contralateral

(adjective)

On the opposite side of the body.

Related Terms

Examples of contralateral in the following topics:

  • Organization of Motor Neuron Pathways

    • Cortical upper motor neurons originate from Brodmann areas 1, 2, 3, 4, and 6, then descend into the posterior limb of the internal capsule, through the crus cerebri, down through the pons, and to the medullary pyramids, where about 90% of the axons cross to the contralateral side at the decussation of the pyramids.
    • Most of them will cross to the contralateral side of the cord (via the anterior white commissure) just before synapsing.
    • The anterior corticospinal tract descends ipsilaterally in the anterior column, where the axons emerge and either synapse on ventromedial lower motor neurons in the ventral horn ipsilaterally or descussate at the anterior white commissure where they synapse on ventromedial lower motor neurons contralaterally.

  • Trochlear (IV) Nerve

    • The trochlear nucleus is unique in that its axons run dorsally and cross the midline before emerging from the brainstem—so a lesion of the trochlear nucleus affects the contralateral eye.
    • The unique features of the trochlear nerve, including its dorsal exit from the brainstem and its contralateral innervation, are seen in the primitive brains of sharks.

  • Spinal Reflexes

    • The crossed extensor reflex is contralateral, meaning the reflex occurs on the opposite side of the body from the stimulus.
    • To produce this reflex, branches of the afferent nerve fibers cross from the stimulated side of the body to the contralateral side of the spinal cord.
    • There, they synapse with interneurons, which in turn, excite or inhibit alpha motor neurons to the muscles of the contralateral limb.

  • Facial (VII) Nerve

    • In an upper motor neuron lesion, called central seven (central facial palsy), only the lower part of the face on the contralateral side will be affected due to the bilateral control to the upper facial muscles (frontalis and orbicularis oculi).

  • Somatic Sensory Pathways to the Cerebellum

    • There it makes a synapse with the dendrites of two neurons that send their axons bilaterally to the ventral border of the lateral funiculi (transmit the contralateral corticospinal and spinothalamic tracts).

  • Bell's Palsy

    • If the problem resides in the facial nerve itself (peripheral palsy) all nerve signals are lost on the ipsilateral (same side of the lesion) half side of the face, including to the forehead (contralateral forehead still wrinkles).

  • White Matter of the Cerebrum

    • It is the largest white matter structure in the brain, consisting of 200 to 250 million contralateral axonal projections.

  • Mapping the Primary Somatosensory Area

    • The homunculus is like an upside-down sensory or motor map of the contralateral side of the body.

  • Medulla Oblongata

    • The base of the medulla is defined by the commissural fibers, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem; below this is the spinal cord.