NEURO LEC 9 TRACTS Flashcards
sensory information vs. sensation
sensory information: stimulus that causes nerve impulses
sensation: awareness of stimuli
role of the thalamus and cortex in somatosensation
the thalamus relays to the somatosensory cortex which detects sensation, leading to perception
motor homunculus
medial to lateral: legs, head, arms, face
sensory homunculus
legs, trunk, arm, face
projection neurons
long axons that transmit sensory info over long distances (ex: SC to brain)
A first order neuron starts at the ____ and goes to the _____
Periphery
Brainstem/SC
A second order neuron starts at the ____ and goes to the _____
SC/Brainstem
Thalamus
A Third order neuron starts at the ____ and goes to the _____
Thalamus
Somatosensory Cortex
Where is the cell body of a 1st order neuron found?
Dorsal root ganglion
How are spinal tracts named?
Origin and end of their 2nd order neuron
Concious vs Divergent pathways
Concious- Discriminitive information (example: pin point sharp pain)
Divergent- Not discriminitive (Example: achey pain in the entire limb)
Nonconcious relay pathways provide ______ information to cerebellum
nonconcious proprioceptive information
ex: coordination, balance, and posture adjustment
The dorsal tract is considered (Concious and/or divergent)
Whereas the Anteriolateral pathway is (Concious and/or divergent)
Dorsal- Concious
A/L - Both
For crude awareness, sensory info must get to ________
For concious awareness it must get to the _________
Thalamus
Somatosensory cortex
What are the 2 concious relay pathways
Dorsal columns and Anteriolateral columns
Senses of the dorsal column?
Conscious Proprioception, light touch, stereognosis, two point discrimination
remember its conscious so it will be detailed
Senses of the anterolateral column?
Discriminitive pain, temperature, crude touch
DCML 1st order neuron
peripheral receptors to medulla (gracile/cuneate nucleus)
DCML 2nd order neuron
medulla (gracile/cuneate nucleus) to VPL of thalamus
DCML 3rd order neuron
VPL of thalamus to contralateral primary somatosensory cortex
The dorsal column crosses sides in the ________
Internal arcuate fibers in the Medulla
The dorsal column travels from the medulla to the thalamus as Nucleus Gracilis OR Cuneatus
Gracilis is for ____ wherewas Cuneatus is for _________
Gracilis - lower body sensation
Cuneatus - upper body sensation
Where is the secondary somatosensory gyrus and what info does it process?
just behind the primary one
process more complex sensory information - stereognosis, sensory memories (past tactile experiences)
what are the two “types” of the spinothalamic tract?
anterolateral spinothalamic tract
paleospinothalamic tract
Anterolateral spinothalamic tract 1st order neuron
dorsal root ganglion to dorsal horn of SC
Anterolateral spinothalamic tract 2nd order neuron
dorsal horn of SC to VPL of thalamus
Anterolateral spinothalamic tract 3rd order neuron
VPL of thalamus to contralateral primary and secondary somatosensory cortex
The Dorsal column crosses in the _________ whereas the anteriolateral column crosses in the ___________
Medulla
Spinal Cord (same level it enters)
What is the difference between the anterior spinothalamic tract and the lateral?
Anterior- Crude touch
Lateral- Fast nocioception and temperature
True or false: The anterior and the lateral spinothalamic pathways ascend seperately in the spinal cord
False. they only seperate inside of the brain
In the anteriolateral tract, A-Delta fibers handle….
Fast nocioceptive sensation
- quick and precise
In the anteriolateral tract, A-delta and C fibers both handle…..
Temperature
In the anteriolateral tract, C fibers handle…..
Crude touch, dull aching pain
- slow and less precise
What is the region of the spinal cord called where the Anteriolateral tract crosses?
Anterior Commissure
If someone has a lesion on the R side of their spinal cord, their sense of crude touch will be effected (Contralaterally/Ipsilaterally) whereas their sense discrimitive touch will be effected (Contralaterally/Ipsilaterally)
Crude touch- Contralaterally; Anterior Spinothalamic (crosses at SC entry level)
DIscrimitive touch- Ipsilaterally (DCML doesnt cross until medulla!)
Note: this has to do with where it crosses
If a slow nociceptive signal reaches concious awareness, it goes through what pathway?
Spino-emotional
Slow medial nociceptive pathways are: (Divergent/Concious/Non-concious)
Divergent
The slow-medial nociception tract is a divergent pathway and will lead to what 3 responses following pain?
emotional response
autonomic activation (inc HR)
reflexive actions (looking at injury)
What spinal tract deals with you looking at an injury after it happens?
Spinomesencephalic (slow-medial nociception)
Goes to the superior colliculus and periaqueductal grey - the former deals with vision and is in the posterior midbrain while the latter deals with control pain sensations
Spinomesencephalic tract plays a role in inhibiting or controlling pain sensations
Slow-Medial Nociception 1st order neurons are always what kind of fibers?
C fibers
1st order neuron of the slow-medial nociception pathway
C fibers to dorsal horn of SC
2nd order neuron(s) slow-medial nociception pathway
spino-emotional: medial/intralaminar thalamuc nuclei –> emotional and cognitive areas
spinomesencephalic: superior colliculus, periaqueductal gray (orienting and pain modulation)
spinoreticular: reticular formation (arousal, attention)
Slow-Medial Nociception pathways cross where?
Immediately in the spinal cord
where is subconscious temperature transmitted to?
reticular formation, thalamus, subcortical nuclei, and hypothalamus
if subconscious temperature does not reach conscious awareness, it affects…
arousal and autonomic regulation
–> HR, BP, sweating (automatic bodily function adjustment)
spinocerebellar tract functions
unconscious postural movement adjustment
spinocerebellar tract is conscious/divergent/nonconscious and relays info from what region of the body?
nonconscious, LE and lower body
What are the spinocerebellar tracts?
postero/dorsal spinocerebellar tract
cueneocerebellar tract
anterior/ventral spinocerebellar tract
rostrospinocerebellar tract
What is the only spinocerebellar tract that crosses?
Anterior/ventral spinocerebellar
Where does the dorsal spinocerebellar and the cuneocerebellar tract cross?
They dont cross.
Where is the clarks nucleus for 1st order neurons in the dorsal spinocerebellar tract found?
C8/T1-L2
Note: because this tract is only for the Lower body!
what is the function of the posterior/dorsal spinocerebellar pathway?
Carrying unconscious proprioceptive information from the LOWER extremity and trunk
what is the 1st order neuron of the posterior spinocerebellar tract
muscle spindles, GTOs, and joint receptors in LE to dorsal horn of SC (Clarks nucleus)
what is the 2nd order neuron of the posterior spinocerebellar tract
Clarks nucleus to cerebellum via inferior cerebellar peduncle
what is the function of the cuneocerebellar tract
Carrying unconscious proprioceptive information from the UPPER extremity
where do the 1st and 2nd order neurons of the cuneocerebellar pathway synapse?
lateral cuneate nucleus in medulla
where does the cuneocerebellar tract enter the cerebellum through?
inferior peduncles
The dorsal spinocerebellar and the cuneocerebellar go through the _____ peduncle whereas the Anterior spinocerebellar tract goes through the _____ peduncle
Inferior Peduncle
Superior Peduncle
Describe the crossing that happens at the anterior spinocerebellar tract
Most fibers cross twice to end up on same side, whereas some fibers go to contralateral side. Each side of brain receives fibers from BOTH sides of body to assist in coordination.
what are the functions of the anterior/ventral spinocerebellar tract?
carries proprioceptive info from the LOWER body to the cerebellum, especially related to muscle activity and movement patterns
what is the 1st order neuron for the anterior/ventral spinocerebellar tract?
muscle spindles, GTOs, and joint receptors in LE to dorsal horn of SC
what is the 2nd order neuron for the anterior/ventral spinocerebellar tract?
dorsal horn of SC –> SUPERIOR cerebellar peduncle –> cerebellum
Where does the anterior/ventral spinocerebellar tract’s cross?
First in spinal cord immediately, then again in cerebellum
True or false: The Rostrospinocerebellar tract crosses in the spinal cord
False, it does not cross!
What does the reticulospinal tract control?
Posture
what is the function of the rostrospinocerebellar tract?
transmits proprioceptive info
Where does the rostrospinocerebellar tract relay information from?
From cervical spinalcord + T1 to cerebellum at both inferior AND superior peduncles
what are the primary output cells of the cortex
pyramidal cells
what are the 3 fiber types of white matter?
projection fibers
commissural fibers
association fibers
What do projection fibers connect?
Connect cortex with other areas of CNS
what is an example of a projection fiber
internal capsule
internal capsule
bundle of myelinated nerve fibers that act as a major communication pathway between cortex and brainstem/SC
- coordinates voluntary movement
what 3 structures surround the internal capsule
putamen
globus pallidus
caudate nucleus
What do association fibers connect?
Connect nearby parts of the brain within the same hemisphere
what are 4 examples of association fibers?
cingulum
short association fibers
superior longitudinal fasciculus
inferior longitudinal fasciculus
What do commissural fibers connect?
Connect identical parts of the R and L cortex to eachother
what are 2 examples of commissural fibers?
corpus callosum
anterior commissure
Motor tracts that originate in the cortex are _______ whereas if they originate in the brainstem they are __________
Pyramidal
Extrapyramidal
(extrapyramidal=outside cortex)
what do motor tracts synapse with?
alpha motor neurons
gamma motor neurons
interneurons in brainstem/SC
In the cortex, Posture/gross movements synapse (medially/laterally)
Whereas fine movements synapse (medially/Laterally)
Gross = medially
Fine = Laterally
what are pyramidal tracts?
motor pathways that control voluntary movement
where do motor pathways originate?
pre central cortex
what is the difference between the primary motor cortex and the premotor cortex?
primary motor cortex: voluntary movement
premotor cortex: planning and coordination of movement
what are the two “types” of the corticospinal tract?
lateral (distal) cortiospinal tract
medial (proximal) corticospinal tract
The Pyramidal Corticospinal tract does what?
Lateral- Fractional distal limb movements
Medial- automatic/proximal trunk postural movememts
where does the lateral corticospinal tract originate from?
primary motor cortex
where does the medial corticospinal tract originate?
premotor cortex
where does the lateral corticospinal tract descend through?
lateral funiculus
where does the medial corticospinal tract descend through?
medial funiculus
where do the medial and lateral corticospinal tracts synapse?
on interneurons or motor neurons in the ventral horn
where does the lateral corticospinal cross?
pyramidal decussation of medulla
where does the medial CST cross?
uncrossed
flexor extensor rule
MNs for flexor muscles: posteriorly in ventral horn
MNs for extensor muscles: anteriorly in ventral horn
proximal distal rule
MNs for proximal muscles: medially in the ventral horn
MNs for distal muscles: laterally in the ventral horn
What does the pyramidal (descending) corticobulbar tract do?
Motor control at the face
where does the corticobulbar tract cross?
at the brainstem at different levels for each cranial nerves
postcentral somatosensory cortex?
receives sensory input to guide motor planning and execution
anatomy of the motor pyramidal tracts
the tracts for the legs are more lateral
the tracts for the face are more medial
what are extrapyramidal tracts?
they originate outside the cerebrum and are responsible for involuntary movement and postural control, coordination/gross motor skills
What are the 3 extrapyramidal tracts called?
Reticulospinal
Vestibulospinal
Rubrospinal
What does the reticulospinal tract control?
Posture and gross movements of the trunk and proximal muscles
anticipatory movements
where does the reticulospinal tract cross?
uncrossed
What does the vestibulospinal tract control?
maintains balance and posture based on position of head
neck, back, and postural muscles
where does the vestibulospinal tract cross?
medial: brainstem
lateral: uncrossed
what is the function of the rubrospinal tract?
facilitates upper limb distal muscle activity
where does the rubrospinal tract cross?
midbrain (at red nucleus)
*rubro means red
tracts that are active during intense emotions
ceruleospinal
raphespinal
ceruleospinal tract. origin
locus coeruleus (junction of midbrain and pons)
ceruleospinal tract neurotransmitter
norepinephrine
ceruleospinal tract function
provides tonic facilitation of spinal motor neurons for motor control
raohespinal tract origin
raphe nuclei (upper medulla)
raohespinal tract neurotransmitter
serotonin
raohespinal tract function
modulates spinal motor neurons influencing motor and emotional responses
What is the purpose of the premotor cortex?
Prepares for movement (especially movement that involves multiple joints)
What is the purpose of the supplementary motor cortex?
Active prior to initiating movments that require specific sequence
Identify this part of the brain
Supplementary motor cortex
Identify this part of the brain
Premotor cortex
