INTS 9: Motor and Sensory Pathways Flashcards
Where do the main descending motor pathways originate from?
- they originate from the cerebral cortex and the brainstem
Where do the principal descending motor pathways act on?
- they act via lower motor neurons on skeletal muscles
Which motor pathways originate from the cerebral cortex?
Via where?
- corticospinal tracts: via spinal cord
- corticobulbar tracts: via brainstem
Which motor pathways originate from the brainstem?
- vestibulospinal tracts
- reticulospinal tracts
- rubrospinal tracts
- tectospinal tracts
Give a brief description of what somatosensory pathways do
- they carry information from the periphery (skin, joints) into the CNS
- relaying information relating to
- fine touch
- pressure
- vibration
- crude touch
- pain
- temperature
Which two motor pathways originate from the primary motor cortex?
- corticospinal pathway
- corticobulbar pathway
What is the neuron from the primary motor cortex to the spinal cord (or brainstem) known as?
- upper motor neuron
What is the neuron from the spinal cord (or brainstem) to the muscle known as?
- lower motor neuron
What does it mean that the body is represented somatotopically in the primary motor cortex?
- a specific region of the body can be mapped to a specific region in the nervous system
What does this diagram show?
- they are projections of the corticospinal (a) and corticobulbar (b) tracts from the primary motor cortex through the internal capsule
Describe how the corticospinal fibres are distributed throughout the brain
How do they form the lateral corticospinal and anterior corticospinal tract?
- see image below
- 85-90% of corticospinal fibres cross in the medulla (the decussation of the pyramids) to form the lateral corticospinal tract
- the remaining 10-15% form the anterior corticospinal tract
What movements do the lateral corticospinal tract and anterior corticospinal tract control?
- lateral corticospinal tract:
- skilled voluntary movements
- anterior corticospinal tract:
- postural adjustments following limb movements
Describe the pathway and function of the vestibulospinal tract
- the vestibulospinal tract conveys signals from the inner ear (vestibular apparatus) to the musculature
- it controls movements of the neck muscles and postural adjustments by facilitating extensor muscles and inhibiting flexor muscles
- image shows the posterior view showing origin of vestibulospinal tracts from pons/medulla
Describe the pathway and function of the rubrospinal tract
- fibres originate from the red nucleus in the midbrain
- they travel through the brainstem and synapse on lower motor neurons innervating the flexor muscles of the upper limbs
Describe the pathway and function of the vestibulospinal tract
- fibres originate from the reticular formation of the pons and medulla
- they control the orientation of the body towards or away from stimuli