Neurological Physiotherapy

Name the 3 Ascending (Sensory) Pathways

Dorsal Column Medial Lemniscus Tract

Spinocerebellar Tract

Spinothalamic Tract

Name the 5 Descending (Motor) Tracts

Extrapyramidal Tracts:

Reticulospinal Tract

Vestibulospinal Tract

Rubrospinal Tract

Tectospinal Tract

Pyramidal Tract:

Corticospinal tract

What are the DCML tract sensory receptors?

Mechanorecepetors

• meissners corpuscles

• merkels discs

• pacinian corpuscles

• ruffini endings

Proprioception

• muscle spindles

• golgi tendon organs

What is the DCML pathway responsible for?

fine (discriminative) touch

vibration sensation

proprioception

stereogenosis

Define Proprioception

Proprioception is the body's ability to sense its position, movement, and orientation in space.

Define stereogenosis

Stereognosis is the ability to recognize and identify objects by touch alone, without the use of vision

What is a mechanoreceptor?

Mechanoreceptors are specialized sensory receptors that respond to mechanical stimuli such as pressure, vibration, and stretch.

Where are meissner’s corpuscles located?

Found in the skin, particularly in the fingertips, palms, soles, and lips.

What do meissner’s corpuscles do?

Detect light touch, vibration, and texture.

What are meissner’s corpuscles adaptation?

Rapidly adapting, meaning they respond quickly to changes in stimuli but stop firing if the stimulus remains constant.

Where are Merkel’s Discs located?

Located in the epidermis (outer layer of skin), especially in the fingertips and lips.

What is the function of Merkel’s discs?

Detect sustained pressure, texture, and fine details.

What is Merkel’s disc adaptation?

Slowly adapting, meaning they continue to respond as long as the stimulus is applied.

Where are Pacinian Corpuscles located?

Found deep in the skin, as well as in muscles, joints, and internal organs.

What is the function of Pacinian Corpuscles?

Detect deep pressure, vibration, and proprioceptive information.

What is the adaptation of Pacinian Corpuscles?

Rapidly adapting, making them ideal for detecting changes in pressure or vibration.

Where are Ruffini endings located?

Located in the dermis and joint capsules.

What is the function of Ruffini endings?

Detect skin stretch, sustained pressure, and joint movement.

What is the adaptation of Ruffini endings?

Slowly adapting, providing continuous feedback about skin stretch and joint position.

Where are muscle spindles located?

Found within skeletal muscles.

What is the function of muscle spindles?

Detect changes in muscle length and the rate of stretch.

What is the role of muscle spindles?

Help regulate muscle tone and coordinate movement by triggering reflexes, like the stretch reflex (e.g., knee-jerk reaction).

Where are golgi tendon organs located?

Located at the junction between muscles and tendons.

What is the function of golgi tendon organs?

Detect tension within a muscle during contraction.

What is the role of golgi tendon organs?

Prevent muscle damage by triggering the Golgi tendon reflex, which relaxes the muscle when excessive force is detected.

Explain the First-Order Neurons (Sensory Receptors ➔ Medulla) route for the DCML tract

Signal travels via afferent fibers through the dorsal root ganglion (DRG) into the spinal cord

• Axons ascend ipsilaterally in the dorsal columns:

  • 👉 Fasciculus gracilis (Lower limb & trunk)

  • 👉 Fasciculus cuneatus (Upper limb & trunk)

• Synapse occurs in the nucleus gracilis & nucleus cuneatus in the medulla

Explain the route Second-Order Neurons (Medulla ➔ Thalamus) for the DCML tract

• Axons from the nucleus gracilis & nucleus cuneatus decussate (cross over) in the medulla

• Travel through the medial lemniscus

• Terminate in the ventral posterolateral (VPL) nucleus of the thalamus

Explain the Third-Order Neurons (Thalamus ➔ Somatosensory Cortex) route for th DCML tract

• Neurons project from the VPL nucleus of the thalamus to the primary somatosensory cortex (Postcentral gyrus, Parietal lobe)

• The brain interprets:

  • Type of sensory input

  • Intensity

  • Location

Explain the presentation of a Spinal Cord Lesion in the DCML tract

• Ipsilateral loss of fine touch, vibration, and proprioception below the lesion

• Example: Right-side lesion at T6 ➔ Sensory loss in right leg

Explain the presentation of Lesion in the DCML Above the Medulla

After Decussation (Above Medulla)

• Contralateral loss of fine touch, vibration, and proprioception

• Example: Left medial lemniscus lesion ➔ Sensory loss on the right side of the body

What is the spinocerebellar tract responsible for?

unconscious proprioception

coordination of movement

regulating muscle tone

Where does the spinocerebellar tract terminate?

Cerebellum

What would lesions in the spinocerebellar tracts cause?

ipsilateral coordination deficits but not sensory loss, unlike DCML and spinothalamaic lesions.

Can cause ataxia (uncoordinated limb movement)

Dysmetria (inability to control movement distance)

Intention tremor (during movement)

What is the function of the spinothalamic tract?

pain (nociception)

temperature sensation

crude touch and pressure (less precise than DCML pathway)

What happens in the spinothalamic tract at First-Order Neurons (Sensory Receptors ➔ Spinal Cord)

• Detected by:

  • 👉 Nociceptors: Detect pain

  • 👉 Thermoreceptors: Detect temperature

  • 👉 Mechanoreceptors: Detect crude touch

• Pathway:

  • Signal travels via afferent fibers through the dorsal root ganglion (DRG)

  • Enters the spinal cord

  • Synapses immediately in the dorsal horn (substantia gelatinosa or nucleus proprius)

What happens in the spinothalamic tract at Second-Order Neurons (Spinal Cord ➔ Thalamus)

• Decussation:

  • Axons cross over (decussate) immediately in the spinal cord (within 1-2 levels)

• Pathways:

  • 👉 Lateral Spinothalamic Tract: Transmits pain & temperature

  • 👉 Anterior Spinothalamic Tract: Transmits crude touch & pressure

• Destination:

  • Fibers project to the ventral posterolateral (VPL) nucleus of the thalamus

What happens in the spinothalamic tract Third-Order Neurons (Thalamus ➔ Somatosensory Cortex)

• Thalamus Role:

  • VPL nucleus of the thalamus sends sensory information to the primary somatosensory cortex

• Pathway:

  • Signal travels through the internal capsule

• Interpretation:

  • The brain processes and localizes pain, temperature, crude touch, and pressure

  • Occurs in the parietal lobe (postcentral gyrus)