sensory root

(noun)

The proximal end of a dorsal afferent nerve that is attached to the spinal cord.

Related Terms

  • sympathetic root
  • parasympathetic
  • motor root
  • lacrimal gland

Examples of sensory root in the following topics:

  • Trigeminal (V) Nerve

    • The ophthalmic and maxillary nerves are purely sensory.
    • The trigeminal ganglion is analogous to the dorsal root ganglia of the spinal cord, which contain the cell bodies of incoming sensory fibers from the rest of the body.
    • From the trigeminal ganglion, a single large sensory root enters the brainstem at the level of the pons.
    • Immediately adjacent to the sensory root, a smaller motor root emerges from the pons at the same level.
    • Schematic illustration of the trigeminal nerve (labeled Sensory root above) and the structures it innervates in the face and mouth.
  • Parasympathetic (Craniosacral) Division

    • Each has three roots entering the ganglion (motor, sympathetic, and sensory roots) and a variable number of exiting branches.
    • The motor root carries presynaptic parasympathetic nerve fibers (general visceral efferent fibers) that terminate in the ganglion by creating a synapse for the postsynaptic fibers traveling to target organs.
    • The sympathetic root carries postsynaptic sympathetic fibers (general visceral efferent fibers) that traverse the ganglion without creating a synapse.
    • The sensory root carries general sensory fibers (general somatic afferent fibers) that also do not create a synapse in the ganglion.
    • Some ganglia also carry special sensory fibers (special visceral afferent) for taste sensation.
  • Overview of the Spinal Cord

    • Thirty-one pairs of spinal nerves (sensory and motor) branch from the human spinal cord.
    • The posterior root is the sensory (afferent) root that carries sensory information to the brain from other areas of the body.
    • The anterior root is the motor (efferent) root that carries motor information to the body from the brain.
    • The swelling found in the posterior root is the posterior (dorsal) root ganglion, which contains the cell bodies of sensory neurons.
    • In addition, the cauda equina extends to sensory innervation of the perineum.
  • Spinal Cord Grey Matter and Spinal Roots

    • These ganglia contain cell bodies of sensory neurons.
    • Axons of these sensory neurons travel into the spinal cord via the dorsal roots.
    • The nerve endings of dorsal root ganglion neurons have a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli.
    • The presence of these channels in the dorsal root ganglion gives reason to believe that other sensory neurons may contain them as well.
    • These channels are found predominantly in smaller sensory neurons in the dorsal root ganglion cells and are activated by higher pressures, two attributes that are characteristic of nociceptors.
  • Somatic Sensory Pathways

    • The somatosensory pathway is composed of three neurons located in the dorsal root ganglion, the spinal cord, and the thalamus.
    • The first always has its cell body in the dorsal root ganglion of the spinal nerve.
    • Like other sensory areas, there is a map of sensory space called a homunculus at this location.
    • Sensory nerves of a dorsal root ganglion are depicted entering the spinal cord.
    • The formation of the spinal nerve from the dorsal and ventral roots.
  • Sensory and Motor Tracts

    • The spinothalamic tract is a sensory pathway originating in the spinal cord.
    • Somatosensory organization is divided into the dorsal column–medial lemniscus tract (the touch/proprioception/vibration sensory pathway) and the anterolateral system, or ALS (the pain/temperature sensory pathway).
    • Both sensory pathways use three different neurons to get information from sensory receptors at the periphery to the cerebral cortex.
    • These neurons are designated primary, secondary, and tertiary sensory neurons.
    • In both pathways, primary sensory neuron cell bodies are found in the dorsal root ganglia, and their central axons project into the spinal cord.
  • Overview of the Spinal Nerves

    • Spinal nerves, a part of the peripheral nervous system (PNS), are mixed nerves that send motor, sensory, and autonomic signals between the CNS and the body.
    • Each spinal nerve is formed by the combination of nerve fibers from the dorsal and ventral roots of the spinal cord.
    • The dorsal roots carry afferent sensory axons, while the ventral roots carry efferent motor axons.
    • Its anterior root helps form the coccygeal plexus.
    • Spinal nerves arise from a combination of nerve fibers from the dorsal and ventral roots of the spinal cord.
  • Autonomic Ganglia

    • Autonomic ganglia are clusters of neuron cell bodies that transmit sensory signals from the periphery to the integration centers in the CNS.
    • The dorsal root ganglia lie along the vertebral column by the spine and develop in the embryo from neural crest cells, not neural tube.
    • A dorsal root ganglion (or spinal ganglion) is a nodule on a dorsal root of the spine that contains the cell bodies of nerve cells (neurons) that carry signals from the sensory organs towards the appropriate integration center.
    • The axons of dorsal root ganglion neurons are known as afferents.
    • The nerve endings of dorsal root ganglion neurons have a variety of sensory receptors that are activated by mechanical, thermal, chemical, and noxious stimuli.
  • General Organization of the Somatosensory System

    • In the periphery, the primary neuron is the sensory receptor that detects sensory stimuli like touch or temperature.
    • The cell body of the primary neuron is housed in the dorsal root ganglion of a spinal nerve or, if sensation is in the head or neck, the ganglia of the trigeminal or cranial nerves.
    • At this location there is a map of sensory space referred to as a sensory homunculus. 
    • Periphery: Sensory receptors (i.e., thermoreceptors, mechanoreceptors, etc.) detect the various stimuli.
    • Image representing the cortical sensory homunculus.
  • Somatic Sensory Pathways to the Cerebellum

    • A sensory system is a part of the nervous system responsible for processing sensory information.
    • A sensory system consists of sensory receptors, neural pathways, and the parts of the brain involved in sensory perception.
    • Commonly recognized sensory systems are those for vision, hearing, somatic sensation (touch), taste, and olfaction (smell).
    • Proprioceptive information is taken to the spinal cord via central processes of the dorsal root ganglia (where first order neurons reside).
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