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Chapter 11 - Nervous System - Anatomy & Physiology

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  • What are the two main populations of cells that form nervous tissue?

    Neurons and neuroglia (supporting cells) form nervous tissue.

  • Name the four types of supporting cells in the CNS and their general function.

    Astrcytes, oligodendrocytes, microglia, and ependymal cells support neurons by maintaining environment, myelinating axons, immune defense, and producing cerebrospinal fluid.

  • What are the two types of supporting cells in the PNS?

    Schwann cells (myelinate axons) and satellite cells (support neuron cell bodies).

  • Describe the main parts of a neuron.

    Cell body (soma), dendrites (receive signals), and axon (transmits signals).

  • What types of ion channels are found on neuron membranes and what signals do they generate?

    Non-gated (leak) channels maintain resting potential; gated channels (chemical, voltage, mechanical) generate graded and action potentials.

  • Define nuclei, ganglia, nerves, tracts, white matter, and grey matter.

    Nuclei: neuron clusters in CNS; ganglia: neuron clusters in PNS; nerves: bundles of axons in PNS; tracts: bundles of axons in CNS; white matter: myelinated axons; grey matter: neuron cell bodies.

  • What is the anatomy and function of the myelin sheath?

    Myelin sheath is a fatty layer formed by oligodendrocytes in CNS and Schwann cells in PNS; it insulates axons and increases action potential speed.

  • What are the functional and structural classifications of neurons?

    Structural: multipolar, bipolar, unipolar; Functional: sensory (afferent), motor (efferent), interneurons.

  • What is the resting membrane potential (RMP) of a neuron?

    Typically around -70 mV, due to ion distribution and membrane permeability.

  • Which cells can generate action potentials and where specifically?

    Neurons and muscle cells can generate APs; in neurons, the axon hillock and axon membrane generate APs.

  • Describe the phases of an action potential on the axolemma.

    Depolarization: voltage-gated Na+ channels open, Na+ influx; Repolarization: voltage-gated K+ channels open, K+ efflux.

  • Compare graded potentials and action potentials.

    Graded potentials are local, vary in size, and can summate; action potentials are all-or-none, propagate long distances without decreasing.

  • What is the absolute refractory period and its importance?

    Time during which no new AP can be generated, ensuring unidirectional propagation and discrete signals.

  • Explain the all-or-none phenomenon of an action potential.

    Once threshold is reached, an AP fires fully; stimulus strength does not affect AP size.

  • What is the significance of the threshold voltage in neurons?

    It is the critical membrane potential (~-55 mV) that triggers opening of voltage-gated Na+ channels to start an AP.

  • Describe continuous vs. saltatory conduction.

    Continuous conduction occurs in unmyelinated axons; AP propagates step-by-step. Saltatory conduction occurs in myelinated axons; AP jumps between Nodes of Ranvier, increasing speed.

  • What are EPSPs and their function?

    Excitatory postsynaptic potentials depolarize the membrane by opening Na+ channels, increasing likelihood of AP.

  • What are IPSPs and their function?

    Inhibitory postsynaptic potentials hyperpolarize the membrane by opening K+ or Cl- channels, decreasing likelihood of AP.

  • Define depolarization, repolarization, and hyperpolarization.

    Depolarization: membrane potential becomes less negative; repolarization: returns to resting potential;

    hyperpolarization: membrane potential becomes more negative than resting.

  • What two major factors influence the velocity of action potential propagation?

    Axon diameter (larger diameter = faster) and myelination (myelinated axons conduct faster).