Week 12 Lecture Notes - Motor Pathways and Spinal Cord Lesions

This set of flashcards covers key concepts from the lecture notes on motor pathways and the impact of spinal cord lesions.

What are the two main types of direct motor pathways?

Corticospinal pathways and corticobulbar pathways.

Where do the corticospinal pathways originate?

The cerebral cortex.

What is the function of the upper motor neurons?

They originate in the central nervous system and synapse on lower motor neurons in the peripheral nervous system.

Which part of the brain do corticobulbar pathways terminate in?

The bulbar region of the brainstem.

What do lower motor neurons control?

They control skeletal muscle movement.

What is the role of the anterior corticospinal tract?

It synapses on lower motor neurons for proximal limb and trunk coordination.

What is the result of a complete transection of the spinal cord?

Loss of sensory and motor function below the level of the lesion.

How do indirect motor pathways differ from direct motor pathways?

Indirect motor pathways do not cross in the pyramids and include extrapyramidal tracts.

What is the significance of the pyramids in the context of motor pathways?

Pyramids are where the majority (90%) of corticospinal fibers decussate.

What does a brown-sequard syndrome present with?

Ipsilateral loss of proprioception and motor function, contralateral loss of pain and temperature.

Which cranial nerves have bilateral innervation?

Trigeminal (V), Facial (VII - forehead), Vagus (X), and Hypoglossal (XII).

What happens to sensory pathways below a complete spinal cord lesion?

All sensory perception is lost below the level of the lesion.

What is the clinical presentation of a lower motor neuron lesion?

Flaccid paralysis at the level of the lesion.

What is spinal shock?

Loss of all sensory and motor function at and below the level of the lesion for the first six weeks.

What occurs during the ramping up of the stretch reflex after an upper motor neuron lesion?

Increase in hyperreflexia and spasticity below the level of the lesion.

What do corticobulbar paths carry?

Motor commands for facial and neck muscles via cranial nerves.

What is the clinical usefulness of understanding nerves' somatotopic arrangement?

It aids in localizing lesions based on motor function loss.

In which area of the spinal cord are sympathetic lower motor neurons found?

In the lateral gray horns from T11 to L3.

What happens to bowel and bladder function in a complete transection above T11?

Control of bowel and bladder function is lost.

Which fibers from the hypothalamus are responsible for autonomic functions?

Hypothalamic spinal fibers synapsing on sympathetic and parasympathetic preganglionic lower motor neurons.

What happens during spinal shock?

Temporary loss of all functions below the level of the lesion due to initial flaccidity.

What happens to the muscle function above the level of a spinal cord lesion?

Muscle function remains unaffected above the level of the lesion.

What characterizes the lateral corticospinal tract?

It serves the distal parts of the limbs for skilled voluntary movements.

What is the effect of a higher cervical spinal cord lesion compared to a lower one?

Higher lesions result in more extensive loss of function below the lesion.

What does the term 'decussate' refer to in the context of motor pathways?

The crossing of nerve fibers from one side of the central nervous system to the other.

What is the effect of losing upper motor neuron control over lower motor neurons?

It results in hyperreflexia and spastic paresis.

What clinical signs differentiate an upper motor neuron lesion from a lower motor neuron lesion?

Upper motor neuron lesions cause spastic paresis; lower motor lesions cause flaccid paralysis.

What can cause incomplete spinal cord lesions?

Trauma, space occupying lesions, infections, or ischemia.

What is the expected outcome for motor function in the limbs if a lesion occurs at the cervical level 4?

Loss of function and paralysis below that level; possibly respiratory compromise.

What is the primary function of corticospinal tracts?

To convey voluntary motor commands from the motor cortex to the spinal cord.