13 - Tracts of Spinal Cord (Exam 3) Flashcards
What structure extends from the foramen magnum to L1 of the spine?
Spinal cord
What are the 5 regions of the spinal cord?
- Cervical
- Thoracic
- Lumbar
- Sacral
- Coccygeal
How many pairs of spinal nerves are there?
31
What is the core of the spinal cord composed of, and what shape does it have?
Gray matter
H shape
What are the 2 sections of the gray matter core of the spinal cord?
- Anterior horn
2. Posterior horn
What are the 3 groups found within the anterior horn?
- Medial group
- Central group
- Lateral group
Where in the spine is the medial group found and what does it innervate?
C1-C3 and T1-T2
Neck, trunk, intercostal, and abdominal muscles
Where in the spine is the central group found and what does it innervate?
C1-C6 (spinal root of CN XI)
C3-C5 (phrenic nerves to diaphragm)
L2-S1 (lumbosacral nucleus)
Where in the spine is the lateral group found and what does it innervate?
Cervical and lumbosacral regions
Skeletal muscles of the limbs
What are the 4 groups found within the posterior horn?
- Substantia gelatinosa
- Nucleus proprious
- Nucleus dorsalis (AKA Clarke’s column)
- Intermediolateral cell groups (AKA lateral horn)
What type of sensations does the substantia gelatinosa respond to?
Touch
Pain
Temperature
What type of sensations does the nucleus proprious respond to?
Proprioception
Resolution
Vibration
Where does the nucleus proprious receive information from?
Posterior white column
Where is the nucleus dorsalis found and what is the only type of information it deals with?
T1-L3
Proprioception
What type of information do the intermediolateral cell groups receive?
Visceral afferent information
What are the 3 columns of white matter in the spinal cord?
- Anterior
- Posterior
- Lateral
Ascending tracts carry what type of information?
Afferent information
From periphery to CNS
Descending tracts carry what type of information?
Efferent information
From CNS to periphery
What are the 3 major ascending tracts?
- Posterior column
- Anterolateral system (AKA spinothalamic tract)
- Spinocerebellar tract
What are the ascending and descending tracts composed of?
White matter
What is the major descending tract?
Corticospinal tract
What is another name for the corticospinal tract?
Pyramidal tract
Due to decussation in medulla
What are the 4 extrapyramidal tracts?
- Reticulospinal
- Tecto-spinal
- Rubrospinal
- Vestibulospinal
Do lesions prior to decussation in Ascending tracts produce ipsilateral or contralateral sensory defects?
Ipsilateral sensory defects
Doesn’t cross over before lesion, sensory information lost comes is from one side
Do lesions after decussation in Ascending tracts produce ipsilateral or contralateral sensory defects?
Contralateral sensory defects
Do lesions prior to decussation in Descending tracts produce ipsilateral or contralateral motor defects?
Contralateral motor defects
Do lesions after decussation in Descending tracts produce ipsilateral or contralateral motor defects?
Ipsilateral motor defects
Doesn’t cross over after lesion, results in one-side paresis/weakness
How do exteroceptive and proprioceptive information differ?
Exteroceptive - external stimuli (pain, touch, pressure)
Proprioceptive - internal stimuli (body position)
Where are first order neurons of the ascending pathway typically found?
From the receptor to the spinal cord
Cell body usually in posterior root of spinal cord
Where are second order neurons of the ascending pathway typically found?
From the spinal cord to the thalamus
Usually decussates
Where are third order neurons of the ascending pathway typically found?
From the thalamus to the cortex
What are the 2 pathways of conscious sensory input?
- Posterior column - Medial lemniscal system
2. Anterolateral system
What type of information does the medial lemniscal system deal with?
Non-painful touch
Where do the 1st order neurons of the fasciculus gracilis travel up to and including?
T6
Where do the 1st order neurons of the fasciculus cuneatus travel above?
T6
Where do 1st order neurons of the medial lemniscal system synapse and immediately decussate?
Caudal medulla
Where are the 3rd order neurons of the medial lemniscal system?
Thalamus
What type of information does the anterolateral system deal with?
Crude touch, pain, temperature
What is the anterolateral system also known as?
Spinothalamic tract
Where do the 1st order neurons of the anterolateral system synapse?
Immediately upon entry to the spinal cord
What type of information does the anterior portion of the anterolateral system carry?
Pressure, course touch
What type of information does the lateral portion of the anterolateral system carry?
Pain, temperature
Where do neurons of the spinotectal tract synapse?
Superior colliculus
What type of information do spinocerebellar tracts relay and where do they relay it to?
Information about limb position
Relayed to cerebellum
What 4 tracts are involved in the spinocerebellar tracts?
- Posterior spinocerebellar tract
- Cuneocerebellar tract
- Anterior spinocerebellar tract
- Rostral spinocerebellar tract
What is significant about the posterior spinocerebellar tract?
Ascend ipsilaterally to cerebellum
No 3rd order neurons
DO NOT DECUSSATE
What is the cuneocerebellar tract very similar to?
Posterior cerebellar tract
What type of information does the cuneocerebellar tract carry?
Proprioceptive information from the upper limbs
What is the role of the anterior spinocerebellar tract?
Integrates proprioceptive information with descending motor information
What is the rostral spinocerebellar tract similar to?
Anterior spinocerebellar tract
Does the same thing but for upper limbs
What is significant about the rostral spinocerebellar tract?
NO DECUSSATION
What do lesions of spinocerebellar tracts cause?
Ataxia
Loss of muscle coordination
What are the 3 general steps of the pathway of descending tracts?
- Upper motor neurons
- Lower motor neurons
- Interneurons
Where do most descending tracts decussate?
At the medulla oblongata
What are the main descending tracts?
Corticospinal tracts
What are corticospinal tracts also known as?
Pyramidal tracts
What corticospinal tract does not decussate?
Anterior corticospinal tract
What are the descending tracts that are not corticospinal tracts known as?
Extrapyramidal tracts
Why are the extrapyramidal tracts named as such?
Do not travel through pyramids of the medulla
What are the 4 extrapyramidal tracts?
- Vestibulospinal tract
- Reticulospinal tract
- Rubrospinal tract
- Tectospinal tract
Which extrapyramidal tract is most important to us and why?
Vestibulospinal tract
Stabilizes head during body movement
What 2 tracts is the vestibulospinal tract broken into?
- Medial tract
2. Lateral tract
Where does the reticulospinal tract originate?
Reticular formation
Where does the rubrospinal tract originate?
Red nucleus
Where does decussation of the rubrospinal tract occur?
Midbrain
Where may the influence of the rubrospinal tract be seen with loss of corticospinal tract?
Comatose posturing
What are the 2 types of comatose posturing that may show where a lesion is present?
- Decerebrate posture
2. Decorticate posture
What does decerebrate posture look like?
Extension of both upper and lower limbs
What does decorticate posture look like?
Flexion of upper limbs
Extension of lower limbs
What does decerebrate posture clue into?
Lesion at level of midbrain (red nucleus)
Rubrospinal and corticospinal tracts interrupted
What does decorticate posture clue into?
Lesion rostral to the red nucleus
Corticospinal tract interrupted
What is the role of the tectospinal tract?
Moves head and neck in response to eye movements
