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CNS – Spinal Cord LAB ACTIVITY 9: Neuronal Pathways. Provide the word that best fits each blank. (Word Bank: Contralateral, Corticospinal, Indirect, Medulla oblongata, Primary Motor, Pyramidal, Receptor, Somatosensory, Thalamus, Ventral) Ascending neuronal pathways transmit input from receptors to higher brain centers. These pathways usually consist of three neurons. The first order neuron conducts impulses from the 1) ———————— to the central nervous system, where it synapses with the second order neuron. The second order neuron ascends to the 2) ————————, where it synapses with the third order neuron. Third order neuron route impulses to the appropriate area of the 3) ———————— cortex. Depending on the pathway, sensory tracts ascend to the cerebral cortex can decussate in the spinal cord or at the level of the medulla oblongata. Tracts that deliver input to the cerebellum lack third order neurons and do not decussate. Descending neuronal pathways transmit motor output from the brain toward peripheral effectors. There are two different types of voluntary descending pathways. The direct pathway, also called the corticospinal pathway, involves only two neurons. The cell body of the upper motor neuron, also called a 4) ———————— cell, is located in the 5) ———————— cortex. The axon descends within the 6) ———————— white matter tract, and synapses with lower motor neuron in the 7) ———————— horn of the gray matter. The lower motor neuron extends to peripheral effectors that are under voluntary control, such as skeletal muscles. Axons in the direct motor pathway decussate at the level of the 8) ————————, so the primary motor cortex of each cerebral hemisphere is responsible for fine motor control of the opposite, or 9) ———————— side of the body. All other motor pathways, called 10) ———————— pathways, consist of more than two neurons and involve input from motor nuclei within the brain. These pathways are responsible for control of posture and coarse movements of the limbs.

CNS – Spinal Cord
LAB ACTIVITY 9: Neuronal Pathways. Provide the word that best fits each blank. (Word Bank: Contralateral, Corticospinal, Indirect, Medulla oblongata, Primary Motor, Pyramidal, Receptor, Somatosensory, Thalamus, Ventral)
Ascending neuronal pathways transmit input from receptors to higher brain centers. These pathways usually consist of three neurons. The first order neuron conducts impulses from the 1) ———————— to the central nervous system, where it synapses with the second order neuron. The second order neuron ascends to the 2) ————————, where it synapses with the third order neuron. Third order neuron route impulses to the appropriate area of the 3) ———————— cortex. Depending on the pathway, sensory tracts ascend to the cerebral cortex can decussate in the spinal cord or at the level of the medulla oblongata. Tracts that deliver input to the cerebellum lack third order neurons and do not decussate.
Descending neuronal pathways transmit motor output from the brain toward peripheral effectors. There are two different types of voluntary descending pathways. The direct pathway, also called the corticospinal pathway, involves only two neurons. The cell body of the upper motor neuron, also called a 4) ———————— cell, is located in the 5) ———————— cortex. The axon descends within the 6) ———————— white matter tract, and synapses with lower motor neuron in the 7) ———————— horn of the gray matter. The lower motor neuron extends to peripheral effectors that are under voluntary control, such as skeletal muscles. Axons in the direct motor pathway decussate at the level of the 8) ————————, so the primary motor cortex of each cerebral hemisphere is responsible for fine motor control of the opposite, or 9) ———————— side of the body.
All other motor pathways, called 10) ———————— pathways, consist of more than two neurons and involve input from motor nuclei within the brain. These pathways are responsible for control of posture and coarse movements of the limbs.

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