gaps between the myelin sheath, called Nodes of Ranvier.
    • Axons enclosed by a myelin sheath are called myelinated axons, forming the white matter in the nervous system.
    • Axons lacking a myelin sheath are called unmyelinated axons, making up the gray matter in the nervous system.

    Nerve Impulse Propagation

    • The myelin sheath insulates the axon, leaving only Nodes of Ranvier where action potentials can occur.
    • This type of nerve impulse propagation, where the action potential jumps from one node to the next, is called saltatory conduction, significantly increasing the speed of transmission.

    Synapse

    • A synapse is the junction between two neurons or between a neuron and an effector organ.
    • Each synapse consists of:
      • Presynaptic neuron: The neuron sending the impulse.
      • Axon: The nerve fiber extending from the presynaptic neuron.
      • Synaptic knobs: Round endings of the axon.
      • Synaptic vesicles: Membranous sacs within the synaptic knobs containing neurotransmitters (e.g., acetylcholine, norepinephrine, dopamine).
      • Synaptic cleft: The gap between the two neurons.
      • Dendrite: The nerve fiber receiving the impulse from the presynaptic neuron.
      • Receptors: Located on the dendrite, these receive the neurotransmitter from the axon.
      • Postsynaptic neuron: The neuron receiving the nerve impulse from the presynaptic neuron through the synapse.

    Neuron Classification (Structure)

    • Unipolar neuron: A single nerve fiber extends from the soma, dividing into a dendrite and an axon. Found in sensory neurons involved in reflexes or detecting stimuli.
    • Bipolar neuron: A dendrite and an axon extend independently from the soma. Found in sensory neurons for special senses (vision, olfaction, hearing).
    • Multipolar neuron: One axon and multiple dendrites extend from the soma. Found in interneurons within the brain and spinal cord.

    Neuron Classification (Function)

    • Sensory or afferent neuron: Conducts nerve impulses from the body to the brain or spinal cord. Dendrite endings may be modified as nerve receptors. Usually unipolar in structure.
    • Interneuron: Relays nerve impulses from sensory neurons to motor neurons. Located entirely within the brain or spinal cord. Involved in processing and integrating information. Usually multipolar in structure.
    • Motor or efferent neuron: Conducts nerve impulses from the brain or spinal cord to effector organs (muscles or glands). Usually multipolar in structure.
      • Accelerator motor neurons: Increase activity in effector organs.
      • Inhibitory motor neurons: Decrease activity in effector organs.

    Neuroglia Classification

    • Astrocytes: Star-shaped cells found between neurons and blood vessels. The most abundant glial cells, forming the blood-brain barrier. Their functions include structural support, transporting substances, and removing excess ions and neurotransmitters.
    • Microglial cells: Small, ovoid cells. Function in structural support and phagocytosis (immune protection).
    • Ependymal cells: Cuboidal or columnar cells. Form a porous layer allowing substances to diffuse between interstitial fluid and cerebrospinal fluid.
    • Oligodendrocytes: Resemble astrocytes but have fewer processes and are arranged in rows along nerve fibers. Produce myelin sheaths within the brain and spinal cord.

    Divisions of the Nervous System

    • The human nervous system consists of the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
    • CNS: Consists of the brain (cranial cavity) and spinal cord (vertebral cavity). These serve as the main control centers for all body functions.
    • PNS: Consists of nerves derived from the brain and spinal cord (12 pairs of cranial nerves and 31 pairs of spinal nerves), linking the CNS to the body.
    • PNS: Further divided into the Sensory (afferent) nerves and Motor (efferent) nerves.
      • Sensory nerves: Transmit impulses from the body to the CNS.
      • Motor nerves: Transmit impulses from the CNS to effector organs.
    • Motor nerves: Divided into the Somatic Nervous System (SNS) and the Autonomic Nervous System (ANS).
      • SNS: Regulates voluntary contraction of skeletal muscles.
      • ANS: Regulates involuntary control of smooth muscles, cardiac muscles, and glands.

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