Skip to main content
Back

Fundamentals of the Nervous System and Nervous Tissue

Control buttons has been changed to "navigation" mode.
1/28
  • What are the three overlapping functions of the nervous system?

    Sensory input: gathering information about internal and external changes.
    Integration: processing and interpreting sensory input.
    Motor output: activation of effector organs producing a response.

  • What are the two principal parts of the nervous system?

    Central nervous system (CNS): brain and spinal cord, integration and control center.
    Peripheral nervous system (PNS): nerves outside CNS, connects CNS to body.

  • What are the two functional divisions of the peripheral nervous system (PNS)?

    Sensory (afferent) division: conveys impulses to CNS.
    Motor (efferent) division: transmits impulses from CNS to effectors.

  • What are the subdivisions of the motor (efferent) division of the PNS?

    Somatic nervous system: voluntary control of skeletal muscles.
    Autonomic nervous system: involuntary control of smooth muscle, cardiac muscle, and glands; includes sympathetic and parasympathetic divisions.

  • What are neuroglia and neurons?

    Neuroglia: small cells that support and protect neurons.
    Neurons: excitable cells that transmit electrical signals.

  • Name the four main types of neuroglia in the CNS and one key function of each.

    Astrocytes: support neurons and control chemical environment.
    Microglial cells: defensive cells that phagocytize debris.
    Ependymal cells: line CNS cavities and circulate cerebrospinal fluid.
    Oligodendrocytes: form myelin sheaths around CNS axons.

  • What are the two major neuroglia in the PNS and their functions?

    Satellite cells: surround neuron cell bodies, similar to astrocytes.
    Schwann cells: form myelin sheaths around peripheral nerve fibers, aid regeneration.

  • What are the special characteristics of neurons?

    Extreme longevity, amitotic (do not divide), high metabolic rate requiring oxygen and glucose, and have a cell body plus one or more processes.

  • What is the function of the neuron cell body (soma)?

    Biosynthetic center synthesizing proteins, membranes, and chemicals; contains nucleus and rough ER (Nissl bodies); part of receptive region.

  • What are dendrites and their function?

    Short, branched processes that receive input and convey messages toward the cell body as graded potentials.

  • Describe the structure and function of the axon.

    Single long process starting at axon hillock; conducts nerve impulses away from cell body; ends in axon terminals that release neurotransmitters.

  • What is myelin and its function in neurons?

    Myelin is a whitish, protein-lipid sheath that insulates axons and increases the speed of nerve impulse transmission.

  • How is myelin formed in the PNS and CNS?

    In PNS, Schwann cells wrap around axons forming myelin segments.
    In CNS, oligodendrocyte processes wrap multiple axons forming myelin sheaths.

  • What are the structural classifications of neurons?

    Multipolar: many dendrites, one axon (most common).
    Bipolar: one dendrite, one axon (rare).
    Unipolar: single T-shaped process (sensory neurons).

  • What are the functional classifications of neurons?

    Sensory neurons: transmit impulses to CNS.
    Motor neurons: carry impulses from CNS to effectors.
    Interneurons: connect sensory and motor neurons within CNS.

  • What is resting membrane potential and why is it important?

    Resting membrane potential is the voltage difference across the plasma membrane at rest, typically around -70 mV, essential for neuron excitability.

  • What factors generate the resting membrane potential?

    Differences in ionic composition between intracellular and extracellular fluids and selective permeability of the plasma membrane to ions.

  • What are the main types of gated ion channels in neurons?

    Chemically gated (ligand-gated), voltage-gated, and mechanically gated channels.

  • Define depolarization and hyperpolarization in terms of membrane potential changes.

    Depolarization: membrane potential becomes less negative, increasing chance of impulse.
    Hyperpolarization: membrane potential becomes more negative, decreasing chance of impulse.

  • What are graded potentials?

    Short-lived, localized changes in membrane potential that can be depolarizations or hyperpolarizations, triggered by opening of gated ion channels.

  • What is an action potential and how does it differ from graded potentials?

    Action potential is a brief, large depolarization that propagates along axons without decay, enabling long-distance neural communication; graded potentials are localized and decay with distance.

  • What is the all-or-none principle of action potentials?

    An action potential either occurs fully when threshold is reached or does not occur at all.

  • How does myelination affect action potential conduction?

    Myelination increases conduction speed by insulating axons and enabling saltatory conduction, where impulses jump between nodes of Ranvier.

  • What are the three groups of nerve fibers based on diameter, myelination, and speed?

    Group A: large, myelinated, fast (150 m/s).
    Group B: medium, lightly myelinated, moderate speed (15 m/s).
    Group C: small, unmyelinated, slow (1 m/s).

  • What is a synapse and what are its two main types?

    A synapse is a junction for neuron communication; main types are chemical synapses (use neurotransmitters) and electrical synapses (gap junctions).

  • How do chemical synapses transmit signals?

    Neurotransmitters released from presynaptic neuron cross synaptic cleft and bind to receptors on postsynaptic neuron, causing graded potentials.

  • What are EPSPs and IPSPs?

    EPSPs (excitatory postsynaptic potentials): depolarize membrane, increase likelihood of action potential.
    IPSPs (inhibitory postsynaptic potentials): hyperpolarize membrane, decrease likelihood of action potential.

  • What is synaptic summation?

    Process where multiple EPSPs and IPSPs combine temporally or spatially to influence whether a postsynaptic neuron reaches threshold to fire an action potential.