Lecture 17: Pathways

Question 1

Ascending

Answer 1

from the periphery to the center

Question 2

Descending

Answer 2

from the center to the periphery

Question 3

Common features of ascending and descending pathways

Answer 3

• presence of synaptic relays
• integration of information
• topographic organization (motor and sensory maps)

Question 4

Typical features of pathways within the central nervous system involve the presence of:

Answer 4

synaptic relays
the integration of information from different pathways
topographic information

Question 5

Ascending Pathways include

Answer 5

first order neurons
second order neurons
third order neurons

Question 6

First-Order neurons

Answer 6

primary afferent neurons

Question 7

Second-order neurons

Answer 7

relays between first-order neurons and brain centers; typically in the spinal cord and the brain stem

Question 8

Third order neurons

Answer 8

commonly in thalamic nuclei.

Question 9

Afferent fibers enter the spinal cord through the _____.

Answer 9

dorsal columns

Question 10

________ typically terminate in rexed laminae I and II

Answer 10

Small, unmyelinated fibers

Question 11

_______ terminate in laminae III and IV, and muscle afferents (Ia and II) terminate anywhere from lamina V to lamina IX

Answer 11

larger sensory fibers

Question 12

The dorsal columns of the spinal cord carry information from ____ to the _____.

Answer 12

sensory neurons in the spinal ganglia to the brain

Question 13

The ascending fibers of the dorsal column pathway terminate in the _______.

Answer 13

cuneate and gracile nuclei in the medulla (sense of touch)

Question 14

Articular and group I muscle receptors travel in the _____________ and make a relay in nucleus Z before joining and medial lemniscus.

Answer 14

dorsolateral funiculus

Question 15

The spinothalamic tract consists of ____-

Answer 15

the axons of neurons whose bodies lie in the dorsal and intermediate parts of the gray matter

Question 16

The Spinothalamic Tract: The Axons cross the midline and travel along the ______.

Answer 16

contralateral side of the spinal cord in the ventrolateral funiculus

Question 17

The Spinothalamic Tract: This tract coveys the ______.

Answer 17

sensations of touch, pressure, temperature, and pain

Question 18

The Spinocereberllar Tracts: The cerebellum receives information from _____

Answer 18

peripheral sensory receptors

Question 19

The cerebellum receiver information from peripheral sensory receptors by means of ______.

Answer 19

the dorsal, central, and rostral spinocerebellar tracts; the cuneocerebellar; and the spino-cerebellar tract

Question 20

Ascends in Clarke’s column. Carries information from proprioceptors in the lower extremeties. Also has projections to nucleus Z and the VPL thalamus.

Answer 20

Dorsal (DSCT)

Question 21

carries information from upper extremities

Answer 21

Cuneocerebellar

Question 22

ascends laterally in the central horm. Carries FRA information from the lower extremities and afferent (sensory) signals.

Answer 22

Ventral (VSCT)

Question 23

carries FRA information from upper extremeties. Also carries efferent signals.

Answer 23

Rostral (RSCT)

Question 24

Spinoreticular Tract: Ascends in the ______ directly to the reticular formation.

Answer 24

ventrolateral fasciculus

Question 25

The spinoreticular tract plays a role in _____________.

Answer 25

controlling the sense of pain.

Question 26

Corticospinal Tract: The pyramidal tract consists of ______.

Answer 26

two major groups of axons. Axons of the first group go down to the spinal cord (corticospinal tract)]

Question 27

Corticospinal Tact: Some fibers leave the pyramidal tract and _____.

Answer 27

innervate the motor nuclei of the cranial nerves (corticobulbar tract).

Question 28

Pyramidal Tract = ______ + ______

Answer 28

Corticospinal Tract + Corticobulbar Tract

Question 29

Pyramidal Tract

Answer 29

30% from M1 30% from premotor and supplementary motor 40% from somatosensory areas

Question 30

Lateral CST

Answer 30

contains 80% of the fibers that decussate at the brain stem. Has direct projections to both INs and MNs.

Question 31

Ventral CST

Answer 31

contains about 20% of the fibers that do not decussate. Mostly controls axial trunk muscles.

Question 32

Corticobulbar Tract

Answer 32

exits at the pyramids. Controls cranial nerves (such as facial muscles and articulators)

Question 33

Rubrospinal tract originates in the _____

Answer 33

red nucleus

Question 34

Rubrospinal Tract receives input from ______.

Answer 34

the motor cortex, the cerebellum, and the olives

Question 35

Rubrospinal decussates at ______.

Answer 35

midbrain and descends adjacent to the lateral CST; it also has projections to the olives.

Question 36

function of Rubrospinal Tract

Answer 36

nobody knows for sure, but it is suspected of being of major importance for motor coordination.

Question 37

The rubrospinal tract crosses the midline __________.

Answer 37

close to its origin and brances to other brain structures, including the interpositus nucleus of the cerebellum, the olives, and the vestibular nuclei

Question 38

The rubrospinal tract is part of the ____ loop

Answer 38

cerebellum-red nucleus-olive-cerebellum loop

Question 39

Main inputs of the vestibulospinal tracts.

Answer 39

the cerebellum and the labyrinth

Question 40

Lateral VST: comes from the LATERAL VESTIBULAR NUCLEUS. Descends ipsilaterally to the ____________. Makes connections with INs.

Answer 40

lumbar level

Question 41

Lateral VST plays a role in _____.

Answer 41

the control of posture

Question 42

Medial VST comes from the MEDIAL VESTIBULAR NUCLEUS. Descends ipsilaterally to the _________. Makes connections with INs.

Answer 42

mid-thoracic level

Question 43

Medial VST plays a role in _____.

Answer 43

the control of posture and perhaps head position.

Question 44

Vestibulospinal Tracts: Vestibular nuclei receive main inputs from the ____ and the _______.

Answer 44

cerebellum and the labryinth

Question 45

Vestibulospinal Tracts: _________ nucleus give rise to the lateral vestibulospinal tract and the medial vestibular nucleus is the origin of the medial vestibulospinal tract.

Answer 45

Neurons in Deiters'

Question 46

Medial RST

Answer 46

to spinal INs (ipsilaterlaly). Its effects are mostly inhibitory.

Question 47

Lateral RST

Answer 47

to INs in the ventral parts of the spinal cord. Postural control of proximal extensor muscles

Question 48

Reticulospinal Tract is suspects of _____.

Answer 48

brining the startle reaction

Question 49

Tectospinal Tract: it comes from the neurons in the ________.

Answer 49

superior colliculus.

Question 50

Tectospinal Tract: It decussates and plays a role in _______.

Answer 50

motor reactions to visual stimuli (head orientation to visual stimuli by controlling the neck muscles)

Question 51

Interstitiospinal Tract: It comes from the neurons in the _______.

Answer 51

midbrain

Question 52

Interstitiospinal Tract function is ______.

Answer 52

a mystery