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Fundamentals of Anatomy & Physiology: Nervous Tissue and Nervous System

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  • What are the two main types of cells in nervous tissue?
    Neurons for intercellular communication and Neuroglia (glial cells) that support and preserve nervous tissue structure.
  • What are the anatomical divisions of the nervous system?
    The Central Nervous System (CNS) and the Peripheral Nervous System (PNS).
  • What are the main functions of the Central Nervous System (CNS)?
    Processes sensory data, coordinates motor commands, and performs higher brain functions like intelligence, memory, learning, and emotion.
  • What does the Peripheral Nervous System (PNS) include and do?
    Includes all nervous tissue outside CNS and ENS; delivers sensory info to CNS and carries motor commands to peripheral tissues.
  • What are the functional divisions of the PNS?
    Afferent division carries sensory info to CNS; Efferent division carries motor commands from CNS to muscles, glands, and adipose tissue.
  • What are the two subdivisions of the efferent division of the PNS?
    Somatic nervous system (SNS) controls skeletal muscles; Autonomic nervous system (ANS) controls smooth, cardiac muscle, and glands.
  • What is the Enteric Nervous System (ENS)?
    A network of 100 million neurons in the digestive tract walls that coordinates visceral reflexes locally without CNS input.
  • What are the main parts of a typical neuron?
    Dendrites, cell body (soma) with nucleus and perikaryon, and a single long axon with axon terminals.
  • What is the function of dendritic spines?
    Fine processes on dendrites that receive information from other neurons, covering 80–90% of neuron surface area.
  • What is the axoplasm and axolemma?
    Axoplasm is the cytoplasm inside the axon; axolemma is the plasma membrane covering the axoplasm.
  • What is axonal transport?
    Movement of materials between the cell body and axon terminals along neurotubules, powered by mitochondria, kinesin, and dynein.
  • Name the four structural classifications of neurons.
    Anaxonic, Bipolar, Unipolar (pseudounipolar), and Multipolar neurons.
  • What distinguishes unipolar neurons?
    Axon and dendrites are fused with the cell body off to one side; most sensory neurons of the PNS.
  • What are the three functional classifications of neurons?
    Sensory neurons, Motor neurons, and Interneurons.
  • What are the types of sensory receptors based on location and function?
    Interoceptors (internal systems), Exteroceptors (external environment), and Proprioceptors (position and movement).
  • What are the main types of neuroglia in the CNS?
    Astrocytes, Ependymal cells, Oligodendrocytes, and Microglia.
  • What are the functions of astrocytes?
    Maintain blood-brain barrier, provide structural support, repair nervous tissue, guide neuron development, and control interstitial environment.
  • What do ependymal cells do?
    Line ventricles and central canal, produce and circulate cerebrospinal fluid (CSF) with their cilia.
  • What is the role of oligodendrocytes?
    Form myelin sheath around CNS axons to insulate and increase action potential speed.
  • What is the function of microglia?
    Smallest neuroglia that migrate through nervous tissue to remove debris, wastes, and pathogens by phagocytosis.
  • What neuroglia are found in the PNS?
    Satellite cells that surround ganglia and regulate interstitial fluid, and Schwann cells that form myelin sheaths around axons.
  • What is Wallerian degeneration?
    Degeneration of the axon distal to an injury, followed by Schwann cells forming a path for new axon growth.
  • What is resting membrane potential?
    The electrical potential of a resting cell, typically around −70 mV, established by ion concentration differences and membrane permeability.
  • What ions are most important in establishing resting membrane potential?
    High extracellular sodium (Na+) and chloride (Cl−); high intracellular potassium (K+) and negatively charged proteins.
  • What is the sodium-potassium exchange pump's role?
    Uses ATP to eject 3 Na+ ions and bring in 2 K+ ions, stabilizing resting membrane potential.
  • What are the three types of gated ion channels?
    Chemically gated (ligand-gated), voltage-gated, and mechanically gated ion channels.
  • What is an action potential?
    A propagated electrical impulse along an axon, triggered when membrane potential reaches threshold (−60 to −55 mV).
  • What is the all-or-none principle of action potentials?
    An action potential either occurs fully when threshold is reached or not at all, regardless of stimulus strength.
  • What are the steps in generating an action potential?
    1) Depolarization to threshold, 2) Activation of voltage-gated Na+ channels, 3) Inactivation of Na+ channels and activation of K+ channels, 4) Return to resting potential.
  • What is the difference between continuous and saltatory propagation?
    Continuous occurs in unmyelinated axons with stepwise depolarization; saltatory occurs in myelinated axons with impulses jumping between nodes of Ranvier.
  • How does axon diameter affect action potential speed?
    Larger diameter axons have lower resistance and conduct impulses faster.
  • What are the three types of axons based on diameter and myelination?
    Type A (large, myelinated, fast), Type B (medium, myelinated, intermediate speed), Type C (small, unmyelinated, slow).
  • What is a synapse?
    A specialized site where a neuron communicates with another cell, involving a presynaptic neuron and a postsynaptic neuron or effector.
  • What are the two types of synapses?
    Electrical synapses with direct cell contact and chemical synapses using neurotransmitters across a synaptic cleft.
  • What is the function of acetylcholine (ACh) at cholinergic synapses?
    ACh is released by presynaptic neurons, binds to postsynaptic receptors, causing depolarization, and is broken down by acetylcholinesterase.
  • What are excitatory and inhibitory neurotransmitters?
    Excitatory neurotransmitters cause depolarization and promote action potentials; inhibitory neurotransmitters cause hyperpolarization and suppress action potentials.
  • What are neuromodulators?
    Chemicals released by axon terminals that alter neurotransmitter release or postsynaptic response, with long-term and slow effects.
  • What are examples of neuromodulators?
    Neuropeptides like opioids (enkephalins, endorphins, dynorphins) and dissolved gases like nitric oxide (NO) and carbon monoxide (CO).
  • What is temporal summation?
    Rapid, repeated stimuli at a single synapse that combine to increase postsynaptic potential.
  • What is spatial summation?
    Simultaneous stimuli at multiple synapses that combine to affect the postsynaptic neuron.
  • What is presynaptic inhibition and facilitation?
    Presynaptic inhibition decreases neurotransmitter release; presynaptic facilitation increases neurotransmitter release at the presynaptic membrane.