The Spinal Cord and Periphery Flashcards
Where do the sensory axons enter the spinal cord?
Dorsal horn
Where do the motor neurons have their spinal cord?
Ventral horn
How is the white matter arranged in the spinal cord?
It is arranged in 3 columns: posterior, lateral and anterior
What is carried in the corticospinal/ pyramidal tract?
Motor impulses from the motor cortex to the skeletal muscles
What is carried in the posterior/dorsal column?
Touch, tactile localisation, vibration sense and proprioception
What is carried in the lateral spinothalamic tract?
Pain and temperature
What is the function of the corticospinal tract?
Control of voluntary skilled movements
Where does the corticospinal tract start?
Motor cortex (area 4)
What is the blood supply to the corticospinal tract?
MCA
Where do the corticobulbar fibres go to?
Contralateral cranial nuclei
Where do the corticospinal fibres decussate?
Pyramids of the medulla
Where are upper and lower motor neurons found?
Upper - above the level of decussation
Lower - below the level of decussation
How are 1st, 2nd and 3rd order neurons differentiated?
1st Order - Receptor to dorsal root/ CrN ganglion
2nd Order - Ganglion to thalamus
3rd Order - Thalamus to Parietal Cortex
Where are the cells bodies of the 2nd neurons in the posterior column found?
Lower Medulla
What is the 2nd order neuron called in the posterior column and where does it pass?
Medial lemniscus: passes through the medulla, pons and midbrain to the thalamus
Where does the 3rd order neuron end in the posterior column?
They pass through the internal capsule and radiate to the post-central gyrus (Area 2,1,3)
Where do the first order neurons in the lateral spinothalamic tract end?
Grey matter
Where do the 2nd order neurons decussate in the lateral spinothalamic tract?
Level of entry at the spinal cord
Where do the 3rd order neurons of the lateral spinothalamic tract end?
Post central gyrus
What is a reflex?
An involuntary stereotyped pattern of response brought about by a sensory stimulus
What are the steps of a stretch reflex?
1) Tendon stretched
2) Intrafusal Muscle Fibres Stimulated
3) Sensory Neuron Activated
4a) Monosynaptic reflex arc
4b) Polysynaptic reflex arc to inhibitory interneuron
5a) Muscle contraction
5b) Reciprocal Innervation
What are the steps in a flexor reflex?
1) Pain stimulus
2) Sensory neuron activated
3) Polysynaptic reflex arc
4a) Flexion and withdrawal from noxious stimulus
4b) Crossed extensor response to contralateral limb (only in weight bearing limbs)
What happens to reflexes when there are UMN lesions?
They are exaggerated
What happens to the tone with an UMN lesion?
Increased tone - spasticity
What happens to the tone with a LMN lesion?
Decreased tone - flaccidity
