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Peripheral and Autonomic Nervous System Study Guide

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  • Connective tissue coverings of a nerve
    The three layers are endoneurium (around individual axons), perineurium (around fascicles), and epineurium (around the entire nerve).
  • Main nerve plexuses
    The cervical, brachial, lumbar, and sacral plexuses are networks of nerves that supply limbs and body regions.
  • Is there a thoracic plexus? Why or why not?
    No, because thoracic spinal nerves mostly form intercostal nerves instead of plexuses.
  • Purpose of nerve plexuses
    Plexuses allow nerves to redistribute fibers so that each limb muscle receives fibers from multiple spinal nerves, providing redundancy.
  • Wrist drop and associated nerve
    Wrist drop is caused by damage to the radial nerve, leading to inability to extend the wrist.
  • Nerve associated with carpal tunnel syndrome
    The median nerve is compressed in carpal tunnel syndrome, causing numbness and weakness in the hand.
  • Pathway of vision and site of decussation
    Visual signals travel from retina to optic nerve, cross at the optic chiasm (decussation), then to the brain.
  • Difference between dorsal and ventral rami
    Dorsal rami carry sensory and motor fibers to the back; ventral rami carry fibers to the limbs and anterior body.
  • Difference between rami and roots
    Roots are the initial spinal nerve branches (dorsal root sensory, ventral root motor); rami are branches after the spinal nerve forms.
  • Fibers contained in dorsal and ventral rami
    Both dorsal and ventral rami contain mixed fibers: sensory and motor neurons.
  • Functions of cranial nerves
    Cranial nerves can be sensory, motor, or mixed, controlling senses, muscles, and autonomic functions.
  • Meaning of mixed cranial nerves
    Mixed nerves carry both sensory and motor fibers.
  • Cranial nerves carrying somatic motor, sensory, and parasympathetic fibers
    Some cranial nerves carry somatic motor, sensory, and parasympathetic fibers, e.g., the vagus nerve (CN X).
  • Bell’s Palsy and associated nerve
    Bell’s Palsy is facial paralysis caused by dysfunction of the facial nerve (CN VII).
  • Role of the phrenic nerve
    The phrenic nerve controls the diaphragm and is essential for breathing.
  • Funny bone nerve
    The 'funny bone' sensation is caused by hitting the ulnar nerve.
  • Difference between afferent and efferent neurons
    Afferent neurons carry sensory information to the CNS; efferent neurons carry motor commands from the CNS.
  • Sympathetic division slogan
    "Fight or flight" describes the sympathetic nervous system's role in stress responses.
  • Parasympathetic division slogan
    "Rest and digest" describes the parasympathetic nervous system's role in conserving energy and digestion.
  • Sympathetic vs. parasympathetic fiber length
    Sympathetic preganglionic fibers are short; postganglionic fibers are long. Parasympathetic preganglionic fibers are long; postganglionic fibers are short.
  • Neurotransmitters in sympathetic division
    Sympathetic preganglionic neurons secrete acetylcholine; postganglionic neurons mostly secrete norepinephrine.
  • Neurotransmitters in parasympathetic division
    Both preganglionic and postganglionic parasympathetic neurons secrete acetylcholine.
  • Neurotransmitter in somatic nervous system
    Somatic motor neurons release acetylcholine at neuromuscular junctions.
  • Effects of sympathetic division on heart rate, pupil size, respiratory rate
    Sympathetic activation increases heart rate, dilates pupils, and increases respiratory rate.
  • Effects of parasympathetic division on heart rate, pupil size, respiratory rate
    Parasympathetic activation decreases heart rate, constricts pupils, and decreases respiratory rate.
  • Location of sympathetic preganglionic fibers
    Sympathetic preganglionic fibers originate in the thoracolumbar region of the spinal cord (T1-L2).
  • Neuron chains in somatic vs. autonomic divisions
    Somatic division uses a single neuron from CNS to muscle; autonomic division uses a two-neuron chain (preganglionic and postganglionic).
  • Parasympathetic vs. sympathetic innervation targets
    Parasympathetic division mainly innervates visceral organs for rest functions; sympathetic innervates organs for fight or flight responses.
  • Craniosacral vs. thoracolumbar divisions
    Parasympathetic division is craniosacral; sympathetic division is thoracolumbar.