The Somatosensory and Motor Pathways Flashcards

1
Q

Characteristic of neural pathways when they cross from one side of the CNS to the other at some point along their journey.

A

Decussation

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2
Q

Characteristic of neural pathways when they consist of two or three neurons that contribute to successive tracts of the pathway.

A

Relay

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3
Q

Characteristic of neural pathways where they exhibit a precise spatial relationship among the tract fivers that reflect orderly mapping of the body.

A

Somatotopy

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4
Q

Characteristic of neural pathways where they are paired on the right and left with a member of the pair present on each side of the spinal cord or brain.

A

Symmetry

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5
Q

Neurons of the ascending pathway whose cells bodies reside in a ganglion. Conduct impulses from the cutaneous receptors of the skin and from proprioceptors to the spinal cord or brain stem.

A

First-Order Neurons

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6
Q

Neurons of the ascending pathway whose cell bodies reside in the dorsal horn of the spinal cord or in the medullary nuclei. Transmit impulses to the thalamus or cerebellum.

A

Second-Order Neurons

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7
Q

Neurons of the ascending pathway that have cell bodies in the thalamus. Relay impulses to the somatosensory cortex of the cerebrum.

A

Third-Order Neurons

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8
Q

Formed by the paired tracts of the dorsal white column (fasciculus cuneatus and fasciculus gracilis) and the medial lemniscus.

A

Dorsal Column-Medial Lemniscal Pathways

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9
Q

Location of neurons in the Dorsal Column-Medial Lemniscal Pathways

A

First-order neurons enter the dorsal root of the spinal cord, then enter the dorsal white column on the same side without synapsing. The synapse with second-order neurons occurs. in the nucleus cuneatus and nucleus gracilis in the medulla. These fibers cross over and ascend in the medial lemniscus to the thalamus, where they synapse with third-order neurons. Thalamic neurons then transmit impulses to the somatosensory cortex.

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10
Q

Function of Dorsal Column-Medial Lemniscal Pathways

A

Transmits sensory impulses from general sensory receptors of the skin and proprioceptors, which are interpreted as discriminative touch, pressure, and limb and joint position.

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11
Q

Arises in the medulla and terminates int eh thalamus.

A

Medial Lemniscus

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12
Q

Consists of the lateral and ventral spinothalamic tracts. Located in the lateral and ventral white columns.

A

Spinothalamic Pathways

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13
Q

Location of neurons in the Spinothalamic Pathways

A

First-order neurons enter the dorsal root of the spinal cord and synapse with second-order neurons in the dorsal horns. Fibers cross to the opposite side before ascending. Synapse with third-order neurons in the thalamus. Thalamic neurons then convey impulses to somatosensory cortex.

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14
Q

Function of the Spinothalamic Pathways

A

Transmits impulses concerned with pain, temperature, crude touch, and pressure to opposite side of brain for interpretation by somatosensory cortex.

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15
Q

Consists of the ventral and dorsal spinocerebellar tracts. Convey information to the cerebellum.

A

Spinocerebellar Pathway

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16
Q

Location of neurons in the Spinocerebellar Pathways

A

First-order neurons enter the dorsal root of the spinal cord and synapse with second-order neurons in the dorsal horn on the same side of the cord. Fibers ascend without crossing and terminate in the cerebellum . (No third-order neurons.)

17
Q

Function of the Spinocerebellar Pathways

A

Transmits impulses from trunk and lower limb on the same side of the body to the cerebellum for subconscious proprioception.

18
Q

Consists of the pyramidal cells of the motor cortex and the neurons of subcortical motor nuclei.

A

Upper Motor Neurons

19
Q

Consists of ventral horn motor neurons. Directly innervate the skeletal muscles.

A

Lower Motor Neurons

20
Q

Send impulses through the brain stem to the spinal cord without synapsing. Consists of the lateral and ventral corticospinal tracts.

A

Pyramidal Tracts

21
Q

Location of neurons in the lateral corticospinal tracts

A

Pyramidal cells of motor cortex of the cerebrum cross over in pyramids of the medulla. Descend along the lateral white column. Synapse with lower motor neurons in the ventral horn.

22
Q

Location of neurons in the ventral corticospinal tracts

A

Pyramidal cells of motor cortex cross over in the spinal cord. Descend along the lateral white column. Synapse with lower motor neurons in the ventral horn.

23
Q

Function of pyramidal tracts

A

Transmite motor impulses from cerebrum to spinal cord motor neurons which activate skeletal muscles on opposite side of the body. A voluntary motor tract.

24
Q

Includes all motor pathways that are not pyramidal. Multisynaptic. (Name the tracts.)

A

Indirect Pathways. (Includes reticulospinal tracts, vestibulospinal tracts, rubrospinal tracts, and tectospinal tract)

25
Q

Location of neurons in reticulospinal tracts

A

Originates in the reticular formation of the brain stem. Includes both crossed and uncrossed fibers. Descends along the medial and lateral white columns. Synapse with lower motor neurons in the ventral horn.

26
Q

Function of the reticulospinal tracts

A

Transmits impulses concerned with muscle tone and many visceral motor functions. May control most unskilled movements.

27
Q

Location of neurons in vestibulospinal tracts

A

Originates in the vestibular nuclei in the medulla of the brain stem. Fibers descend without crossing. Descends along the ventral white columns. Synapse with lower motor neurons in the ventral horn.

28
Q

Function of the vestibulospinal tracts

A

Transmits motor impulses that maintain muscle tone and activate ipsilateral limb and trunk extensor muscles and muscles that move the head. Helps maintain balance during standing and moving.

29
Q

Location of neurons in rubrospinal tracts

A

Originates in the red nucleus of the midbrain of the brain stem. Fibers cross to the opposite side just inferior to the red nucleus. Descends along the lateral white columns. Synapse with lower motor neurons in the ventral horn.

30
Q

Function of the rubrospinal tracts

A

Transmits motor impulses concerned with muscle tone of distal limb muscles (mostly flexors) on opposite side of the body.

31
Q

Location of neurons in tectospinal tracts

A

Originates in the superior colliculus of the midbrain of the brain stem. Fibers cross to the opposite side of the spinal cord. Descends along the lateral white columns. Synapse with lower motor neurons in the ventral horn.

32
Q

Function of the tectospinal tracts

A

Turns head so eyes can follow a moving object.