Neuroscience: Spinal Control of Movement

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Questions and Answers

What anatomical structure serves to anchor the spinal cord to the coccyx?

Anterior median fissure

Conus medullaris

Filum terminale (correct)

Denticulate ligaments

Which part of the gray matter contains the cell bodies of somatic motor neurons?

Dorsal root ganglion

Lateral horns

Posterior horns

Anterior horns (correct)

How many pairs of spinal nerves are there?

31 (correct)

Which funiculus is primarily responsible for carrying pain and temperature sensations?

Lateral funiculus Signup and view all the answers

What is the role of the denticulate ligaments?

Stabilize the spinal cord Signup and view all the answers

Which tract is involved in voluntary movement in the limbs?

Corticospinal tract Signup and view all the answers

Where do the dorsal and ventral roots of the spinal cord fuse to form spinal nerves?

Laterally Signup and view all the answers

Which pathway is primarily involved in the coordination and balance of movements?

Reticulospinal tract Signup and view all the answers

Which type of roots emerge from the dorsal side of the spinal cord?

Sensory roots Signup and view all the answers

What is indicated by the term 'decussate' in relation to spinal cord pathways?

Pathways that cross over to the opposite side Signup and view all the answers

What is the role of the receptor in a reflex arc?

It detects a change in the environment. Signup and view all the answers

What is the purpose of the inhibitory interneuron in the stretch reflex?

To inhibit the antagonist muscle. Signup and view all the answers

Which type of reflex is characterized by moving a body part away from a painful stimulus?

Withdrawal Reflex Signup and view all the answers

What occurs during the crossed extensor reflex?

The affected limb flexes while the opposite limb extends. Signup and view all the answers

What does the Golgi tendon reflex primarily monitor?

Excessive force in the tendon. Signup and view all the answers

How do alpha and gamma motor neurons function during a reflex?

They work together to maintain sensitivity. Signup and view all the answers

In the context of spinal reflexes, which component is responsible for integrating sensory information?

Integration center Signup and view all the answers

What is a characteristic feature of the flexor reflex?

It causes the flexor muscles to contract. Signup and view all the answers

What is the primary function of cutaneous reflexes?

To provide protective and postural functions Signup and view all the answers

Which spinal injury classification indicates the worst condition?

Complete (A) Signup and view all the answers

Which of the following is true for anterior cord syndrome?

Pain and temperature sensation is lost Signup and view all the answers

In Brown-Sequard syndrome, what characterizes ipsilateral loss?

Motor function and proprioception Signup and view all the answers

What is a common cause of central cord syndrome?

Degenerative changes in the cervical spine Signup and view all the answers

Which function remains intact in anterior cord syndrome?

Dorsal column functions Signup and view all the answers

What is a significant prognostic feature of Brown-Sequard syndrome?

Good prognosis for recovery Signup and view all the answers

In the context of spinal cord injuries, what does ASIA stand for?

American Spinal Injury Association Signup and view all the answers

Which condition is primarily associated with conus medullaris syndrome?

Disc herniation or spinal stenosis Signup and view all the answers

What reflexive response occurs as a result of painful cutaneous stimuli?

Contraction of extensor muscles on the opposite limb Signup and view all the answers

Study Notes

Spinal Control of Movement

The course is Neuroscience
The presenter is Dr. Meeyoung Kim from the Physiotherapy Department at the University of Sharjah
The lecture covers Ekman chapter 12 on spinal control of movement

Anatomy of the spinal cord
Spinal reflexes
Spinal cord injury

Spinal Cord Anatomy

Terminates: at L1/L2 vertebral level (conus medullaris)
Dura extends: to S2 vertebral level
Conus medullaris: the terminal portion of the spinal cord
Filum terminale: a fibrous extension of the pia mater that anchors the spinal cord to the coccyx
Denticulate ligaments: delicate shelves of pia mater that attach the spinal cord to the vertebrae
31 pairs of spinal nerves: attached to the cord by paired roots
- Cervical nerves are named for the inferior vertebrae
- Other nerves are named for the superior vertebrae
Cervical and lumbar enlargements: sites where nerves serving the upper and lower limbs emerge
Cauda equina: a collection of nerve roots at the inferior end of the vertebral canal

Cross-Sectional Anatomy of the Spinal Cord

Anterior median fissure: separates anterior funiculi
Posterior median sulcus: divides posterior funiculi
Epidural space: contains fat
Subdural space
Subarachnoid space
Pia mater
Arachnoid
Dura mater (spinal dural sheath)
Bone of vertebra
Dorsal root ganglion
Body of vertebra
Spinal meninges

Structures - Spinal Cord

Paired denticulate ligaments: extend from pia mater to dura mater, stabilizing side-to-side movement
Blood vessels: along the surface of spinal pia mater within the subarachnoid space.

Cross-Sectional Anatomy

Gray matter: cell bodies, neuroglia, and unmyelinated processes
- Posterior horns: sensory, all interneurons
- Lateral horns: autonomic, T1-L2
- Anterior horns: motor, cell bodies of somatic motor neurons
Spinal roots: ventral (somatic and autonomic motor) and dorsal (DRG: dorsal root ganglion)

Gray Matter: Organization

Dorsal half: sensory roots and ganglia
Ventral half: motor roots
Dorsal and ventral roots fuse laterally to form spinal nerves
Four zones are evident in gray matter: somatic sensory (SS), visceral sensory (VS), visceral motor (VM), and somatic motor (SM)

White Matter in the Spinal Cord

Fibers run in three directions: ascending, descending, and transversely
Divided into three funiculi (columns): posterior, lateral, and anterior.
Each funiculus contains several fiber tracts:
Fiber tract names reveal origin and destination
Fiber tracts composed of axons with similar functions
Pathways decussate (cross over)
Most consist of two or three neurons
Most exhibit somatotopy (precise spatial relationships)
Pathways are paired (one on each side of the spinal cord or brain), includes pain and temperature and light touch and proprioception, and motor.

White Matter: Pathway Generalizations

Ascending tracts:
Dorsal white column, carry conscious proprioception and light touch
- Fasciculus gracilis
- Fasciculus cuneatus
Posterior spinocerebellar tract
Anterior spinocerebellar tract- carry unconscious proprioception
Lateral spinothalamic tract- carry pain and temperature
Anterior spinothalamic tract
Descending tracts:
Lateral reticulospinal tract-
Lateral corticospinal tract-
Rubrospinal tract-
Medial reticulospinal tract-
Anterior corticospinal tract-
Vestibulospinal tract-
Tectospinal tract

5 Components of a reflex arc

Receptor
Sensory neuron
Integration Center (CNS)
Motor neuron
Effector

Muscle Sensory Receptors (Proprioceptors)

Muscle spindle: responds to stretch, includes intrafusal fibers and gamma motor neurons
Golgi tendon organ: responds to muscle tension, including Ib fibers

Muscle Spindles

Intrafusal muscle fibers allow for variable sensitivity to stretch
Primary sensory axons that terminate on the central region sense stretch- type 1A fiber
Type 2 fibers only check for change in length
Gamma motor axons regulate the tension of the intrafusal fibers

Stretch Reflex

Agonist and antagonist muscles are involved
Reciprocal inhibition is important for flexor reflexes

Alpha-Gamma Coactivation

Both alpha and gamma motor neurons are activated to maintain sensitivity to stretch

Deep (Golgi) Tendon Reflex

Inverse stretch reflex
Muscle contracts; GTO increases firing; excitatory interneuron; inhibitory or antagonistic muscle; Homonymous muscle relaxes and antagonist muscle contracts

Comparison of Muscle Spindle and GTO

Diagrams comparing the response of muscle spindle and GTO in active contraction and passive stretch
Active contraction: Muscle spindle shortens, affarent activity increases. Muscle length shortens.
Passive stretch: Muscle spindle lengthens, afferent activity increases. Muscle length increases

Withdrawal Reflexes

Moving a body part away from a stimulus (pain or pressure). Reflexively pulling hand away from hot stove via flexor reflexes

Crossed Extensor Reflexes

Occur simultaneously with the flexor reflex
Example: Flexion causes leg to pull up; crossed-extensor straightens the other leg to receive body weight and maintains posture.

Cutaneous Reflexes

Cutaneous stimuli are transmitted via Ad fibers, inducing contraction of flexor muscles in the stimulated limb and inhibiting opposing extensor muscles. The stimulation also causes extensor muscle contraction in the opposite limb. This is a posture-correcting reflexive measure.
Spinal pathway is polysynaptic, utilizing various spinal interneurons with reciprocal innervation.

Spinal Cord Injury

The ASIA Impairment Scale (A-E) grades spinal cord injury
A complete injury (A) lacks motor and sensory function in sacral roots (S4-5)
Incomplete injuries (B-E) show various levels of motor and sensory preservation

Cord Syndromes

Central Cord: Typically involves elderly with hyperextension injury, affects central cord before reaching peripheral cord of upper extremities, resulting in upper extremity strength loss and lower extremity spinothalmic tract loss, diminished pain/temperature sensation. prognosis is generally good.
Anterior Cord: May be caused by direct damage to anterior spinal cord, flexion injuries (whiplash), bony injury, and anterior spinal artery thrombosis. It results in complete motor paralysis below the injury level; pain and temperature sensations are lost, however vibration, proprioception, are likely intact. prognosis is generally good.
Brown-Sequard: Hemisection (incomplete/partial transverse) of the spinal cord results in ipsilateral loss of motor function, propioception and vibration sense. Contralateral (opposite) loss of pain and temperature sensation. prognosis is good.
Conus Medullaris: Presents as a secondary condition to disc herniation, spinal stenosis, or a mass at the conus medullaris. Results in bowel and bladder dysfunction and lower extremity loss, possibly areflexic bowel and bladder, and flaccid anal sphincter.
Cauda Equina presents as a condition of injury to multiple lumbosacral spinal nerve roots. Results in: areflexia, variable motor/sensory loss in lower extremities, sciatica, bowel and bladder dysfunction, saddle anesthesia

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