Transcript Nervous circuits

Nervous Circuits
Reverend Dr David C.M. Taylor
School of Medicine
[email protected]
http://www.liv.ac.uk/~dcmt
Our objectives in this plenary
 To use our understanding of the case to
 Be able to distinguish between upper and lower motor
neuron lesions
 To gain an understanding of the spinal reflexes
 To start to understand the control of movement
Mrs Webster
 Experienced one-sided weakness in her arm and face
 In principle the problem could lie in the periphery (spinal
motor neurones etc.,)
 Or it could lie centrally (with the motor neurones or
pathways that control the spinal motor neurones)
So?
 We need to distinguish between upper and lower
motor neurones.
 Upper motor neurones are in the motor cortex
 Lower motor neurones are in the spinal cord - think
about the knee jerk reflex
Upper motor neurones
This image of an homunculus has been
removed to avoid breach of copyright
 The descending fibres cross in the medulla en route
to the spinal cord
Pathway
This image of descending motor
pathways has been removed to avoid
breaching copyright
Click on the black box to view video
Knee jerk reflex
stretch receptor
in muscle
contraction
of muscle
spinal motor
neurone
Monosynaptic Reflex
Tap tendon just below patella
stretch muscle
extensor contracts
activate receptors
extensor a mn
Renshaw cell
flexor relaxes
flexor a mn
inhibitory
interneurones
Simple withdrawal reflex
More fully…
Full crossed extensor reflex
Simple scheme
Plan
Idea
Cortical
association
areas
Execute
Premotor and
motor cortex
Movement
Overview of control
Plan
Execute
Basal ganglia
Idea
Cortical
association
areas
Lateral
cerebellum
Premotor and
motor cortex
Movement
intermediate
cerebellum