Functional Heirarchy of the Motor System Flashcards
Which nuclei in the brain control the higher order reflexes that control posture and balance?
Brain stem nuclei
Where do the brainstem nuclei receive inputs about voluntary movements from?
Cerebral cortex, basal ganglia and cerebellum
Which four systems in the CNS control movement?
Descending control pathways, basal ganglia, cerebellum and local spinal cord/brain stem pathways
Where does the spinal cord receive descending input from?
Brainstem and corticospinal tract
At what levels does sensory input enter the CNS?
Spinal cord, brainstem and cortical level
What happens to APs in a stretch reflex?
The number of APs increase
What is a monosynaptic reflex?
A reflex that directly activates the alpha-motoneurones to the agonist muscle causing contraction (no interneurons are involved
What is reciprocal inhibition?
The agonist muscle contracts and the antagonist muscle relaxes
What are the steps in an inverse stretch reflex?
1) Activation of inhibitory interneurones to the agonist muscle and a decrease in contraction strength
2) Activation of excitatory interneurones to antagonist muscles
3) Information about muscle tension ascends in the dorsal columns to the somatosensory cortex
What is the advantage of the Golgi-tendon organ reflex?
It prevents muscles contracting so hard that the tendon insertion is torn away from the bone
What is the function of a flexor reflex?
They withdraw part of the limb away from stimuli and towards the body
What are the steps in a flexor reflex?
1) Increased activity in flexor muscles of the affected part
2) Antagonistic extensors are inhibited
3) Contralateral extensors are excited
4) Contralateral flexors are inhibited
5) Sensory info ascends to the brain in the contralateral spinothalamic tract
