Week 2 Module 2: The Spinal Cord and Spinal Cord Injury

There are _____ pairs of spinal nerves

31

There are _____ cervical

8

There are ____ thoracic

12

There are ____ Lumbar

5

There are ____ sacral

5

There is ____ coccygeal

1

The spinal nerves are located/enclosed in…

The vertebral column

The spinal nerves exit below their….

Corresponding vertebrae

Where does the spinal cord end?

Just below the L1 and L2 vertebrae region

What is the portion of the spinal cord that extends past the L1 and L2 region called?

Cauda equina

What covers the spinal cord?

The same meningeal layers that cover the brain- pip mater (innermost), arachnoid mater, and dura mater (outermost)

The meningeal covering of the spinal cord extends…

Past the end of the spinal cord to the L4 level

The CSF filled meningeal space between L2-L4 is called?

Lumbar cistern

The lumbar cistern is the site for…

Lumbar punctures/spinal taps

Spinal taps at the lumbar cistern is usually testing for what kind of conditions?

MS

Meningitis

What are the two main functions of the spinal cord?

It carries sensory information from your environment to your brain where it can be processed

Contains spinal reflexes

What are affect pathways?

Ascending tracts that carry information to the brain

What are efferent pathways?

Descending tracts that transport signals from the brain to peripheral sites, such as motor neurons (which results in movement)

Skeletal muscles are under…

Voluntary control

Smooth muscles are under…

Involuntary control

What is the pathway of afferent neurons or the afferent tract?

Sensory information is sensed by receptors in the skin and other organs → the sensory information travels to the spinal cord through the ascending tract when it is then taken to the brain to be processed

What is the pathway of efferent neurons or the efferent tract?

The brain determines it wants to move → the motor information is sent to the spinal cord through→ the motor information travels through the spinal cord to the peripheral nervous system (motor neurons) to produce movement

What is housed in the dorsal root ganglions?

The cell bodies of afferent neurons

The cell body of an afferent neuron has a…

Single axon that divides into two branches

What are the two branches that the single axon of an afferent neuron separates into?

A pathway connected to the sensory organ

A pathway that carries sensory information the spinal cord via the dorsal root

Where are the cell bodies of efferent neurons located?

In the ventral horn of the spinal cord

Where do efferent axons leave the spinal cord?

Through the ventral root

After exiting the spinal cord through the ventral root, where do efferent signals travel and synapse?

They travel through spinal nerves to the neuromuscular junction where they synapse with skeletal muscle cells

What is an upper motor neuron?

A neuron where it’s nerve cell originates in the brain’s cerebral cortex and travels to the spinal cord (these include cranial nerves nuclei)

What is a lower motor neuron?

A neuron whose nerve cell originates in the spinal cord and connects to skeletal muscle (these include cranial nerve fibers that connect to muscles)

What is the function of an upper motor neuron?

It plans and initiates voluntary movement

What is the function of a lower motor neuron?

It connects the signal sent from the upper motor neuron to the muscles to produce movement

What is the spinal reflex arc?

A reaction based on sensory input that does not need to be first processed by the brain before it produces reflexive movement

The is no ________ processing when the spinal reflex arc is activated or occurs

Conscious

What is the synaptic process of the spinal reflex arc?

A sensory axon sends information between an inter neuron and a motor neurons in the ventral horn

Where do synapses occur during the spinal reflex arc?

All within the spinal cord

The ascending spinal cord tracts carry sensory information to the…

Brain stem

Thalamus

Cortex

What is the pathway sensory information takes as it goes through the ascending spinal cord tracts to the brain?

Sensory input from a receptor → afferent axon (LMN) → dorsal ganglia → dorsal root (PNS) → synapse → dorsal horn (CNS)

The descending spinal cord tracts carry motor information from…

The cortex through the internal capsule, thalamus, and brain stem to the spinal cord

What is the pathway motor information takes when going through the descending spinal cord tracts?

Motor output from the brain → efferent axon (UPN) → ventral horn (CNS) → synapse → ventral root (PNS to LMN to Motor spinal nerve) → skeletal muscle

What do ventromedial pathways control?

Locomotion

What controls posture?

The brain stem

What are a part of the ascending tracts (sensory)?

Dorsal columns

Lateral spinothalamic tracts

Posterior spinocerebellar

Spinocerebellar tracts

What are the dorsal columns of the ascending tracts responsible for?

Touch, pressure, vibration, and proprioception

What is the function of the lateral spinothalamic tracts?

Carrying conscious sensory information a to the cortex on the opposite side of the body

What is the function of the spinocerebellar tracts?

Unconscious proprioception

What are the components of the descending tracts (motor)?

Lateral corticospinal tract

Vestibulospinal tracts

What is the longest tract along the descending tract?

The lateral corticospinal tract

What is the arterial corticospinal tract responsible for?

Volitional (planned and executed) motor control of the opposite side of the body and carries motor signals from the primary motor cortex in the brain down the spinal cord to the muscles of the trunk and limbs

Where do the vestibulospinal tracts originate?

The brainstem

What is the function of the vestibulospinal tracts?

Facilitation of extensor tone, these muscles support adequate upright sitting posture

Pain, temperature and touch travel…

To the opposite or contra lateral side of the brain stem

What is the origin of the dorsal columns/medial lemniscus?

Peripheral receptors: first order-neuron synapses in the medulla

What is the function of the dorsal columns/medial lemniscus?

Conveys information about light touch and conscious proprioception

What is the origin of the spinothalamic tracts to?

Dorsal horn of the spinal cord

What is the function of the spinothalamic tract?

Conveys discriminative information about nociception and temperature

What is the origin of the spino-emotional, spinomesencephalic, and spinoreticular tracts?

Dorsal horn of the spinal cord

What is the function of the spino-emotional, spinomesencephalic, and spinoreticular tracts?

Non-localized perception of pain, arousal, reflexive, motivational, and analgesic responses to nociception

Where do the posterior spinocerebellar and cunocerebllar tracts originate?

High-fidelity paths originate in peripheral receptors; first-order neurons synapse in nucleus dorsal is or medulla

What is the function of the posterior spinocerebellar and cuneocerebellar tracts?

Conveys conscious proprioception information

What is the origin of the anterior spinocerebellar and rostrospinocerebellar tracts?

Internal feedback tracts originate in the dorsal horn of the spinal cord

What is the function of the anterior spinocerebellar and rostrospinocerebellar tract?

Conveys information about activity in motor tract pathways and spinal interneurons

What is the origin of the lateral corticospinal tract?

Supplementary motor, pre motor, and primary motor cerebral cortex

What is the function of the lateral corticospinal tract?

Contra lateral fractionation of movement, particularly of hand movements

What is the origin of the medial corticospinal tract?

Supplementary motor, premotor, and primary motor cortex

What is the function of the medial corticospinal tract?

Control of neck, shoulder, and trunk muscles

What is the origin of the rubrospinal tract?

Red nucleus of midbrain

What is the function of the rubrospinal tract?

Facilitates contra lateral upper limb extensors

What is the origin of the reticulospinal tract?

Reticular formation in medulla and pons

What is the function of the reticulospinal tract?

Facilitates postural muscles and gross limb movements

What is the origin of the lateral vestibulospinal tract?

Vestibular nuclei in medulla and pons

What is the function of the lateral vestibulospinal tract?

Ipsilaterally facilitates motor neurons to extensors; inhibits motor neurons to flexors

What is the origin of the ceruleospinal tract?

Locus coeruleus in the brainstem

What is the function of the ceruleospinal tract?

Enhances the activity of inter neurons and motor neurons in spinal cord

What is the origin of the raphespinal tract?

Raphe nucleus in the brainstem

What is the function of raphespinal tract?

Enhances the activity of inter neurons and motor neurons in the spinal cord

What is transection of the spinal cord?

Complete severing of the cord, resulting in interruption of all sensory and motor information below the LEI

What can cause transection of the spinal cord?

Traumatic injury such as MVA, gunshot, sports and recreation accidents, knife wounds

What is compression of the spinal cord?

Impingement of the cord from trauma, tumor, or vertebral degenerative joint disease

What happens when infection impacts the spinal cord?

The integrity of the cord may become compromised

What is an example of a condition/infection that impacts the spinal cord?

Polio- it causes damage to the cell bodies in the ventral horn causing LMN loss

What are degenerative disorders of the spinal cord?

Degenerative disease the can damage the motor spinal cord tracts

What is an example of a degenerative disorder of the spinal cord?

ALS- bilateral degeneration of the ventral horn and pyramidal tracts (affecting both the UMN and LMN)

What is spinal shock?

Absence of spinal reflexes, reduction of muscle tone, and paralysis

What happens when spinal shock resolves? (The resolution of spinal shock)

Spasticity

Return of motor function and sensation

Hyperreflexia

Presence of primary reflexes such as the babinski sign

When does spinal shock occur?

Immediately after a spinal cord injury

What often causes spinal shock?

High-impact and direct- trauma, resulting in loss of spinal cord function caudal to the level of the injury

What is phase 1 of spinal shock?

0-1 days

Areflexia/hyporeflexia

Loss of descending facilitation

What is phase 2 of spinal shock?

1-3 days

Initial reflex return

Denervation and supersensitivity

What is phase 3 of spinal shock?

1-4 weeks

Initial hyper-reflexia

Axon supported synapse growth

What is phase 4 of spinal shock?

1-12 months

Final hyper-reflexia

Soma supported synapse growth

What is the average duration of spinal shock?

4-12 weeks

Injury at the motor sensory level is hard to classify because…

Impairment may vary, regarding where sensation is impaired and where motor function is impaired

How is a spinal cord injury classified regarding the affect neurological level?

Based on the lowest level of the spinal cord with intact function

What is tetraplegia?

Cervical injury causing sensory and/or motor loss to all four limbs, the trunk, and bowel and bladder control

What is paraplegia?

Impairment of loss of motor and/or sensory function in the thoracic, lumbar, or sacral segments of the spinal cord, the UEs are generally unaffected

What is a complete spinal cord injury?

There is no motor or sensory function below the LEI

What is an incomplete spinal cord injury?

Some sensation and/or motor function is still present below the LEI and there is a better prognosis

What is ASIA?

The American Spinal Injury Association

What is stage A on the ASIA impairment scale?

Complete

No sensory or motor function is preserved in the sacral segments S4-S5