8: Physiology - Spinal reflexes, upper motor neurons and the control of movement Flashcards
Which type of neuron co-ordinates pairs of agonist/antagonist muscles to relax and contract in tandem to produce movement?
Excitatory and inhibitory interneurons
Which type of interneuron acts on
a) quadriceps femoris
b) biceps femoris
in the knee jerk reflex?
a) Excitatory interneuron, producing knee extension
b) Inhibitory interneuron, preventing knee flexion
What are the three simplified steps in motor movements?
1. Strategy - thought re: what you’re out to do and the best way to do it
2. Tactics - sequence of muscle movements required to fulfill aim
3. Execution - activation of muscle groups to fulfill aims
Which parts of the CNS are responsible for
a) strategy
b) tactics
c) execution
of motor movements?
a) Neocortical areas (i.e areas outwith the motor cortex), basal ganglia
b) Motor cortex, cerebellum
c) Brainstem, spinal cord
What is the main motor pathway we need to know about?
Corticospinal tract
Where does the corticospinal tract start?
Pre-frontal gyrus i.e motor cortex
Where does the corticospinal tract decussate?
Pyramids of the medulla
85% of fibres swap sides
What is formed when 85% of motor fibres decussate at the pyramid of the medulla?
Lateral corticospinal tract
What is formed by the 15% of corticospinal tract fibres which DON’T decussate at the pyramids of the medulla?
Anterior corticospinal tract
still on the ipsilateral side
Which muscles are supplied by the
a) lateral corticospinal tract
b) anterior corticospinal tract?
a) Upper and lower limbs
b) Trunk (postural muscles)
When do anterior corticospinal tract fibres decussate?
At the spinal nerve levels of the muscles they supply
Which tracts, when allowed to excite muscles unopposed, cause
a) decorticate posturing
b) decerebrate posturing?
a) Rubrospinal tract
b) Reticulospinal tract
