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Nervous System Fundamentals - Anatomy & Physiology

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Terms in this set (31)

  • Primary function of the nervous system

    The nervous system is the major integrator of body function, working with the endocrine system to regulate homeostasis through rapid electrical signals and chemical messengers.

  • Characteristics of neurons

    Neurons are excitable nerve cells that transmit electrical signals, have extreme longevity, are amitotic, and have a high metabolic rate requiring continuous O2 and glucose.

  • Structural classification of neurons

    Neurons are classified by their processes: multipolar (most common), bipolar (rare), and unipolar (sensory neurons in dorsal root ganglia).

  • Three basic regions of a neuron

    1. Cell body: biosynthetic center with nucleus.
    2. Dendrites: receive graded potentials.
    3. Axon: transmits impulses to other cells.

  • Function of dendrites

    Dendrites are thin, highly branched extensions that serve as the receptive area for receiving graded potentials, providing a large surface area for information collection.

  • Role of the axon hillock

    The axon hillock is the cone-shaped region of the soma where the threshold is reached to initiate an action potential.

  • Myelin sheath function and composition

    The myelin sheath protects and electrically insulates axons, increasing impulse speed up to 150 times. In the PNS, it is formed by Schwann cells with gaps called Nodes of Ranvier.

  • Neuroglia types in the PNS

    1. Schwann cells: form myelin sheaths.
    2. Satellite cells: cover neuron cell bodies in ganglia.

  • Neuroglia types in the CNS

    1. Astrocytes: maintain chemical environment.
    2. Microglia: phagocytic cells.
    3. Ependymal cells: line brain ventricles.
    4. Oligodendrocytes: form CNS myelin sheaths.

  • Definition of a nerve

    A nerve is a cord-like organ containing axons, blood vessels, and connective tissue layers: endoneurium, perineurium, and epineurium.

  • Connective tissue layers of a nerve

    1. Endoneurium: surrounds each axon.
    2. Perineurium: surrounds fascicles.
    3. Epineurium: surrounds entire nerve.

  • Central vs Peripheral Nervous System components

    CNS: brain, spinal cord, interneurons, glial cells.
    PNS: all nerves and ganglia outside CNS, including afferent and efferent fibers.

  • Somatic Nervous System characteristics

    Voluntary system with afferent and efferent fibers from brain and spinal cord; uses acetylcholine as the only neurotransmitter.

  • Autonomic Nervous System functions

    Involuntary control of smooth, cardiac muscle, glands; includes sympathetic, parasympathetic, and enteric divisions; uses acetylcholine and norepinephrine.

  • Sympathetic Nervous System features

    Mobilizes body for 'fight or flight'; thoracolumbar origin; increases heart rate, blood pressure, blood sugar; neurotransmitters are acetylcholine and norepinephrine.

  • Parasympathetic Nervous System features

    Rest and digest functions; craniosacral origin; decreases heart rate and blood pressure; increases digestion; uses acetylcholine as neurotransmitter.

  • Resting membrane potential

    Difference in electrical charge across the neuron membrane at rest, approximately -70mV, due to ionic concentration differences and membrane permeability.

  • Factors maintaining resting membrane potential

    1. Electrical attraction by fixed anions.
    2. Greater permeability to K+ than Na+.
    3. Active Na+/K+ ATPase pump maintaining ion gradients.

  • Depolarization vs Hyperpolarization

    Depolarization: membrane potential becomes less negative (toward zero).
    Hyperpolarization: membrane potential becomes more negative than resting.

  • Graded potentials

    Local changes in membrane potential that vary with stimulus intensity and decline over distance.

  • Action potential initiation

    Summation of depolarizing graded potentials opens voltage-gated Na+ channels at the axon hillock once threshold (~-55mV) is reached.

  • Absolute and relative refractory periods

    Absolute refractory period: no new AP can be generated.
    Relative refractory period: strong stimulus can trigger AP.

  • Factors affecting conduction velocity

    1. Axon diameter: larger diameter increases speed.
    2. Myelin sheath: insulates and increases conduction rate.

  • Multiple sclerosis impact

    Autoimmune attack on CNS myelin (oligodendrocytes) causing decreased conduction, leading to neuromuscular symptoms.

  • Nerve fiber groups and conduction speeds

    Group A: large, myelinated, 15-130 m/s.
    Group B: intermediate, lightly myelinated, 3-15 m/s.
    Group C: small, unmyelinated, ≤1 m/s.

  • Functional classification of neurons

    Afferent: sensory, toward CNS.
    Efferent: motor, away from CNS.
    Interneurons: connect sensory and motor neurons within CNS.

  • Types of synapses

    Electrical synapses: direct ion flow, synchronize neurons.
    Chemical synapses: neurotransmitter release across synaptic cleft.

  • Steps of chemical synapse transmission

    1. Ca2+ gates open.
    2. V-SNARE and T-SNARE bind.
    3. Vesicle docks.
    4. Neurotransmitter released.
    5. Binds postsynaptic receptors.
    6. Opens ion channels.

  • Excitatory vs inhibitory synapses

    Excitatory: open Na+ and K+ channels, cause EPSPs.
    Inhibitory: open K+ or Cl- channels, cause IPSPs.

  • Neurotransmitter termination methods

    1. Enzymatic degradation.
    2. Reuptake into presynaptic terminal.
    3. Diffusion away and systemic destruction.

  • Synaptic integration types

    Temporal summation: rapid impulses from one neuron.
    Spatial summation: simultaneous impulses from multiple neurons.