Ascending + Descending Tracts 26 Flashcards
Def. Nuclei
Cluster of nerve cells within the CNS
Def. Ganglia
- structure containing nerve cell bodies outside (generally) of the central nervous system
- mass of grey matter within the CNS (ie. Basal ganglia)
Def. # order neuron
Neuron location in particular order
1st 2nd 3rd….
Def. Tracts
Bundles of axons with common origin and common termination
Def. Fasciculus and lemniscus
Other terms for bundles of axons, specific tracts we talk about for ascending
Def. Ipsilateral
Same side of the body
Def. Contralateral
Opposite side of the body
Def. Decussation
Cross over of axons within CNS
Peripheral nervous system includes?
Purpose?
Spindles, GTOs, skin receptors, joint receptors, free nerve endings
- involved in ascending tracts
Central nervous system components?
Brain, brain stem, cerebellum, spinal chord
The brainstem includes what components?
Midbrain
Pons
Medulla
Spinal chord anatomy:
Grey matter contains?
Cell bodies
Inter neurons
Somatotopic organization
White matter contains?
Myelinated axons
Ascending and descending tracts
(White because it’s myelinated)
Ascending tracts are associated with?
Sensory system
- brings sensory info UP to brain
Descending tracts are associated with?
Motor system
- brings motor commands DOWN to muscles
Where is cerebral spinal fluid?
Flows through the central canal
Key feature of the medulla
Important location where a lot of tracts Decussate “cross over”
(Also contains nuclei)
Pons and midbrain
Part of the brainstem
A lot of nuclei that allow subconscious functions
(Breathing swallowing bladder control etc)
Cerebellum
“Integrator” of sensory information
- fine motor control and motor learning
Thalamus
‘Grand central station’
Deep within cortex
Many nuclei receive ALL sensory info: peripheral, visual, vestibular info
Transmits too all locations within the cortex
‘VPL’ ventral posteriolateral nucleus
Central sulcus separates what parts of the brain?
Frontal and parietal lobes
Dorsal column
Only ascending tracts
Most myelinated axons (fastest transmission)
Newer system (Proprioception, vibration, fine touch - evolved from older system ex. Pain)
Anterolateral column of spinal chord
Both ascending and descending tracts Slower tracts (less myelinated) Older system (crude touch, pain, temp)
Name all ascending tracts (top to bottom)
Fasciculus gracilis (lower limb) Fasciculus cuneatus (upper limb muscles) Dorsal spinocerebellar tract Ventral spinocerebellar tract Lateral spinothalamic tract Anterior spinothalamic tract
Name all the descending tracts (brain down to periphery)
Lateral corticospinal tract Medullary reticulospinal tract Pontine reticulospinal tract Lateral vestibulospinal tract Anterior corticospinal tract
Descending motor output originates? Innervates? Modulates? Controls?
- multiple brain systems and descends through multiple tracts
- alpha gamma and inter neurons within the spinal chord
- modulates spinal chord neural processing
- controls voluntary & reflexive movement
Corticospinal tract transmits? Associates with? Important for?
- voluntary motor commands to motor neurons in SC
- motor cortex associated with Contralateral muscles (axons Decussate to other side)
- important in controlling skilled movements
3 main descending tracts?
Corticospinal tract
Vestibulospinal tract
Reticulospinal tract
3 main ascending tracts?
Medial leminscal system
Anterolateral spinothalamic tract
Spinocerebellar tract
Pathway of the corticospinal tract
Begins motor cortex M1 Through internal capsule Partial decussation within medulla - 75-90% do (innervate limbs) - 10-25% don't (innervate axial muscles)
Reticulospinal tracts coordinates what type of movement?
Originates?
Direction of travel?
Terminates?
- automatic movements (locomotion and posture)
- originates in “reticular formation” (2 tracts- pons and medulla)
- travels ipsilateral
- terminate at all SC segments
Difference between pontine reticulospinal tract and medullary reticulospinal tract?
Pontine
-medial
-excites ipsilateral extensor muscles (help support our weight)
Medullary
-lateral
-inhibits excitory axial muscles (help relax extensors)
Vestibulospinal tract (VS tract) transmits?
Subconscious motor commands to extensor muscles to maintain balance
Vestibular tracts signals are generated from where? Where do they go and how? What does it control?
- signals generated within the vestibular system (accelerations)
- transmitter to vestibular nuclei via the 8th cranial nerve
- controls ipsilateral muscles
Two vestibulospinal tracts are?
Medial VS tract
-controls neck muscles
Lateral VS tract
-descends directly to ipsilateral extensor muscles
Ascending sensory pathways send what type of input?
Sensory input
Ascending sensory pathways originates in?
Peripheral sensory receptors (first order neurons)
Ascending sensory pathways ascend through what columns?
Dorsal column
- medial lemniscal system
Anterolateral column
- spinothalamic and spinocerebellar pathways
Medial lemniscal system transmits what type of information?
Transmits proprioceptive, fine touch, and vibration info from peripheral receptors to somatosensory cortex
Medial lemniscal system tracts ascend through
The dorsal column
Key feature of the axons of the medial lemniscal system?
Axons are the most myelinated
Fastest conduction velocity
Sensations from one side of the body of the medial lemniscal system associate with?
Contralateral somatosensory cortex
Spinothalamic tracts transmit what signals? From where? To where?
Transmits pain, temp, and crude touch
From periphery
To areas within cortex
Receptors on one side of the body from spinothalamic tracts associate with?
The somatosensory cortex
What are the two spinothalamic tracts?
Lateral spinothalamic tract
-pain and temp
Anterior spinothalamic tract
-crude touch and pressure
Spinocerebellar tracts transmits info from where? To where and why?
Information from the peripheral receptors (spindles! GTOs, skin etc)
To the cerebellum
For sensory integration
Receptors from one side of the body of the spinocerebellar tract are associated with?
The ipsilateral cerebellum
Path of the. Spinocerebellar tracts
Ascends in the lateral column via the dorsal and ventral spinocerebellar tracts
