Lecture 17: Pathways Flashcards
Ascending
from the periphery to the center
Descending
from the center to the periphery
Common features of ascending and descending pathways
- presence of synaptic relays
- integration of information
- topographic organization (motor and sensory maps)
Typical features of pathways within the central nervous system involve the presence of:
synaptic relays
the integration of information from different pathways
topographic information
Ascending Pathways include
first order neurons
second order neurons
third order neurons
First-Order neurons
primary afferent neurons
Second-order neurons
relays between first-order neurons and brain centers; typically in the spinal cord and the brain stem
Third order neurons
commonly in thalamic nuclei.
Afferent fibers enter the spinal cord through the _____.
dorsal columns
________ typically terminate in rexed laminae I and II
Small, unmyelinated fibers
_______ terminate in laminae III and IV, and muscle afferents (Ia and II) terminate anywhere from lamina V to lamina IX
larger sensory fibers
The dorsal columns of the spinal cord carry information from ____ to the _____.
sensory neurons in the spinal ganglia to the brain
The ascending fibers of the dorsal column pathway terminate in the _______.
cuneate and gracile nuclei in the medulla (sense of touch)
Articular and group I muscle receptors travel in the _____________ and make a relay in nucleus Z before joining and medial lemniscus.
dorsolateral funiculus
The spinothalamic tract consists of ____-
the axons of neurons whose bodies lie in the dorsal and intermediate parts of the gray matter
The Spinothalamic Tract: The Axons cross the midline and travel along the ______.
contralateral side of the spinal cord in the ventrolateral funiculus
The Spinothalamic Tract: This tract coveys the ______.
sensations of touch, pressure, temperature, and pain
The Spinocereberllar Tracts: The cerebellum receives information from _____
peripheral sensory receptors
The cerebellum receiver information from peripheral sensory receptors by means of ______.
the dorsal, central, and rostral spinocerebellar tracts; the cuneocerebellar; and the spino-cerebellar tract
Ascends in Clarke’s column. Carries information from proprioceptors in the lower extremeties. Also has projections to nucleus Z and the VPL thalamus.
Dorsal (DSCT)
carries information from upper extremities
Cuneocerebellar
ascends laterally in the central horm. Carries FRA information from the lower extremities and afferent (sensory) signals.
Ventral (VSCT)
carries FRA information from upper extremeties. Also carries efferent signals.
Rostral (RSCT)
Spinoreticular Tract: Ascends in the ______ directly to the reticular formation.
ventrolateral fasciculus
The spinoreticular tract plays a role in _____________.
controlling the sense of pain.
Corticospinal Tract: The pyramidal tract consists of ______.
two major groups of axons.
Axons of the first group go down to the spinal cord (corticospinal tract)]
Corticospinal Tact: Some fibers leave the pyramidal tract and _____.
innervate the motor nuclei of the cranial nerves (corticobulbar tract).
Pyramidal Tract = ______ + ______
Corticospinal Tract + Corticobulbar Tract
Pyramidal Tract
30% from M1
30% from premotor and supplementary motor
40% from somatosensory areas
Lateral CST
contains 80% of the fibers that decussate at the brain stem. Has direct projections to both INs and MNs.
Ventral CST
contains about 20% of the fibers that do not decussate. Mostly controls axial trunk muscles.
Corticobulbar Tract
exits at the pyramids. Controls cranial nerves (such as facial muscles and articulators)
Rubrospinal tract originates in the _____
red nucleus
Rubrospinal Tract receives input from ______.
the motor cortex, the cerebellum, and the olives
Rubrospinal decussates at ______.
midbrain and descends adjacent to the lateral CST; it also has projections to the olives.
function of Rubrospinal Tract
nobody knows for sure, but it is suspected of being of major importance for motor coordination.
The rubrospinal tract crosses the midline __________.
close to its origin and brances to other brain structures, including the interpositus nucleus of the cerebellum, the olives, and the vestibular nuclei
The rubrospinal tract is part of the ____ loop
cerebellum-red nucleus-olive-cerebellum loop
Main inputs of the vestibulospinal tracts.
the cerebellum and the labyrinth
Lateral VST: comes from the LATERAL VESTIBULAR NUCLEUS. Descends ipsilaterally to the ____________. Makes connections with INs.
lumbar level
Lateral VST plays a role in _____.
the control of posture
Medial VST comes from the MEDIAL VESTIBULAR NUCLEUS. Descends ipsilaterally to the _________. Makes connections with INs.
mid-thoracic level
Medial VST plays a role in _____.
the control of posture and perhaps head position.
Vestibulospinal Tracts: Vestibular nuclei receive main inputs from the ____ and the _______.
cerebellum and the labryinth
Vestibulospinal Tracts: _________ nucleus give rise to the lateral vestibulospinal tract and the medial vestibular nucleus is the origin of the medial vestibulospinal tract.
Neurons in Deiters’
Medial RST
to spinal INs (ipsilaterlaly). Its effects are mostly inhibitory.
Lateral RST
to INs in the ventral parts of the spinal cord. Postural control of proximal extensor muscles
Reticulospinal Tract is suspects of _____.
brining the startle reaction
Tectospinal Tract: it comes from the neurons in the ________.
superior colliculus.
Tectospinal Tract: It decussates and plays a role in _______.
motor reactions to visual stimuli (head orientation to visual stimuli by controlling the neck muscles)
Interstitiospinal Tract: It comes from the neurons in the _______.
midbrain
Interstitiospinal Tract function is ______.
a mystery
