Descending Motor Pathways Flashcards
What is the role of the motor areas in the cerebral cortex?
Control of voluntary movement and coordination of motor functions
Includes primary motor cortex and premotor cortex
List the structures involved in the control of movement.
- Primary motor cortex
- Premotor cortex
- Supplementary motor area
- Basal nuclei
- Cerebellum
- Brainstem
- Spinal cord
- Thalamus
Describe the route of the corticospinal tract.
Originates in the cortex, descends through corona radiata, internal capsule, brainstem, and decussates in the medulla before reaching the spinal cord
What are the main functions of the corticospinal pathways?
Control of voluntary, discrete, skilled movements, especially in distal parts of the contralateral limbs
Compare the function of lateral pathways and ventromedial pathways.
- Lateral pathways: voluntary movement
- Ventromedial pathways: posture and locomotion
Describe the difference between upper and lower motor neurons.
- Upper motor neurons: cell bodies in cortex and brainstem, do not reach target organs
- Lower motor neurons: cell bodies in brainstem and spinal cord, innervate target organs/muscles
What are some major signs of upper motor neuron lesions?
- Increased muscle tone
- Spasticity
- Increased deep tendon reflexes
- Clonus
- Abnormal reflex (e.g., Babinski reflex)
What are some major signs of lower motor neuron lesions?
- Reduced muscle tone
- Flaccid paralysis
- Decreased tendon reflexes
- Fasciculation
- Atrophy
What does the primary motor cortex (M1) control?
Somatotopic representation of contralateral body parts, primarily hands and muscles of speech
What is the role of the premotor cortex (PMC)?
Involved in planning and control of movement, responds to external stimuli
What is the function of the supplementary motor area (SMA)?
Involved in motor planning and pre-programming movement sequences
What are the components of the basal nuclei?
- Caudate nucleus
- Putamen
- Globus pallidus
- Subthalamic nucleus
- Substantia nigra
What disorders are associated with basal nuclei dysfunction?
- Muscle rigidity
- Resting tremor
- Hypokinesia
- Bradykinesia
- Chorea
What is the corticospinal tract primarily responsible for?
Voluntary, discrete, skilled movements
What is the lateral corticospinal tract?
Formed by axons that crossed the midline in the pyramidal decussation, controls voluntary movement of the contralateral limbs
What does the anterior corticospinal tract control?
Voluntary movement of axial and girdle muscles and proximal limb muscles
What is the role of the extrapyramidal system?
Regulates involuntary motor functions to maintain posture and fine-tune voluntary movements
What is posture?
Position of body and its parts relative to each other, balancing movement and stability
What sensory information is integrated for posture control?
- Muscle proprioceptors
- Vestibular apparatus
- Visual inputs
What is decorticate posturing?
Flexion of upper limb and extension of lower limb due to corticospinal tract interruption
What are the signs of decerebrate posturing?
Extension of limbs, indicating structural lesions at or inferior to the red nucleus
What occurs with a lesion above the Red nucleus?
Disinhibition
This refers to the loss of inhibitory control over motor functions.
What is the effect of the rubrospinal tract on upper limb movement?
Flexion
The rubrospinal tract promotes flexion of the upper limbs.
What is the effect of the vestibulospinal tract on lower limb movement?
Extension
The vestibulospinal tract promotes extension of the lower limbs.
